Phases of Design
1) Customer Requirements 2) Specification Development 3) Conceptual Design 4) Detail Design 5) Specification of Production 6) Manufacture 7) Recycle
Design for X (DFX) X is a Variable Name
• Design for Manufacture Design for X (DFX)
Design for X (DFX) • Design for Environment
• Design for Disassembly Design for X (DFX)
• Design for Maintenance
• Design for Safety
Design for Assembly • Methods consists of a design review by – Design and development personnel – Production personnel • The technique imposes – Discipline – Objectiveness • The technique also imposes – Exciting rivalries – Defensive postures within an organization Aspects of Design for Assembly • DFA is applicable to – Products consisting of 20 -200 parts – Mainly for mechanical parts (not electronic circuits) – Dimensions lie between those of watches and cars • No specialized knowledge of the means of production is needed • Requires 1-2 days to perform for a product • Often 30% improvement in the assembly cost • Can be performed in the various stages in the design process and repeated
Design for Assembly (Criteria) • Execution of assembly operations – Storing – Handling • Identifying • Picking-Up • Moving – Positioning • Orientating • Aligning – Joining – Adjusting – Securing – Inspecting Design for Assembly (Criteria) • Standardization of assembly operations • Possible use of existing assembly equipment and tools • Possible use of standard assembly tools
Design for Assembly (Criteria) • Number of operations in overall assembly • Favorable sequence (preassembly, parallel assembly) Design for Assembly (Criteria) • Possibility of automation • Freedom from possible assembly errors • Avoidance of damage to components
Design for Assembly (Criteria) • Avoidance of special training of the assembly staff • Maintenance of safe working conditions • Observance of ergonomic standards Questions Raised During DFA • Is it possible to eliminate part of the process? – Are there inherently different material needs – Can the product be assembled if the part is integrated with another part? • What is cost to deliver a part to the place of assembly and give correct spatial orientation and position needed for assembly? • What does it cost to carry out the actual assembly of the part?
Design for Assembly Guidelines • During the operation of the product, does the part move relative to all other parts already assembled? – Only gross motions should be considered – Small motions that can be accomplished by elastic hinges, for example, are not sufficient for a positive answer.
• Must the part be of a different material than, or be isolated from all other parts already assembled? – Only fundamental reasons concerned with material properties are acceptable. Pneumatic 1 - Screw (2) (steel) Piston 2 - Cover (steel) Sub-Assembly 3 - Spring (steel) 4 - Piston stop (nylon)
5 - Piston (aluminum)
6 - Main block (plastic)
Design for Assembly Worksheet
1 2 3 4 5 6 7 8 9 Name of Assembly c) ) l r s e g n a s s e (¢ i e e e l n o y
u
i i l (s t rt rt rt )] b t r l l d d
a n n n rt e m s a a a u o d i e u ) a (6 m v f o o t e p p p i i ca i o
co co n
n t t i u t
f
co s m r r + t (7 m s
a i a
a d o g n t N n m t e e ) * ra
n h i
cu i re
e r n o re . u p p i i m l l e n o e g
l i -m (4 o 4 e i u i t [ D . rt t a a p rri o s e e . d m o e b i g I i 0 e t i u u o )*
n -d n h
ra w n m m t ca s F Es n n m rt i o i i a e ra e t T t (2 n a a co u h i h e p w m t Pa M M N p T O O
TM = Total manual assembly time 3 * NM design efficiency = = CM = Total cost of manual assembly TM CM NM TM NM = Theoretical minimum number of parts Pneumatic 1 - Screw (2) (steel) Piston 2 - Cover (steel) Sub-Assembly 3 - Spring (steel) 4 - Piston stop (nylon)
5 - Piston (aluminum)
6 - Main block (plastic)
Worksheet for Pneumatic Piston
1 2 3 4 5 6 7 8 9 Name of Assembly c) ) l l r s e g n a a s s e (¢ i e e e n o y
u u
i i l (s t rt rt rt )] b t r l l d d
n n n n rt e m s a a a u o d i e ) a a (6 m v f o o t e p p p i i ca i o
co co n
t t i u t
f
co s m r r + t (7 m m s
a i
a d o g n t N n m t t e e ) * ra
n h i
cu i i re
e r n o re . u p p i i m l l e n o e g g
l i (4 o 4 e i u i i t [ D . rt t a a p
rri Pneumatic Piston o s e e . d m e b i g I i 0 e t i u u o )*
n -d -d n h
