Gate 2 Group 27 2012
Gate 2:Product Disection
In Gate 2, we will first review how our team completed Gate 1, with attention to what worked well, as well as what areas need to be improved upon. Next, we will be dissecting the product, and recording each step of the disassembly. We will then identify and analyze each subsystem, and how each subsystem is related to the others. We will then review each subsystems' design and placement, and consider how the GSEE factors were taken into consideration.
Preliminary Project Review
Cause for Corrective Action
Our work and management methods from Gate One could use a fair amount of revision, although we did perform well in certain areas. One thing that worked out well was that one person set up the wiki page so that everything was organized, and all titles and links were set up so that the other group members would only have to copy and paste text from a word document into their allocated sections. We will continue this for Gate two, by dissecting the drill as a group, and then allocating different parts of the analysis to each person. We will do this because in the first gate we executed fair allocation of different tasks to different people. This balanced the workload and made the project much more manageable for each person. Also, there was effective communication through email, as well as text messaging and phone calls. The group emails made sure that everyone had a record of what each person was responsible for, whereas text messages and phone calls were beneficial for more immediate communication, such as confirmation of meeting times. Also, some of us went to talk to the professors or the TAs, and it significantly improved the quality of our project. We will now plan to complete our project earlier so that the project can be reviewed more completely with the help of the professor or a TA. We will be continuing these beneficial processes for Gate Two.
Some of our work and management methods needed more revision and improvement in order to do better on Gate Two. The group’s time management needs the most improvement. In Gate One, we started very close to the deadline, and had to cram in order to get the project done, with no time for review, which was really needed. For Gate two, we immediately started on the project just after Gate One was due. We also developed a detailed timeline for the project, indicating when each section should be completed by, along with a final completion date that was two days before the final project was due. This is a significant improvement over the last project, because in Gate one, we handed in the project at the last minute, and noticed that there was need for revision. By finishing a few days in advance, we give ourselves time to revise our project before it is due, which improves each individual component as well as the fluidity of the report as a whole. Another aspect that needed improvement was that our group did not meet enough. For all future projects, we will try to meet at least every week, Wednesdays after class. Additional meetings will be held if necessary, as Gate two requires a lot of group collaboration. The increase in meeting frequency allows for each member to revise his section earlier, thus requiring less revision in the end. More frequent meetings also allow the group to increase its communication withing creating the project, allowing for more fluidity between sections. Additionally, some members of the group are less experienced with technical writing, and tend to use things such as vague terms rather than exact values, and other such mistakes. Because of this, the group will use the meetings to review everyone’s work, and to help each other improve their technical writing. With more frequent meetings, the more frequent review will help everyone improve at a faster rate, requiring less time for revision.
An important part of understanding the product dissection is understanding the difficulty involved with each step of the disassembly process. The following rating system and tool chart is meant to inform the average homeowner who would be looking to disassemble the drill by letting them know how hard each step is going to be and any special tools needed to complete the task.
Table 4.1: Difficulty Chart
|Easy||Tasks labeled as easy take from 10 seconds to a minute to complete. The action required is simple and easy for the average homeowner to understand and requires little physical force, something a child could perform. The process requires very little knowledge of machines, and only requires basic skills like turning a screwdriver or cutting a label.||Removing the housing screws|
|Medium||Tasks labeled as medium take from 1 to 5 minutes to complete. The action required is simple and easy for the average homeowner to understand but requires moderate physical force, approximate several pounds of force, and the use of one or more tools. There is still little knowledge of machines required, only turning or prying things open.||Removing the left hand thread star drive screw|
|Hard||Tasks labeled as hard take 5 to 10 minutes to complete. The action required is complex and hard for the average homeowner to understand. The action may require heavy physical force and the use of heavy tools or machinery. The force required may be significant enough to require a power-tool, or a tool capable of delivering a large force, such as a hammer. The knowledge required involves an understanding of simple machines and how they interact.||Removing the Chuck from the Clutch|
Chart 4.2 describes all of the tools necessary for dissection of the drill as well as how each tool is used.
