Gate 3 - Product Overview and Analysis - Group 6 2012
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With the product having been dissected in gate 2, the group can now analyze it more thoroughly. This gate includes a standard project management table that shows how everything is going for each member and possible corrective actions that may need to be taken. Along with that there is the component summary. This contains a parts list for the impact wrench and how each part is manufactured. The product analysis goes through the engineering decisions made during the design of the product. There is a solid modeling portion with a rendered view as well as some engineering drawings of the parts assembled. The engineering analysis shows how the analysis process would be used during the designing phase. Finally, the design revision portion recommends three possible changes for the product.
Project Management: Coordination Review
Cause for Corrective Action
The following table shows each members responsibilities and any changes that need to be made to make the gate progress smoothly.
Table 1.1: Assessment of Intra-Group Communication and Coordination
|Management Roles||Goals||Successes||Challenges and Resolution|
|Project Manager and Intra-Group Communications Coordinator||
|Technical Expert: Communications Technology||
|Technical Experts: Dis-assembly Technicians||
Product Archaeology: Product Evaluation
Here is a list of each component of the impact wrench and how it was manufactured.
Component Summary of all parts sources:
This part contains the analysis of many parts of the Impact Wrench. There is a complexity scale at the bottom of this section.
FUNCTION: The housing of the impact wrench is the largest of all the components. It is the piece which contains all of the other components. It is also the piece which the user will hold while operating the tool. Without the housing, the tool would be an inoperable mess of components. All of the energy is brought into the housing, consumed, and then the excess is expelled out of the bottom. Any aesthetic qualities of the tool will be present on this piece, as it makes up almost all of what the customer sees when judging the tools appearance.
PART GEOMETRY: At the bottom of the housing is the handle. It is about 4 inches long and has two rubber grips for the user’s comfort. On this handle you will also find the attachment of the air inlet, right next to the excess air’s out let. The upper half of the housing is almost cylindrical in shape. It is about 6 inches long and 2 ¾ inches in diameter. The center of this cylinder is completely hollow to allow the other components to be tightly placed inside. The Housing is quite heavy and weighs about a kilogram.
MANUFACTURING METHOD: The housing is made from die-cast aluminum. It has been polished to a very fine finish for aesthetics. Due to the quality of the finish it was difficult to find the extrusion lines, but one was quite evident at the back of the handle. The housing has been cast very thick, over ¼ inch in places. The tool is meant to be operated with an input air pressure of 90psi. We suspect that the housing was built this thick in order to withstand the internal pressures the air is exerting on it. Upon inspection, tapped holes are present at all angles, implying that after casting the housing would have to have been machined as well. Since the housing is the only part a typical user will ever see, it has been adorned with decorative logos as well as an interesting gouge cutting around the entire tool. This “seam” is meant to make the tool more attractive as a way of addressing a societal concern that customers would rather buy attractive products over unattractive ones.
COMPONENT COMPLEXITY: The housing of the impact wrench is by far the most complex piece of the tool; it is the largest piece, it handles all of the energy transfers and user interactions, and was made using several processes. This is a level 5 part (see scale).
FUNCTION: The valve sleeve is a small brass tube, permanently attached inside of the housing. It contains the plunger. The valve sleeve can be seen as the border between the machine’s operation and the user interfaces: the plunger is, in a sense, a gate valve that the user adjusts to determine how much air is allowed into the motor. The valve sleeve then directs the adjusted air into the motor after the trigger has been pulled, allowing the motor to turn.
PART GEOMETRY: The valve sleeve is a long, hollow, brass cylinder about ¾ inches in diameter. The cylinder is 1 ½ inches long and completely hollow. When the tool is held, the sleeve is going to be in the position of a tipped over can (radius perpendicular to the ground). On the bottom of the sleeve is a hole about ¼ inch in diameter. This hole is where the air enters the sleeve once the trigger has been pulled. At the top of the valve is another ¼ inch hole which is where the air exits after passing over the plunger. On both sides of the sleeve there are 3 holes drilled and a long narrow slot. These holes connect to small pockets within the housing. It is believed that these holes are used for giving excess air a place to expand into to create equal pressure on the inside and outside of the valve sleeve to prevent damaged caused by pressure building inside of the sleeve. The sleeve is open on both ends of the cylinder; however, the plunger has a shape which closes off each end of the sleeve once it is in place. Brass was most likely chosen because of its resilience as all of the holes in this part will be subject to lots of high energy fluid friction. This part is invisible to the user and has no aesthetic purpose.
