Gate 3 Group 27 2012
In Gate 3, we used the information gathered from Gate 2's dissection to analyze the drill. We did an analysis of several main components, taking into consideration its shape, tool and manufacturing marks, material, function, location and interaction with other components. We also made 3D models of the components using AutoDesk Inventor Professional 2013. The parts were then assembled in Inventor. For one of the components, we did an example of what how an engineering analysis might have been applied to one of the components. Using the information gathered from the analysis, we then suggested several design revisions for the drill at the component level. These design revisions are based on considerations of the GSEE factors.
Cause for Corrective Action
For Gate 2, the revisions that we followed significantly improved the project. Meeting times were established in advance, and deadlines were set before the project was supposed to be submitted. This gave us time for review. One thing that was working well was having one person set up the wiki page, outlining the page setup. With one person doing this, it helps eliminate redundancy and keeps everything in a logical order. This also helps those other group members who have less experience with editing a wiki, as they only need to copy and paste their part of the project. Another effective practice was the use of multiple means of communication. Email was used to send detailed messages with allocated tasks, and text and phone calls were used for more immediate communication, usually relevant to meeting reminders. As we did in Gate 1, we visited the professor during office hours, which helped with explaining which parts needed more detail, as well as reorganizing parts of the wiki so that it was more logically ordered in a manner that represented a technical report. We attempted to continue these practices throughout Gate two to continue to improve the project.
Some problems that arose during the completion of Gate 2 was that although we had planned meetings in advance, one or more group members would cancel at the last minute. Also, other members that did show up sometimes came with their work incomplete or greatly lacking in substance and detail. This was by far the most significant problem the group experienced, as it hindered the progress of the entire sequence of the plan. Some parts of the project must be completed before another can, so when a group member showed up without his part, the project could not continue. This also left no time for the revision of that part, or the other following parts as everything was being completed too close to the deadline. To correct this problem, group members are encouraged to make a stronger commitment to the group, and to have better time management. In previous works, if a member didn't have a part of the project done, and that part was necessary for another part, it would impede the whole project. To fix this, any part of the project that had dependent parts is to be completed at the meeting. This requires more meetings, and is not as time efficient, as it usually results in an excessive number of people working on a single part. This correction brings the advantage that one persons lack of effort will not severely impede the rest of the group. This solution is not the most time efficient, however is it resistant to problems like missed deadlines.
For each component, we listed what the component was, what its function in the drill was, how many of each component was used in the drill, the material we suspected it was made out of, and the manufacturing method used. The manufacturing method was determined based on common marks left by each method on the part. The following chart shows a the manufacturing method, a description of the method, what marks it leaves on the part, and an example of those markings on one of the parts.
Table 3.1.2: Component List
|Method||Description|| Indications of
|Injection Molding||Forcing molten plastic into a permanent mold|| Parting Lines
|Die Casting||Pouring or forcing molten metal into a die|| Parting Lines
|Forging||Shaping metal through compressing forces applied by dies|| Flash
Part is fairly flat shaped
|Rolling|| Reduces thickness of a metal by compressing
it under high pressure mechanical means
|Very flat metal|
|Drawing||Pulling Material through a die to get desired shape||Metal has stretch marks|
|Grinding||Abrasive cutting tool with thousands of cutting edges||Smooth surface finish|
Table 3.1.2: Component List
|2||Bottom Clip||Fastener||1||Steel||Rolling, Forged|
|3||Bit Holder||Hold extra drill bit||1||Steel||Rolling, Forged|
|4||Screw Bit||Drive Screw head||1||Steel||Forged|
|5||Pressure Pin||Hold Shell Together||2||Steel||Rolling, Forged|
|6||Direction Selector||Change Direction of current||1||Plastic||Injection Molding|
|7||Trigger Assembly||Regulate Current||1||Plastic/metal||Injection Molding/ Die casting|
|8||Motor Washer||Keep gears and gear separate from motor||1||Steel||Die Casing|
|9||Motor Mount||Attach motor to shell||1||Plastic||Injection Molding|
|10||Motor Mount Screws||Attach motor to mount||2||Steel||Forged|
|11||Motor||Convert electrical energy into rotational mechanical||1||Steel||Drawing|
|12||Motor Collar||Label/ Protect Motor||1||Steel||Rolling|
|13||Plastic Gear||Transfer rotational energy, alter torque, angular velocity||3||Plastic||Injection Molding|
|14||Planetary Gear Housing||Transfer rotational energy||1||Steel||Die Casting|
