Group 7 - Black & Decker Jigsaw Gate 2
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Preliminary Project Review
Work Proposal Analysis
The work proposal was a good reference for how we operated as a group dissecting the Black and Decker jigsaw. Our tools list was very comprehensive, but after dissection we only used a fraction of the tools listed. We did not have any use for a flat head screw driver, pliers, point chisel, or a hammer. The product was very consumer friendly in terms of disassembly. After we analyzed the graded results of gate 1, our group realized that some of our strengths and weaknesses were true. As a group our revision skills were poor and that issue needs to be focused on in the following gate assignments. Our group has become closer and we are not afraid to call each other to meet up for an extra meeting which is going to beneficial to the quality of our work.
Management Proposal Analysis
So far, our management proposal is working out quite well. We only had to make a couple adjustments to the original proposal because we realized that we anticipated our abilities unrealistically. Our Gantt chart is right on schedule except for our preliminary project review. On our Gantt chart we were supposed to complete the preliminary project review prior to starting our dissection but this proved to be an illogical way of organizing gate 2. To adequately complete the preliminary project review, we would need to have almost completed gate 2 so that we could analyze what worked and what didn’t. Other than that we are progressing as projected with our dissection and report expected to be completed by the 24th of October. After that we will upload it to the wiki.
Our weekly meeting idea has been a great benefit for the productivity of our group. We followed this part of the management proposal almost verbatim. Every week we have met at 3:30 pm on Thursdays to recap how the current element of the project is progressing and if we needed more meetings we scheduled them. We have had perfect attendance at these meetings and they all were surprisingly productive.
The area of our management proposal that needed the most revising from gate 1 to gate 2 was the job assignments and descriptions. Upon receiving our graded gate 1 we realized that some of our jobs needed to be reassigned. We didn’t reassign our jobs because of anyone’s performance, just because we realized it was unrealistic to expect so much from one person. The most noticeable mistake on our gate 1 was grammar and writing mistakes. To combat that, the job of editor is now added to everyone’s task. This goes hand in hand with the idea that 5 heads are better than 1. A updated list of everyone’s jobs can be found in Table 1-2 in our job requirements section.
|Product Dissection By Steps|
|Step||Description||Tool Required||Difficulty (1-10)||Photograph of Parts Involved|
|1||Using a number two Phillips-head screwdriver, the seven screws that attached the two sides of the body together were removed. This step was simple, but after this was done we realized the base plate would have to be removed in order to separate the two sides of the body. The removal of the base plate should have occurred prior to the removal of the screws, but this oversight did not damage our product, or hinder our ability to continue with the dissection.||#2 Philips head screwdriver, hands||2|
|2||Naturally the base plate was removed next. This was done by loosening the exterior gear, normally used to adjust the cutting angle, enough to remove the base plate completely. The two pieces that make up the base plate came apart naturally, and required no effort.||hands||1|
|3||The clear plastic blade guard located on the front of the saw simply slid out of the groove on the interior of the jigsaw. When the two body pieces are connected the blade guard is quite sturdy and stable, however when one side of the saw is removed the guard can be removed simply by pulling it out.||hands||1|
|4||The power cord popped out of its enclosure similarly to the way the blade guard was removed, therefore this step was very easy.||hands||1|
|5||The trigger assembly was held in place by vertical posts at the corners of the assembly, so the removal was done by lifting it vertically out of its place. This procedure was just as straightforward as the previous two so consequently there were no problems.||hands||1|
|6||The removal of the blade assembly was the first real challenge we faced when dissecting the saw. This was done by lifting the motor slightly to gain access, and then maneuvering the blade assembly perpendicularly to the body. We chose to do this before the removal of the motor due to space constraints, and it turned out to be the intelligent choice.||hands||7|
|7||Since the blade assembly had been removed in the previous step, the motor assembly was removed with no trouble. This was done by lifting it, as well as the transmission, out of the body. We figured the transmission and motor would be easier to disassemble out of the saw, where there was more access, so that is what we did.||hands||3|
|8||The motor was detached from the gears that powered the movement of the blade assembly by sliding the gears off of the drive shaft.||hands||1|
|9||The grip located on the handle of the saw was attached similarly to the blade guard, and was easy to remove.||hands||1|
|10||The motor was dissected further by separating the inside and outside of its assembly. The inside which is attached to the drive shaft was not attached to the outside of the motor in any physical manner, so it was removed by sliding it laterally.||hands||2|
- This table maps out the dissection of the Black & Decker Jigsaw by our group. Explanations of our difficulty scale and our intended disassembly opinion can be found below.
