. . Guide

1 Table of Content

Introduction 3 Common Problems 31 Webbing/ Marks/ Thinning 31 Applications 4 Chill marks / Thinning 33

The Vacuum Forming Process 6 Finishing and Trimming 34 Basic principles of vacuum forming 7 Clamping 8 Troubleshooting guide 41 Heating 8 Auto-level / Sheet Level 8 Contact 45 Pre-stretch ( Bubble) 8 Vacuum 9 Plug Assist - Only available on HD and TF Series 9 Cooling and Release 9 Trimming and finishing 9

Plastics materials and their characteristics 10 Overview typical 11 Acrylonitrile Butadiene Styrene – (ABS) 13 – High Impact Polystyrene (HIPS) 14 – (P.C. / LEXAN/ MAKROLON) 15 – (PE, HDPE, LDPE, PE FOAM) 16 Co- – (PETG / VIVAK) 17 Acrylic - PMMA – (Perspex, Oroglas, Plexiglas) 18 – (PP) 19 Polyvinylchloride – (PVC) 20

Mould Material and Mould Design 21 1- Modelling Clay, Plaster 22 2- Wood 22 3- Cast Epoxy Resins 23 4- Foam 24 5- 3D /Rapid prototyping/Additive 25 25 6- Aluminium - Cast 26 7- CNC machined tooling board or model board 26 Male and Female Moulds 27

Mould Design: Basic Considerations 28 Angles 28 Venting 29 Undercuts 29 Male and Female Moulds 30

2 Formech - Vacuum Forming Guide Introduction

Thermoforming has been around for a very long Once you’ve got to grips with the contents of time, and has transformed the world that we live in. this guide, there will be just one question left It is a process that has helped to make items from unanswered; what are you going to make? the simplest of trays, to car interior parts, sets and costumes in Hollywood blockbuster movies, life saving medical equipment, and even components for space exploration. The possibilities of this production method are endless, with applications seen in almost every you can think of. Despite seeing and using thermoformed plastics every day, not everyone has even heard about before, let alone had the chance to use it to design and manufacture something fresh out of their own imagination.

‘Thermoforming’ is used to describe any process Helmets Polycarbonate in which heat is used to shape and mold , body formed on a although in this guide we will be talking specifically Formech 1372 about ‘vacuum forming’, which can certainly be considered part of the thermoforming family, only with some very important extras.

The simplest description of the vacuum forming process is that of a sheet of plastic having heat applied to it until it softens, before being draped over a mold. A strong suction of air, or ‘vacuum’, is Mask DUESITH - Body formed on a Formech applied from below, attracting the soft plastic over 300XQ the mold to adopt its shape. Once cooled, the mold can be removed, leaving just a perfectly formed plastic component. A very simple process, but one which is hugely popular, effective, fast, and easy. The early 1900s saw the development of the first thermoforming machines. They were big, and took up a huge amount of space. We’re glad to say that things have changed a bit since then, and thermoforming equipment today can be so small it might fit on a school desk. Air conditioning units ABS - Body formed on In this guide we will be exploring the potential of a Formech 686 the Formech vacuum forming machine that you have available, covering all aspects of how to use it, what to use it for, how to produce your molds to form over, and all the tricks of the trade that go along with it. This document will be your one stop guide which you can refer back to at any point during a project that involves vacuum forming, to find all the answers, hints and tips you might be looking for.

3 Formech - Vacuum Forming Guide Applications

Aeronautical Manufacturers Computer Industry > Interior Trim Panels, Covers and Cowlings Internal > Manufacture of Screen Surrounds sections for NASA Space Shuttle > Soft Transparent Keyboard Covers Enclosures Agricultural Suppliers and Ancillary Equipment

> Seed Trays, Flower Tubs, Animal , Clear Design Industry Growing Domes > Production of prototypes and Pre-Production Runs > Calf Milking Receptacles, Machines Parts > Lawn- > Prototype Concepts for other Plastic Processes mower Enclosures and Covers Architectural Model Makers > Training Aids for Students Studying Polymers and > Production of Miniature Parts for Architectural Plastic Processing Models > Prototypes Automotive and Vehicular Industry > Manufacturing Enclosures for Specialist Electronic > Wheel Hub Covers, Ski- and Storage Racks, Equipment Wind Tunnel Models, Parts for All Terrain Vehicles > Anti-Static Component Trays Truck Cab Door Interiors, Wind and Rain Deflectors > Scooter Shrouds, Mudguards, Bumpers and Pro- tective Panels > Battery and Electronic Housings, Prototype and Mask HIPS - Body formed Development work on a Formech 300XQ > Utility Shelves, Liners, Seat Backs, Door Inner liners and Dash Surrounds > Windshields, Motorcycle Windshields, Golf Cart Shrouds, Seats and Trays > Tractor Shrouds & Door Fascia, Camper Hardtops and Interior Components

Building and Construction Industry Radio Controlled Car - Body > Drainpipe Anti Drip fittings formed on a Formech 686 > Roof Lights, Internal Door Liners, PVC Door Panels, Producing Molds for Concrete Paving Stones and Special Bricks > Molded Features for Ceilings, Fireplaces and Porches

Boat Building industry > Boat Hulls, Covers and Hatches Electrical Enclo- sures, Dashboards

Chocolate industry Luggage acrylic - Body > Manufacture of Chocolate Molds for Specialised formed on a Formech 1372 Chocolates > Easter Eggs etc. and Packaging

4 Formech - Vacuum Forming Guide Applications

Film and Media Industry Souvenir Industry > Manufacture of Costumes and Sets > Animation > Making parts for and molds to cast craft souvenirs Models and Mock Ups for Computer Simulation Sports Industry > Helmets, Guards and Gum Shields Furniture Manufacturing Industry Theatre > Chair and Seat Backs > Manufacture of Props, Sets and Costumes > Cutlery tray inserts > Kitchen Unit Panels and Storage Modules Toy Industry > Games, Action Figures, Packaging, Dolls, and Hospitals and Medical Applications Prototyping > Radiotherapy Masks for Treatment of Cancer Patients > Pressure Masks for Burn Victims > Parts > Dental > Parts for Wheelchairs and Medical Devices for the Disabled

Machinery Manufacturers > Fabricating machine guards and electrical enclo- sures Golf Car Parts Acrylic Capped ABS - Body formed Model Car and Aircraft Industry on a Formech 1500 > Production of bodies fuselages and other parts for models

Museums > Variety of applications within Science and Natural History Museums

Packaging and related Industries > Point of Purchase > Trays and Plates > Cosmetic Cases and Packages Props Acrylic Capped ABS - Body formed on a Formech > Electronics and Cassette Holders FMDH660 > Products, Products Food Trays, Cups and Fast Food Containers

Plastic Sheet > Testing and Sampling of Extruded Sheet Industry > Exterior Signs Point of Sale Displays

Sanitary Industry > Bathroom Fittings Acrylic capped ABS Kayak seat - Body formed on a > Bathtubs, Jacuzzis and Whirlpools > Shower Sur- Formech HD Series rounds, Shower Trays and Retrofit Shower Components

5 Formech - Vacuum Forming Guide The Vacuum Forming Process

In its simplest form the process consists essentially greater detail later in this guide - see section Mould of inserting a sheet in a cold state and Mould Design.) into the forming area, heating it to the de- sired temperature either with just a surface heater The typical process steps can be identified as or with twin heaters and then raising a mould follows: clamping, heating, pre-stretch, plug assist, from below. The trapped air is evacuated with the cooling with air and spray mist, release and trimmi- assistance of a vacuum system and once cooled ng. They are examined more closely under the sub a reverse air supply is activated to release the headings on page 8 and 9. plastic part from the mould. The process is shown in diagram on page 7. In its advanced stage pneu- matic and hydraulic systems complimented with sophisticated heat and process controllers allow high speed and accurate vacuum forming for those Cup cake POS display - Body heavy duty and high end volume applications. formed on a Formech 686

The thermoforming industry has developed despite two fundamental shortcomings. Many other ther- moforming processes use a resin base in powder or pellet form. Vacuum forming begins further down the line with an extruded plastic sheet which incurs an additional process and therefore an extra cost to reach this stage. In addition, there is generally an area of material which is cut away from the formed part which unless reground and recycled has to be considered as waste and accounted for in any costings made. However these problems have been invariably resolved by strict control of sheet quality and by clever mould design to minimise the amount of waste material. Throughout this manual you will find useful hints and techniques to assist in maximi- sing the potential from this process.

