Group 16 - DeWalt 4 1/2 in Angle Grinder Gate 4

Revision as of 18:03, 28 November 2012

Introduction

In this phase of the project our group completed our reverse engineering process by reassembling our product and gathering information from the reassembly process. In Project Management our group describes how we have worked through the challenge presented in Gate 3, as well as discussing why our current group structure has prevented further challenges from arising. Once this had been completed our group did the reassembly and created a step-by-step process so that our product could be reassembled without significant prior knowledge of the product. After this our group analyzed the helical bevel gear, one of the primary mechanisms in our product, and considered both its purpose and the equations governing its motion. Our group then recommended three system level design revisions that would improve the overall functionality of the product. All of these can be found under Product Archaeology. Lastly, in Conclusions our group considered all of the information we have gathered over the course of this project in order to make detailed conclusions about the original design of our product.

Project Management

As described in Gate 3, our group's last remaining issue is the attendance of one group member. This member did not attend for the meeting where we divided the assignments for this gate, thereby preventing him from taking on or contributing to any of the gate components. Several times now he has been told when and where the group will be meeting, but he has failed to attend or give a valid reason for missing. Our group divided the work in such a way that we will still complete this gate efficiently, even without this member's help. For Gate 3 this method proved workable, as the workload was not too severe for four people to complete. We therefore have avoided assigning this member important tasks (or any tasks in this case) and will be mitigating the problem through the same means used before. This solution has been an effective method of preserving the overall project quality without severely impacting any of the other members.

Besides this attendance problem, our group has no remaining internal problems. All of the solutions provided since Gate 2 (and listed below) have been effective:

• Not knowing how to use the wiki: Our group's functional knowledge of the wiki has been enough to allow effective technical communication because of the previous steps taken to learn how the wiki works.
• No out of class meetings: While our group does not have regularly scheduled meeting time, we have done well at getting most of the group together when the Project Manager gives a couple days' notice. This has allowed our group to adapt and function in a way that would not be possible if all communication was via email.
• An unevenly distributed workload: With the exception of the aforementioned member, the work has been divided as fairly as possible, with considerations for the amount of work involved in any part taken into consideration. For this gate, the instructor provided a breakdown of the point allotments for each section, which aided our group in assessing how much time each part would entail. We thus were able to come up with a fair distribution of work.

Product Archaeology

Product Reassembly

Product Reassembly

Difficulty Scale

In order to describe the difficulty of each step during the reassembly process our group will use the classifications outlined in Table 1. These classifications don't just consider the time involved in any given step, but also take into account the tools required, accessibility of the parts, required force, and overall intuitiveness. In addition, some of the steps may have required creative approaches as all of the factory tools and machines would not have been accessible when reassembling by hand. Any of these creative approaches are listed under the Challenges section, as they would be necessary for an average user to reassemble the product while only using household tools.

Reassembly Instructions

The information in Table 2, in combination with the Challenges section, is intended to give a set of full instructions so that a user not familiar with the product could easily reassemble it. In addition, the original factory methods for assembly are described, as well as comparisons to the disassembly process. These are intended to highlight the ideal methods for reassembly and point out key deviations from the disassembly process for individuals who have greater resources or completed the disassembly themselves respectively. Lastly, pictures of the product at the end of each step are provided so the user can check their work and make sure they have connected the right parts.

• Before beginning reassembly, the following tools will be needed
  • Phillips-head Screwdriver
  • Torx Drivers:T-5, T-10, T-15
  • Needle-nose Pliers
  • 3/8" Crescent Wrench
  • 10 mm Socket
  • Hammer