|15||Planetary Gear Post||Transfer rotational energy||1||Steel||Die Casting|
|16||Metal Gear||Transfer rotational energy, alter torque, angular velocity||3||Steel||Die Casting|
|17||Ball Bearing Lock||Stop Planetary gear housing from rotating||8||Steel||Die Casting, Grinding|
|18||CCW Thread Screw||Attach Chuck to shaft||1||Steel||Forged|
|19||Chuck Holder||Allows user to rotate chuck without rotating shaft||1||Plastic||Injection Molding|
|20||Chuck||Holds drill bit||1||Steel||Die Cast/ Milling|
|21||C-Clip||Keep shaft from sliding along axis||1||Steel||Rolling, Forged|
|22||Position Ring||Ratchet Position Collar||1||Steel||Rolling, Forged|
|23||Position Collar||Adjust spring tensioner||1||Plastic||Injection Molding|
|24||Spring Tensioner||Adjust spring tension||1||Plastic||Injection Molding|
|25||Spring||Apply variable force to ball bearing lock||1||Steel||Forged|
|26||Bearing Washer||Keep Ball bearing lock under pressure||1||Steel||Rolling, Forged|
|27||Shell||Hold all components||1||Plastic||Injection Molding|
|28||Clutch Housing|| Hold Planetary gearbox, attach parts to shell,
Hold ball bearing locks, provide threads for tension adjuster
The overall function of the position collar is to allow the user to adjust the torque under which the drill bit begins to slip. It does this by rotating the spring tensioner, which is fitted on a threaded part. When the collar rotates, it causes the tension adjuster to move one way or the other on the threads, increasing or decreasing the force exerted by the spring. This causes more resistance in the clutch, preventing the planetary gear housing from slipping. The position collar also has ridges in it so that when the user rotates the clutch, they can feel a click for each different position. These positioned are labeled on the part, thus allowing the user to remember what setting they had the drill on. The label and the ratcheting feel of the part are included in the design because it lowers the cognitive effort on part of the user in order to adjust the maximum torque that can be applied.
The component has a very simple system flow, which is User input --> force regulation. The component is rotated by the user, which adjusts the force exerted by the spring. Thus, the system flow of the component is simple.
The position collar is plastic, and is generally shaped like a tapered cylinder, with a ring on the inside. It has axial symmetry, with the exception of a few features. With a diameter of about 2" and a length of about 1", the part is one of the largest in the drill. This is partly due to the fact that it is a exterior part, and it contains other parts in side of it. It has such a large diameter because a larger diameter requires less effort from the user to rotate the part. It also has recessed areas on the outside to allow the user to grip the part. On the inside, there are four rectangular shaped ridges, which the spring tension adjuster slides. One of these is larger than the rest, which allows the tension adjuster to be put on only one way, thus making the assembly process easier.
Several factors influenced the design of this part, including desired function, and the GSEE factors. The material the part is made from is plastic, and was probably chosen because the part has complex geometry, and it isn't subjected to any high stresses in the drill. It also has visible riser marks, and a parting line that can barely be seen because it runs along the edge of the part. The part also has a tapered shape, and thus it could be easily separated from two mold halves. Plastic is the optimal choice because it is cheap, easy to shape, and has enough strength to perform the desired function. The plastic also has a a slightly rough surface finish. This surface finish has a practical function, as it allows the user to grip the part and rotate it without his or her fingers slipping. When designing the product, global concerns were kept in mind, and as such, this part has no English words on it. Instead, it has the numbers 1 through 10 on it, and a picture of a drill for the maximum torque. This was implemented this way so that English is not required to use the product. Economic considerations were implemented with the choice of plastic, as it can be molded quickly, and thus requires no milling or other manufacturing methods after it is produced. Most plastics are cheaper than metal. With the process of injection molding, there is very little waste material, because the material required is just that which goes into the mold and the little extra material that is in the filling nozzle of the mold. This benefits the product from an economical and environmental aspect. The color of the part is black, which has some societal influence, because black is considered a basic color, and is generally not associated with any particular group of people. Thus, when the black part is on the drill, it is not likely to cause anyone to react negatively to it, whereas a different color such as pink or green may influence a person's decision to buy the product.
The position ring is a simple part with a complexity rating of 4 (Simple), consisting of one material and no joined pieces. It has rotational symmetry, with the exception of a few features. It has two functions, to adjust the spring tensioner, it is made by injection molding, a common practice now, and has a simple shape. Because of these factors, the overall complexity of the part can be justified as simple.