ra n m m t ca s F Es n n m rt i o o i i a e ra e t t (2 n a a co u h i h e p w w m t Pa M M N p T T O O 6 1 30 1.95 00 1.5 3.45 1.38 1 Main Block 5 1 10 1.50 02 2.5 4.00 1.60 1 Piston 4 1 10 1.50 00 1.5 3.00 1.20 1 Piston Stop 3 1 05 1.84 00 1.5 3.34 1.34 1 Spring 2 1 23 2.36 08 6.5 8.86 3.54 0 Cover 1 2 11 1.80 39 8.0 19.60 7.84 0 Screw
TM = Total manual assembly time 42.25 16.90 4 3 * NM design efficiency = = 0.29 CM = Total cost of manual assembly TM CM NM TM NM = Theoretical minimum number of parts 1 - Snap on cover Redesigned and stop (plastic) Pneumatic 2 - Spring (steel) Piston 3 - Piston (aluminum)
4 - Main block (plastic)
Worksheet for Redesigned Piston
1 2 3 4 5 6 7 8 9 Name of Assembly c) ) l l r s e g n a a s s e (¢ i e e e n o y
u u
i i l (s t rt rt rt )] b t r l l d d
n n n n rt e m s a a a u o d i e ) a a (6 m v f o o t e p p p i i ca i o
co co n
t t i u t
f
co s m r r + t (7 m m s
a i
a d o g n t N n m t t e e ) * ra
n h i
cu i i re
e r n o re . u p p i i m l l e n o e g g
l i (4 o 4 e i u i i t [ D . rt t a a p
rri Pneumatic Piston o s e e . d m e b i g I i 0 e t i u u o )*
n -d -d n h
ra n m m t ca s F Es n n m rt i o o i i a e ra e t t (2 n a a co u (re-design) h i h e p w w m t Pa M M N p T T O O 4 1 30 1.95 00 1.5 3.45 1.38 1 Main Block 3 1 10 1.50 00 1.5 3.00 1.20 1 Piston 2 1 05 1.84 00 1.5 3.30 1.34 1 Spring 1 1 10 1.50 30 2.0 3.50 1.40 1 Cover & Snap
TM = Total manual assembly time 13.29 5.32 4 3 * NM design efficiency = = 0.90 CM = Total cost of manual assembly TM CM NM TM NM = Theoretical minimum number of parts Design for Automated Assembly (Concepts) • Layered design • Direct drive systems – Clamshell base – Helical or gear vs. – Sequential assembly Belt/pulley – Uni-directional • Common fasteners • Self-alignment – Minimize screws – Chamfer/countersink – Snap fasteners – Posts/locating stops • Minimize springs • Combine detail parts – Molded – Screws & washers – Compression coil – Plastic moldings – Extensive coil – Castings • Minimize cables • Symmetry – Integrated packaging – Solid connectors
Example of Layered Assembly Snaps
Snaps Compliance and Assembly Avoid Better Best
Bottom Part Bottom Part Both Parts No Chamfers Chamfered Chamfered Chamfered
Self Alignment of Parts This part could be oriented in any direction
These parts can be oriented only one way
Hole to accept Hole to accept “D” shaped hole swaged part notched part Nesting of Parts
This part could be This part has a “nest” to placed in any orient and help it secure orientation and not be secured
Nonfunctional External Feature for Orientation This slot would Pin to help orient slot be hard to detect
Chamfer to help orient slot Symmetry Orientation Required
Preferred
Tangling
These parts can tangle easily
The same parts redesigned, will not tangle Tangling (continued) Parts that Springs with open interconnect will not loops will tangle feed
A fillet will keep the parts from interconnecting
Springs with closed loops will not tangle
Methods to Avoid Jams (1 of 2) Direction of Flow This results in shingling
Base causes leading edge to be lower A nonfunctional corner can than trailing edge eliminate this problem Methods to Avoid Jams (2 of 2)
Mating surfaces with sharp edges can cause jams
A groove can prevent Rounded corners jams by centering the part can prevent jams
Avoid designs that require fasteners Substitutes for Fasteners
Design parts that snap together Joining Moving Parts without Fasteners
C-Clip
Chamfered Surface Snaps
Fasteners Preferred: Have flat vertical sides for vacuum pickup
Socket Head Fillister Head Hex Head
Avoid Round Side Slant Side
Round Head Flat Head Cables and Connectors
Example of a slave circuit board
Avoid: Preferred: Components that are connected Components that are with cables to circuit board plugged on a slave circuit board
Cables and Connectors
Example of a secured cable
If the use of a cable cannot be avoided. Then a robot can locate the Have the cable plugged into a dummy connector and plug it in. connector to locate the cable end. Avoid: Three motions required for insertion
Slot Motion and Preferred: Only one motion required Design
Snaps
Design for ME2110 Assembly
• Keep it Simple Starting Areas
Alien • Easy Access to All Machines Parts (So they can Safe be replaced) Zone
• Easy to Set Triggers Viruses
• Start Assembly Now