Group 24 - Swingline Electric Stapler

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Latest revision as of 11:25, 10 December 2007

Executive Summary

The purpose of this page is to provide a detailed product analysis of the Personal Electric Stapler manufactured and designed by Swingline.

Our stapler converts electric power to mechanical energy using a motor, a system of gears and a circuit board. When a small sensor is depressed in the mouth of the stapler by the packet of papers, it sends a signal to the circuit board which engages the motor. The motor spins a series of gears and the end result is a successfully stapled packet of papers.

To better understand how this process worked we all disassembled the stapler. After seperating the main components we created a disassembly table and a parts list. And we also created a 3D CAD Drawing to help explain the motion of the moving parts.

Reassembly proved more difficult than the disassembly because we cut the wires connecting the motor to the circuit board. We had to splice these back together and find a place for them.

In the After Assembly section of this report you will our recommendations for improvements and our final conclusion.

Introduction

The Swingline Personal Electric Stapler is a popular office appliance with a retail price of $39.95. It can staple up to 15 pages at one time, runs on both AC and battery power, and holds 210 staples.

Group 24 Members

David Sheffield (Group Leader)
Joe Marzello
Nick Rhode
Shawn Hammerton
Mark Okraksinkski

Before Disassembly

The product that our group was assigned was an electric stapler made by Swingline. Before disassembling the product, our knowledge was very limited in how it works or the components inside. However, we can make several obvious assumptions from current knowledge of staplers. The purpose of an electric stapler is to staple pages together or to bind two pages or more pages together. This is useful because in a report several pages long, they can be kept organized chronologically and won’t be separated from each other. An electric stapler is more advanced than your regular stapler because instead of using your hand to push the staple in the page, it is automatically done for you. You slide your pages under the designated area, the stapler triggers, and activates a staple binding your pages.

Our knowledge was limited in how the stapler works, what components it may entail, and what different materials are used. We know that it uses electrical components such as wires and a switch board because it needs the electrical energy to transfer it into mechanical energy. This mechanical energy is the part that actually does the stapling. In order to accomplish this, it must have some mechanism to drive the staple into the paper. We also know that a small motor is used to power this mechanism and the motor is powered by our electrical energy. We can predict that the system may use gears to transfer motion, but we are not sure of the orientation or how many. The materials used in the production of the stapler are hard to predict because many materials would be feasible solutions. We do in fact know that plastic is used for the protective casing. The other materials that we assume are used in some components would be steel and magnets for the motor and other types of metal for smaller components that need to be strong such as screws.

When we received the product we tested it out and it did work. We plugged it into the wall using the electricity from the outlet and put batteries in the bottom of it. Both methods worked and let the stapler run flawlessly. It did emit a sound from all the movement that was going on underneath the protective casing. The sound was not like a normal stapler but more forceful and fast paced. You could hear some components moving around and then the louder sound of something drive the staple down.

Energy Transfer

The picture on the right side below this paragraph is a 3D CAD Drawing of the main components of our stapler. The motor, powered by electricity from an electrical outlet, spins at a high rate of speed and through gear reduction it spins the large gear (2) causing the swing arm to pivot, therefore forcing the piece of metal down that pushes the staple into the paper (this being the rotational to linear energy transfer). There is a video to the left which will clarify my explanation.

