Group 3 - Black and Decker Drill

Latest revision as of 11:13, 8 December 2006

Executive Summary

We disassembled, analyzed, and reassembled a Black & Decker power drill. This drill is a DR 202, 120 V, 50/60 Hz, 5 A, 0-1350 revolutions per minute power drill

We took each component of the drill apart and analyzed it to determine the function and why each part was made of it material and shape. This helped us better understand how the drill worked on the component level.

By analysis and research, we were able to determine what each component was, and produced CAD drawings and pictures of each component. After all this information was gathered, we reassembled the drill.

Assembly was fairy easy and basically the reverse of the disassembly process.

After we disassembled, analyzed, and reassembled the Black & Decker power drill we gained a better comprehension of how the drill worked.

Introduction

This product is a Black & Decker Drill which is designed to use different size bits to drill holes in various materials. The drill runs by changing electrical energy into mechanical energy inside the drill motor. The drill also has a reverse function.

Each member was responsible for the following parts of the project:

Shawn Lazarus (Disassembly & Presentation)

Christopher Sendlak (Group Leader, Disassembly & Reassembly & Manufacturing Processes)

Angela Davis (Reassembly & Web Site)

Jennifer Tewes (Disassembly & Reassembly & Web Site)

Jerry Theresanathan (Disassembly & Pictures & Presentation)

Before Disassembly

Purpose

The Black and Decker Drill is used to drill holes into various materials (i.e. wood, sheetrock). The drill uses an AC current from a wall and directs electricity to a motor to create rotational motion. This motion is transferred to the gears in order to create rotation within the drill bit.

Operation

The product works and runs smoothly by changing AC power from a power outlet into mechanical energy in the drill to turn the bit. This is demonstrated best when the drill's trigger is pulled because you can hear the motor and the cooling fan rotating.

Amount of Components

We estimated that the drill is made of approximately ten components. These ten components include:

1. Motor
2. Trigger switch
3. Cord
4. Drill bit
5. Level
6. Cooling fan
7. Casing
8. Direction switch
9. Trigger lock
10. Chuck
11. Screws
12. Gears

Types of Materials

We estimated that the drill is made of approximately five materials. These five materials include:

1. Plastic
2. Rubber
3. Steel
4. Copper wiring
5. Water (Liquid in level)

Disassembly Procedure

Disassembly Process Table

After Disassembly

Part Table

Part Number	Part Name	Number of Parts of This Type	Part Material & Reason for Material	Function	Reason for Shape	Part Manufacturing Process	Image of Part	CAD File
1	Housing	1	Plastic Non-conducting to shield user from electricity and moving parts inside Rubber (grip) Comfort to user	To contain all components, and make the drill user-friendly	To contain all of the components inside and to allow the user to easily use the drill	Injection Molding
2	Screws	11 (Casing Screws) 2(Long Screws)	Metal Strength and longevity of part	Holds separate components together	Phillips head to allow for easy alignment during manufacturing	Machined
3	Level	1	Plastic (externally) Strength and durability Liquid (internally) To allow for the bubble to balance in the liquid	Shows the user if the drill is being held horizontally	To effectively allow for the bubble to be read easily and to show if the drill is horizontal	Injection Molding
4	Keyless Chuck	1	Plastic (externally) Comfort of use for user Steel (internally) Strength and longevity	Place for the bit to be held	To allow for the drill bit to be held in place easily	Injection Molding and Machined
5	Wiring	1	Copper Conductor of electricity Plastic (insulation) Shield other components from electricity	Supplies power to components	To supply enough power to the components but also small enough to fit into tight spaces in the drill	Extruded
6	Cord	1	Plastic (externally) Shield user from electricity Copper wiring (internally) Conductor of electricity	Supplies power to the whole drill	Allows for the cord to be flexible and fit into a standard power outlet	Extruded
7	Trigger	1	Plastic Shield user from electricity on the inside	Contols the speed	Easily conforms to the users fingers to allow for easy use	Injection Molding
8	Chip	1	Silicon Conductor of electricity and computational power	Controls the power supply	Allows for efficient power control	Silicon Dipping Implantation
9	Armature Coil	1	Copper Conductor of electricity	Allows for the generation of power	Many coils to more effectively produce current	Copper wire wound around central axel(Insulated)
10	Commucator	3	Metal Strength and durability	Allows transfer of electricity in the coil of the central axis	Cylindrical and formed around the axial to be able to connect effectively to the field and the axial which allows for the rotation of the components	Sheet Metal Forming and Machining
11	Reverse Switch	1	Plastic Strength and comfort for user	Changes the direction that the chuck rotates in	Allows of ease of use by the user and to efficiently switch the direction of the current.	Injection Molding
12	Armature Axel	1	Metal Strength and durability	Allows for motor rotation	Allows for easy rotation because it is a cylindrical shape	Machined
13	Cooling Fan	1	Plastic Light weight and durability	Draws air into the drill to cool down the motor	Fin shape to sufficiently draw air over the drill components	Injection Molding
14	Field	1	Copper Conductor of electricity	Allows for power generation from the motor	Many coils allow for the effective generation of power	Copper wire wound on Injection Molded plastic encased in formed sheet metal
15	Heat Sink	1	Metal Strength and longevity	Regulates the rotation of the spindle, aides in dissipation of heat	Ridges to control the rotation and the holes to allow for heat to escape	Die Cast
16	Armature	1	Metal Conductor of electricity	Facilitates transfer of power from the coil	Circular to encase the coil and to effectively transfer the electricity to the other components	Die Cast
17	Cord Clamp	1	Metal(Aluminum) Durability	Holds the cord in place	To hold the wires down without being bulky to get in the way of other components	Sheet metal forming
18	Casing of copper coil and metal rings	1	Plastic Light weight and non-conductor of electricity	Protects and insulates the coil	Formed around the field to contain the electricity that the field forms	Injection molding
19	Brushes	2	Carbon Longevity to withstand repeated friction	Contact commuter determines drive direction	To make efficient contact with the commutator	Machined
20	Brush Holders	2	Metal(Brass) Strength and longevity to withstand friction	Hold the brushes stationary	To effectively hold the brushes in place	Sheet metal forming
21	Coil Springs	2	Metal Conductor of electricity	Regulates power supply to the brushes	Spring shape efficiently regulate power to the brushes	Sheet metal forming
22	Gear and Pinion	3	Metal Strength and Durability	Transfers motion to the chuck	To allow for maximum amount of rotational motion transfer along the drill head	Extruded
23	Plate	2	Metal Strength and longevity	Holds the gears in place	To hold all of the gears in place without causing unnecessary friction	Die Cast
24	Cloth Washer	1	Cloth Good cushion to prevent parts from rubbing together	Reduces friction due to the rotating gears and chuck	Circular to fit on the axial and thick to cushion the rotating parts from each other	Machining
25	Magnetic Insulator	1	Cardboard Insulator	Insulates the copper coil from outside interference	Inside of the coil and shaped like the coil to insulate the coil and to minimize space taken up by the insulator	Machining
26	Circuit Box	1	Plastic Insulator of electricity	Controls the speed of motor	To contain all of the internal components effectively in as small of a space as possible	Injection Molding (casing) Machining(Inside components)