The motor performs the function of turning electrical energy into mechanical energy. This is achieved by taking in electrical energy from the battery through the motor terminals, then by using a series of loops of copper wire around an armature, an electromagnetic force is created around the current carrying wire. The magnetic field created causes the current carrying wire to experience force in opposite directions which in turn causes the motor to spin, turning electrical energy into mechanical rotational energy. The driveshaft is attached to a drive gear which turns the planetary gears inside the gearbox. The motor’s driveshaft also has a small fan on it which when the motor is spinning, forces heat out of the drill through the slots in the plastic housing.
The motor is in the shape of a cylinder. At one end of the cylinder are the wire terminals that take in electrical energy from the battery. Contained within the cylinder are the driveshaft, fan, copper wire wrappings and electromagnet which perform the main function of the motor. At the opposite end of the cylinder from the wire terminals is the mounting plate that mounts the motor to the gearbox. Attached to the driveshaft is the drive gear which protrudes past the mounting plate. The motor is primarily a three dimensional component as it acts in both reverse and forward directions and has energy flow in the direction of the driveshaft, the heat exhaust and the electrical input. The motor is approximately 2.2 inches in length and 1.5 inches in diameter. The cylindrical shape of the motor has to do with the motor’s functionality. The copper wire and electromagnet contained within the motor housing have to be equidistant from the current carrying wire to ensure a steady torque. This can only be achieve by having the motor have a cylindrical shape. The motor weighs approximately one pound-force. The motor housing , driveshaft, drive gear and bearings are made of steel. The motor end cap, fan blades and mounting plate are made of plastic. The wire terminals, wire wrappings and current carrying pieces are made of copper. For the steel components, the function of the motor is the primary cause for material use. Steel is strong and can handle the speed and torque produced by the motor. The plastic pieces are influenced primarily by part geometry and manufacturing methods. The complex geometry of the end cap, fan blades, and mounting plate make injection molding the easiest way to form the parts, thus plastic is the best material. The pieces made of copper are required by component function to be highly conductive and thus copper is the appropriate choice for material. The GSEE factors that influenced the material choice are societal and environmental. The safety of the motor is a factor that influenced the choice of steel for certain motor component. The product lifecycle is also a factor considered in material choice, the motor and its internal components are not meant to be replaced so materials that have minimal wear over time, thus the steel, copper, and heavy plastic material choices. The motor doesn’t serve any aesthetic purpose. It is not seen by the user and if the drill works properly, shouldn’t ever be seen by the user. The surface finish of the motor is a smooth brushed steel. This is so that no parts of the motor housing can get inside of the motor. This is also so that a serial number for the motor can be applied and easily read.
The primary methods of manufacturing used to create the motor and its components are injection molding for the plastic components, drawing and fabrication of stock material for the metal components, and pulling for the copper wire. The plastic mounting plate and motor end cap both have riser marks on them which indicate places where the mold pressed together and liquid material was injected into the mold. The primary reason for injection molding was the material shape, the complex geometry needed for the fan blades, mounting plate, and end cap could only be achieved economically through the use of plastic injection molding. The steel pieces were made either by fabricating pieces of sheet metal or by pulling. The motor drive gear was manufactured by pulling steel through a form in the shape of the gear. The steel cylinder housing was made by cutting a piece of sheet metal and bending it into a circular form. The steel wire inside the motor was made by pulling steel through a circular die. The copper wire was made the same way as the steel wire. The shape of the component was the primary reason for all of the manufacturing processes used. The GSEE factors that influenced the manufacturing processes are mostly economic. Injection molding is without question the cheapest way to create complex geometry out of plastic. Injection molding can also be completed by unskilled labor making manufacturing costs much cheaper. The use of fabrication and drawing to create the metal components are also the cheapest way to create the part geometry required.
The motor is a very complex component. It inputs electrical energy and outputs mechanical energy through the use of an electrically created magnetic field. The part takes into considerations the laws of thermodynamics and physics in order to function properly. The complexity can also be seen by the amount of manufacturing processes and materials used to create the component.
Scale for complexity of a component:
Table 3.2.1: Complexity Chart
|Function||Add 1 point for each function|
|Form||Add 1 point for every reverse curve|
|Manufacturing Method|| Add 2 points for each manufacturing |
method required to make the part
|Moderately Complex||6-8 Points|
|Highly Complex||9+ Points|
Solid Model Assembly