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Resource Guide RESOURCE GUIDE THE ULTIMATE GUIDE TO PLASTIC INJECTION MOLDING TERMINOLOGY FIRST EDITION 1 The GreenLeaf Industries team is passionate about integrating Engineered Quality, Reliable Delivery and Cost Containment into every design and project. We are a family owned, made in America manufacturer that is committed to supporting our clients and the Plastic Injection Molding Industry. It is our pleasure to introduce our latest resource guide to help designers, engineers and purchasing professionals navigate the world of plastic injection molding. A ADDITIVE MANUFACTURING – This is actually the technical term for 3-D printing. It is the process of manufacturing a three-dimensional object by placing layer on top of layer based on a specific CAD model. AGING – Refers to the change of a material with time under defined environmental conditions, leading to either improvement, or the deterioration of certain properties. ALLOY – A composite material made by blending polymers (or copolymers) with other polymers or elastomers under predetermined conditions. ANGLE PINS – Pins that are placed at an angle and fit freely into a slide. Because the pins are at an angle, a cam action is created as the mold opens, and this moves the slide out of the way prior to part ejection. Angle pins may be called “horn pins.” ANNEALING – The process of heating a molded plastic article to a predetermined temperature and slowly cooling it to relieve stresses caused by the manufacturing process. This secondary process is occasionally required for injection molded parts. ANTISTATIC AGENT – An agent added to the molding material (or applied on the surface of the molded object) to make it less conductive, whereby hindering the fixation of dust. AUTOMATIC MOLDING – Repeatedly going through the entire injection molding cycle, including the ejection process, without human assistance. B BACK TAPER – A reverse draft used in a mold to prevent molded articles from drawing freely. BACKING PLATE – A plate used in mold construction, as a support for the cavity blocks, guide pins, bushings, etc. BLISTER – A raised area on the surface of a molded part that is caused by the pressure of gases inside it on its incompletely hardened surface. BLUSH – Is simply a clouded discoloration of plastic in areas that come under high stress. When located at the gate (a high stress location) it is called “gate blush.” 2 BOSS – A projection on a plastic part designed to add strength, facilitate alignment during assembly, or provide strength in an area where fasteners are installed. BUBBLE – An internal pocket (void) of air or other gas trapped within a space of plastic due to poor part design, poor mold design, or poor processing. BURN – When the air temperature inside the mold exceeds the flash point of the plastic, a “burn mark” is made. If something is “burned” in molding, it shows evidence of thermal decomposition through some discoloration, distortion and localized destruction of the surface of the plastic. C CARBON BLACK – Is a black pigment produced by the incomplete burning of natural gas or oil. It is widely used as filler… particularly in the rubber industry. Because it possesses useful ultraviolet protective properties, it is also used for injection molding compounds where the item is intended for outside weathering applications. CASE HARDEN – It is a term used when hardening the surface of a piece of steel to a relatively shallow depth. CAST – To form a “plastic” object by pouring a fluid monomer-polymer solution into an open mold where it finishes polymerizing. CAVITY – A depression in a mold, which usually forms the outer surface of the molded part. Depending on the number of such depressions, molds can be designated as single cavity or multi- cavity. CENTER GATED MOLD – An injection mold wherein the cavity is filled with molding material through a “sprue”, or gate, directly into the center of the part. CHALKING – This term represents a dry, chalk-like appearance or deposit on the surface of a plastic. It is sometimes known as a “haze” CHROME PLATING – An electrolytic process that deposits a hard film of chromium metal onto working surfaces of other metals in the event that resistance to corrosion, abrasion or erosion is required. CLAMPING PLATE – A plate fitted to a mold and then used to fasten the mold to a molding machine. CLAMPING FORCE – In injection molding, it is the pressure that is applied to the mold to keep it closed while molten plastic is injected at very high pressures. COLD SLUG – This is what we call the first material to enter an injection mold. It gets its name from the fact that when it passes through the sprue orifice, it is cooled below the effective molding temperature. COLD SLUG WELL – It is the space directly opposite of the sprue opening, inside an injection mold, 3 to trap the cold slug. COMPRESSIVE STRENGTH – The crushing load (at failure) divided by the original sectional area of the specimen. CONDUCTIVE PLASTICS – Materials that allow a current or charge