Despite the above disadvantages vacuum forming Tray HIPS - body formed offers several processing advantages over such on a TF686 others as blow, rotational and . Fairly low forming pressures are needed therefore enabling comparatively low cost tooling to be utilised and relatively large size mouldings to be economically fabricated which would be otherwise cost prohibitive with other processes. Since the moulds witness relatively low forces, moulds can be made of relatively inexpensive materials and mould PETG digitally printed on fabrication time reasonably short. This results in the reverse - Body formed comparatively short lead times. It provides the per- on a Formech xxx fect solution for prototype and low quantity requi- rements of large parts as well as medium size runs utilising multiple moulds. (Moulds are discussed in

6 Formech - Vacuum Forming Guide The Vacuum Forming Process

Basic principles of vacuum forming

1. Clamping frame, aperture plate & table 2. Material clamped and tool (mould) mounted on table

3. Heating the clamped material 4. Material pre-stretched & table up

5. Vacuum applied 6. Cooling, release & table down

7 Formech - Vacuum Forming Guide The Vacuum Forming Process

Clamping Auto-level / Sheet Level - not available on all the The clamp frame needs to be sufficiently powerful machines enough to ensure the plastic sheet is firmly held du- A photo-electric beam is activated under the sheet ring the forming process. It can handle the thickest of plastic during the heating cycle. If the sheet material likely to be formed on the machine – up of plastic sags down and breaks the beam, then to 6mm with a single heater and up to 10mm with a small amount of air is injected into the bottom the twin heater machines. If an automated process chamber under the sheet, thus lifting the sheet to is used the operation of the moving parts must be stop it from sagging until the sheet clears the beam. guarded and interlocked to avoid accidental da- mage. In addition, a safety guard must be provided Pre-stretch ( Bubble) - Not available on all the to protect the machine operator at all times. machines Once the plastic has reached its forming tempe- Heating rature or “plastic” state it can be pre-stretched to Heaters are generally infra-red elements mounted ensure even wall thickness when the vacuum is ap- within an aluminum reflector plate. In order to plied. The method of controlling the bubble height obtain the best vacuum forming results, using any should be that consistent results are obtainable. material, it is essential that the sheet is heated uni- Vacuum, air pressure, and optional aids such as a formly over its entire surface area and throughout plug assist are then used to assist in moulding the its thickness. In order to achieve this, it is necessary heated, stretched plastic. to have a series of zones that are controlled by ener- gy regulators. Ceramics do have some disadvantage in that their high thermal mass makes them slow to warm up (approx 15 minutes) and slow in their response time when adjustments are made. More sophisticated quartz heaters are available which have less thermal mass enabling more rapid response time. Pyrometers enable accurate heat temperature control by sensing the melting tempe- rature of the sheet and interacting with the opera- ting process control. Precise temperature readout is also available with a computer controlled system working in unison with the pyrometers. Twin heaters Quartz Heaters are also recommended when forming thicker mate- rials as they assist in providing more uniform heat penetration and faster cycle times. Twin quartz heaters are advisable when forming high temperature materials with critical forming temperatures. By close control of areas of heat intensity, heat losses around the edges caused by convection air currents and absorption from clamp areas can be fully compensated for and consistent results achieved on a continuous basis. Cost savings can also be considerable if quartz heaters are spe- Pre-Stretch cified, as there is an adjustable percentage power drop when the heaters are in the rear position during the forming process.

8 Formech - Vacuum Forming Guide The Vacuum Forming Process

Vacuum removed. Holes, slots and cut-outs are then drilled Once the material is suitably heated a vacuum can into the part. Other post- include be applied to assist in forming the sheet. A vacuum decoration, printing, strengthening, reinforcing and pump is used to draw the air trapped between the assembly. sheet and the mould. The vacuum pumps vary from diaphragm pumps to dry and oil filled rotary vane A variety of different trimming methods are used to pumps. With larger machines a vacuum reservoir trim the product from the sheet. The type of equip- is used in conjunction with a high volume capacity ment best suited depends largely on the type of vacuum pump. This enables a two stage instan- cut, size of the part, draw ratio, thickness of material taneous vacuum to be applied ensuring rapid moul- and the production quantity required (see page 38 ding of the heated sheet (before the sheet tempera- for trimming and finishing methods). Thin ture drops below its ideal forming temperature). parts are normally trimmed on a mechanical trim press – otherwise known as a rollerpress. Plug Assist - Only available on HD and TF Series Plug assisted vacuum forming (moulding) is used when straight vacuum forming is unable to distri- bute the thermoplastic sheet evenly to all areas of the mold. To help spread the sheet out more even- ly, a device known as a plug is utilized to push the sheet into the mold before the vacuum is applied. This process enables more of the thermoplastic material to reach the bottom of the mold and thus more material is available to fill the corners of the mould and limit the plastic from thinning out.

Cooling and Release - Not available on all the machines Plug assist Once formed, the plastic must be allowed to cool before being released. If released too soon then deformation of the moulding will result in a reject part. To speed up the cooling cycle high speed, fans are fitted and activated once the part is formed. A spray mist option is also available whereby nozzles are attached to the fans and a fine mist of chilled water is directed onto the sheet. This, in conjunc- tion with the fans can speed up the cooling cycle by up to 30% and is also beneficial in controlling the shrinkage of the moulded parts. Mould temperature control units are also available which regulate the temperature within the mould ensuring accurate and consistent cooling times when cooling crystalline and crystallizing polymers such as PP, HDPE and PET. Cooling Fan System

Trimming and finishing Once the formed part has cooled and been re- moved from the machine the excess material is

9 Formech - Vacuum Forming Guide Plastics materials and their characteristics

Plastics comprise a wide range of materials but control is used to monitor the heating process. fundamentally fall into two groups – thermoset and In summary, the forming temperature bands for thermoplastic, the latter being a material which, amorphous materials is much wider and as a re- due to the molecular structure, has the property sult are easier to process in comparison to their of softening repeatedly when heated and harde- semi-crystalline counterparts. In other words they ning once cooled. also have what have a much better melt strength and will not is known as a ‘memory’ enabling a formed part to sag as much as the melt transition temperature is revert to its original state when reheated. reached.

It is the thermoplastic type that is used specifically for thermoforming and therefore we will concen- trate on this category in this section.

Polymers are made up of molecules which in turn are made up of atoms. These atoms have many different combinations which all have different properties and contain a wide range of additives Racing car HIPS - Vacuum formed on to give each material its own characteristics. There a Formech 1372 is constant research being carried out to develop new materials suited to an ever increasing range of applications. Later in this section we have provided a breakdown of the more common materials used for thermoforming, their characteristics and the applications to which they are most suited.

Thermoplastics are split into two different groups – amorphous and crystaline. Crystalline thermoplas- tics contain an ordered manner of molecules and amorphous contain a random arrangement.

