Group 20 - Black and Decker Jig Saw-Gate 4

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Management Overview

There have been no major problems or causes for corrective action. One small problem we have had is completing the work as a group instead of just finishing most of the work individually. I believe working as a group will help the quality of our work and make sure everyone is doing their equal part in this project. To solve this problem we scheduled an extra meeting this week on top of our regularly scheduled meeting. This extra meeting was very productive and we got a lot of work done, and it solved our issue of getting more work done as a group instead of working individually.


Reassembly Table

\'\'\'Ease of Reassembly Key\'\'\'

To quantify the difficulty of each reassembly step, several factors must be taken into consideration. These factors include:

  • Tools required to complete step
  • Time required to complete step
  • Complexity (number of part interactions)

Each step’s difficulty can be described numerically on a scale ranging from 1 to 5. A difficulty of 1 indicates that the three factors mentioned above are minimal. A difficulty of 5 indicates that the part to be reassembled required tools, was time consuming, had multiple interactions, or was some combination of these. Due to the nature of the various assemblies involved, there were instances where several parts had to be assembled simultaneously. In this case, each part will be assigned a difficulty as well as the overall difficulty of the assembly. The overall difficulty of the specific assembly will be noted with an asterisk.

\'\'\'Table 4-1: Reassembly Table\'\'\'
\'\'\'Step\'\'\' \'\'\'Parts\'\'\' \'\'\'Description\'\'\' \'\'\'Tool Used\'\'\' \'\'\'Ease of Reassembly\'\'\' \'\'\'Image\'\'\'
\'\'\'1\'\'\' Field assembly/Armature assembly Placed the armature assembly inside the field assembly so that the copper coils on the field assembly match the magnets on the armature assembly None 1
Figure 1: Field Assembly Click to View

\'\'\'2\'\'\' Thrust Plate Match up the three holes on the thrust plate with the two rods and shaft on the end of the armature assembly and slide the thrust plate on the end None 1
Figure 2: Thrust Plate Click to View

\'\'\'3\'\'\' Counterweight Fit the counterweight over top of the thrust plate matching up the same two rods and shaft on the armature assembly with the square end of the counterweight on the bottom None 1
Figure 3: Counterweight Click to View

\'\'\'4\'\'\' Gear Attach the rod on the gear to the armature assembly through the counterweight and thrust plate so that the teeth on the gear and the teeth on the shaft of the armature assembly match up None 1
Figure 4: Gear Click to View

\'\'\'5\'\'\' All above parts/ Plastic housing Placed the field and armature assemblies, thrust plate, counterweight and gear all connected, inside of the plastic housing so the gear is at the front of the housing None 1 4*
Figure 5: Assembly Click to View

\'\'\'6\'\'\' Trigger Assembly Fixed the trigger assembly to the handle on the top of the plastic housing so the only thing sticking out of the housing was the trigger None 2
Figure 6: Trigger Assembly Click to View

\'\'\'7\'\'\' Shaft Assembly Placed the shaft assembly on the end of the gear inside the plastic housing lining up the rod on the gear and the center oval hole of the shaft assembly None 2
Figure 7: Shaft Assembly Click to View
\'\'\'8\'\'\' Brush Boxes Plugged in brush boxes by attaching the wires on the brush boxes and the plugs on the field assembly Tweezers were used to plug the two brush boxes into the bottom of the field assembly where they were difficult to reach 3
Figure 8: Brush Boxes Click to View
\'\'\'9\'\'\' Blade Guard Attached the blade guard to the housing by sliding it into the slot on the front of the housing None 1
Figure 9: Blade Guard Click to View

\'\'\'10\'\'\' Actuator and gear assembly Placed the actuator and gear assembly in the bottom of the plastic housing so the gear assembly is sticking out of the housing and the teeth on the actuator line up with the teeth on the inside of the gear assembly None 2
Figure 10: Blade guardClick to View