MANUFACTURING PROCESS: The sleeve fits a plunger inside of itself very tightly, so it had to be made with a high tolerance. It most likely started out as a plain brass cylinder which was then machined to have its center drilled out then reamed for precision. The holes perpendicular to its axis were likely drilled in as well, but with much less precision, as some burs were found. The sleeve was then soldered into place inside of the housing, as can be seen by the marks where the brass and aluminum meet.
PART COMPLEXITY: The sleeve was made with high tolerances but has a simple shape and design. Its main function is to direct air into the motor and holding the plunger could be seen as a secondary function. This part remains static during its entire life cycle. This part has a complexity of level 2 (see chart).
FUNCTION: The plunger is in essence a gate valve. It is connected to a switch on the outside of the tool which allows the user to rotate the plunger. It is an obstruction inside of the valve sleeve, and as it is rotated it becomes less obstructive to the air flow, allowing more air to pass through the valve. It can also be turned in a direction would direct the air in a direction which would allow the motor to spin in reverse.
PART GEOMETRY: The plunger is, for the most part, 2 concentric cylinders sharing a central axis. The plunger weighs about 13 grams. It is 2 ¼ inches long. One of the cylinders is ¾ inches long and ¼ inch in diameter. This end of the valve is connected to the switch. It is a stem and has no purpose except to connect the valve end to the switch end. On the other end is a cylinder about 1 ¼ inches long and ½ inch in diameter. This is the end that sits in the valve sleeve. It has a very smooth finish and was polished to a precise diameter in order to fit tightly into the sleeve. There are also cuts made at a depth of 3/8 of an inch, ¾ inches long, parallel to the axis, and spanning the diameter of the valve. These cuts create an open space inside of the sleeve for air to enter. When both of these cuts are lined up with the air inlet and outlet respectively, air can pass through the sleeve once the trigger has been pulled.
MANUFACTURING PROCESS: The plunger is made of aluminum and appears to have been made by machining processes. It would have started as an aluminum cylinder and then spun on a lathe to create the two separate diameters on either end. There are chamfers on the large end and cut marks on the smaller end which lead to this conclusion. The valve end has a very smooth surface which enables it to fit tightly into the sleeve and this was accomplished with an abrasive process. The cuts in the valve end have obvious tool marks and were not intended to be precise. There are also holes on both ends of the plunger, which would have been drilled out.
PART COMPLEXITY: Part of the plunger was made with precision, but most was not. The function of the part is also quite simple and the part remains still while tool is in operation. This is a level 3 part (see complexity chart).
FUNCTION: The trigger is the main piece of the tool that will be used for controlling its operation. With a simple push of a button, the user initiates a mechanism that opens the air inlet and allows the tool to operate. Releasing this button will cause a spring to push the mechanism back out, preventing air flow and halting the tools operation. Due to the fact that this piece is responsible for directing the user’s signal into the internal mechanisms, it has been made to reflect Societal concerns surrounding comfort under extended use and intuitive design. It has a curved face and is made of smooth plastic with rounded edges for comfortable use. The idea of a trigger is very user friendly, at least in the US, where nearly everyone knows how a trigger switch is operated.
PART GEOMETRY: The trigger itself is really 2 separate pieces which have been permanently attached to each other. The first is a small plastic button about 1 inch long and ½ inch wide. It is ½ inch thick and has a slight curve on its face to allow a person’s finger to rest on it comfortably. The second part is an aluminum shaft 1 ½ inches long and 3/16 inches in diameter. One end of the shaft is permanently attached to the button and the other end has a groove cut into it to allow it to interact with the tipper valve. It also has a flat surface cut onto it where a pin would rest. This pin would prevent the stem from moving too far inward or outward. The total weight of the trigger is only about 9 grams.
MANUFACTURING PROCESS: The plastic portion of the trigger was injection molded, as injection marks are evident on the back side. Plastic was chosen because it is an economical way to make a comfortable, sturdy button. The stem is cylindrical; however, the finish is very fine and does not appear to be the result of turning. This fine finish and simple shape imply that it was likely made from a cast. These two separate components were most likely glued together using simple adhesive.
PART COMPLEXITY: The trigger is two simple pieces glued together to perform a single function: the transfer of a user signal to open a valve. For this reason it has been rated as a level 3 part (see chart).