Disassembly Process Table

Step #	Process	Tool(s)	Level of Difficulty
1	Remove the black feet revealing the four screws on the bottom plate	Hand	Easy
2	Unscrew those four screws	Hand and phillips head screwdirver	Easy
3	The shell base can now be seperated from the bottom plate	Hand	Easy
4	This exposes numerous wires, you can unhook the paper sensor and power jack. To do this just pull lightlty on them	Hand	Easy
5	The top protective case can now be removed from the shell base by pulling up, you may need to wiggle it.	Hand	Easy
6	You will notice that the top case cannot be fully seperated because it is attatched by wires. You can simply cut the three wires to completely free the piece.	Hand and wire cutters	Easy
7	Unscrew the eight screws and remove the washers that hold down the motor mount.	Hand and phillips head screwdriver	Easy
8	Unscrew the two screws (gearbox scews b) on the side of the gearbox that are holding the brace and gear a in place. The brace and gearbox a will easily come off.	Hand and phillips head screwdriver	Medium
9	The whole assembly of the gearbox and swingarm mount can be lifted from the shell base and taken out to free up some space	Hand	Easy
10	With the gearbox and swingarm out of the shell base you can further dissassble them. Unscrew the two screws (gearbox scews a) on the top edge that will seperate the motor mount into two halves	Hand and phillips head screwdriver	Easy
11	Slide the two external gears (a and b) off the drive shaft	Hand	Easy
12	The motor and swing arm lever/mount can now be freed from the motor mount	Hand	Easy
13	The swing mount gets further disassembled by detatching the swing are lever.	Hand	Easy
14	Remove the two slip washers on the outsdie of the swing arm mount	Hand	Medium
15	Slide the swing arm pivot bar and spacer ring out of the swing arm lever	Hand	Easy
16	Unscrew the screw that is fastening the swing arm head to the staple contact head mount and swing arm head.	Hand and phillips head screwdriver	Easy
17	Moving back into the shell base; The circuit board is resting in a grove and can now be removed by lifting up	Hand	Easy
18	Flip the shell base upside down, remove the spring loaded spring on top of the pin and the washer	Hand	Medium
19	Mount the strike plate onto the shell base with two screws (strike plate screws)	Hand and phillips head screwdriver	Easy
20	On the same end as the strike plate there is a screw holding the staple tray to the shell base; unscrew that	Hand and phillips head screwdriver	Easy
21	The whole staple tray can now be removed from the shell base by lifting it out of its groves	Hand	Easy
22	Unhook the large spring to the staple tray	Hand	Easy
23	Remove the small spring mounting pin which will free the small tray spring	Hand	Easy
24	Remove the mounting pin which will free the tray release switch and small tray spring	Hand	Easy