Generally speaking amorphous materials, e.g. POS PETG - Vacuum Polystyrene and ABS are easier to vacuum form as formed on a they do not have such a critical forming tempera- Formech 508FS ture. When heat is applied amorphous materials becomes soft and pliable – when it reaches this state it is known as its Transition Temperature (Tg). If heated to a higher temperature it reaches a Viscous state (Tv). The changes occur over a range of temperatures and enable the operator to have a fairly wide forming range.

Semi-crystaline and crystaline materials, e.g. Polyethylene and Polypropylene have a far more critical forming temperature as they go rapidly from the Tg state to Tv a change known as the Melt Monopoly board game Transition Temperature (Tm). When using crystalline - Vacuum formed on a materials is imperative that accurate temperature Formech 686

10 Formech - Vacuum Forming Guide Plastics materials and their characteristics

Overview typical plastics

Material Glass Transition Tem- Rec. mould tempe- Rec. forming tem- Drying tempera- Drying perature rature perature ture time ABS 88-120°C / 82°C / 150-180°C / 70-80°C / 1 hour per mm 190.4-248°F 179.6°F 302-356°F 158-176°F HIPS 100°C / 82°C / 150-175°C / n/a n/a 212°F 179.6°F 302-347°F PC 150°C / 127°C / 170-205°C / 90°C-110°C / 1mm: 1hr 302°F 260.6°F 338-401°F 194-230°F 3mm: 4hrs 4mm: 10hrs PE -125°C / 90°C / 150-180°C / n/a n/a -193°F 194°F 302-356°F PETG/PET 70-80°C / 60°C / 120-160°C / n/a n/a 158-176°F 140°F 248-320°F PMMA 100°C / 82°C / 150-175°C / 70-80°C / 1mm: 1hr 212°F 179.6°F 302-347°F 158-176°F 3mm: 4hrs 4mm: 10hrs PP 5°C / 90°C / 150-180°C / n/a n/a 41°F 194°F 302-356°F PVC 90°C / 80°C / 140-190°C / n/a n/a 194°F 176°F 284-374°F

Note: Values stated are intended as a guide only and for actual values you should refer the material specification from the plastic manufacturer.

Different thermoplastics have different characte- temperature and length of drying time depends ristics and are better suited to specific applications. on the material and the thickness. It is advisable Ideally the material should be easy to form with a to contact our office who will advise exactly what low forming temperature, good flow characteristics drying temperature and time is required for mate- and thermal strength, high impact strength and low rials. shrinkage on cooling. To improve thermal stability E.g.: Polycarbonate with a thickness of 3mm would in certain materials like, for example, PVC, stabili- require 4 hours at a drying temperature of 90-110°. sers are added to help prevent degradation when In the following pages we will look at the more com- heated. monly used plastics and list their properties, features Certain materials are known as Hygroscopic – na- and some of the more popular applications for mely that they absorb moisture which if not predried which they are used (Typical application examples of prior to forming will result in moisture blisters which thermoformed products are listed on pages 4 & 5). will pit the surface of the sheet resulting in a reject In table page 12, you will find a selection of more part. It is a common misconception that the blisters commonly used materials and the approximate hea- are as a result of too much heat. This in turn can ting times required using a single heater Formech lead to incorrect heating cycles being entered which machine equipped with Quartz elements (if twin in turn cause problems with definition on the fini- heaters are used then the heat cycle can be reduced shed part. (To avoid the pitting the operator is forced by up to 30%). into forming the part before the plastic has reached These are given as a guideline only as many diffe- its forming temperature). To overcome this problem rent grades of materials exist and other factors it is therefore necessary for hygroscopic materials to which affect timescales. be predried in an oven before forming. The drying

11 Formech - Vacuum Forming Guide Plastics materials and their characteristics

Approx. heating Approx. heating Plastic Thickness Plastic Thickness time (seconds) time (seconds) ABS 1mm / 0.04“ 40 PP 1mm / 0.04“ 50 1.5mm / 0.06“ 60 1.5mm / 0.06“ 75 2mm / 0.08“ 80 2mm / 0.08“ 100 3mm / 0.12“ 120 3mm / 0.12“ 150 4mm / 0.16“ 160 4mm / 0.16“ 200

HIPS 1mm / 0.04“ 30 PS 1mm / 0.04“ 30 1.5mm / 0.06“ 45 1.5mm / 0.06“ 45 2mm / 0.08“ 60 2mm / 0.08“ 60 3mm / 0.12“ 90 3mm / 0.12“ 90 4mm / 0.16“ 120 4mm / 0.16“ 120

PC 1mm / 0.04“ 60 PVC 1mm / 0.04“ 30 1.5mm / 0.06“ 90 1.5mm / 0.06“ 45 2mm / 0.08“ 120 2mm / 0.08“ 60 3mm / 0.12“ 180 3mm / 0.12“ 90 4mm / 0.16“ 240 4mm / 0.16“ 120

PE 1mm / 0.04“ 50 Note: This is a selection of more commonly used 1.5mm / 0.06“ 75 materials and the approximate heating times 2mm / 0.08“ 100 required using a single heater Formech machine 3mm / 0.12“ 150 equipped with quartz elements 4mm / 0.16“ 200

PETG 1mm / 0.04“ 30 1.5mm / 0.06“ 45 2mm / 0.08“ 60 3mm / 0.12“ 90 4mm / 0.16“ 120

PMMA 1mm / 0.04“ 40 1.5mm / 0.06“ 60 2mm / 0.08“ 80 3mm / 0.12“ 120 4mm / 0.16“ 160

12 Formech - Vacuum Forming Guide Plastics materials and their characteristics

Acrylonitrile Butadiene Styrene – (ABS)

Properties Hard, rigid amorphous thermoplastic with good impact strength and weather resistance. It contains a rubber content which gives it an improved impact resistance. Available with different textures and finishes in a range of thickness. Needs drying. Available in Fire Retardant and UV stabilised grades.

Formability Good - forms to a high definition.

Hygrocospic Yes - pre drying required at approx 80°C / 176°F (1 hour per mm).

Strength Good - High Impact.

Shrinkage Rates 0.3 - 0.8%.

Availability From stock.

Solvent / Methyl Ethyl Ketene (MEK), Toluene and Dichloromethane Solvent will make filler paste. Finishing / Machines well with Circular Saws, Routers and Band saws - takes all sprays. Can be Guillotined and Roller cut. Clear Not Available.

Colours Black / White / Grey and limited colours.

Applications Luggage, Caravan Parts, Vehicular Parts, Sanitary Parts, Electrical Enclosures.

Price Medium.

Stockist Contact your local Formech office (see end of this guide)

Toy cover Car parts Props

13 Formech - Vacuum Forming Guide Plastics materials and their characteristics

Polystyrene – High Impact Polystyrene (HIPS)

Properties One of the most widely used materials. An easy forming amorphous thermoplastic. Thermoforms with ease utilising low temperatures and fast cycle times. Available with different textures and patterns. No pre drying required. Poor UV resistance - not suitable for outdoor applications.

Formability Very Good - forms to a high definition.

Hygrocospic No.

Strength Medium to Good impact strength.

Shrinkage Rates 0.3 - 0.5%.

Availability From stock.

Solvent / Filler Dichoromethane, Toluene. Filler can be made from dissolved plastic in solvent.

Finishing / Machining Needs special etch primer before spraying. Good machining with all methods.

Clear Yes - Styrolux (Clarity not to quality of PETG/ PC/ PMMA).

Colours All colours and also available in a Flocked finish ideal for presentation trays and inserts. Applications Low cost and disposable items, toys and models, packaging and presentation, displays. Price Low - Medium.

