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Gate 3: Product Examination

Purpose:

The purpose of gate 3 is to discuss the subsystem components gathering as much information as is possible. The following sections and information will be gathered, discussed, and analyzed in this presentation.

Project Management: this portion will update the reader on how well the group is working together as a team. Any issues in this regard will be presented here.

Component Summary: This section will identify the various components within the produce. All manufacturing data will be recorded, and the actual manufacturing processes will be analyzed.

Product Analysis: The engineering design decisions behind seven subsystem components will be analyzed, and discussed.

Solid Modeled Assembly: A solid modeling program of choice will be used to make a three dimension model of four to five components.

Engineering Analysis: A key component or function will be chosen, and an explanation of how engineering analysis would have been used in the development and testing of the component will be discussed.

Design Revisions: Observations made in dissection the drill will not be put into application of how the drill can be improved. Three main revisions will be made based on performance, cost effectiveness, and GSEE factors.

Cause for Corrective Action

Our group has worked well together so far this semester. For this gate we decided that the most convenient method to tackle the project was to assign each group member one of the sections stated in the purpose statement. This allowed each member two and a half weeks to tackle their assignment, and discuss any issues with other members of the group. This being the case we have not had any issues with this approach. The deadline to hand the assigned portion of the project is two days before the gate is due. This allows enough time for the Wiki editor to create a professional presentation.

Component Summary

Component Summary Table
Part Name	Description	Manufacturing	Reason for Materials	Reason for Shape	Forces Applied	Functional/Cosmetic	Quantity	Complexity	Picture
Washer	Holds the torque adjuster to the rest of the drill, separates the ball bearings from the falling out of their bearing holes, separates the gear assemblies	Sheet metal stamping	Steel because of its availability and to keep down cost	Standard	Normal forces applied from the materials that the washer is separating	Functional	3	1
Ball Bearings	Allows the chuck to gear assemblies spin almost frictionaly from the clutch	Cold forged in dies	Steel because of demand for strength and durability	Standard	None	Functional	6	1
Gear Shifter	Shifts a gear between a lower gear ratio for high torque, and a higher gear ratio for higher speed	Machined	Steel because of demand for rigidness	Allows for easy shifting back and forth in linear direction	Normal force to slide the shifter between gears	Functional	1	1
Spring	Applies tension towards the gear shifter to keep it form moving freely	Coiling	Steel because its common and has a consistent elastic modulus with life cycle	Coil shape because of the principles of a spring	Mostly compressive forces in design	Functional as it keeps the spring in place	1	1
Motor Cage	Holds the motor to direct power into the gear assemblies	Plastic injection molding	Plastic because it is easy to mold, inexpensive, and also absorbs any motor vibrations	Circular to form to the shape of the motor	None	Functional as it holds the motor in place	1	1
Sliding Gear	Gear that slides between the higher and lower gear	Plastic injection molding	Plastic possible for easier shifting with lighter weight than metal gear	Circular so that it can easily switch between the gear assemblies	None	Functional as it is the gear that changes between the low and high gear speeds	1	1

Product Analysis

Trigger

• Component Function: The trigger is one of the most important components on this drill due to the fact that it is the component that the user interacts with most frequently. The function of this component is to allow the user to use the drill, and that being said, the trigger performs only this function in this drill.

• Component Form: The general shape of the component is roughly that of a rectangle. There are no truly notable properties of the trigger, and it is primarily a three dimensional component. The dimensions for the trigger are roughly (as seen looking at the side of the drill): Length: 3 cm, Width: 2 cm, and Height: 4 cm. The rather large, and generic shape of the component allows for moderate ergonomic comfort for a wide variety of users. The rough weight of the trigger is about 100 grams, and it is made out of plastic. Manufacturing the trigger from plastic was a good idea because the shape is not overly complicated, and an injection mold would not have been tremendously complicated to make for the trigger. Of the four GSEE factors that were used to design this trigger the economic factor would weigh most heavily. Making the trigger out of plastic (as opposed to metal or ceramic) keeps the material, and manufacturing cost of the component low. There is no aesthetic purpose to the component, it is simply there to perform the function of a trigger.