FUNCTION: The fins are an important part of the impact wrench system. From the flow of compressed air they turn the rotor which allows for a rotational force to be made. They move in and out of the rotor depending on their position at that moment because of the cylinders shape and the rotation of the rotor. The environment that they are in is secluded since they are in the housing so most outside elements and factor would not affect them.
PART GEOMETRY: In general the fins are rectangular with one of the lengths being an arc and they are all axial symmetric. Primarily thus component is 2-D but does have a thickness to it. The dimensions of the fins are a length of 1.449 inches, height of 0.103 inches, and a width of 0.534 inches. The components shape is coupled to how it performs due to the fact that has the curve at the one end with a small slit. They are shaped to allow a certain amount of air to turn the rotor just like a turbine so types of aerodynamics were necessary in the design of the fins. Roughly this component weighs 1 gram. They are so light due to the fact that they need to be able to be movable in the system. The fins are made of a fibrous material then coated in a resign. Manufacturing processes did not affect this due to the fact that they are more difficult to make. There is no specific material needed to function it just needs to be light. In this case none of the GSEE factors make much of an influence. Aesthetically this part looks nice due to the material it is made of however that is not the intention and nothing was done special to make them look nice since they are in the casing.
MANUFACTURING PROCESS: The fins were made in a method similar to that of carbon fiber. Fabric was set up then vacuum formed with resign to make the piece durable for its function. Since the choice of material was fabric this greatly affected the manufacturing process do to the fact that this is one of the few ways to do this. This manufacturing process is environmentally friendly and the material is degradable making it a good choice for the environment.
PART COMPLEXITY: On the complexity scale the fins are rated as a level 3. This is rated as such due to the fact that it is a simple shape and it interacts with the rotor to create energy.
Shown above with "fins"
FUNCTION: The rotor in an impact wrench has an important function in the fact that it with the fins is what changes pneumatic energy to rotational energy. The compressed air flows into the housing to the rotor which turns with the help of the fins which is starting the process of the turning necessary for the torque to be output. Due to fact that the rotor is in the housing is does not have to deal with any outside elements allowing for minimal wear and for high performance.
PART GEOMETRY: Generally speaking the rotor is in the shape of a cylinder. The entire part is symmetric including the cuts for the fins. The dimensions for the part are a length of 2.817 inches and a diameter of 1.439 inches. The shape of the rotor is important in the fact that it needs to be able to spin freely inside the cylinder but still have enough weight and volume to create a high enough rotational force. This being said the rotor weighs approximately 266 grams. This component is made of steel and this is due to the need of weight and strong material. This also could be seen as a manufacturing decision because it could be mass produced very easily. Going with this theme, it also could be said that an economic factor could have been involved due to the fact that the part can be made decently cheap. Since the rotor is inside the housing it was unnecessary for the manufacturer to give the part any finish or color as can be seen by the fact that it is basic steel.
MANUFACTURING PROCESS: The rotor was manufactured by a machining process by a CNC mill/lathe. This can be seen due to the marks that were made by the machines on the part. The fact that the rotor is steel impacted the manufacturing choice because they allow for easy and precise cut on steel. Shape also affects the process chosen due to the cuts that needed to be made on the rotor for the placement of the fins. Again due to the easiness of mass production, this process affected the product in a sense economically.
PART COMPLEXITY: On the complexity scale, the rotor is rated at a level 3. This is because it is a simple cylinder however it is what starts the change of pneumatic energy to rotational energy.
FUNCTION: The hammers in the impact wrench are an important part of the process that allows great amounts of torque to be output from it. The function of the hammers is to take the rotational inertia from the anvil and magnify it to create a high torque output. The two hammers are held together by the bushing and the hammer cage and when the anvil turns the bushing, the hammers move in accordance to the shape of the bushing and their movement amplifies the force. This is the only function made by the hammers.
PART GEOMETRY: In general, each hammer is in the basic shape of a rectangular oval. Both hammers are made identical to each other. They are symmetrical all the way around, have a half cut out section on the top for hammer pin, and on the bottom there is a similar cut but are elongated to allow more movement. The center has a hole that allows for the movement of the bushing and the top and bottom edges are filed down. The dimensions of this part are a length of 1.944 inches, height of 0.553 inches, and a width of 1.424 inches. The components shape is coupled to the function that it performs because the center cut out to allow the bushing to turn it in a way that it creates an impact force increasing the torque. The hammers roughly weigh 98 grams apiece. The hammers are both made of steel and were done so that there would be enough weight behind each part to create the force to do its job. Different GSEE factors were probably considered when choosing this material. Steel is decently cheap compared to other strong and heavy materials that could be used which allows for the product to be sold at a reasonable price which goes under the economic factor. Environmentally, steel is recyclable so I won’t be sitting around in a dumb for years unlike other materials. Aesthetically this piece is very basic mainly due to the fact that it is not seen from the outside of the casing. The color of the hammers is basic steel without any finish because none is necessary.