to travel through it. Conductive plastics are hybrid polymers that are electrically conductive or static dissipative. These plastics are engineered, using additives such as copper, silver, aluminum, carbon black and carbon fibers, to have conductivity characteristics. CONTINUOUS SERVICE TEMPERATURE – The maximum temperature above which mechanical and electrical properties are degraded over the lifetime of the item. COOLING CHANNELS – Channels or passageways located within the body of a mold through which a cooling medium can be circulated to control the mold temperature and remove heat as the molten plastic cools. COOLING FIXTURE – A fixture holding the shape of a molded piece to maintain the proper shape, or dimension, of a molded part after it is removed from the mold. It is used until the part is cool enough to retain its shape without appreciable distortion. CORE – A term describing a male element within a die, which produces a hole or recess inside the part. It also refers to a part of a more complex mold, used to mold undercut parts. CORE PIN – A pin that is being used to mold a hole. CORING – The process of removing excess material from the cross section of a molded part to attain a more uniform wall thickness. CRAZING – The small “hair-like” cracks on or beneath the surface of a plastic part. It sometimes is an indicator of imminent material fracture. CREEP – The tendency of a plastic material to move slowly, at the molecular level, over a period of time under the influence of stresses. Over long periods of time these tiny movements add up, changing part dimensions. Manufacturing engineers designing parts for applications having a consistent high pressure will consider creep when choosing their materials. CRYSTALLINITY – A state of molecular structure in resins which denotes uniformity and compactness of the molecular chains that form the polymer. Normally the condition can be attributed to the formation of solid crystals with a definite geometric form. CURE – To change the physical properties of a material by chemical reaction to make it more stable & functional. The process may include condensation, polymerization, or vulcanization. CURING TEMPERATURE – The proper temperature at which a molded product is subjected to curing. CYCLE – The complete sequence of operations involved in a process, or part of a process, is a cycle. In molding, the cycle time is the period, or elapsed time, between a certain point in one cycle and the same point in the next. 4 D DAYLIGHT OPENING – Clearance between two plates of a press in the open position. DECORATION (OF PARTS) – After injection molding, a secondary operation where the part is printed (decorated) by screen printing, pad printing, heat transfer, or similar methods. DEFLASHING – Covers the range of finishing techniques used to remove the flash (excess, unwanted material) that occurs on plastic parts such as cutting, scraping, filing, sanding, milling or tumbling. DEGRADATION – A damaging change in the chemical structure of a plastic resulting from such things as heat, light exposure, and general weathering. DELAMINTATION – The splitting of a plastic material along the plane of its layers. It is the condition of physical separation, or loss of bond, between laminate plies. DENSITY – Weight per unit volume of a substance, expressed in units such as grams per cubic centimeter or pounds per cubic foot. DESSICANT – A substance that can be used for drying plastic pellets because of its affinity for water. DESTATICIZATION – Is the act of treating plastic materials to minimize their accumulation of static electricity. DETERIORATION – A permanent change in the physical properties of a plastic evidenced by impairment of these properties. DIMENSIONAL STABILITY – The ability of a plastic part to retain its precise shape over time. Different plastic materials have different dimensional stability characteristics, and the dimensional stability of some plastics are even affected by moisture. DISCOLORATION – Any change that occurs from the original color that likely has resulted from overheating, light exposure or chemical exposure. DISHED – Showing a symmetrical distortion of a flat, or curved, section of a plastic object.As normally viewed, it now appears concave, or more concave than intended. DISPERSION – Finely divided particles of a material, that is in suspension inside another substance. DOMED – A symmetrical distortion of a flat, or curved, section of a plastic object. As normally viewed, it now appears convex, or more convex than intended. DOWEL – A pin used to maintain alignment between two or more parts of a mold. DRAFT – The degree of taper of a sidewall or the angle of clearance designed to facilitate removal of parts from a mold. DRY COLORING – A method occasionally used by fabricators for coloring plastic by tumble blending 5 uncolored particles of plastic material with selected dyes and pigments. DUROMETER HARDNESS – The hardness of a plastic material, as measured by the Shore Durometer.
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