• Manufacturing Methods: The manufacturing method most likely used for this part is that of injection molding. There are ejector pins on the inside of the trigger body that would incline one to suspect this manufacturing method. Since the material is plastic this method would make the most sense given the geometry of the part.

Battery

• Component Function: The function that the battery performs Is to deliver power to the motor which allows the drill to perform its fastening function. This is the only function that the battery performs, and the flows associated with it are electrical energy flowing to the motor. The battery is attached to the bottom of the drill so the environment functions in are whatever environment the consumer chooses to use the drill.

• Component Form: The general shape of the batter is that of a rectangular cube. There are no notable properties about the battery, and it is primarily three dimensional. The dimensions of the battery are as follows: Length: 15 cm. Width: 7 cm. Height: 6 cm. The component roughly weighs 450 grams, and the material of choice for the battery is primarily plastic. The plastic body serves as a convenient material from a manufacturing and cost stand point (cheap, and easy to manufacture). The environmental factors that influenced this design is due to the fact that the plastic is a robust form. This allows the user to operate the drill in adverse conditions without having to worry about corrosion or destroying the battery because of dropping it on the ground etc. The color of the component is black, and the reason for this is that it nicely compliments the orange casing of the drill, and allows the consumer to see that it is a Black and Decker drill quickly.

• Manufacturing Methods: The most likely manufacturing method used was that of injection molding. This is evidenced by parting lines that show where the battery casing came together around the internal workings of the battery. The material choice is plastic , and since the geometry and dimensions are not overly complex the most cost efficient method is that of injection molding.

Casing

• Component Function: The function of the body casing is too contain, or attach all the components of the frill (motor, trigger, chuck, etc.). The casing has two primary functions: contain/attach all other components, and give a good ergonomical grip for the consumer, and as such there are no flows associated with the component.

• Component Form: The shape is roughly that of a pistol, and has no notable properties. It is also primarily three dimensional. The dimensions of the drill are: Length of base: 15 cm. Height (when stood up by it’s base): 35 cm. Width: roughly 10 cm. The components shape is primarily ergonomical. It allows the user to comfortably grip the product, and use it for it’s intended purpose. The component is rather light and weighs roughly 275 grams. The component is made from mainly plastic, but also has portions that are rubber for increased user comfort. Again, the easiest way to manufacture this component is through the use of injection molding. There is no specific material required for this component as there are drills that are also made from metal, however the plastic serves as a more economical material and keeps the manufacturing and thus the consumer cost down. The component is colored a mix of bright orange and black. This is simply to allow the component to quickly be identified as a Black and Decker drill.

• Manufacturing Methods: There are ejector pins and parting lines which give weight to the idea that indeed injection molding used to manufacture this component. The shape is rather complex, and therefore the best way to achieve the desired geometry was to utilize the injection molding process.

Slip gear

• Component Function: The main function of the slip gear is to engage one of two sets of gears that vary the speed of the drill. This is the only function of the drill. The component is a high temp environment as the gears are constantly spinning at relatively high rpms.

• Component Form: The shape of the component is circular with gear teeth on the inner, and outer portion of the ring, and it is primarily a three dimensional component. The shape must be circular as the design is that of a planetary gearing system where the ring moves between the two gears at the users discretion to adjust the speed of the drill. The outer diameter of the gear is 3.5 cm and the inner diameter is 2.5 cm. The depth the gear is about 2 cm. The component roughly weighs 45 grams, and the material of choice is a high quality plastic. The plastic stands out from the rest of the plastic in the drill due to the fact that the component sees higher temperatures and more wear and tear through the life cycle of the drill. This is purely a performance decision. Environmental factors were present in the design due to the fact that it would be in a much more rough operating condition than any other plastic part in the drill. There is no aesthetic purpose to this component as it is hidden within the drill.

• Manufacturing Methods: From inspecting the component it appears that it was made in an investment casting. It was a much higher tolerance mold as parting lines are non existent.

Slip Gear Spring

• Component Function: The function of this component is to create an interface between the user and the gearing system within in the drill. The spring is attached to the slip gear, and is the mechanism by which the slip gear engages one of the two gearing systems within the drill. This is the only function of this component. The environment of the spring is within the drill, so it does, presumably, see higher temperatures than the external portion of the drill.

