Group 39 - Black and Decker Drill
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Revision as of 14:02, 8 December 2006
Contents |
Executive Summary
We received a DR202 Black and Decker corded drill. We disassembled the drill, analyzed all components, and then reassembled it. There were approximately 20 mainline components and about 15 small end parts with maintance only requiring a standard (flathead/phillips) screwdriver to do the work.
The major functioning parts to this product were the housing encasement, chuck, fan assembly, 5A motor, and the power cord.
Every member of the team had a specific component to the final project. The delegation of work for each person was appropriate so all members had an equal share. As far as the ergonomics to these tasks, there was very little that gave us (sophomore engineers) any trouble with any stage of this project.
The company, Black and Decker, has done a great job over the past 90 years to ensure a safe, reliable, and cost effective product.
Introduction
This product is a Black & Decker Drill model DR202. This is a corded drill (6') which runs off of AC current. It is used to drill holes into various materials as well as drive or remove screws. It has a 15 position keyless chuck and variable speed (depending on the trigger pull). It also has a switch to reverse the direction of the drive.
Each member was responsible for the following individual parts of the project, as well as the parts that the group was responsible for as a whole:
Baumgardner, Brad (Group Leader, Presentation & Wiki page)
Ennis, Jacob (Disassembly, Pictures & Wiki page)
LaVerde, Shawna (Before Disassembly & Wiki page)
Rauch, Samuel (CAD)
Robitaille, Zack (After Assembly & CAD)
Shibuya, Yuta (Assembly)
Before Disassembly Section
Purpose
The purpose of a drill is to producing holes in solid materials by using a drill bit and to insert, tighten, loosen or remove screws by using a screwdriver head. The drill bit is removable with cutting edges on one end and the shank at the other which is attached to the chuck of the drill. There are different types of drill bits, shank and chuck combinations designed for different purposes, like producing a higher torque. Detachable screwdriver heads are also called bits and come in different sizes and styles. The drill bit and screwdriver head work by the drills electric motor rotating them at high speeds. This drill contains a solid state phase control circuits that allow it to only use AC power, which also gives it the ability to change speeds, go in reverse and torque control.
Operation
The drill works great. The drill bit moves clockwise, however you can switch it to turn counterclockwise. The ability to rotate clockwise is used in drilling and inserting/tightening screws, whereas counterclockwise motion is used to loosen or remove screws. The drill runs on AC power from the power outlet into mechanical power to the keyless chuck.
Components
Our estimation of the amount of components in this product is 35. Some examples of the main parts include:
- Motor Assembly
- Cooling Fan
- Direction Switch
- Trigger
- Cord
- Level
- Chuck
- Gears
- Shell
- Trigger Lock
- Gear Assembly
Materials
We assumed that there are 5 different types of materials used in the drill. Some examples of materials we found are:
- Rubber
- Metal
- Plastic
Disassembly Procedures
Disassembly Process Table
| Step # | Process | Tool(s) | Level of Difficulty |
|---|---|---|---|
| 1 | Remove the (9) 3/4" screws that hold the housing together and pull the right side off, setting the left side down on the counter to be further disassembled. Pull the level and the bit holder from their form fit between the two halves. | # 15 Torx or flathead screwdriver and hands | Easy <2minutes |
| 2 | Remove power cord bracket, by removing (2) 3/4" screws | # 15 Torx or flathead screwdriver | Easy <1minute |
| 3 | Remove the power cord and trigger by pulling it up from the groves in the casing. | Hand | Easy <5seconds |
| 4 | Remove the directional switch (located above the trigger) by pulling up and out(away from the trigger) | Hand | Easy <5seconds |
| 5 | Remove all the internals from the drill By pulling up on them from the housing. Use both hands when removing the motor and gears. | Hands | Easy <10seconds |
| 6 | Remove the Chuck and gear assembly by pulling them off the drive shaft of the motor. Keep them all assembled as they were on the drive shaft and set them aside for now. | Hands | Easy <10seconds |
| 7 | Now go to the motor. Remove the armature rotor (inner part of the motor) by pulling it out from the Stator (outer part of the motor). When doing this you must press inward on both brushes at the rear of the stator. | Hands and small flathead screwdriver | Fairly easy <1minute |
| 8 | Remove both 1 7/8" screws at the rear of the stator. | # 15 Torx or flathead screwdriver | Easy <30seconds |
| 9 | Pry apart the stator from the part that holds the brushes attached to the rear of the stator. It will pry apart hard. *Note: The part with the numbers lines up with the black wire on the rear left. | Hands and small flathead screwdriver | Medium <1minute |