Table 4.2: Tool Chart
|Flat Head Screwdriver||Screwdriver meant for screwing and unscrewing flathead screws. Also works as small pry-bar|
|Phillips Head Screwdriver||Screwdriver meant for screwing and unscrewing phillips head screws|
|Torx Screwdriver||Screwdriver meant for screwing and unscrewing star head screws|
|Allen Wrench Set||Set of allen wrenches meant for screwing and unscrewing allen head screws. Also good for removing E and C clips|
|Box-Cutter||Razor blade knife used for cutting various materials|
|Combination Pliers||Pliers used for removal of uncommon threaded components|
Table 4.3 shows a step by step process for how to disassemble the drill. Each step is numbered, and then gives a description of what to do. The difficulty is listed as describe in table 4.1. The tool required is then listed, followed by an image of the parts to be separated.
Table 4.3: Disassembly Process
|1||Remove the seven right sole housing screws with a phillips head screw driver||Easy||Phillips Head Screwdriver|
|2||Create cardboard layout of drill||Easy||N/A|
|3||Place corresponding screws in diagram||Easy||N/A|
|4||Remove metal crimp on battery port||Easy||Flat Head Screwdriver|
|5||Cut battery port sticker along shell seam||Easy||Box-Cutter|
|6||Remove plastic shell piece with flathead screwdriver||Easy||Flat Head Screwdriver|
|7||Take connected subsystems out of plastic shell using plyers||Easy||Combination Pliers|
|8||Remove motor connections with a flathead screwdriver||Easy||Flat Head Screwdriver|
|9||Remove motor/gear assembly form clutch/chuck assembly by rotating and then pulling
This step is more difficult because it requires the user to realize that the parts have a groove that cannot be seen, thus requiring the part to be rotated before removal. The force required to rotate and separate is minimal.
|10||Remove planetary gearbox form motor||Easy||N/A|
|11||Pull off motor washer||Easy||N/A|
|12||Remove motor mount screws with phillips head screwdriver||Easy||Phillips Head Screwdriver|
|13||Remove motor cover||Easy||Flat Head Screwdriver|
|14||Remove eight ball bearings from gearbox||Easy||N/A|
|15||Remove planetary gears||Easy||N/A|
|16||Remove secondary planetary gears from gearbox||Easy||N/A|
|17||Remove star drive bit in drill chuck (left hand thread)
This step is more difficult because the screw turns in a different direction compared to most screws. Without realizing this, the user could tighten the screw instead of loosen it, and thus make their task even more difficult. The screw also has a coating on it, making it resistant to turning. This requires several foot-pounds of torque to overcome.
|Medium||Star Head Screwdriver|
|18||Remove chuck from clutch with allen wrench. Put the allen wrench in the chuck and tighten it, with the short end in the chuck. Then secure the shaft to something secure, like a vice, and then hit the allen wrench with a hammer. This requires a strong hit with the hammer. This should be done so that the allen wrench rotates counter clockwise when looking at the end of the chuck.
This step is difficult because it isn't obvious how to remove the chuck, and it is unlikely that someone would figure this out without a solid understanding of machines. The force required is also too much to be done by hand, and thus requires a hammer and a vice.
|19||Pry off grip ring from chuck.
This step is more difficult because the screwdriver can slip and hit the users hand. It requires a few pounds of force to force the screwdriver into the gap and to control it to keep it from slipping and hitting the users hand.
|Medium||Flat Head Screwdriver|
|20||Remove c-clip from clutch head.
This step is more difficult because the clip rotates, thus one hand and tool must be used to secure it in place, whereas the other hand must pry off the clip. It is apparent how the clip is removed, however it is somewhat difficult to perform.