Stockist Contact your local Formech office (see end of this guide)

Mask 3D cover POS Display

14 Formech - Vacuum Forming Guide Plastics materials and their characteristics

Polycarbonate – (P.C. / LEXAN/ MAKROLON)

Properties Hard, rigid clear amorphous material with high impact resistance and good fire rating. Self extinguishing. Requires high forming temperatures. Needs drying. Excellent clarity. Similar properties to Acrylic.

Formability Good.

Hygrocospic Yes - Drying temperature 90° C / 194°F. 1mm - 1 hr. 3mm - 4hrs. 4mm - 10hrs.

Strength Very good impact strength.

Shrinkage Rates 0.6 - 0.8%.

Availability From stock.

Solvent / Filler Between PC components Dichloromethane or MEK solvent. Care must be taken with solvents as PC is a stress sensitive material and can be adversely affected by the solvents at its weak points. Most proprietary can be used to join PC with metal, glass and wood. Finishing / Machining Good for screen and digital printing. Good machine qualities. Can be ultrasonical- ly welded, drilled and tapped. Takes spray. Clear Yes.

Colours Translucent and solid colours. Opal and diffuser patterns. Available in a variety of embossed textures. Applications Light diffusers, Signs, Machine Guards, Aircraft trim, Skylights, Riot Shields, Guards and Visors. Price Expensive.

Stockist Contact your local Formech office (see end of this guide)

Mask 3D cover POS Display

15 Formech - Vacuum Forming Guide Plastics materials and their characteristics

Polyethylene – (PE, HDPE, LDPE, PE FOAM)

Properties PE is a semi-crystalline thermoplastic with similar forming properties to PP. Good heat control with sheet level required for successful forming. High shrinkage rates but good chemical resistance and strength. Available also as a cross linked closed cell foam (PLASTAZOTE) - ideal for packaging and liners.

Formability PE - Difficult PE FOAM - Good but form at lower temperatures to prevent surface scorching. Hygrocospic No.

Strength Very good impact strength.

Shrinkage Rates LDPE - 1.6 - 3.0% HDPE - 3.0 - 3.5% Availability From stock.

Solvent / Filler No solvent.

Finishing / Machining Does not take spray. Takes some specialist inks.

Clear Translucent - Goes clear when in its plastic state - occurs within temperature band of approx 10°C and provides excellent indicator to forming temperature. Colours Black / white and colours available.

Applications Caravan Parts, Vehicular Parts, Enclosures and Housings.

Price Inexpensive.

Stockist Contact your local Formech office (see end of this guide)

Bicycle HDPE PE Foam Suitcases HDPE

16 Formech - Vacuum Forming Guide Plastics materials and their characteristics

Co-Polyester – (PETG / VIVAK)

Properties An easy forming amorphous thermoplastic. FDA approved for food applications. Optically very good with excellent fabricating performance. Thermoforms with ease utilising low temperatures and fast cycle times. Can be sterilised and is resilient to a wide range of acid oils and alcohols. Not recommended for use with highly alkaline solutions.

Formability Very Good - forms to a high definition. Forming range 80 -120°C / 176-248°F.

Hygrocospic Not normally required. If sheet is exposed to high humidity conditions for an extended time then pre-drying is required - 8 hours at 60°C / 140°F.

Strength Good - High Impact.

Availability From stock.

Solvent / Filler Cementing can be done using solvents or commercial glues. Can be Ultrasonically Welded. Finishing / Machining Can be Guillotined, Saw Cut or Routered. Cutting and also possible up to 3mm. Paints and Inks for Polyester can be used for printing on PETG. Clear Yes.

Colours Limited - Contact Supplier.

Applications Point of Sale and Displays, Medical Applications.

Price Expensive (competitive with other clear materials e.g. PC/ PMMA).

Stockist Contact your local Formech office (see end of this guide)

POS Display Medical mask POS Display

17 Formech - Vacuum Forming Guide Plastics materials and their characteristics

Acrylic - PMMA – (Perspex, Oroglas, Plexiglas)

Properties A high quality hard amorphous plastic with good clarity that can be worked after forming. NOTE: Only extruded sheet is suitable for vacuum forming effectively. Cast Acrylic will not respond well as it displays a very small usable plastic zone. As a result it will only produce general contours with large drape radii. Needs drying. Often replaced by PETG - see separate heading.

Formability Tends to be brittle and is temperature sensitive.

Hygrocospic Yes - Consult supplier for drying times.

Strength Medium to High strength.

Shrinkage Rates 0.3 - 0.8%.

Availability Ex stock - 2 weeks.

Solvent / Filler Tensol, Solvent and gap filler.

Finishing / Machining Prone to Shatter. Takes cellulose and enamel spray. Good for hand working.

Clear Yes.

Colours Solid colours.

Applications Signs, Roof Lights and Domes, Baths and Sanitary Ware, Light Diffusers.

Price Expensive.

Stockist Contact your local Formech office (see end of this guide)

Rooflights POS Display Bank signage

18 Formech - Vacuum Forming Guide Plastics materials and their characteristics

Polypropylene – (PP)

Properties PP is a semi-crystalline thermoplastic which has difficult form characteristics with sheet sag inevitable. Chemically inert and very flexible with minimum moisture absorption make it suitable for a wide range of applications. High forming temperature but no drying required. Many grades of PP are available containing fillers and additives. Co polymer as opposed to homo-polymer PP is recommended for vacuum forming, as the copolymerisation process helps reduce stiffness and broaden the melt and glass transition temperatures increasing thermoforming ability.

Formability Difficult - Translucent material goes clear when in its plastic state - occurs wit- hin temperature band of approx 10°C / 50°F and provides excellent indicator to forming temperature. Good temperature control required in conjunction with a sheet level facility. Hygrocospic No.

Strength Very good impact strength.

Shrinkage Rates 1.5 - 2.2%.

Availability From stock.

Solvent / Filler No solvent.

Finishing / Machining Does not take spray.

Clear Translucent.

Colours Black / white and colours available.

Applications Luggage, Food Containers, Toys, Enclosures, Medical Applications, Chemical Tanks. Price Inexpensive.

Stockist Contact your local Formech office (see end of this guide)

Insert tray

19 Formech - Vacuum Forming Guide Plastics materials and their characteristics

Polyvinylchloride – (PVC)

Properties Strong, tough thermoplastic with good transparency in thinner gauges. Good chemical and fire retardant properties. Highly resistant to solvents. Thicker materials are rigid with good impact strength ideally suited to outdoor industrial applications.

Formability Forms well but with a tendency to web.

Hygrocospic No.

Strength Good.

Shrinkage Rates N / A - Contact Supplier.

Availability From stock - Sheet or Reel.

Solvent / Filler Toluene may be used - no others solvents suitable. Hot air weld or glue.

Finishing / Machining Does not take spray. Takes some specialist inks.

Clear Yes - Different web widths available with thickness from 150 microns - 750 microns. Colours Black / white and colours available.

Applications Packaging, Machine Guards and Car Trim.

Price Inexpensive.

Stockist Contact your local Formech office (see end of this guide)

Blister PVC / APET Chocolate packaging Marine Pod

20 Formech - Vacuum Forming Guide Mould Materials and Mould Design

Mold design is for most people the most exciting and rewarding part of the vacuum forming process. It is here that you can draw upon everything that is in your imagination as a designer, an artist, or an engineer, and realize it in a real physical object. The mold, sometimes called the ‘tool’, is the object which is placed on the table of the vacuum forming machine over which heated plastic will be formed. This mold is the most important part of the vacuum forming process, as without its considered and purposeful design, there would be limited success in the forming process.