\'\'\'11\'\'\' Screw Put all seven screws in the holes of the plastic housing and screw them in to attach both outer housing pieces together Philips head Screwdriver used to screw in and tighten the screws 3
Figure 11: Screw Click to View
\'\'\'12\'\'\' Shoe Assembly Placed the shoe assembly on the bottom of the housing with the big hole of the shoe assembly facing the front of the saw where the blade goes None 2
Figure 12: Shoe Assembly Click to View
\'\'\'13\'\'\' Blade Support Slid the blade support through the shoe assembly placing it on the bottom of the shoe assembly with the spinning round pieces facing the front for the blade to slide through it and the holes on the blade support, shoe assembly, housing and actuator line up None 2
Figure 13: Blade support Click to View

\'\'\'14\'\'\' Locking Screw Put the locking screw through the blade support and shoe assembly into actuator inside the housing of the saw None 1
Figure 14: Locking Screw Click to View

\'\'\'15\'\'\' Actuator, gear assembly locking screw Turn the gear assembly on the outside of the housing which turns the actuator on the inside to tighten the locking screw and secure the shoe assembly and blade support to the housing None 2
Figure 15: Actuator Click to View


\'\'\'Originally Disassembled\'\'\'

The original assembly process in the factory was much the same as when the team reassembled the saw. The parts were arranged in the same linear fashion. The differences however were that the team had to manually place all the parts in, in a relatively in efficient manner, while the original process was in an assembly line style with efficient and accurate placement of parts. They utilized robotic machinery which is necessary for the company to mass produce the saw.

\'\'\'Comparison: Disassembly to the Reassembly\'\'\'

The reassembly of the jigsaw is thought to be assembled in the same manor that it would be in if the saw was originally purchased. This can only be assumed because schematics available do not show wire layout. The reassembly is thought to be an improvement on the original assembly because the housing does not need to be forced close. The differences between the reassembly and the disassembly were cascading from the brush boxes. The pieces inside the brush boxes were sideways that shortened the wire that resulted in the motor having to be rotated. After the brush boxes were readjusted, the housing closed more easily which suggest that the compensates are now organized in the proper positions.

System Redesigns

The jigsaw is limited in its abilities to negotiate curves. The user would have to rotate the entire saw about a fragile axis; the oscillating blade. If attempted incorrectly or haphazardly, the blade could fail. Since not every cut is straight, a saw should be able to easily maneuver a curve. This can be achieved by rotating the blade, about the vertical axis, with respect to the user’s grip. The process to change the original jigsaw design to that of a rotating blade can be done by placing a rotating knob above the blade and flat counter weight with a rounded one such that the entire unit is free to turn. Having this redesign would increase performance and make the saw more versatile than that of similar saws. This redesign is a societal factor because it widens the range of perspective users by enhancing the functionality.

Figure 16: Safety Trigger, click to view

Saws in general are dangerous. This jigsaw has the capacity to be very dangerous. The saw has a very intuitive gripping system. It is obvious where and how the saw should be held. The problem that arises from this is that the triggering mechanism could be engaged inevitably in transit just by being held properly. The triggering mechanism is designed in a very agronomical manor but there should be safety compote to this. We propose that there is a thumb activated button that would be a prerequisite to pulling the trigger. Once the switch is pushed with the thumb the trigger would simultaneously be pulled by the same hand. After thee saw is started then the switch may be released. A switch on this nature would make the saw safely manageable while plugged in.

Jigsaws are used to cut a variety of materials including metal, wood and plastic. Each of these materials responds differently to the saw. For this reason, Black and Decker offers different blades which are optimized for cutting a specific material. The saw does not, however, allow the user to control the speed at which the blade oscillates. Therefore, the third design revision that we propose is to include a speed controller with the saw. This would consist of a potentiometer located on the side of the saw, allowing the user to select the desired speed. By controlling the speed, it would be possible to make more precise cuts, especially around curves. Other models include a speed controller right in the trigger; however, this would require the user to maintain constant pressure on the trigger which may become tiring after a while. The addition of a speed controller would affect the “control” subsystem. It would use an extra user input to modify the output of the motor.