Lecture #8 Design for Manufacturing DfM
Phases of Design ) Customer Requirements 2) Specification Development 3) Conceptual Design 4) Detail Design 5) Specification of Production 6) Manufacture 7) Recycle 2
Design for X (DFX) Design for Manufacture X is a Variable Name
Design for X (DFX) Design for Assembly 4
Design for X (DFX) Design for Environment Design for Disassembly 5
Design for X (DFX) Design for Maintenance Design for Safety 6
Design for Assembly Methods consists of a design review by Design and development personnel Production personnel The technique imposes Discipline Objectiveness 7
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 production means is needed Requires -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 8
Design for Assembly (Criteria) Execution of assembly operations Storing & Retrieval Handling Identifying, Picking-Up, Moving Positioning Orientating, Aligning Joining Adjusting Securing Inspecting 9
Design for Assembly (Criteria) Standardization of assembly operations Use of existing assembly equipment and tools Use of standard assembly tools 0
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 2
Design for Assembly (Criteria) Avoidance of special training of the assembly staff Maintenance of safe working conditions Observance of ergonomic standards 3
Questions Raised During DFA Is it possible to eliminate part of the process? Can the product be assembled if the part is integrated with another part? What is the cost to deliver a part to the assembly with correct spatial orientation and position? What does it cost to carry out the assembly of the part? 4
Design for Assembly Guidelines During product operation, does the part move relative to other parts? Consider only gross motions Small motions can be accomplished by deformation (such as elastic hinges). Must the part be of a different material than other parts? 5
Pneumatic Piston Sub-Assembly - Screw (2) (steel) 2 - Cover (steel) 3 - Spring (steel) 4 - Piston stop (nylon) 5 - Piston (aluminum) 6 - Main block (plastic) 6
Design for Assembly Worksheet 2 3 4 5 6 7 8 9 Name of Assembly 7 Part I.D. Number Number of times the operation is carried out consecutively Two-digit manual handling code Manual handling time per part Two-manual insertion code Manual insertion time per part Operation time (sec) (2)*[(4) + (6)] Operation cost ( ) 0.4 * (7) Figures for theoretical minimum parts Estimation TM = Total manual assembly time CM = Total cost of manual assembly NM = Theoretical minimum number of parts TM CM NM designefficiency 3 * NM = = TM
Pneumatic Piston Sub-Assembly - Screw (2) (steel) 2 - Cover (steel) 3 - Spring (steel) 4 - Piston stop (nylon) 5 - Piston (aluminum) 6 - Main block (plastic) 8
Worksheet for Pneumatic Piston 2 3 4 5 6 7 8 9 Part I.D. Number Number of times the operation is carried out consecutively Two-digit manual handling code Manual handling time per part Two-digit manual insertion code Manual insertion time per part Operation time (sec) (2)*[(4) + (6)] Operation cost ( ) 0.4 * (7) Figures for theoretical minimum parts Estimation 6 5 4 3 2 2 30 0 0 05 23.95.50.50.84 2.36.80 00 02 00 00 08 39.5 2.5.5.5 6.5 8.0 3.45 4.00 3.00 3.34 8.86 9.60.38.60.20.34 3.54 7.84 0 0 Name of Assembly Pneumatic Piston Main Block Piston Piston Stop Spring Cover Screw TM = Total manual assembly time CM = Total cost of manual assembly NM = Theoretical minimum number of parts 42.25 6.90 4 TM CM NM design efficiency 3 * NM = = TM 0.29 9
Redesigned Pneumatic Piston - Snap on cover and stop (plastic) 2 - Spring (steel) 3 - Piston (aluminum) 4 - Main block (plastic) 20
2
Worksheet for Redesigned Piston 2 3 4 5 6 7 8 9 Part I.D. Number Number of times the operation is carried out consecutively Two-digit manual handling code Manual handling time per part Two-digit manual insertion code Manual insertion time per part Operation time (sec) (2)*[(4) + (6)] Operation cost ( ) 0.4 * (7) Figures for theoretical minimum parts Estimation 4 3 2 30 0 05 0.95.50.84.50 00 00 00 30.5.5.5 2.0 3.45 3.00 3.30 3.50.38.20.34.40 Name of Assembly Pneumatic Piston (re-design) Main Block Piston Spring Cover & Snap TM = Total manual assembly time CM = Total cost of manual assembly NM = Theoretical minimum number of parts 3.29 5.32 4 TM CM NM design efficiency 3 * NM = = TM 0.90 22
Design for Automated Assembly (Concepts) Layered design Clamshell base Sequential assembly Uni-directional Self-alignment Chamfer/countersink Posts/locating stops Combine detail parts Screws & washers Plastic moldings Castings Symmetry Direct drive systems Helical or gear vs. Belt/pulley Common fasteners Minimize screws Snap fasteners Minimize springs Molded Compression coil Extensive coil Minimize cables Integrated packaging Solid connectors 23
Example of Layered Assembly Snaps Snaps 24
Compliance and Assembly Avoid Better Best No Chamfers Bottom Part Chamfered Top Part Chamfered Both Parts Chamfered 25
Self Alignment of Parts This part could be oriented in any direction These parts can be oriented only one way Hole to accept swaged part Hole to accept notched part D shaped hole 26
Nesting of Parts This part could be placed in any orientation and not be secured This part has a nest to orient and help it secure 27
Nonfunctional External Feature for Orientation This slot would be hard to detect Pin to help orient slot Chamfer to help orient slot 28
Symmetry Orientation Required Preferred 29
Tangling These parts can tangle easily The same parts redesigned, will not tangle 30
Tangling (continued) Parts that interconnect will not feed Springs with open loops will tangle A fillet will keep the parts from interconnecting Springs with closed loops will not tangle 3
Methods to Avoid Jams ( of 2) This results in shingling Direction of Flow Base causes leading edge to be lower than trailing edge A nonfunctional corner can eliminate this problem 32
Methods to Avoid Jams (2 of 2) Mating surfaces with sharp edges can cause jams Rounded corners can prevent jams A groove can prevent jams by centering the part 33
Substitutes for Fasteners Avoid designs that require fasteners Design parts that snap together 34
Joining Moving Parts without Fasteners C-Clip Snaps Chamfered Surface 35
Fasteners Preferred: Have flat vertical sides for vacuum pickup Socket Head Fillister Head Hex Head Round Side Avoid Slant Side Round Head Flat Head 36
Cables and Connectors Example of a slave circuit board Avoid: Components that are connected with cables to circuit board Preferred: Components that are plugged on a slave circuit board 37
Cables and Connectors Example of a secured cable If the use of a cable cannot be avoided. Have the cable plugged into a dummy connector to locate the cable end. Then a robot can locate the connector and plug it in. 38
Avoid: Three motions required for insertion Slot Motion and Design Preferred: Only one motion required Snaps 39
Design for ME20 Assembly Keep it Simple Easy Access to All Parts (So they can be replaced) Starting Areas Backboard Easy to Set Triggers Ball Storage Loose Balls Start Assembly Now Defensive Players Ball Supply 40