Successful mold design will enable the machine operator to produce high definition, high quality vacuum formed products, to the production amount required before mold degradation (when the mold begins to lose its shape or stability). There are a few considerations to make when designing your mold, from its shape, to the material used, to airflow, to size, and spacing, but don’t worry; in this section of the guide we will take you through each consideration, and have you making perfect custom molds which produce perfect vacuum formed products.

Mold Materials There are a wide variety of mold materials available to choose from, from clay, to wood, to MDF, resin and more, which can be selected based upon a list of requirements for the designer and the final vacuum formed product. • How many times will the mold need to be vacuum formed? • How much detailing will the mold involve? • How are you going to shape or tool the mold? • How much does the mold need to cost? Is there a budget? • How much time do you have to produce the mold? These are all questions that need to be considered before selecting the mold material. Here we will go through each material one by one, covering its benefits and drawbacks, which should help you make the correct choice in your mold material choices.

21 Formech - Vacuum Forming Guide Mould Materials and Mould Design

1- Modelling Clay, Plaster 2- Wood

Modelling clay is widely used as a mold material Wood and MDF are very popular mold materials due to its incredible ease of shaping and very low due to their low cost and ease of tooling. Using a cost. For simple mold designs the designer might range of simple woodworking tools and techniques, even use just their hands to shape and mold the the designer is able to produce a mold with relative material to their desired shape. This makes it an ease which is capable of withstanding hundreds of ideal material for producing a one-off item, or to vacuum forming cycles. prototype a product quickly. If using wood, harder woods are recommended One big disadvantage of clay is its fragility, or lack due to their close-knit grain and higher strength, of strength. It performs well for a limited number which also makes them more resistant to heat. of forming cycles before becoming brittle, at which To increase wooden mold strength even further, point cracks will begin to appear and shape will finished molds might be sealed with varnish to be lost. This makes it ideal for only a very short increase their production run lifespan, although this production run. is something seen mainly in industry rather than in smaller workshops, and so this is by no means Clay molds will need to be dried completely before necessary for single or small run production. being vacuum formed to ensure that they hold their shape during the vacuum forming process. The heat MDF is especially easy to work with, with designers and pressure applied during a forming cycle will often stating that “it cuts like butter”, which is very most likely deform any clay mold that has not been true. MDF is not as strong as wood, but certainly allowed to dry thoroughly. Dried clay molds will performs well in the vacuum forming process, also likely require few or no venting holes applied, whilst providing a fast and effective mold making as the material is relatively porous and will allow air material. to flow through it. It should be possible to push a wire through the clay before it has dried to create All woods will expand and contract with every vacuum holes. heating and cooling cycle, which means that over extended use they will display visible degradation with cracks and deformity. That said, this material is a favoured material in education and small factories Shaping and smoothing due to its cost, time, and ease of tooling benefits. the sculpted clay Venting holes will need to be applied to most wood and MDF molds.

Sculpting ready to be vacuum formed

Wooden tool Vacuum formed mould

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3- Cast Epoxy Resins

Epoxy resin begins life in liquid form, most often two separate liquids which are mixed together; the resin, and a hardener agent. When combined and mixed thoroughly, they can be poured into a prepared mold and allowed to set, creating a very hard and very durable mold to be vacuum formed. These resins are available in many different varieties, and can take anything between 30 minutes and 12 hours to set completely.

Imagine having a large animal shaped jelly mold. This would be the perfect mold to use to create a vacuum forming mold using resin. Having coated the inside of the jelly mold with a silicon release agent spray to encourage the final resin mold to be released, mixed resin can be poured in and allowed to set, following the manufacturers instructions. You could also pour resin into a mold you have made yourself out of wood, or a vacuum formed part made previously.

This is a good example of how a mold might be made quickly, easily and cheaply using clay, and allowed to dry. Once the clay mold has been vacuum formed, the newly formed plastic shape can then be used to cast epoxy resin within, creating an incredibly durable and strong replica of the original clay mold, perfect for repeated forming cycles.

The main benefit of resin as a mold material is its long life and durability. Unlike clay, a well-made resin mold will be fit to withstand hundreds of forming cycles with little or no visible sign of aging, or decrease in quality of the vacuum formed product.

The only real draw backs of molds from resin are the relatively high expense, length of time required, and the need to source or make an original mold within which to pour the resin in its liquid form. Resin is also a non-porous material, which means that no air can pass through it, therefore venting holes will need to be applied for most molds made from this material.

23 Formech - Vacuum Forming Guide Mould Materials and Mould Design

4- Foam

Foam material can be one of the cheapest, and easiest materials to shape. When we talk about foam, we mean large sheets of building insulation foam that can be cut to the desired shape very quickly, using a machine or hand saw, or a hot wire cutter. Using a variety of both hand and machine tools, detail can be added and some very impressive molds produced. Due to this ease of working, it is a popular material for prototyping or single run vacuum forms. We recommend that you use a foam with a small bubble structure so that you get a good quality end result, that is less likely to crumble.

It may be quick and easy to work with, but be warned, foam material has a very low level of heat resistance, and its shape will be affected by the heat produced during a forming cycle. This means that a foam mold may only be suitable for a handful of vacuum forms. To increase its cycle life and to encourage ease of mold release, a foam mold might have a layer of aluminium tape, or simple aluminium kitchen foil applied to any surface which will come into contact with heated plastic material. This will greatly reduce any stress caused by heat. It is also a very light material, and with the vacuum forming process relying on the movement of air, it is advisable to secure the mold to the vacuum forming machine table before with some double sided tape, before beginning the forming process.

24 Formech - Vacuum Forming Guide Mould Materials and Mould Design

4- 3D Printing/Rapid prototyping/Additive manufacturing

This is where vacuum forming and computer alternative mold materials might well be better technology meet in the middle, and we find suited to school projects or simple designs, but no ourselves with a wonderful tool with which to one can discount 3D printing as a real benefit to produce a mold to be vacuum formed. 3D printers designers during the mold design process. have become increasingly cheaper and much more common in recent years, and can be found in most schools and workshops around the country. They allow an object to be designed using Computer Aided Design (CAD), which can then be printed as a 3D physical object using a wide variety of materials. This allows the designer complete control over the size, dimensions, and specifics of the object to be printed, which can be produced sitting in front of a computer rather than in a workshop using traditional tools and materials. Alternatively, 3D printing files can be downloaded from online sources, and scaled up or down as desired. Either way, they can be printed with the single click of a 3D printed mold mouse.

The types of materials and processes used to 3D print objects vary widely in both characteristics and cost, but two processes which are commonly used are FDM and PolyJet. The FDM process produces a high quality and heat resistant mold, which is porous by design with no need for venting holes. The PolyJet process also produces high quality results, whilst being known for producing very smooth finished surfaces, although does not produce a porous mold, and so venting holes will Vacuum formed mould need to be considered at the CAD stage. When 3D printing using either of these processes, it is advisable to use ABS or polycarbonate materials over PLA material. This is simply to ensure that the 3D printed mold will perform well when exposed to heat and pressure during the vacuum forming process. PLA molds are known to lose their shape much more quickly than ABS and polycarbonate 3D printed molds.