|Medium||Allen Wrench and Combination Pliers|
|21||Remove metal position ring||Easy||N/A|
|22||Take off position collar||Easy||N/A|
|23||Remove spring tensioner, spring and washer||Easy||N/A|
|24||Remove tape from trigger box||Easy||N/A|
|25||Remove tabs surrounding trigger box with small knife||Easy||Box-Cutter|
|26||Remove trigger spring||Easy||N/A|
(*N/A denotes step can be done by hand)
Intent For Disassembly
After the disassembly of the drill we determined that although most of the drill is intended for disassembly, there are a few components that are not meant to be taken apart. Due to the nature of the drill and the warranty informations provided in the box it can be assumed that most of the drill's subsystems need to be easily accesible both for the initial assembly and to perform maintenance on the drill. First, the plastic housing that contains the drill's major subsystems can easily be removed using a single common size phillips head screwdriver. This signals that the drill's subsystems are meant to be easily accesible. The next part of the drill that is meant to be taken apart is the drill's trigger system. It can be accessed be removing a series of plastic tabs from the trigger housing and allows direct access to the trigger circuitry. Again, the easy access can be explained by the need for drill maintenance. The clutch and chuck are easily removed from the the motor by unscrewing 4 screws. This along with the fact that the motor input wires are also easily detachable signals that the motor of the drill is meant to be easily replaced. The difficulty we had separating the the clutch from the chuck infers that the although they are meant to be disassembled, it may only be done by someone with the right tools and experience such as a company maintenance technician or a tool repair man. The clutch itself can be further disassembled be easily removing a few more screw which signals that the it is meant to be disassembled, either to add lubricant or replace cracked ball bearings. The chuck itself is not meant to be disassembled. It is sealed together by a factory made bond which can not be reversed. This is because of the design of the chuck, if taken apart the chuck does not easily go back together and if broken, requires a replacement chuck; it is essentially unfixable if broken.
Arrangement of Subsystems
The subsystems arrangement is quite complex as most of the subsystem connections are mechanical. The outer housing is held together using simple Philip head screws. The housing holds the trigger switch, electronic circuit, led, the direction changing switch, the motor. The battery latches on to the housing at the bottom. The torque controller is connected to the motor and is latched onto the housing to hold it into place. The chuck is connected to the torque connector.
The whole product is can be broke down into different subsystems as follows:
Battery (highlighted in green)
Switch and control unit (highlighted in orange)
The motor (highlighted in black)
The torque control unit (highlighted in red)
Chuck (highlighted in blue)
The subsystems are arranged very methodically and in a simple way, which makes understanding the function and the of transfer of energy of each component very easy and this intern makes the product repairability high.
The battery transfers energy to the motor by converting chemical energy to electrical energy. This energy then passes through the control system which houses the trigger and the direction knob. The signal form the user to the machine is processed through the trigger and direction switch which is connected to the electronic unit housed right adjacent to it and this unit transfers the energy to the motor for either clockwise or counterclockwise movement based on the user signal input. The motor then transfers the energy mechanically to the Torque control unit which houses a few axels that is connected to the torque control knob. This torque control know is connected to the chuck using a screw which is connected through the center of the chuck by a star screw bit and a grip ring connected to the torque control unit. The speed of the drill is changed by the user signal input through the torque control unit.
Each subsystem is well designed and is placed in the appropriate place in order of hierarchical transfer of energy and usability. Thought the torque control unit can be moved and added to the switch and control unit by manipulating the integrated circuit to process the user signal, it is better to the placed just as the product is designed, as this is the most comfortable for the user. Adding the torque control to the housing unit makes it hard to control the many switches on one single hand. But with control units distributed and placed in such a way that it can be controlled using two hands makes the product a much better and well designed one, and easily accepted by the consumers for its usability.
Connection of Subsystems
The drill contains several subsystems which work together, transmitting energy and signals across systems boundaries. Each system was designed to function with the adjacent system, and to work with its corresponding subsystems. The drill as a whole is a system designed to use signal flow to convert energy flow. The drill uses physical input from the user, and uses it to convert electrical energy into rotational mechanical energy. It does this through a series of subsystems, beginning at the battery, and then having electrical current flow through the trigger assembly, then to the LED and motor. The motor then converts this electrical energy into rotational mechanical energy. The clutch takes input flow from the user and regulates the amount of torque that the drill can exert. The regulated mechanical energy is then transferred to the chuck, which has jaws that grip and transfer rotational energy to the end bit.