Table 2:Instructions for Reassembly

Step	Tools	Description	Difficulty	Original Assembly	Disassembly Comparison	Image
1	None	Slide the electromagnet into the main housing with the wires towards the bottom. Each wire must go through one of the holes at the bottom of the housing along with the wire nearest to it. The electromagnet will be a very tight fit, and will require a lot of pressure.	Challenging	A machine would have fit through the holes and pulled the wires out while a press simultaneously forced the magnet into the housing.	This will be the reverse of the disassembly process, however feeding the wires through the two holes will be a challenge that was not present before. This will significantly increase the difficulty, because the wires must be controlled while the magnet is being pressed in.
2	Needle Nose Pliers	Use the needle nose pliers to take the shorter of the two wires from each electromagnet side and connect them to the lead above the brush spring.	Easy	This step would have been done by hand, the same way in the factory.	This is the reverse of disassembly. No significant deviations.
3	10 mm Socket, Hammer	Take the bottom shaft bearing (it has a slightly larger interior hole than the top shaft bearing) and replace the rubber coating. Then force the bearing onto the metal nub at the bottom of the drive shaft. It must be forced all the way down (not just to the nub). To do this, place the bearing over the nub, and then place the socket on the bearing, with the drive shaft firmly secured. Then use the hammer to tap the socket until the bearing is pressed onto the nub.	Challenging	This part was shrink fitted on in the factory	This is the reverse of disassembly but will be more difficult because a instead of just forcing the bearing off, it must be controlled and the drive shaft must be stabilized as it is forced back down.
4	T-5 Torx Driver, Needle Nose Pliers	Realign the plastic brush support over its hole, and screw the Torx screw in to secure it. Now pull the spring back and place it on the plastic ledge of the housing. Then insert the brush into its holder, sliding the wire through its hole. Use needle nosed pliers to connect the lead to the nearest metal slot. Repeat for other side.	Moderate	A machine would have moved the pre-assembled brush into position and then screwed it down. The leads would then be connected by hand at a later point. (All wires would be connected at once)	This is the reverse of disassembly. No significant deviations
5	10 mm Socket, Hammer, 3/8" Crescent Wrench	Slide the fan baffle on the top of the drive shaft (concave side down). Then align the bearing and use the method described in Step 3 to force it on. Next, push the pinion onto the shaft. It should be tight, but can be forced by hand. Finally, screw the nut on with the 3/8" crescent wrench.	Challenging	All of this assembly would have been done by machine in a factory. It would have followed the same steps except that the bearing would have been shrink fitted on.	This is the reverse of disassembly. The only notable difference is for replacing the bearing, which is already described in Step 3.
6	None	Slide the narrow end of the switch bar through the rectangular hole at the base of the housing. Once the narrow end reaches the switch hole, press the plastic switch against the switch bar in order to clip it back on.	Easy	A machine would have followed the same process in order to slide the bar in and then quickly press the plastic switch on.	This is the reverse of disassembly. No significant deviations
7	T-5 Torx Driver	Slide the black retaining bracket into the housing and then screw it down with the four T-5 screws. Place the drive shaft assembly inside the bracket (bottom first) and slide it in until the fan baffle is flush with the top of the housing.	Easy	A machine would have followed the same process to assembly the part in a factory.	This is the reverse of disassembly. No significant deviations.
8	T-10 Torx Driver	Place the gearbox on top of the housing. It will not fit unless the pinion is turned to align with the helical gear. Then screw the four T-10 screws down to secure the gearbox.	Moderate	This part would have been attached and secured using a machine in a factory. Because of higher control of the part, the machine would have been set to make sure the helical gear aligned with the pinion the first time.	This is the reverse of disassembly. No significant deviations.
9	Phillips-head Screwdriver	Place the gear cover on the back of the gearbox and secure it by screwing the four screws in.	Easy	A machine would have done this step in factory.	This is the reverse of disassembly. No significant deviations.
10	Needle Nose Pliers, Phillips-head Screwdriver	Place the half of the lower housing with five holes on the bottom of the main housing. It has a groove that will allow the switch bar to slide in. Now place the electronic switch in the open space (button towards the bar). Then take the long wires from the electromagnet and connect them to the leads at the bottom of the switch with needle nose pliers. Then take the two wires from the power cord and connect them to their respective sides of the switch (black to black, white to white). Lastly, screw down the two screws on the electronic switch to secure all of the wires in place.	Moderate	All of this would have been done by hand in a factory. These steps would be performed at the same time that the leads from the brushes were connected.	This is the reverse of disassembly. No significant deviations.
11	T-10 Torx Driver	Place the second half of the lower housing on top of the first half, and secure the five screws that hold them together.	Easy	A machine would have performed this step in a factory.	This is the reverse of disassembly. No significant deviations.
12	Phillips-head Screwdriver	Place the guard clamp around the forward ring of the gearbox, and bring the two ends of the clamp together. Next, push a screw through the non-threaded end of the clamp, and then use the screwdriver to screw it into the other end. The two ends must be held together close to the connection while the screw is aligned and screwed in, which can be difficult for only one person.	Challenging	In a factory a machine could easily perform the steps described above because it is not limited to just two "hands". It could therefore hold the guard together and screw the screw in with ease.	This is the reverse of disassembly, however it is more challenging because the screw and two ends of the guard clamp must all be aligned at once, while the screw is simultaneously screwed in. This is much more difficult than just unscrewing the screw as was done during disassembly.
13	None	Slide the backing flange over the small shaft coming out of the gearbox. Next, slide the clamp nut partway on, and then screw it on until it is tight.	Easy	This step would have been done by a machine in a factory. It would have used the same steps listed.	This is the reverse of disassembly. No significant deviations.

Challenges

Mechanisms

Conclusions

Design Revisions

Changeable Gear Box

Adjustable Handle

Attachment Connections

Links to Other Gates

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