Presentation on theme: "Hernan Joglar 2.875 Mechanical Assembly John SharkeyFall 2001 Page 1 2.875 Mechanical Assembly and its Role in Product Development Pencil Sharpener Project."— Presentation transcript:
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page Mechanical Assembly and its Role in Product Development Pencil Sharpener Project Report N o 3 November 14, 2001 Hernan Joglar John Sharkey
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 2 Part list
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page Figure 1. Pencil sharpener parts numbered as in the Part List
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 4 Input contact Intermediate contact Edge Output contact Safety lever pin Figure 2. Details of contacts and features in gearbox cover
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 5 Figure 3. Details of contacts and features in battery compartment housing Mating features Electric in-out contacts Red and black electric wires Electric contact rivets
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 6 Pencil Sharpener Indentured Parts List
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 11 Assembly Choreography (Gross and fine motions, features where parts are gripped and mated, lead-ins, and auxiliary operations) 1.Create the Gearbox Cover Subassembly (sa6) a.Solder the red wire (part 24) to the input contact. b.Solder the blue wire (part 25) to the output contact. c.Rivet gearbox cover contacts to the gearbox cover (parts 23 and 26) 2.Create the Cutter Unit Subassembly (sa7) a.Place the blade holder on a flat surface. b.Put the blade on the blade holder with the cutter edge facing the slot. The blade should fit into the space provided between the prongs so that the hole in the blade gets aligned with the one in the blade holder. c.Insert the bolt through the aligned holes. The bolt must be held with one finger while the nut is grabbed with a tool and screwed from the other side. d.For final tightening, hold the bolt with a Phillips head screwdriver while the nut is tightened on the other side.
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page Create the Battery Compartment Subassembly (sa4) a.Rivet the contacts (part 12) to the battery compartment housing (part 11). b.Install the battery installation paper guide inside the battery compartment. The drawings must face the interior; the blank face should be at the side where the in/out contacts are and the tabs must be folded to each side on top of the battery compartment so that they are pressed between the battery compartment housing and the sharpener base (part 5)once the latter is installed. 4. Create Motor/Gearbox Subassembly (sa5) a.Place the gearbox housing (part 15) on a flat surface with the gear compartment facing up. b.Grab the output gear (part 16) from end of its shaft where the peg is not squared. Insert the other end of the shaft in its hole in the gearbox housing so that the squared peg goes into the hole. c.Take the intermediate gear (part 17) by the input pinion teeth and insert it in the intermediate gear pin that is attached to the gearbox so that the output pinion faces down. Rotate the intermediate gear to ensure proper gear mesh. d.Repeat this last operation with the driven gear (part 18). e.Place lubrication (part 22) on all parts inside the gearbox.
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 13 f. Insert the safety lever (part 21) on its pin in the gearbox housing. The safety lever must be placed with its prong facing up. This prong must stay outside the gearbox cover when that part is installed; therefore it is important at this point to observe that lever positioning allows the right location of the prong. g. Place the gearbox cover (sa 6) on top of the gearbox housing. This is a difficult mate for two reasons: i. The safety lever must be held so that it doesn’t rotate about its pin. ii. The ends of the blue and red wires must stay outside the gearbox. In order to circumvent the above difficulties, the gearbox housing must be held with one hand with the thumb finger holding the safety lever so that it doesn’t rotate. Then, the gearbox cover must be grabbed with the other hand while pressing the wires against the edges at the corresponding sides of the cover. It is very important for appropriate electrical connection that the wires come out the gearbox at the same side where their corresponding contacts are. Subsequently, the cover should be installed on the gearbox by first making coincide the edges of both parts located at the end opposite to where the motor is. Once the cover is installed, the wires must be slid around the edges until they reach the squared holes that will be left for them to come out at both sides of the Motor/Gear Subassembly.
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 14 h.Press the gearbox cover against the gearbox to make both parts fit and to enable the intermediate electrical contact to store the tension that will let it keep pressing the output gear. i.Install the self threaded screw that attaches the gearbox cover to the gearbox (part 19). j.Turn the gear housing upside down so that the cover is at the bottom and in contact with a flat surface. k.Take the Cutter Unit Subassembly and insert the square hole in the blade holder on the square peg in the output gear shaft. l.Test the circuit inside the gearbox by connecting the blue and red wires to a circuit tester while pressing the safety lever and the cutter unit. The instrument should indicate that the circuit is closed. m.Solder the black wire (part 14) to the electric motor (+) terminal (part 20). n.Solder the blue wire (part 25) to the electric motor (-) terminal. o.Insert the electric motor in its compartment in the gearbox housing. Rotate the motor until it fits the motor location pegs. The negative terminal must be placed at the same side where the blue cable is coming out the gearbox housing. When that is accomplished, the motor will not rotate any more. Its rim will then be inserted in the motor location hole and the motor gear will engage the driven gear inside the gearbox. p.Test the gear engagement by rotating the cutter unit and listening to the noise of the motor rotating. Note: the motor fixture described in DFC Project Report # 2 has been deleted in the above sequence.
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 15 5.Create the Battery Compartment Cover Subassembly (sa3) a.Rivet the contacts (Part 8) on the battery compartment cover (part 9). b.Using an adhesive, place the rubber foot (part 10) on the battery compartment cover. 6.Create the Base Subassembly (sa2) a.Using an adhesive, place the rubber foot (part 6) on the sharpener base (part 5). b.Attach the battery compartment cover subassembly to the sharpener base. First insert the rims on the battery compartment cover in the corresponding slot on the sharpener base. Then press both parts against each other on the opposite end until the snap fit attaches both parts together. 7.Complete assembly (sa1) a.Grab the battery compartment housing, turn it upside down and place it on the gear/motor subassembly. The rims on the battery compartment housing must be slid inside the slots provided at both sides of the gearbox housing. When in its correct position, the circular rim in the battery compartment housing is inserted in the circular slot in the bottom of the electric motor. b.Solder the black wire to the in/out contact in the battery compartment housing that is located at the same side as the safety lever. c.Solder the red wire to the remaining in/out contact in the battery compartment.