3D printing a mold to be vacuum formed certainly opens up many new possibilities and challenges for designers and manufacturers during the mold making process. 3D printing a single small object can often take in excess of 12 hours, and so Final part

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5- Aluminium - Cast 6- CNC machined tooling board or model board

Aluminium is a favoured material for molds used in CNC is a method used widely in industry to cut mass production lines using vacuum forming. It is materials to shape, using a rotary cutting tool incredibly strong whilst remaining incredibly light, whose path is controlled by a computer. With and allows heat to dissipate quickly following the the mold material laid stationary on a machine’s forming cycle, reducing the need to cool it down table, the tool then works its way around above between cycles on lengthy production lines where it, changing its height and direction, cutting away temperatures can get very high. It can be machined material as it goes. This is a method of tooling by human control or CNC, or can be cast to the which is unlikely to be readily available for High desired shape. Just like CNC, it is unlikely to be School level students, but never the less not found in High School workshops, impossible. Because it is so widely used in industry, but certainly helps give context to the range of it is important it receives a mention in this guide. mold materials available to designers and engineers within the mold making process. Materials for which CNC is widely used might include MDF, tooling/model board, aluminium or Alwapor porous board. All of these cut relatively easily and produce molds perfectly suited to vacuum forming, whilst providing a high level of control and detail. Just like 3D printing, all the hard work takes place behind a computer, with the physical shaping of the materials being done by an automated machine. Tooling paths can be produced on a computer using specialist software, or downloaded from various online sources.

Cast aluminium

26 Formech - Vacuum Forming Guide Mould Materials and Mould Design

Any suitable existing object

One of the most enjoyable parts of design and is being inspired by the world around you, and using ‘organic’ objects to aid the design process. This can be true of the designs that you draw on , and also of the materials you use, and mold materials are no different.

Imagine making a number of plastic plant pots using vacuum forming as your production method. You might need to design and produce six identical plant pot molds from a suitable material listed above, dedicating time, effort, money, materials, and hard work to the process. Alternatively, you might choose to simply use six existing terracotta plant pots as your molds. They are both strong and heat resistant, and the correct shape to be vacuum formed over. This alleviates a great deal of time and resources, enabling you to move through your production process much more effectively.

This use of an existing physical object is not exclusive to simple terracotta plant pots, rather it is wide reaching and applies to many objects all around you. So long as the object you choose is both heat resistant and strong, as well as abiding by some very simple mold design basic requirements (see page 15) it may well make the perfect mold for the project you are completing.

27 Formech - Vacuum Forming Guide Mould Design: Basic Considerations

In addition to mold materials, any designer must also think about mold design requirements when designing their mold. In this section we will explore just a few brief, but absolutely essential require- ments for mold design, so listen up, this is impor- tant.

Draft Angles

When designing a mold it is important to think about working draft angles into the design. These are very slight tapers which are applied to the outer edges of the mold, and any substantial angles within. They aid both the distribution of plastic material during the vacuum forming process, and mold release. These inward tapers do not need to be dramatic or hugely visible, although the bigger the draft angle, the more successful the vacuum for- ming process and mold release will be. It is recom- mended that draft angles should be a minimum of 3o - 5o.

Imagine vacuum forming over a perfect 10cm cube of wood material. The cube would be lifted into the heated plastic material when raising the machine table, and when the vacuum pump is applied the material would be sucked straight down to form over the sides of the cube. This means that the ma- terial will be stretched thinner than desired, creating weak spots in the final vacuum formed product. This is called ‘thinning’. If we now think about mold release, the uniform cube shape does not lend itself well to this process. The heated plastic will have stretched, formed, and importantly cooled over the cube mold. We know from earlier in this guide that plastic shrinks during the cooling process, which means that in this case it will now be formed very tightly around the cube mold, creating a situation where it will be very difficult to release the mold without damaging the formed plastic.

Now, imagine this same 10cm cube, only with the 4 outer edges with 5o draft angles applied. The plastic material would not be nearly as stretched during the forming process, nor would the cooled plastic clamp around the wooden mold, making for much easier mold release, and this, is the magic of draft angles.

28 Formech - Vacuum Forming Guide Mould Design: Basic Considerations

Venting Undercuts

We know that vacuum forming relies heavily on Undercuts are very rarely seen in any vacuum airflow to attract heated plastic over a mold. It’s forming mold. 99% of molds will have no undercuts quite simple; the greater the amount of airflow, the at all, and there is very good reason for this. more successful the vacuum forming process will Imagine vacuum forming over a dining plate, which be. With this in mind, every mold produced should has a very visible undercut all the way around have venting holes considered. These are holes its outer edge. During the forming cycle plastic which are made from the top of the mold, right material would be formed over, and indeed under the way through the mold material and out of the the plate itself. This would make it impossible to base, creating a channel for air to flow completely remove the dining plate from the formed plastic through. They do not need to be a huge diameter material. This simple consideration should be and can in fact be just 1.5mm wide, and can be applied to all mold designs, with every effort made drilled using a simple pillar or hand . These small to avoid undercuts at every turn. holes will not be visible on the final vacuum formed product. If undercuts are an unavoidable element of mold design, then there are some methods which may Knowing where to apply them is easy. Any place on assist you in a successful form and mold release. a mold where there is a recess or notable groove will need a venting hole or two. This will create an air • Use putty or clay to fill in the spaces within the channel which when the vacuum pump is applied, undercut during the forming process will attract the heated plastic into that specific area • Complete the vacuum forming process with of the mold. Think of any part of a mold where flexible material, like Polyethylene foam plastic will need to be formed within it rather than • Us a tool which is made up of multiple over it. These are the key spots where venting holes intersecting pieces, which once vacuum formed can will be essential. be dismantled and removed

29 Formech - Vacuum Forming Guide Mould Design: Basic Considerations

Male and Female Moulds

There are basically two kinds of moulds: male Several factors will affect the decision as to which (positive) and female (negative). is more suited and below we provide a few useful pointers. See figures below: The top surface of a moulding (the part not in contact with the mould) is invariably the better finished surface, since it cannot pick up any marks such as dust particles from the tool itself. This factor alone may dictate whether a male or female mould is required. Often a male tool is much easier to make and more suitable for a single deep-draw object. On the other hand, a compartment tray with Male mould divisions, would typically be of female construction.

Figure below shows a combined male & female tool for a clam pack:

Female mould Combined male & female tool for a clam pack

Formed and die cut clam pack

A greater degree of definition is achieved on the side of the plastic in contact with the mould. The choice of a male or female should be considered so that the side requiring the highest definition is the one in contact with the mould especially thicker plastics.

30 Formech - Vacuum Forming Guide Common Problems (and their simple solutions)

Webbing/ Chill Marks/ Thinning

Webbing Apart from the tool design, webbing usually occurs > Too much material for the job (fig.6) when you cannot sufficiently control the flow of the heated sheet as the tool is raised into the sheet. When the vacuum is applied it will always suck down first the part of the sheet that has the least resistance. If you were to imagine draping a cloth over your tool, rather than a plastic sheet, then the resulting fig.6 folds and pleats would identify the possible problem areas that your plastic sheet will encounter during the forming process. The cause of this can be any of the following: > Deep male moulds in close proximity to each > Mould/Tool too high in relation to its base area other (fig.7) (fig.4) fig.7

fig.4

> Sharp vertical corners with minimal draught angles (fig.5)

fig.5

31 Formech - Vacuum Forming Guide Common Problems (and their simple solutions)

Webbing (continuation) The following solutions can often overcome the > A frame attached to the plug assist that comes webbing caused by multiple male moulds: down as the table is raised helps to force the mate- rial down between the tools and reduce webbing. Slow vacuum down to gently introduce the va- > (fig.12) cuum to reduce the chance of webbing > Use a smaller sheet size so that the mould/tool stretches the material more (fig.8) fig.12

fig.8

> Place angled blocks around the corners to use up > Try using a female tool instead of a male tool if the excess material. (fig.9) webbing occurs between parts of the tool. (fig.13)

fig.13

fig.9

> Fix wires or steel blades to the clamping frame to restrict the sheet movement as the tool/mould is > Increase tool height/add 45 degree apron to tool raised into the sheet. (fig.10) base to use up excess material that cause webs. (fig.14) fig.10