MANUFACTURING PROCESS: A couple different manufacturing processes were used to make the hammers. First they were machined with a mill and then cut with a lathe. There are machining lines on the outside of the part while the areas that were cut with a lathe have rough marks and ununiformed chips in the steel. The fact that steel was used along with its shape impacted this decision because they needed to cut it decently precise because their shape is what makes the increase in torque. The way that the middle of the hammer is cut out could only be done by a lathe due to the shape and proximity. An economic factor was involved in these production choices because this part can be mass produced helping make the product cheaper.
PART COMPLEXITY: On the complexity scale the hammer is rated at a level 4. This is due to the fact that it deals with the change of energy, it is constantly in motion, and it has multiple manufacturing methods.
FUNCTION: The rear cover of the impact wrench is a more essential part that people may think. It needs to be able to withstand the pressure coming into the housing and to not leak out any of it. Along with that, the regulator switch is also connected to the back cover which lets the impact wrench work at certain speeds or in reverse. The rear cover also has to be able to withstand outside elements along with variables such as being dropped or placed in an area where damage may occur.
PART GEOMETRY: The basic shape of the rear cover is an oval. For the most part is basically a 2-D component with some 3-D features. This component is axis symmetrical however the indents specifying the regulatory setting and the switch are not due to the functionality. This component’s dimensions are a length of 3.65 inches, a width of 2.55 inches, and a height of 1.00 inches. The components shape is coupled with its performance in the fact that its needs to be perfectly flush with the housing and it also has to be made simplistic so the controls are easier for the user to understand. The rear cover also has an approximate weight of 93grams. The rear cover is made of aluminum and this is due to several reasons. One is for the strength that is necessary for the part. Another is for the manufacturing process in the fact that it needed to be an easy material to work with. Economically there is a reason for the decision for aluminum due to price. Environmentally it is also good due to recyclability. Due to the visibility of the rear cover the need for aesthetics is necessary. The component is finished with a smooth gloss finish to make it look presentable.
MANUFACTURING PROCESS: The manufacturing method used on the rear cover was the use of a CNC mill. This was used to get the details necessary into the part. Also, it is a decently precise process and reasonably quick. It is decently cheap in the economic factor sense. This method was probably also chosen due to that it is made of aluminum. Aluminum is strong but not as strong as steel and needed a process that would allow the part to be made with limited error which also goes along with its complex features.
PART COMPLEXITY: The complexity scale for the rear cover is a level 5. This is due to the fact that it is a complex geometry and that it is involved with the regulation of air and has to deal with the incoming pressure.
To measure the complexity of the components we will be considering the parts function, shape, and how it was manufactured.
The shape is directly tied to the complexity of its development. A component which requires many processes to turn it from a material to a useable shape will be given a higher rating for its complexity.
A component whose function is quite simple, or even remains static for its entire life cycle will be deemed very simple. Also, the more components it interacts with, the more complex it will be rated.
This scale will go from 1 to 5 in order of increasing complexity:
Level 1—Very simple. A component made from only one manufacturing process and in contact with only one other component. A component at this level will likely remain static during its entire life cycle
- Ex. A Pin
Level 2—Less simple. This component may have been made from more than one process. However, its function will be similar to that of a level 1 component.
- Ex. A Spring
Level 3—Simple Moving parts. This component will be simple in shape, but have a more complex function. Its manufacturing process will have been simple, but it will interact with another part to transfer energy.
- Ex. The Rotor
Level 4—Complex Moving parts. This component will have a similar function to a level 3 component, but its shape will be physically complex or intricate and perhaps require multiple manufacturing methods to get to its required form.
- Ex. The Anvil
Level 5—very complex. This component will have very complex or intricate geometry and also have more than one function. It is likely to interact with many other components and be involved in many functions and/or energy transfers.
- Ex. The Housing
We chose to solid model the following parts of the Impact Wrench:
- Hammer Cage
- Hammer Pin
We chose these due to the interaction between them and how important they are to how the wrench operates. These are the parts that cause the impact and energy transfer in the wrench.