Battery to Trigger Box
The battery is connected to the trigger box via a plug and wires. The plug is permanently housed inside the base of the drill, and is positioned so that the metal connections of the battery will contact the the wire terminals when the battery is placed in the drill. The two metal prongs of the plug fit into the metal-lined slots of the battery, forming a metal-to-metal physical contact. The metal prongs are each connected to a separate wire, which leads to connections on the circuit board of the trigger box. The battery supplies electrical energy, with an electric potential of 12 volts. The electrons flow through the wire connected to the negative polarity battery connection, then through the circuit and back to the battery again into the positive polarity terminal. The trigger box signals the amount of current to be drawn from the battery by limiting the amount of electricity that can flow through the circuit. The trigger box is connected to the battery so that it can limit the amount of electricity going through the rest of the circuit. Without this connection there would be no control over the energy flowing through the system. Economic considerations involved in the battery to trigger box connection are shown in the fact that these parts are not doing any heavy duty work, so material of choice is plastic as it minimises the total cost of production. Material choice can also be shown to be a societal consideration as plastic helps with safety since this part is the main handler of electricity and plastic is not a conductor of electricity.
Trigger Box to Motor
The physical connection between the motor and trigger box is composed of two wires, leading from the trigger box to the connection tabs on the back of the motor. The wires are soldered to the trigger box. The other end of the wire is soldered to a metal clip, which fits on the tab of the motor. The only mass flow is the flow of electrons which is negligible. Based on the signal input form the user onto the trigger box, the trigger box sends regulated amount of electricity which is the energy from the battery to the motor. And this connection exists because the motor needs a regulated amount of electrical energy so that the user may have the proper mechanical energy for the application. The connection of wires form the trigger box to the motor should be strong so that there is not disconnection of it, which would cause failure of the device. Thus the connections show have good grade wires and well soldered joints. Last but not least,the dynamo used in this drill is a low power type of motor bringing the cost down by not having to use a larger battery or one with higher voltage.
Motor to Clutch
Physically, the motor is connected to the clutch by a planetary gear box. The planetary gear box cosists of six gears, three of which are plastic and three of which are metal. The first set of gears are plastic because plastic is the cheaper material adn they do not need to withstand as much stress as the second set of gears. That being said, the second set of gears is metal because they need to withstand higher amounts of stress as the torque increases. There is also a drive gear in the center that spins the three gears around it. The clutch regulates the torque of the motor. The clutch is operated by turning the plastic piece to the setting of the desired torque. No mass is transfered between the clutch and the motor. The power from the motor is regulated by the clutch. The motor will only work if there is a signal received from the trigger, and the clutch needs to manually be turned inorder for it to use the desired amount torque. The reason the motor and clutch are connected is to ensure that the right amount of torque is used. Too much torque could damage what is being worked on and not enough torque prevents the task from being accomplished. It is very important that the gears in the Clutch stay in place and they require a material hard enough to hold them in place and able to prevent deformation so as to not displace the gears if under pressure. There are global, societal, economic, and environmental factors that influenced this connecton. The clutch is directly connected to the motor to ensure that the torque is regulated. Both parts are also composed of some plastic which helps lower the cost and weight of the product. The connection between the motor and the clutch influences the performance of the drill because the clutch regulates how much power is used. Different settings on the clutch equal different amounts of torque.
Clutch to Chuck
The clutch is attached to the chuck by a threaded screw, which required a lot of torque to unscrew. The Clutch takes mechanical rotational energy and transfers it directly to the Chuck. The clutch limits the amount of torque that can be put on the system by letting the system slip at a certain torque. The clutch can only be signaled by the operator; however, the chuck is signaled by the drill and the operator in a joint effort to tighten the chuck keys around the drill bit. The clutch and chuck are connected to ensure that the correct bit of torque is used during the task. Although, the external ends of the connection of the two parts is covered with plastic for the reasons of keeping the cost of production and weight of the product down the insides and the external most parts are metal because they will be the parts doing the heavy duty work of the whole system. Moreover, having metal to make the connection between the two parts increase the safety grading for hazardous situations where other materials such as plastic could easily break and send parts flying.