• Component Form: The general shape is hard to describe, but it is basically a rod with two prongs at the end which go out at a 45 degree angle from the rod (when looking from the side). It is axial symmetric, and one of the more intricate and interesting components of the drill. It is primarily a three dimensional component. It is roughly 7 cm in length. The shape is necessary so that the user can move the spring at the top of the drill, and the slip gear can oscillate between gearing systems within the drill. The component material appears to be a medium grade steel. The properties of this component are that it must be fairly robust. It has to withstand the slamming of the user from gear to gear without shearing, and ceasing to function as a gear shifter. Steel is good for this purpose as it has a relatively high tensile strength, but is also fairly ductile. This would be an environmental design decision. It also falls under the economic GSEE factor due to the fact that steel is a fairly inexpensive material (not as inexpensive as plastic, but still on the cheaper side none the less). The component has no aesthetic purpose as it is hidden within the drill, however, the color is a generic silver metallic.

• Manufacturing Methods: The manufacturing method most likely used to create this part was most likely metal forming. The material choice and shape of the component makes this the most likely manufacturing process used. This is because the shape could simply be cut to the rough dimensions, and then bent into the desired shape through the use of a die. This is a less expensive alternative to creating a mold for the part.

Solid Modeled Assembly

The reasons for choosing these three components are because they are one of if not the most important components that the drill uses to perform its function. These three gears form one gear assembly which is used and appears three times in the drill in conjunction with each other and the motor of the drill. The motor of the drill spins these sets of gears depending on which torque setting is selected and this makes these three components vital in the operation of the drill.

We used AutoDesk Inventor for our CAD package. The reason we chose this is because one of our group members has a fair amount of experience in Inventor. He took classes three separate years in high school and has a good understanding of how Inventor works.

Engineering Analysis

1. Problem Overview:

What function or component can turn electrical energy into mechanical energy?
How much torque will this component have to put out?
How fast will this component need to rotate?
How efficient should this component be?
What size will the component need to be in order to fit into the design of the drill?

2. Diagram:

3. Assumptions:

Friction is neglectful.
12 volts from battery is constant.
Energy is conserved.

4. Governing Equations:

T = PW 9.554 / n
T = torque (Nm)
PW = power (watts)
n = revolution per minute
efficiency=Power out(watts from shaft)/Power in(watts from battery)

5. Calculations

An engineer would take into account the torque that a drill of an average consumer would need. According to blackanddecker.com this drill has a motor with a torque of 130 in-lbs. It also lists the top rpm as 1200. An engineer would consider a suitable torque range and max rpm acceptable to perform the functions expected by this drill. Not only would this motor have to meet these requirements but would also have to meet the size requirements to fit well into the mold. The electrical energy supplied by the battery is also only 12 volts with a maximum compacity of 500 recharges which means that the engineer would need to choose a fairly efficient motor that does not have a huge draw on the battery.

6. Discussion

Here is a list of all the qualifications that can be considered by the engineer in deciding on which motor to use.

• A range of torque values are established.
  
  • Range is from minimum to maximum torque.
    
  • Range is most likely based on hands on testing with different types of screws and materials being screwed into.
    • Material and screws based on average needs in households since the target audience is the common household/handyman.
      
• A range of rpm values are also established.
  
  • There is a need for a motor that handles variable rpms well.
    
  • Not only is there research into how much torque is needed for a certain screw and material, but also an optimum rotational speed is developed as well.
    
• This motor must meet a certain efficiency level.
  
  • The power source is 12 volts and has a maximum capacity which means that the motor cannot draw too much power to drain the battery quickly just to meet the torque and rpm ranges.
    
  • An engineer would also have to take in surveys or do hands on tests of how long they want this drill to last between recharges.
    
• This motor must not be too heavy nor take up too much space.
  
  • The idea behind a household drill is that it is compact, lightweight, and does the expected jobs around the house with ease.
    
  • Consider the cylindrical size constraints and motor weight range based on making this drill as compact and lightweight as possible.
    

Design Revisions