Drill Head and Gear Box Assembly

Part Name	Picture	CAD File
Whole Front Assembly
Drill Head Assembly
Gear Assembly
Gear and Plate Assembly
Small Gear Assembly
Small Gear
Small Washer
Small Plate
Large Gear
Large Washer
Large Plate

Design Changes on the Component Level

A change that could be made on the component level of the drill would be to mold the bit holder and level into the plastic housing. This could be accomplished by setting holder and level to one side of the two housing halves, because in the current design the bit holder and the level are placed between the two halves of the housing. This would be advantageous because these pieces would not be able to slide around in their current slots, and it could also decrease assembly time. Unfortunately, there are no components on the inside of the drill that could be combined because most of the parts need to rotate separately to allow the drill to function.

Assembly

Assembly Process Table

After Assembly

Disassembly vs. Reassembly Discussion

The disassembly and reassembly process were basically the reverse of each other. It took less time to disassemble then to reassemble because during reassembly we had to make sure that everything was properly aligned. When the drill was disassembled it basically fell out of the housing once the two halves were separated. To reassemble the drill it took more time to properly align all of the components. The exact same tools were used for both disassembly and reassembly. The entire drill was able to be reassembled with relative ease but it is suggested that it is not used for an extended period of time because of the grease that was lost form the gears during the disassembly process.

Operation

The drill works by converting electrical energy from the AC power cord to mechanical energy to rotate the spindle and motor. The now mechanical energy allows the chuck to rotate and the drill to operate. Also, a magnetic field exists between the stator and the armature. This allows for a current to be produced in the field, which in turn produces a voltage that is controlled by the trigger. This control allows for the variable speeds of the drill. The commutator allows the drill to run on direct power (DC) instead on alternating (AC) power. It does this by periodically reversing the direction of the current produced by the motor. This produces rotational motion that is transformed along the spindle to the chuck. The reverse switch allows for the change in direction of the current which in turn changes the direction in which the chuck rotates. The fan on the spindle allows for the constant cooling down of the gears and other rotating parts.

Analysis Discussion

Thermodynamic analysis could be used to determine the threshold condition that will cause the drill to overheat and possibly start on fire. A working prototype of the drill or an actual drill could be used as the model for this test. Stress analysis could be used to determine the wear and tear on the chuck from repeated use. The model for this again could be a working prototype or an actual drill. Another type of analysis that could be is strength and durability testing on the plastic housing. This is important because the consumer does not want to buy a product that will break the first time it is dropped. A model that could be used for this is a working prototype.

Design Changes and Recommendations

One design change could be to have another handle on the drill along the chuck. This would provide more stability for the user because the center of mass is above the handle, making it top heavy and awkward to hold. This extra handle would allow for the user to more easily support the drill. This handle could also be removable so that a consumer who does not like this extra handle, or if the handle was to get in the way in a small space then it could be removed. This could be accomplished with clips on the casing that this extra handle could be attached. A second design change could be to have a cord that is retractable, this would allow the user to easily store the drill and not have cords tangle up. Another feature that could be changed would be to allow the chuck to fit various size bits. This would allow the user to customize the drill to their own specifications. This can be accomplished by having the option for the user to change the chuck so that a different bit sixe could be used. At a marketing standpoint this is a good ploy because the company will be able to make more money off of the different chucks that they sell. The product would also be more appealing to consumers too; they would like the idea that the drill has more features than other brands, as well as the idea that they can just use one drill for any size bit. Also the company could make the housing from recyclable plastic. This is a way to cut down on material cost for the company because they could recycle the plastic from old or broken drills. This could be accomplished by having consumers return their broken drills for a discount or some other marketing ploy. These could make the drill a more desirable product for consumers, which in turn would make the company more productive.

References

Black & Decker. (2003). Instruction Manual for Models DR201, DR202, DR211, DR220, DR403, DR501 and DR601. Towson, MD: Author.

Commutator (electric). (2006, September 18). In Wikipedia, The Free Encyclopedia. Retrieved 14:06, November 22, 2006, from http://en.wikipedia.org/w/index.php?title=Commutator_%28electric%29&oldid=76368620