- The number scale shown after the third bullet on each step displays the difficulty of the particular process. This scale was designed to be simple, understandable, and easily comparable to the other steps in the dissection. In this scale a (1/10) is a process which takes little to no effort at all, and a (10/10) is one which is very intricate and very difficult. A (1/10) involves no tools and little force from the hands. Sliding the grip out of the Jigsaw was a (1/10) because it took little time and required no effort with the component simply sliding out of its place. A difficulty of (10/10) is something that required outside tools and multiple hands. Multiple opinions are required to successfully disassemble a (10/10) and special care has to be taken to avoid damaging ourselves or the product. Our difficulty scale is based off of the opinion of someone with prior experience with power tools. Our technical expert had prior work experience as a tools specialist at Sears and with his knowledge aided us in taking apart the product and deciding on a fair difficulty scale. It is fair to make our scale based off the opinion of an experienced worker because that type of person is intended to take the product apart. The average person who uses the Jigsaw isn’t expected to have to take the part apart and if something breaks internally, they would probably return it to the place of sale. With this in mind, the only people who would take the Jigsaw apart would be experienced and our scale is written towards them.
- Outer Shell Assembly
- This part of the jigsaw was most certainly meant to be disassembled as it was very easy, and straightforward to do so.
- Base Plate
- This part was also meant to be disassembled because with it in place there is no access to the internals of the saw.
- Blade Guard
- This component of the saw is meant to be removed from the body, in order to give access to the blade assembly.
- Power Cord Assembly
- The power cord was also designed to be removed in order to give access to the internals of the saw.
- Trigger Assembly
- This part was intended to be removed in the case repairs were needed on either the trigger or the wiring.
- Blade Assembly
- While the difficulty of this step would initially suggest it was not meant to be removed, but the stress this piece endures makes it vulnerable to problems, so it needs to be accessible if this becomes the case.
- Motor Assembly
- This part while easy to remove could have been as difficult as the previous step; it just happened that we removed the blade assembly first. That being the case, it was meant to be removed with the same reason the blade assembly was meant to be removed.
- The separation of the transmission and the motor was meant to be disassembled. This is known simply because of the ease of disassembly.
- While this part does not have any importance to the functionality of the saw, it was designed to be removed in the case a new one was to be installed.
- This part was initially meant to be disassembled as seen in step seven, and then meant to be further disassembled for the same reason, which was to gain access in the case of problems and repair.
- Overall Intended Disassembly
- When we stated in the above individual intended disassembly analysis whether the component was intended for disassembly we meant if it was intended for a certain type of person. Black & Decker wouldn’t necessarily have intended the Jigsaw to be disassembled by the average user. If the average user needed something fixed on the Jigsaw they would probably return it to the store they bought it from and then from there it would be sent to a warranty center. Whether or not a component was intended to be disassembled was directed towards whether or not a warranty technician. Granted, the Jigsaw can be taken apart by most people regardless of their expertise but the product was intended to be disassembled by qualified technicians if something needs to be fixed.
|Part #||Part Name||Part Function|
|1||Armature Assembly||The assembly of the motor and it's components|
|2||Field Assembly||Provides the power to the motor, allowing it to rotate|
|3||Switch Assembly||The control switch for the oscilating blade|
|4||Clamshell Set||Houses the motor, wiring, and most of the components in the jigsaw|
|5||Brush and Spring||Transmits power to the field assembly|
|6||Brush Box||Holds the brush and spring|
|7||Thrust Plate||A major component of the motor assembly|
|8||Counterweight||Provides a counterweight allowing the thrust plate to hold the motor parts together|
|9||Gear Assembly||This gear assembly is used to aid the rotor in moving the saw blade|
|10||Roller||A major component of the motor assembly|
|11||Actuator||A locking gear mechanism|
|12||Gear Assembly||This gear assembly is used to tighten the locking screw|
|13||Shoe Assembly||Gives the user a plate to manipulate for more control of the product|
|14||Blade Support||A support for the blade assembly|
|15||Locking Screw||A locking mechanism used to hold the shoe assemly in place|
|16||Guard||A safety mechanism providing a guard for the user from the dangerous blade|
|17||Button Lock||A mechanism that allows the user to lock on the speed of the blade|
|18||Elbow||A support for the shoe plate|
|20||Shaft Assembly||An assembly attached to the motor to allow for movement|
|21||Blade Clamp||Holds the blade in place|
|22||Screw||This screw fastens the shaft assembly|
|23||Bearing Sleeve||Cylindrical Support|
|24||Cord Protector||A safety mechanism providign a guard from electrical leakage|
|25||Cord, 8 ft.,18-2||The cable that supplies the electrical energy from the outlet to the product|
|26||Lead Assembly||A component of the power transmitter|
|27||Lead Wire Assembly||A series of wires connecting to the field assembly|
|28||Screw||This screw fastens the switch component|
|29||Clamp Cord||A component of the switch|
|30||Name Plate||Displays the name of the product and the company that created it|
|31||Screw||This screw hold the two pieces of the orange casing together|
|33||Lead||Wiring components for the motor|
|34||Lead||Wiring components for the motor|
|44||Gel Grip||A comfortable and stable grip allowing the user extended control of the product|
|45||Baseplate||A component used to hold the gel grip in place|
|861||Kit Box||The box that the jigsaw is strored in (Not included in our project)|
Product Dissection Assessment Questions
Document the connection of subsystems
- The Black and Decker Jigsaw is a power tool whose main function is to convert electrical input to mechanical output in the blade motion. This is done by a series of subsystems including the motor, transmission, and the blade assembly. These subsystems are interconnected through various ways which allows for the transfer of energy, signals, and mass between the systems. When all the systems act in synergy, the overall process of moving the blade up and down at high oscillations is achieved.