> Add draught angle/radius corners to allow the material to flow over the tool/mould/. fig.14 (fig.11)

fig.11 32 Formech - Vacuum Forming Guide Common Problems (and their simple solutions)

Chill Marks Thinning CHANGE IMAGES When raising a deep draw mould into a heated When heated plastic material is overly stretched sheet, the point which first makes contact cools, during the forming process, it causes the material to reducing its flow characteristics and producing become thin and weak in certain places. Solutions an uneven flow of material at the top which thins to this are again, very straight forward. down the sidewalls as the vacuum is applied (figure • Increase draft angles around the sides of the below). This can be eliminated by increasing the mold draught angles and ensuring the mould is not too • Decrease the height of the mold cool. The pre-stretch facility (bubble) is also a useful • Use thicker material feature in overcoming this problem. • Modify the design in certain areas

33 Formech - Vacuum Forming Guide Finishing and Trimming

Finishing and Trimming

With vacuum forming there are secondary processes and operations required before a finished part will be ready for the customer. Once the formed part has cooled and been removed from the machine the excess ma- terial is removed, holes, slots and cut-outs are drilled into the part. Other post forming processes include decoration, printing, strengthening, reinforcing and assembly. 3 axis router

A variety of different trimming methods are used to trim the product from the sheet. The type of equipment best suited depends largely on the type of cut, size of the part, draw ratio, thickness of material and the production quantity required. They are also factors to consider when determining the investment cost of such equipment. Below are listed some of the more popular methods adopted. Thin gauge parts are normally trimmed on a mechanical trim press – otherwise known as a Rollerpress. Heavy gauge parts can be removed, placed into trim “jigs” or fixtures and trimmed with Vertical most of the methods listed on the following pages.

Roller press

34 Formech - Vacuum Forming Guide Finishing and Trimming

Considerations tool for production. This all takes time and needs to be added to the total delivery time (including Over time you will usually be able to build up a the actual production of the parts) to work out gut feel for which particular plastic processing me- when the parts will be on your doorstep. thod is best suited to your particular product. In order to do a comparison to the other processes Example: Let’s assume that you intend to pro- that are available, you will need to take note of duce a vacuum formed machine cover based on the following factors: the following:

Quantity: The amount of parts you wish to pro- Specification: duce are critical in determining not only if vacuum Material: 2mm red high impact polystyrene. forming is the right process for this particular job, Size: 330mm x 180mm x 50mm high. but also the number of tools you need to make Quantity: 500 off per annum. To be produced in and the total forming area. If time is limited, then batches of ten at a time. you may decide to invest in a greater numbers of tools in order to complete the job in less time.

Price: Very few customers adopt the approach of “money’s no object”. There is always a good reason why a product has been produced in a par- ticular manner and this is usually cost related. As a general rule once the quality and delivery issues have been established then price usually becomes the deciding factor in which process will be used, although occasionally there are exceptions. Machine cover showing the top side and the Finish: What sort of finish do you require? What underside.This part would fit comfortably on market is the part going in to? Is the part going our 300XQ machine and because of the small to be seen? Is it for indoor or outdoor applica- quantities and the size of the part we would form tion? How many post forming operations will be the part one up. In this particular case you could required in order to turn the vacuum forming into only fit one tool on the table of the 300XQ. If the finished part? you wanted to produce 500 parts in one go then usually this kind of part would be produced two Accuracy: The more accurate the part the more up on one of our larger machines. The benefits of expensive it becomes to produce. Vacuum for- increasing the number of tools used to form the ming will not have the consistency of injection parts is that the job is completed in a shorter time moulding, because you are only forming over and so you have reduced labour and machine one face, whereas injection moulding is a totally costs and in addition when multiples of tools are enclosed die, with toleranced surfaces on all sides. used, it usually means that less material is wasted.

Strength: What’s the application? Will the va- cuum forming require additional fabrication in or- der to give it the rigidity it requires? Will the extra parts be glued , welded or fastened in place?

Time: Most processes require CAD these days, either at the design stage or to create the finished

35 Formech - Vacuum Forming Guide Finishing and Trimming

Trimming by hand Trimming with a vertical band saw

Application: single or small batches Application: single or small batches where trimmed edge is not critical. Process: The softer less brittle materials can be scored with a sharp blade (roughly half the Process: The band saw can be used for rough thickness of the material) and then snapped away cutting or more accurately by using a fence or some from you for a clean break. form mounted on the table of the band saw. Popular materials cut by hand would be HIPS, ABS, The band saw will cut all vacuum forming materials. PVC, PP, HDPE & PETG. Finished edge: Leaves a slightly jagged edge that Finished edge: Can leave a sharp edge that may may need scraping and consistency of cut can be need scraping and consistency of cut can be an an issue. issue. Cutting plane: usually vertically by cutting into the Cutting plane: varies surrounding waste material.

Stanley knife

36 Formech - Vacuum Forming Guide Finishing and Trimming

Trimming with a drill press and slitting saw Trimming with an overhead or table mounted router with guide pin/bearing cutter/slitting saw Application: single or smaller production batches where a decent edge and no flange is required. Application: production batches where a good consistent edge is required with a clean cut. Process: The vacuum forming is usually rough cut to remove the excess material and then located over Process: The vacuum forming is usually rough cut a wooden holding jig for support. The side of the on a band saw and then located over a holding jig. forming is then pushed into the rotating slitting saw The forming is then pushed into the rotating slitting and slit all around the circumference to remove the saw and slit all around the circumference. A guide waste from the part you require. This method will pin mounted into the table or a bearing cutter will cut most materials. The drill press needs to be set at determine the path of the cutter as it travels along 3000 RPM approximately to obtain the best cut. the edge of the holding jig. Typical router speed is 20000 RPM approximately which results in a very Finished edge: Leaves a clean accurate edge that clean cut may need slight scraping on the one side only. Finished edge: Leaves a very clean accurate edge Cutting plane: usually horizontally by cutting into that often does not require additional cleaning. the side of the vacuum forming. Cutting plane: usually horizontally by cutting into the side of the vacuum forming or leaving a slight flange with a bearing cutter.

37 Formech - Vacuum Forming Guide Finishing and Trimming

Trimming with a roller press Trimming with a horizontal band saw

Application: production quantities for thin packa- Application: production quantities for materials ging trays and inserts (less than 1mm thick). This ranging from 0.5mm – 3.0mm in thickness. provides a clean accurate cut but usually a small flange is unavoidable. Process: The single or multiple vacuum forming sheet is placed on the conveyor belt of the machine. Process: The vacuum forming is placed upside As the vacuum forming is advanced through the down into a custom made steel rule cutting die and machine the waste material is trimmed from the a polypropylene cutting board placed on top. This remaining part by a horizontal band saw blade. This is then fed through the roller press between the top method will cut most materials. and bottom rollers separating the waste material from the part. This method will cut most thin mate- Finished edge: Leaves quite a reasonable edge, rials. It is not suitable for PMMA because it will tend but it usually requires additional scraping to remove to shatter. burrs caused by the sawblade.

Finished edge: Leaves a very clean accurate edge Cutting plane: always horizontally by cutting into that does not require additional cleaning. the side of the vacuum forming.

Cutting plane: Always vertically by cutting into the waste material around the base of the vacuum forming.

38 Formech - Vacuum Forming Guide Finishing and Trimming

Trimming with a 3 axis router Trimming with a 5 axis router

Application: production quantities for vacuum for- Application: production quantities for vacuum for- mings that require a clean consistent accurate cut mings that require a clean consistent accurate cut with apertures in the top face of the forming and with apertures on all faces of the vacuum forming trimming of the surrounding waste material. and trimming of the surrounding waste material.