Part Table

Part No.	Part Name and Function	# Of This Type	Material and Reason for Choice of Material	Reason for Part's Shape	Manufacturing Process
1	Gear A (transfer energy from gear B to gear C)	1	Nylon (because it reduces friction)	The radius and the number/size of teeth were chosen for the proper gear ratio for energy transfer	Injection molding
2	Gear B (transfer energy from the motor to gear A)	1	Nylon (because it reduces friction)	The radius and the number/size of teeth were chosen for the proper gear ratio for energy transfer	Injection molding
3	Gear C (transfer energy from gear A to the cam wheel)	2	Nylon (because it reduces friction)	The radius and the number/size of teeth were chosen for the proper gear ratio for energy transfer	Injection molding
4	Gearbox Screw A. (holds together the right and left halves of the gear box mount)	2	1020-1040 Steel (it provides adequate strength while maintaining low cost)	Thread spacing and precision chosen because they don't need to withstand any degree of strong vibration. Screw length is chosen because the screw needs to fit deep enough into the to hold the parts together.	Extrusion and Cold Forging
5	Gearbox Screw B. (hold the brace to the gearbox mount)	2	1020-1040 Steel (it provides adequate strength while maintaining low cost)	Thread spacing and precision chosen because they don't need to withstand any degree of strong vibration. Screw length is chosen because the screw needs to fit through the brace and into the hole in the gear box mount.	Extrusion and Cold Forging
6	Brace (prevents gear A from slipping out of position)	1	Nylon (It allows the brace to secure the gear without causing too much friction.	The length of the brace needs to be wider than gear A so that its mounting doesn't interfere with the rotation of gear A. The hole in the center of the brace allows the gear shaft to fit and thus preventing excessive vibration.)	Injection moldeing
7	Cam Wheel (creates a large turning radius to operate the swing arm lever.)	2	Nylon/ABS plastic (The right half of the Cam wheel is made of nylon because it is the part that originates the movement and therefore needs to cut down on friction. The left half of the Cam wheel is made of ABS plastics because all it has to do is attach itself to the right gearbox mount.	The large diameter of the wheel allows for precise control over the motion of the swing arm lever. The ribs in the material act as spokes to strengthen the wheel without adding unnecessary material.)	Injection molding
8	Electric Motor (converts electrical energy to mechanical energy, initiating the motion in the stapler)	1	Copper wire and leads (good electrical conductivity), ABS plastic rear(shock resistant, insulator), Steel drive shaft (sturdy material), Galvanized steel case (rust resistant).	The electric motor is made up of coiled copper wire that creates a magnetic field that is surrounded by 2 permanent magnets. The opposing magnetic fields cause the coiled wires and the drive shaft to spin. All of this is encased in a steel frame with a plastic base.	Extrusion (wire, drive shaft), Injection molding (base), Forming (case, wire).
9	Gearbox sensor (tells the circuit when to stop the motor)	1	ABS plastic (cheap and strong enough to support the spring), steel(is flexible)	The lever on the end of the sensor allows for maximum sensitivity. A strong spring allows the timing returned to the circuit to be precise.	Injection molding (plastic), Extrusion (steel)
10	Gearbox mount(right)(provides a place to mount gears A,B,and C, the right half of the cam wheel, and the brace, and connects them to the shell bottom)	1	ABS plastic (cheap and strong enough to hold things together)	The shape is designed to make all the gears fit together, to align with the Gearbox mount (left), and to fit on the shell bottom	Injection molding
11	Gearbox mount (left) (provides a place to mount the Motor, the gearbox sensor, and the left half of the cam wheel, and connects them to the shell bottom)	1	ABS plastic (cheap and strong enough to hold things together)	The shape is designed to make all the parts fit together, to align with the Gearbox mount (right), and to fit on the shell bottom	Injection molding
12	Staple tray (hold staples)	1	Steel(sturdy material that won't wear with repeated use)	The cavity in the tray is designed to fit Swingline standard staples	Sheet Metal Forming
13	Tray Mounting Screw (hold staple tray in place)	1	1020-1040 Steel (it provides adequate strength while maintaining low cost)	The large flat head on the screw is designed to clamp down on the back of the staple tray holding it in place	Extrusion and Cold Forging
14	Large Tray Spring (puts tension on the staple tray and advances the staples)	1	Steel (must be flexible but still put force on the staple tray)	The spring is long and thin because it has to reach all the way around the staple tray while not interfering with any moving parts.	Extrusion / Forming
15	Small Tray Spring (stores potential energy and puts tension on the tray release switch, the small spring mounting pin, and the sliding part of the staple tray)	1	Steel (must be flexible but still put force on the staple tray)	The 2 small rings on one side of the spring press forward against the back of the sliding part of the staple tray, while the loop on the other side of the spring presses up on the small spring mounting pin holding it in the locked position. When the small spring mounting pin is forced downward it unlocks the staple tray and the spring releases its potential energy, pushing the sliding part of the staple tray out far enough so that it can be pulled out the rest of the way with one's fingers.	Extrusion / Forming
16	Small Spring Mounting Pin (acts as a trigger for releasing the staple tray)	1	steel (needs to be sturdy and resist wear)	The pin is short so that it doesn't get in the way of any other moving parts. It is cylindrical so that it is less likely to jam	Extrusion