Ways of Connections
- The subsystems are connected physically by a series of wiring and through physical contact with each other. The wiring connects the trigger to the power supply which is connected to the motor through different wires. From the motor the systems are connected solely by physical touching connections. The motor turns gears which physically contacts the transmission system through a system of gears. The transmission system acts physically on the blade assembly through the means of a Scotch Yoke. A Scotch Yoke is a way to convert rotational movement to linear movement. A animation of how this works is found in figure 2-2. The blade is connected by a spring force lever.
- The primary signals used in the Black & Decker Jigsaw are sent electronically between the systems. When the user activates the trigger an electric signal is sent activating the motor and allowing power to flow in from the power cord. That is really the only signal between the sub-systems and it involves user interaction. Once the motor has power and is working, there are no signals interacting between the following systems.
- Originally looking at the interactions between the sub-systems there didn’t seem to be any mass transfer. Upon closer investigation it became apparent that there was mass flow in the Jigsaw as a whole. Located in the motor system is a small fan which pushes air through the internal system of the Jigsaw. Though a relatively small task, this interaction is vitally important. Whenever there are moving parts there is friction. This friction acts as heat and to keep the Jigsaw from overheating the fan needs to circulate fresh air through the Jigsaw. Also, whenever there is current running through wires there is resistance acting on that wire. This resistance also causes heat which needs to be dissipated and cooled off using the fans airflow.
- The sub-systems all work together to transfer energy to achieve the end task of moving the blade up and down. Originally the energy is electrical when it enters the Jigsaw from the outlet. This is then transformed into rotational energy by the motor system. The motor system transfers this rational energy to the transmission system using a series of gears. The transmission system is connected to the blade assembly through a Scotch Yoke which transfers the rotational energy into linear energy represented by the oscillating blade system.
Reason For Connections
- The subsystems in the jigsaw are connected because each system shares the task of getting the job done. Together they split the task and lessen the work load on a specific system. The connections of the systems results in a more efficient product and the ability to do more in less time. For example the motor works with the transmission to turn electricity into a rotational energy with an rpm that the Scotch Yoke can handle. These connections allows for each system to accomplish a relatively simple task which when put together, accomplish the Jigsaws goal of cutting. Though the Jigsaw doesn’t work when one system fails, breaking the product up into smaller systems aids in the ease of replacement. If there should be a failure in one system the whole device does not have to be replaced, just the system that malfunctioned. The Scotch Yoke was used because it is one of the cheapest and fail proof ways of converting energy. Only two parts interacting translates the energy which is easy and quick.
Ways the Connections Occur
- The subsystems are connected through electrical wires and through a variety of gears. These wires are soldered in place to keep them from getting loosened by the violent shaking that occurs when the Jigsaw is cutting something. Where the electrical current from the outlet enters the Jigsaw there is a highly insulated wire to avoid shock or sparks. Though our trigger assembly was broken, the wires seem to be clamped or soldered into place inside the mechanism. As stated earlier, the motor is connected to the transmission system though a series of gears which fit together to adjust the revolutions per minute of the system. Also stated earlier, the transmission is connected to the blade assembly through a Scotch Yoke. This Yoke converts the rotational energy of the gears into linear energy in the blade oscillations.
