Gate 3 Group 27 2012

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Introduction

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.

Product Evaluation

Component Summary

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 method	Image
Injection Molding	Forcing molten plastic into a permanent mold	Parting Lines Draft Riser Marks
Die Casting	Pouring or forcing molten metal into a die	Parting Lines Draft Riser Marks
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

#	Component	Function	Quantity	Material	Manufacturing Method	Image
1	Screws	Fastener	11	Steel	Forged
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	1	Plastic	Injection Molding

Product Analysis

Position Collar
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.

Motor
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.

Metal Gears
The metal gears are part of the planetary gearbox. The main function of the metal gears is to transfer rotational energy from the motor to the drill clutch and regulate the torque output of the drill. The planetary gearbox is attached at one side to the motor drive gear, which sends mechanical rotational energy through to the plastic gears, which are attached to a metal disc with a centered drive gear on its opposite face. This centered gear spins the three metal gears on the other side of the gearbox. These interacting gear trains increase the torque of the drill by decreasing the drills speed. The metal gears function within the metal gearbox.

The metal gears are all the same size so that they all interlock without any of the teeth smashing together while the drill is functioning. All three gears are symmetric around the central axis and have eighteen teeth. It acts in three dimensions, as the gear is a rotational object. The shape of the gears are related to the component function being that the gear shape is designed to interlock with the drive gear attached to the metal disc, the other metal gears, and the inner teeth of the planetary gearbox. Each metal gear weighs approximately an ounce. The gears are made completely out of steel. The material choice is primarily influenced by the component function. The gears have to handle the increased torque created by the gearbox, thus the material needs to be strong and ridged. Economically steel is the best choice to perform this function, as steel is a strong, easily fabricated metal. Safety is also an important factor influencing the material choice, steel is a very durable metal and will not chip when strained keeping the drill safe for the user. The gear serves no aesthetic purpose as it is an internal component and is not seen by the user.

The metal gears were made by drawing, or by pulling steel ingots through a form in the shape of the gear and then cut down to size. This is the easiest way to create a small symmetrical gear and the gears have no riser marks or edges to support die-casting. This manufacturing process is mainly influenced by the size of the component and the component design. The simple geometry of the gear and its relatively small size makes drawing the ideal manufacturing process. GSEE influences on the manufacturing process are predominantly economic related. Drawing is a cheap manufacturing process that takes unskilled labor to perform lowering the production costs significantly making it the most economically viable manufacturing process.

The metal gears are not complex. They are made of a single material and produced through a single manufacturing process. They interact with other gears that are similar in shape and material. The gears perform a single movement, spinning around the central axis, which makes their interactions with other components very limited.
Plastic Gears

The function of the plastic gear is to reduce the angular speed and increase torque of the shaft. This simple part has a very basic system flow, with an input of rotational mechanical energy, and an output of regulated rotational mechanical energy. Because the gear is completely enclosed in the drill, it isn’t subjected to any varying working environments. This allows it to be greased with the proper amount and variety of lubricant, allowing the gear to perform its function with minimal friction loss.

The gear has the shape of a flat cylinder, having 18 teeth and axial symmetry, measuring in at 1/4” along its height and ½” along its diameter. The shape of the teeth is a straight pattern, as opposed to a swirl pattern that one might find in a more complex gear system such as a car transmission. This straight design was likely chosen because it is simplistic and easy to make. The gear has slight recessed areas on each surface normal to the axis of rotation. Because weight is not a significant factor for this part, and plastic has a low density, it can be assumed that the recessed surface is to reduce material cost, and perhaps even help to channel the grease as the gear is moving. The parts material choice was made based on two factors: the strength it needed to endure and its cost to manufacture. The plastic gears were chosen to be plastic because they are the first in the series of gear ratio reductions, and thus experience the greatest speed and the lowest stress. This is where saving weight with plastic helps, but more significantly, it reduces the cost of the product. These decisions were also subject to the influence of some of the GSEE factors. Because the part is not seen by the average user, and the user is generally unaware of its existence, it has little influence from global or societal factors. The plastic material is the cheapest available that is still able to perform the desired function, thus making it a good choice from an economic standpoint. Being plastic, it has enough durability to have some recessed areas so that it uses less material. Not only is this economical, but it uses less plastic which is less harmful to the environment.

The gear is completely enclosed in the drill, thus making aesthetic considerations irrelevant. As such, the gears are a tan-yellow color, which is likely just the color of the plastic used without any dyes. The surface finish is smooth but not polished, as this will reduce cost and friction in the product.

The plastic gears were likely to be made via injection molding, as this is the common practice for plastic parts. The gears are also shaped so that they could easily be separated from a mold. Injection molding is a common process in modern industry, and as such it has become one of the cheapest options to manufacture parts, making it a good choice from an economic standpoint.

The plastic gear is one of the simplest parts of the drill, as it has one function, very simple shape, and requires only injection molding to be made. It has a score of 3 on the complexity scale, the lowest possible score. Its interactions with other parts are also very simple, as it rotates on a shaft and comes into contact with the planetary gearbox.

Drill chuck
The Drill chuck has one and only one function that is to securely hold drill bits or other rotary tools in place while drilling. This function is made possible by having three jaws like devices that tightens around the cylindrical base of a drill bit. Since it is a hand chuck,using your hand when the chuck is turned clockwise it pushes the three jaws like devices outward that tighten the base part of the drill bit.

Thanks to its cylindrical shape the chuck is symmetrical around the y-axis. For a rough approximate of the size, it is 6.5 centimeter in height, and the circle at the bottom has a diameter of 4 centimeter. Since it does most of the heavy duty of the hand drill it is mostly made of metal. It weighs about 9.3 ounces. Although the bottom part is made of plastic it is only a cover for the metal part under. In addition, in my opinion the plastic cover at the bottom allows better grip to the person using the drill since it is a hand chuck. Moreover, thanks to these characteristics: parting lines and Riser marks at the bottom and top of the chuck we can safely say that the fabrication methods used was die casting for the metal part of the drill and injection molding for the bottom where the plastic is used.

Component 6
Component 7

Scale for complexity of a component:
The following chart explains a rating system for judging the complexity of each part. Under Form, a reverse curve is any curve or recession that would require the part to be rotated or re-positioned to be made.

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

Simple	3-5 Points
Moderately Complex	6-8 Points
Highly Complex	9+ Points

Solid Model Assembly

Drawings here

Summary here

Engineering Analysis

A component that would use engineering analysis in the design and testing stages of the design process is the planetary gearbox/clutch mechanism. The design statement that would result in an engineering analysis of the gearbox would be the need for a torque increase and speed reduction from the motor to the drill chuck.

Problem Statement
Determine the optimal planetary gearbox configuration that is designed to input mechanical rotational energy from a motor at a certain speed and torque and output mechanical rotational energy at a predetermined torque and speed that can be adjusted by the drill user.

Diagram

Assumptions

• The gears are frictionless
• Motor output speed is variable within a predetermined range
• Motor output torque is variable within a predetermined range

Governing Equations

Discussion
This analysis has a vital impact on the way that the drill performs. Too much torque and the drill becomes unsafe, too little torque and the drill won't be able to turn a drill bit or a screw. The gearbox is the only user adjustable component in the drill and getting an accurate adjustability input is part of the product description.