17	Tray Release Switch (pushes down spring mounting pin, presses cut off button on the circuit board)	1	ABS plastic (cheap. no need for strong support)	The unusual shape of the tray release switch is used so that when it is pressed, it can in turn press both the small spring mounting pin, and the cut off button on the circuit board at the same time.	Injection Molding
18	Tray Release Switch Mounting Pin (provides a pivot point for the tray release switch)	1	Steel (sturdy material)	cylindrical so that the tray release switch can be mounted on it and pivot effectively.	Extrusion
19	Swing Arm Lever (converts circular motion into linear motion)	1	4140-4300 Steel (strong material that won't bend or break under stress	the shape is designed so that it has 2 sliding pivot points which enables it to change the circular motion of the cam wheel into linear motion that can push straight down. The angle of the bar allows more downward force to be applied at the end of the stroke where it meets more resistance.	Casting
20	Swing Arm Head (trips the gear box sensor and provides a place to mount the staple contact head)	1	ABS plastic (cheap, doesn't undergo much stress)	the flag off to the side sticks out in order to trip the gear box sensor. The sides aligns with grooves in the swing arm mount. The studs on the lower portion help to mount the staple contact head.	Injection Molding
21	Staple Contact head (makes contact with the staple, pushing it through the paper)	1	Stainless Steel (needs to keep a sharp, rust free head)	The 2 smaller holes are for it to line up properly with the swing arm head. The larger hole is so the mounting screw can pass through	Rolling/Machining
22	Staple Contact Head Mounting Bracket (locks the staple contact head in place)	1	ABS plastic (low cost. no real need for strong material)	Made to align with the swing arm head and the staple contact head.	Injection molding
23	Staple Contact Head Mounting Screw ( secures the staple contact head and the staple contact head mounting bracket to the swing arm head)	1	1020-1040 Steel (it provides adequate strength while maintaining low cost)	The screw has to be long enough to reach through the staple contact head and the staple contact head mounting bracket.	Extrusion and Cold Forging
24	Swing Arm Pivot Bar (provides a point for the swing arm lever to pivot around)	1	Steel (strong material withstands repeated use)	the design of this piece includes a slit near each end for slip washers to clip on.	Extrusion and Cold Forging
26	Spacer Ring (allows the swing arm lever to fit on the swing arm pivot bar)	1	Steel (strong material, maintains shape)	The inner diameter fits around the pivot bar while the outer diameter fits in the slot in the swing arm lever	Extruded
27	Slip Washer (holds the swing arm pivot bar in place)	2	Steel (strong and flexible)	Not completely circular so that it can be removed.	Casting
28	Swing Arm Mount (guides the swing arm head and aligns with the shell bottom)	1	ABS plastic (intricate structure with no need for much strength)	There are grooves to guide the swing arm head downward. There are 'L' brackets with holes on the bottom so that it can be secured to the shell bottom	Injection Molding
29	Shell Bottom (provides a frame for all of the other parts to be attached to)	1	ABS plastic (low cost, largest single piece)	the shape is designed for all the other components to be mounted on it. It is the only part with the company's logo on it.	Injection Molding
30	Shell Top (protect the stapler)	1	ABS plastic (low cost, second largest single piece)	Designed to be aesthetically pleasing.	Injection Molding
31	Strike Plate (bends staples inward after passing through paper)	1	Steel (must withstand repeated striking)	the shape of the grooves cause the staples to bend inward and lock behind the paper	Casting
32	Strike Plate Screw (secures strike plate to shell bottom)	2	1020-1040 Steel (it provides adequate strength while maintaining low cost)	Screw must reach the hole past the strike plate	Extrusion and Cold Forging
33	Circuit Board & Components (acts as the brain of the stapler)	1	fiberglass board with copper paths	The bottom of the circuit board his a space cut out so it doesn't get in the way of the staple tray. The sides of the circuit board fit into slots on in the shell bottom.	Etching
34	trigger sensor (recognizes that paper has been inserted and sends a signal to the circuit board)	1	Steel(lever), ABS plastic (housing)	The long lever allows for a sensitive, more reliable sensor	Sheet Metal Forming (lever) Injection Molding (housing)
35	Power Input Jack (source of energy)	1	ABS plastic (housing)	the lack of cord directly attached to the stapler makes it easy to move around a desk	Injection Molding (housing)
36	LED (shows that the stapler is ready to accept paper)	1	Clear ABS plastic	Clear cover allows light so show through	Injection Molding
37	Body Screw (fastens the gearbox mount and the swing arm mount to the shell bottom)	8	1020-1040 Steel (it provides adequate strength while maintaining low cost)	The screw is longer than it has to be to ensure it has a more permanent fit	Extrusion and Cold Forging
38	Body Washer (prevent the body screws from slipping out)	8	Steel (strong enough to hold screws in place)	The teeth on the washer compress and bite into the plastic and causing friction that prevents the screw from coming undone.	Casting
39	Large Screw (fastens shell bottom to shell top)	2	1020-1040 Steel (it provides adequate strength while maintaining low cost)	A large screw head makes it easy to access in a tight space	Extrusion and Cold Forging
40	Small Screw (fastens base plate to shell Bottom)	4	1020-1040 Steel (it provides adequate strength while maintaining low cost)	A large screw head makes it easy to access in a tight space	Extrusion and Cold Forging