Creo Parametric 1.0 was used to model the parts. Creo was chosen because of the amount of experience the modeler had with the program. This experience comes from being in MAE 377 where Creo Parametric is the modeling program used. It was also chosen because of the rendering abilities and the ability to produce engineering drawings with ease.
The following drawings were made using Creo Parametric.
- This first is a drawing of the individual parts and they are labeled according to the component summary chart.
- The second drawing is of the parts assembled. It includes an isometric view of the assembly along with an exploded view where the parts are labeled referencing the first drawing. It also includes a cross sectional view of the assembly.
Finally here is the whole assembly fully rendered using the rendering function in Creo Parametric:
A main function in the Impact Gun is to transfer pneumatic energy to rotational energy which is done by the use of fins, a rotor, bearings and a containment cylinder. While designing this function engineers could make use of the Engineering Analysis shown in class or a similar process to maximize performance and make the most of the testing and experimentation. Out of all eight steps of design(as shown in class) the three in which could benefit the most from Engineering Analysis are step 4 embodiment design, step 5 detailed design and step 6 testing and validation.
One consideration in the embodiment design that could benefit from the Engineering Analysis is the concentration of airflow and pneumatic energy to the area of the fin. In this study one could calculate benefits in having the fins separate from the rotor and the advantages from having them be reset in the chamber. This would require the engineering analysis to become a chart to compare differences in governing equations, assumptions and results.
An Analysis could be used in the detailed design step to study various components for their feasibility and strength. Material selection can be greatly optimized through the Engineering Analysis by comparing different materials through putting them through stress analysis and as a result finding the best combination of strength and weight reduction for the components. Another stress Analysis can be used to choose bearing sizes/types to hold the rotor in place. These Analyses would be achieved with mathematical and virtual models.
Finally the Engineering Analysis process can be applied to the Testing and Validation step. Analysis can be applied to the stress tests or safety testing using a real prototype and compare these results to the assumed calculations done earlier in the design. A very important test to be done that would benefit from the Analysis would be the performance tests that measure and plot data such as torque vs. pressure.
To demonstrate the possible analysis performed this is an example Analysis for the early design steps to predict the testing performance of the Function using this numerical analysis and data collection
Engineering Analysis Example
The problem is finding the feasible torque achieved from different pressures from the rotor/fin design using a numerical analysis to predict the outcomes of the later physical tests.
- Assuming Uniform density
- Assuming little to No Friction
- Assuming uniform pressure distribution
- Assuming isothermal system
- Assuming valve is wide open
- Assuming no energy is held by the system and therefore ΔE=0
- Assuming Ideal system
- Assuming Standard Temperature
- Assuming ideal gas behavior for air
- Ein - Eout= ∆Esystem=0
- Eflow= mθ = m((v^2/2)+gz+u+Pϑ)
v=velocity, g=acceleration of gravity, z=height, u=internal energy, P=pressure, ϑ=specific volume
n=revolutions per time, τ=torque Note: dot above letter denotes the fact that the variable is a rate of time
- ṁθin = ṁθout+ ẆShaft
- m ̇((vin^2/2)+hin )= m ̇((vout^2/2)+hout )+2πṅτ
This is the calculation an engineer could use and then plug various values of pressure (pressure is in the equation through enthalpy) into the equation and use a table for the various torques achieved. I have stopped at this calculation because I do not have the equipment or capabilities to measure the velocities at the inlet and outlets of the system. Nor do I have the capabilities to measure the revolutions per time either. These calculations may require simulations and virtual models of the system as well.
The solution check involves studying the results and plotting them to find any patterns for the data. The plot could also be used to find outlying points of data from the majority and in this step an engineer could either try to find out why there was an outlying data point or if the point is in an extreme minority the engineer could make the call to ignore it all together.
Discussion and Interpretation
In this step the Engineer would decide if the data acquired is acceptable for the performance requirements. For example if the average pressure for most air compressors is 50psi and the related torque from the calculations at this pressure is a torque under the average required among other impact guns or under the torque required by the company then the solution analyzed in this step might be disbanded or need to be revised to meet these needs.
This table has four changes that could be made to the components or subsystems to one or more of the GSEE factors.
|Design Change||Primary Components or Subsystems Impacted||Improvements||Tradeoffs|
Pneumatic Rotor to Electric Motor with Battery
Energy Input and Conversion
Plunger to Ball Valve
Regulation by Valve System
Energy Magnification by Hammer
Rotor, Hammer, Anvil Subsystem