Process: The rough cut vacuum forming is placed Process: The rough cut vacuum forming is placed on a vacuum jig on the bed of the machine. The on a vacuum jig on the bed of the machine. The router head will usually rout all the apertures and router head will usually rout all the apertures and slots in the top face and then trim with a slitting slots and then trim all around the circumference of saw all around the circumference of the vacuum the vacuum forming to remove the waste material. forming to remove the waste material. This method This method will cut most materials. will cut most materials. Finished edge: Leaves a very clean accurate edge Finished edge: Leaves a very clean accurate edge that often does not require additional cleaning. that often does not require additional cleaning. Cutting plane: 3 axis for trimming on the X, Y, Z Cutting plane: X and Y axis for cutting into the side axis. 5 axis for additional trimming of slots and of the vacuum forming and the combined X,Y and holes from all directions A + B. Z axis allows for variation in height for top surface routing of the vacuum forming.

39 Formech - Vacuum Forming Guide Finishing and Trimming

Trimming with a robot

Application: production quantities for vacuum for- mings that require a clean consistent accurate cut with apertures all faces of the vacuum forming and trimming of the surrounding waste material.

Process: The rough cut vacuum forming is placed on a vacuum jig on the bed of the machine. The robot head will usually rout all the apertures and slots and then trim all around the circumference of the vacuum forming to remove the waste material. This method will cut most materials.

Finished edge: Leaves a very clean accurate edge that often does not require additional cleaning.

Cutting plane: Trimming on the X, Y, Z axis + addi- tional trimming of slots and holes from all directions A + B.

40 Formech - Vacuum Forming Guide Trouble Shooting Guide

The purpose of the following section is to help the user in overcoming some problems frequently encounte- red in thermoforming. Most of the major problems identified in thermoforming can be traced back inade- quate process control. Improper sheet temperature at the time of forming is a primary source of problems. Poor vacuum control and insufficient cooling are also typical causes. The table below lists the majority of recurring problems in thermoforming along with the suggested courses of action to correct or eliminate the processing problem.

Problem Cause Remedy

Blisters or Bubbles Overheating / sheet heated too - Lower the heater temperatures or reduce rapidly the top heater if using twin heating Excessive moisture - Pre-dry sheet - Pre-heat sheet - Heat from both sides - Keep material wrapped until ready to use Uneven Heating - Check consumption - Increase zone control

Poor Mould Release Mould or part too hot - Increase cooling cycle - Decrease mould temperature Mould undercuts - Increase release time and pressure Mould undercuts - Increase release time and pressure Insufficient draft angles - Increase draft. - Convert mould to female Poor mould surface - Use mould release. Improve mould sur- face

Sheet Scorching Top / bottom surface too hot - Decrease heating cycle time - Decrease heater temperature - Check for faulty heat zones if problem in isolated area. Pre-heat material

Lack of Definition Material too cold - Increase heating time - Increase heater temperature - Increase heater density and/or wattage - If localized problem check heater zone and elements Mould too cold - Ensure mould is at optimum temp. for forming

41 Formech - Vacuum Forming Guide Trouble Shooting Guide

Problem Cause Remedy Insufficient vacuum - Adjust vacuum timings - Check vent holes on mould - Increase number and or diameter of va- cuum holes - Check mould is not restricting vacuum flow - are vacuum tracks in mould adequate? - Check for leakage in vacuum system - Increase vacuum capacity - Check the seal for wear

Webbing Material too hot - Shorten cycle time - Lower heater temperature Insufficient vacuum - Check system for leaks - Increase size of vacuum holes - Check for blocked holes Incorrect Pre-Stretch height - Adjust pre-stretch flow and time Excess material - Reduce material size and use reducing win- dows Poor mould design - Increase radius improve draw ratios - Use plug / ring assist - Use assist blocks to pull out webbing - Increase spacing between moulds - Switch to female mould Vacuum speed too fast - Regulate to suit - Use smaller vacuum holes

Whitening Part removed too early - Part must be below set temp. before remo- ving - Increase cooling cycle - Add extra cooling fans - Utilise a spray mist facility - Use water cooled moulds Uneven part cooling - Increase mould temp. and / or temp. unifor- mity Poor mould design - Redesign. Incorporate ribs / tapers Poor sheet distribution - Check for uneven heating - Use plug assist or pre-stretch for deep draw Excessive mould release pres- - Adjust to suit sure or timing

42 Formech - Vacuum Forming Guide Trouble Shooting Guide

Problem Cause Remedy

Chill Marks Stretching stops when sheet - Increase mould temp makes contact with cold mould/ - Increase plug temp plug Mould design - Use plug to assist mould flow Insufficient pre-stretch - Increase pressure, flow or time Plug tool too cold - Wrap tool with felt or similar

Thinning at corners on Uncontrolled sheet heat - Improve zone control deep draw parts Sheet formed too slow - Use more vacuum - Increase number and size of vent holes Too much pre-stretch - Decrease flow or timing Cold spots - Check elements - Check for draughts Too thin gauge - Increase Uncontrolled material distri- - Use plug assist and/or pre-stretch bution

Tearing of sheet whilst Sheet too hot - Decrease heating cycle time. forming - Decrease temp. settings. - Pre-heat sheet. Sheet too cold - Increase heating cycle time - Increase temp. settings Pre-stretch too large - Reduce time and flow Mould design - Increase corner radius and draw ratio Improper material selection - Consult supplier

Parts stick in mould Part temp. too high - Increase cooling cycle - Lower mould temp - Reduce heating cycle time Mould not fixed on base-board - Mount mould to baseboard ensure it is then fixed to table Insufficient draft - Increase taper Mould undercuts - Increase air eject - Remove part earlier and use cooling jigs - Use retractable undercut segments in mould

43 Formech - Vacuum Forming Guide Trouble Shooting Guide

Problem Cause Remedy Poor mould quality - Polish mould - Use release agent - Remove rough edges from wooden moulds

Nipples on formed parts Sheet too hot - Reduce heating cycle - Reduce heat temp. Vacuum holes too large Plug holes / re-drill

Excessive sag Sheet too hot - Decrease heat cycle time. - Decrease heater temp Sheet area too large - Improve zone control - Ensure auto level feature activated

Marks on finished moul- Dirty mould - Clean mould with air gun after each cycle ding Water droplets - Decrease spray mist - Check all hoses, gaskets for leaks Poor mould surface - Smooth / polish surface Scratched sheet - Inspect handling procedure - Ensure protective film removed im- me- diatly prior to forming

Plastic pulls from clamp Insufficient clamp pressure - Check clamp pressure frame - Adjust alignment - Heat frame prior to inserting sheet Material too cold - Increase heat cycle Wrong material selection - Consult supplier

44 Formech - Vacuum Forming Guide Contact

Formech International Ltd (Headquarters) Unit 4, Thrales End Business Park Thrales End Lane Harpenden Hertfordshire AL5 3NS England Tel: + 44 (0)1582 469 797 Fax: + 44 (0)1582 469 646 Email: [email protected] www.formech.com

Formech Inc 2324 Pinehurst Drive Middleton WI 53562 USA Tel: 312.396.4072 Email: [email protected] www.formechinc.com

Formech Europe Am Wolfsberg/An der L553 76774 Leimersheim Deutschland

Tel: +49 (0) 7272 9549868 0 Fax: +49 (0) 7272 9549868 9 Email: [email protected] www.formech.de

Suppliers of: • Vacuum Forming Machines • Reducing Windows • Spare Parts and Spare Parts Kit • Drying Ovens • Trimming equipment • Tooling – Prototype and Production

45 Formech - Vacuum Forming Guide