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 16 d.Grab the sharpener case (part 7) in one hand and, with the other one, place inside it the Battery Compartment Subassembly (sa 4) and the Motor/Gearbox Subassembly (sa 5), so that the rims in the sharpener case fit the slots in the battery compartment housing and the holes in both parts become aligned. To perform this action prongs are provided in the interior of the sharpener case and the outside of the gearbox housing. These prongs must slide against each other as the insertion is performed in order for the assembly to be accomplished. e. Using a magnetic Phillips head screwdriver insert the battery compartment self threaded screw (part 3) in the aligned hole and tighten it. f.Install the Base Subassembly so that both of its cylindrical screw guides are inserted in the spaces provided on both sides of the gearbox housing. Once these guides reach their position they act as holes and mate with pegs at the opposite side of the sharpener case. This mate allows for the holes in the interior of both of the above features to become aligned. Similarly, the above mate allows the insertion of the rim on the edges of the in the slot on the edges of the sharpener case.
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 17 g.Place and tighten the two self threaded screws that attach the base to the sharpener case. h.Place and tighten the two self threaded screws that attach the base to the battery compartment housing using a Phillips head screwdriver. i.Grab the pencil guide (part 2) with the chamfered rim for pencil guidance facing up. Press the cutter unit down to allow room for the pencil guide to be inserted in the slot between the sharpener case and the gearbox housing. The slot in the interior of the sharpener case must fit the rim in the upper surface of the pencil guide. Release the cutter unit to allow for its circular rim to fit in the hole at the bottom surface of the pencil guide. j.Place the Shavings receptacle by inserting one of the lateral slots on the sharpener case in one of the lateral slots in the receptacle and press on the opposite side to make the snap fit attach both parts together.
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 18 Potential Problems and Risk Areas DescriptionProbabilityImpact Reversed motor polarity wiring (black on +) HighHigh Reversed battery compartment wiring HighHigh Solder joint or wire breakage during gearbox insertion LowHigh Solder joint or wire breakage during motor insertion LowHigh Motor pinion clearance thru gearbox hole HighMed Loss of motor location during final assembly HighMed Improper location of battery compartment on gearbox MedMed Part damage from shaver receptacle insertion (snap fit) MedMed
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 19 Suggested Design Improvements DescriptionImpact Reversed motor polarity wiring (black on +) - Use wire connector instead of solder jointMed Reversed battery compartment wiring (red on right) - Imprint wiring polarity on battery compartment injection moldHigh Solder joint or wire breakage during gearbox insertion - Use wire connector instead of solder joint Med Solder joint or wire breakage during motor insertion - Use wire connector instead of solder joint Med Motor pinion clearance thru gearbox hole - Reduce and control gearbox manufacturing varianceMed Loss of motor location during final assembly - Include snap/fit feature between battery compartment and gearboxHigh Improper location of battery compartment on gearbox - Use wire connectors instead of solder joint Med Part damage during shaver receptacle insertion (snap fit) - Training, coupled with control of manufacturing variationsLow
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 20 Fixtures and Special Tooling Fixtures Riveting fixture. or special tooling, for battery compartment Riveting fixture, or special tooling, for gearbox cover Bending fixture for gearbox cover electrical contacts Bending fixture for battery cover electrical contacts Bending fixture for battery compartment electrical contacts (nice to have) Soldering station and fixture for electric motor (black and blue leads) Soldering station and fixture for battery compartment (black and red leads) Standard Tools and Special Tooling Heat stake tooling for battery compartment electrical contacts Magnetic Phillips head screwdriver (4” length) for battery compartment screw Small wrench, or pliers, for blade screw and nut Wire strippers (22 gage) Wire tinning and pre-form bending Soldering station for gearbox cover Electrical test station for operation of motor/gearbox sub-assembly Lubrication dispenser gun
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 21 Throughput requirement based on production volume –250, workdays/year = 1000 units/day – hours/day = 125 units/hour = 2.08 mins/unit Assembly time per Boothroyd Handling and Insertion Times –Handling Time per unit= (sec/unit) –Location Time per unit= (sec/unit) –Reversible Fastening Time per unit= (sec/unit) –Irreversible Fastening Time per unit= (sec/unit) –Total predicted assembly time= (sec/unit) Note: does not include inspection and test time Measured Handling, Location and Reversible Fastening Times –Test#1309 sec –Test#2222 sec Assembly Efficiency –Three “un-necessary parts: Sharpener case, paper guide, and pencil guide – (sec) Assembly Time Analysis
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 22 Example Assembly Process SA 7 Cutter Unit Assy SA 7 Cutter Unit Inspect SA6 Gearbox Cover Assy SA 6 Gearbox Cover Inspect SA5 Battery Comp. Assy SA 5 Battery Comp. Inspect SA3 Battery Cover Assy SA 3 Battery Cover Inspect SA5a Gearbox Assy SA5a Gearbox Solder SA5a Gearbox Test SA5 Motor/Gearbox Assy SA2 Base Assy SA1 Final Assy SA1 Final Inspect Package & Ship sec sec sec sec 5 sec 33.5 sec sec 20 sec 30 sec Note: Test, inspection and packaging times are SWAGS
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 23 Part Handling: Gross Motion
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 24 Part Handling: Gross Motion (con’t)
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 25 Part Insertion: Fine Motion
Hernan Joglar Mechanical Assembly John SharkeyFall 2001 Page 26 Part Insertion: Fine Motion (con’t)