Assembly Process Table

Step #	Process	Tool(s)	Level of Difficulty
1	Align the swing arm in between the left and right sides of the motor mount. The longer whole on the swing arm lever should be over the pin between the black wheel and the white wheel	Hand	Easy
2	Align right and left half sides of the motor mount with motor	Hand	Easy
3	Secured two halves of the gear box together with two screws on the top edge (gearbox screws a.)	Hand and phillips head screwdriver	Easy
4	Attach two external gears (a and b) to the outside of the motor mount. They easily slide onto drive shafts.	Hand	Easy
5	Mount brace over bigger gear a. Then secure it with two screws (gearbox screws b.)	Hand and phillips head screwdriver	Easy
6	Mount staple contact head onto the swing arm head	Hand	Easy
7	Mount staple contact head mounting bracket onto the swing arm head. Secure this in with a a screw (staple contact head mounting screw)	Hand and phillips head screwdriver	Easy
8	Align swing arm head with whole on the swing arm mount	Hand	Easy
9	Slide spacer ring into smaller whole on the swing arm lever then secure with swing arm pivot bar as a pin	Hand	Medium
10	Secure with the two slip washers on the outside of the swing arm mount	Hand	Medium
11	Attach large spring to the staple tray just by hooking it on	Hand	Easy
12	Align tray release switch and small tray spring, then secure by sliding the tray release mounting pin through the aligned holes	Hand	Easy
12	Tension and secure the small tray spring with the small spring mounting pin	Hand	Easy
13	Mount the strike plate on the shell base. Secure down with two screws (strike plate screws)	Hand and phillips head screwdriver	Easy
14	Place staple tray in the shell base. Make sure the larger pin on the staple tray falls into the groove in the shell base. Slide pin over to one side and put screw into whole so that the pin will not slide anywhere	Hand and phillips head screwdriver	Easy
15	Flip the shell base upside down, place spring on top of pin from the staple tray and secure with slip washer	Hand	Medium
16	Place circuit board into the grooves in the shell base. The circuit components should be facing the rear of the shell base.	Hand	Easy
17	Align the motor mount and swing arm mount with the screw holes on the shell base. Note that the tray has to be in the open position, to do this push the staple tray release switch forward.	Hand	Easy
18	Fasten this down to the shell base with eight washers and eight screws. The screws are tricky to reach with the screw driver, it will be easier if you remove the brace from the side of the motor mount. Just remember to reattach the brace after you finish screwing down all the screws	Hand and phillips head screwdriver	Medium
19	Connect the wires from the circuit board to the switch and motor. Use colors to match them up	Hand and wire cutters	Hard
20	Place top protective casing over the top of motor (make sure the circuit board and wholes are lined up and that the switch and button are lined up) and snap it into place	Hand	Easy
21	Secure the top plate to the shell base with two screws	Hand and phillips head screwdriver	Easy
22	Place electronic components on the underside of the shell base. Snap the paper sensor into slot on bottom side of shell base and attach power jack to bottom plate.	Hand	Easy
23	Snap the bottom plate to the shell base, fasten with four screws (make sure all wires are tucked in neatly)	Hand and phillips head screwdriver	Easy
24	Place black feet over the screws on the bottom plate to hide the screws	Hand	Easy
25	Snap battery protective casing to the bottom plate	Hand	Easy

After Assembly

Disassembly Discussion

Disassembly of the Swingline Personal Electric Stapler was a relatively easy task only taking about 2 hours. All that was needed to disassemble was a small Philips head screw driver and a pair of wire cutters. Once the outside case was removed from the stapler, all of the inner workings could be seen inside. The stapler had many more moving parts and gears than initially anticipated. There were 5 gears used for gear reduction in between the motor and the swing arm that pushed the staples into the paper. There were only two difficulties during disassembly. The first was how to remove things that were attached with wires such as the motor, L.E.D., and the circuit board. We weren’t sure if we could cut the wires because we didn’t know if they had enough slack in them to splice back together during reassembly. We decided to cut the wires because we found a way to get enough slack in them to splice the wires back together. The second difficulty was removing the snap ring that held the spring under the staple tray. The first time it was removed it shot across the desk and was luckily found. On a scale of 1 to 10 with 10 being the hardest we would rate disassembly of the stapler as a 3.

Design Improvements

Overall the stapler was very well designed and served its purpose very well. However, there were a few improvements we thought that Swingline could implement that would make the stapler even better. The first improvement is that the stapler could be made more compact. If the gear ratio and motor were changed slightly this would free up some space within the main compartment. The staple tray could also be made shorter. Doing both of these things in the stapler would take about an inch off of the overall length and a half an inch off of the width. A smaller stapler would take up less room on a desk, something everyone would like. The second improvement is giving the stapler a built in rechargeable Ni-Mh battery. This would make the stapler more portable and would eliminate a cord from an already crowded desk. A rechargeable feature would also save the user from needing to go out and purchasing the currently required two batteries. Making the stapler more convenient would help the stapler sell better, therefore, making Swingline more money.

Analysis Discussion

An analysis in ergonomics, stress, and strength of the product and its components can be used to aid in the design and testing phases. An ergonomic analysis could be used to design a stapler that would better fit the space constraints of an office desk, to include a power cord long enough for the average user, and to design a staple tray that would allow easy reloading of staples. Stress and strength testing on the motor and gear box could be used to design the stapler that would be able to staple through a large amount of pages as well as ensure components stable enough so the product will still function even if dropped or struck. A basic engineering model that could be used would be a CAD drawing of the stapler and its components as well as an actual working model as the scale of the stapler is small enough to do so. For the stapler to function the components must fit together with very little error so it would be appropriate to use precise modeling.