2Two Phases of Assembly Handling Insertion Can be done Manually AutomaticallyHandlingInsertion
3Manual Handling (Affected primarily by geometry) BinsWorkstationFixtureOperatorOperatorReaches into the binGrasps the partTransports and orients the partPre-positions it
4Manual Insertion(Affected by both the part geometry AND the part/parts to which it is placed/fastened/mated to.)BinsWorkstationFixtureOperatorOperator - places/fastens part onto a partially completed assembly/subassembly
5Automatic Assembly (free transfer/non-synchronous system) Gravity Feed TrackBowlFeederWorkheadAssembly Machine -WorkstationsBuffer StockWorkcarrierPartially completed assembly transferring to next stationBufferSpaceParts emptied into a bowl feeder which contain orienting devices.Parts exit feeder go down track in preparation for insertion.
6Schematic of assembly system Four Station Automatic Assembly System for Irrigation Mini-Drippers (Rotary Indexing Machine)Schematic of assembly systemMini-dripper has a base, body, regulator and cover.
7Orienting system for cup shaped parts Automatic Handling (From “Handbook of Feeding and Orienting Techniques for Small Parts,” by Boothroyd, Poli and Murch)Bowl FeederOrienting system for cup shaped parts
8Cost of An Assembly Number of parts Ease with which the parts can be > Handled > Inserted
9Rule #1 - Eliminate Parts Outright elimination of parts. (screws, nuts, washers, etc.- use snap fits)Combining 2 or more distinct parts into a single molded, cast or stamped part.9 parts2 parts
10Eliminate Fasteners If not possible, reduce the number or variety Incorporate the fastening function with another feature1 screw4 screwsSnapScrews aren’t expensive - driving them is!
11Can Parts Be Combined?Since there is no relative motion between the parts - andSince these parts can be made of the same materialWhy not combine them?
12Rule #2 -Design Parts So they can be easily handled and Inserted Bins WorkstationFixtureOperator
13Factors Affecting Manual Handling Time (Cost)* PartSymmetry > End-to-end > RotationalSizeThicknessMass* Reference: G. Boothroyd, “Assembly Automation and Product Design,” Marcel Dekker, NY, 1992
14If the part is Easy to Grasp and Manipulate with One Hand and No Tools
15Examples of Symmetry Parts with end-to-end symmetry Parts with no end-to-end symmetryDowel pinwasherpinbulbnailscrewdiskkey
16Examples of Rotational Symmetry Parts with rotational symmetry.Parts with no rotational symmetry.bulbpinscrewwasherKollmorgendiskkey
19Parts are Difficult to Grasp and Manipulate Flexible - two hands to keep orientation prior to insertion (belts, chains, gaskets)Do not nest or tangleNest or tangle (and degree of severity)Slippery (ball bearings with oil)
20Parts are Difficult to Grasp and Manipulate - continued Due to obscured view/accessNeed Grasping Tools (tweezers, magnets, snap rings, )Due to part size/thicknessTwo handsHeavyLargeExpansion boardComputer chipFragile
21Parts are Difficult to Grasp and Manipulate - continued Sharp/hot/ undesirable to touchGrease on ball bearingPart with adhesiveSticky
22Factors Affecting Manual Insertion* Dog pointNo chamfersChamfersEase of alignment (provide feature to ease insertion)Ease of insertion(affected by clearance, jamming, wedging, pushing against a force)Part jams on cornersSame clearance, no jammingchamfersNegative clearance (press fit) Push against a force* Reference: G. Boothroyd, “Assembly Automation and Product Design,” Marcel Dekker, NY, 1992
23Factors Affecting Manual Insertion - continued Obstructed view and/or obstructed accessTask: Place battery in shaver.View clear? Need to rely on tactile sensing?Access clear? Is there a feature that restricts access to the operator?Self-locating, no need to hold
24Additional Considerations Insert vertically from above (i.e. don’t fight gravity)YesNoProvide features/obstructions to prevent incorrect assembly of the part.
25Additional Considerations Eliminate difficult to control operations - - welding, brazing, gluing, etcEliminate extra operations such as special adjustments, torque adjustments etc.
26Additional Considerations Design products into sub-assemblies that can be assembled and tested separately.‘De-couple’ manual and machine operations.Group manual assembly operations to optimize line balancing.
27Precision needed if you need to do process planning. Assembly AnalysisThree choices to analyze an assembly:Precise quantitative method - such as the Boothroyd approach*.* Reference: G. Boothroyd, “Assembly Automation and Product Design,” Marcel Dekker, NY, 1992Precision needed if you need to do process planning.Use an approximate approach during configuration stage of design?Assembly AdvisorAllow 7-9 sec/part(Compromise approach)(Fails to focus attention on characteristics that make assembly difficult)