Global, societal, economic, and environmental concerns influencing connections
- Of the afore mentioned concerns, economic concerns played the biggest role in the sub-system connections. When a product gets created price is a major limiting condition. If the product costs too much to make, a company will not produce it; and if it costs too much to buy, consumers will not buy it. The Black & Decker Jigsaw was produced with the intention of having a low price for consumers. To achieve this low price, the intersystem connections had to be simple and low key. The Jigsaw achieved that by having the only connections between the systems be through direct wires or through direct contact. This means no extra money had to be spent of wireless signals or indications lights. Environment roles in connection play into the economic roles. Since the connections between the systems are relatively simple, a single system can be replaced instead of having to replace the whole Jigsaw. Since the Jigsaw is cheap as a whole product most consumers will just buy another if something breaks, but that isn’t very environmentally friendly. For instance, having the wires clamped into the trigger assembly rather than soldered shows that this mechanism could be replaced relatively easily in comparison to soldered wires. The sub-system connections don’t really affect the societal concerns except through price. Keeping the Jigsaw at a lower price and easier to use opens power tools up to new groups of people. Primarily power tools were restricted to people who wanted to fix stuff themselves or people who fix things for a living. With the low price, the Jigsaw opened home improvement up anyone who could afford it. Since it is easy to use, the Jigsaw widened the gap and allowed more people to be able to work do home improvement themselves. Like all powertools, the Jigsaw has some safety concerns. There is only a small blade guard that protects the users hand from the blade and if the user does cut his hand, the blade will only stop when the trigger is released. The most obvious connection that affects global concerns is in the wiring. The outlet plug is standard in most American households but as soon as the Jigsaw crosses the border into another country it might need an outlet adapter. Just having an adapter still might not work because some countries use different voltages than America. The Jigsaw might be able to stand up to the change but it is just as conceivable that the wiring might fry and cease to work. To be more specific the Jigsaw will be able to be used oversees if it has the proper adapter and is using the standard U.S. current.
Performance influence on connection type
- The connections are made through wiring and gears. Performance would have been taken into account with these connections in the material that the gears were made out of. The gears are made out of plastic which didn’t strike us as a premium material. The plastic gears are beneficial for performance because they are lighter but they aren’t as sturdy as their metal counterparts. Since the foundation of the product is made up of lower-grade materials the Jigsaw as a whole reflects this with its cheaper price and shorter lifespan. A major aspect of connections type that affects performance is how the motor, transmission and blade assembly are all connected completely. If the motor turns, the blade moves and vice versa, but if the blade gets locked up, it doesn’t move therefore the motor doesn’t turn. This isn’t good because the motor automatically draws more current from the wires to increase the torque. With this increased current, the resistance in the wires increase, increasing the heat generated by the wires. This would have little effect on the sub-systems except that the fan is not turning because the engine is locked up. Having all the systems connected in such a rigid fashion and having the fan included in that connection can negatively affect the performance if the blade locks up.
Arrangement of Subsystems
- The sub-systems are arranged in a logical order in the Jigsaw. To show the arrangement of the sub-systems we just followed the energy flow through the Jigsaw. First the electrical energy that goes into the motor system is converted to mechanical energy and then travels into the transmission system. The mechanical energy is now converted again to a different form of mechanical energy and then goes into the blade assembly. From this and our dissection, the arrangement of the sub-systems is motor system then transmission system then blade assembly. To adequately demonstrate the layout of our sub-systems and their functions look at Figures 2-3, 2-4, 2-5, and 2-6 which can be found lower on this page. Each figure give the input and output of the energy involved in the system.
Reason for subsystem arrangement
- There is a very specific reason for each subsystem to be placed in the order that they are in, and that reason is that the system would not function, or not function as efficiently, if the subsystems were placed in any other fashion. The way that the electrical energy is converted into kinetic energy is very specific as it needs to go through the motor, through the transmission, and then through the blade assembly in order for the product to be functional. Without this order the function of the product would be jeopardized.
Subsystems which cannot be adjacent
- There are many combination's of subsystems that cannot be adjacent, as the only order that the system works in is if the motor comes before the transmission, and the blade assembly comes after. If the order of the subsystems were switched such as if the motor and the blade assembly were adjacent, the product simply would not function. It isn’t possible to connect electrical wires to the blade assembly and expect it to oscillate. The electrical energy needs to go through a specific process to be converted into mechanical energy and this can’t be done out of order.
|Sub-Function, Secondary Functions|
|Sub-Function, Secondary Functions|
|Sub-Function, Secondary Functions|
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"Black and Decker JS510G Parts List and Diagram - Type 1." EReplacementParts.com : Power Tool Parts and Tool Repair. Web. 26 Oct. 2010. <http://www.ereplacementparts.com/black-and-decker-js510g-type-jigsaw-parts-c-4167_4262_4269.html>.