| 10 | Remove the black and white wires from the part which holds the brushes. *NoteThe black wire has a "B" on the side where it goes. | Hands | Easy <5seconds |
| 11 | Now go back to the part with the chuck and gears. Pull the chuck and gears apart into three pieces. | Hands | Easy <10seconds |
After Disassembly
Part Table
| Part # | Part | Quantity | Material | Manufacturing Process | Purpose | Picture |
|---|---|---|---|---|---|---|
| 1 | Housing | 2 Halves (left and right) | Plastic and rubber | Injection Molding | Rubber located around trigger for increased grip. protects all the internal pieces of the motor. |  |
| 2 | 3/4" Screws | 11 | Metal | Metal Casting | Holds pieces of the drill together. |  |
| 3 | 1 7/8" Screws | 2 | Metal | Metal Casting | Holds the stator to the piece on the stator which holds the brushes. |  |
| 4 | Level Holder | 1 | Plastic | Injection Molding | Holds the level in place. |  |
| 5 | Level | 1 | Plastic and water(or liquid) | Injection Molding | For use to get the drill straight when driving screws or drilling holes. |  |
| 6 | Bit Holder | 1 | Plastic | Injection Molding | Holds an extra screw driving bit, which is very handy when changing bits often. |  |
| 7 | Double sided flathead/Phillips bit | 1 | Metal | Metal Casting | For use with flathead or phillips screws. |  |
| 8 | Power Cord | 1 | Insulated Metal | Extruded and Injection Molded | Supplies power to the drill |  |
| 9 | Wire Bracket | 1 | Metal | Die Casting | Holds the power cord sucurely onto the drill |  |
| 10 | Trigger
(also see below) |
1 | Plastic | Injection Molding | Adjusts the speed of the drill by pressure applied to it. |  |
| 11 | Wiring | 2 (1 black, 1 white) | Insulated Metal | Extruded | Makes power connections within the drill |  |
| 12 | Directional Switch | 1 | Plastic | Injection Molded | Adjusts the direction in which the drill turns. |  |
| 13 | Keyless Chuck | 1 | Plastic with a Metal core | Metal Casting and Injection Molded | Holds the bit tightly in place |  |
| 14 | Motor | 1 | Metal, Plastic, Copper Wire | Provides the electrical power for the drill | Drives the drill due to current running through it. |  |
| 15 | Armature Shaft | 1 | Metal | Metal Casting | Spins due to the current created in the motor and drives the gear box which drives the chuck. |  |
| 16 | Commutator | 1 | Copper | Metal Casting and sheet metal forming | Creates an electric field |  |
| 17 | Rotor | 1 | Copper wire (wrapped tightly around the Armature Shaft) | Copper wire is most likely wound by some type of machine. | Spins within the electrical field created. | |
| 18 | Brush Holders | 2 | Metal | Sheet Metal Forming | Hold the brushes in place |  |
| 19 | Brushes | 2 | Graphite | Molded | Makes contact with the commutator. |  |
| 20 | Stator | 1 | Metal, Copper Wire, Plastic | Injection Molding, Die Casting, Copper wrapped around the core | Creates an electric field when electricity is run through it. | |
| 21 | Coil Springs | 2 | Metal | Sheet Metal Forming | Puts tension on the brushes so that they make contact with the commutator. | |
| 22 | Cooling Fan | 1 | Plastic | Injection Molding | Cools off the motor. |  |
| 23 | Gearbox
(also see below) |
1 | Metal | Metal Casting | Creates the mechanical power for the drill. |  |
Trigger Parts Table
| Part # | Part | Quantity | Material | Manufacturing Process | Purpose | Picture |
|---|---|---|---|---|---|---|
| 10a | Housing (Upper) & Trigger Lock Switch | 1 | Plastic | Injection Molding | Holds all components of the trigger. |  |
| 10b | Housing (Lower) | 1 | Plastic | Injection Molding | Holds all components of the trigger. |  |
| 10c | Double Finger Trigger | 1 | Plastic | Injection Molding | Fits the fingers of the user for comfort. |  |
| 10d | Trigger Spring | 1 | Metal | Extruded | Pushes the trigger back to stop the drill when pressure is no longer applied to the trigger. |  |
| 10e | Chip | 1 | Silicone and Copper | Silicone Dipping | Works just like a light dimming switch in that when more pressure is applied to the trigger more power to derived from the drill. |  |
| 10f | Electrical Connection Piece | 1 | Metal | Metal Casting or Sheer Cut | Makes an electrical connection within the trigger. |  |
| 10g | Electrical Connection Piece Spring | 1 | Metal | Extruded | Puts pressure on the Electrical Connection Piece to get a good electrical connection. |  |
| 10h | Slider | 1 | Silicone and Copper | Silicone Dipping | Makes connections with the Chip. |  |
| 10i | Slider Spacer | 1 | Silicone | Sheer Cut | Provides space between the Slider and the Chip. |  |
| 10j | Rear Plate | 1 | Metal | Sheer Cut and Bent | Covers up the rear of the trigger housing. |  |
Gearbox Parts Table
| Part # | Part | Quantity | Material | Manufacturing Process | Purpose | Picture | CAD Diagram |
|---|---|---|---|---|---|---|---|
| 23a | Motor Shaft | 1 | Stainless Steel | Metal Casting | Drives the gears. |  |
|
| 23b | Plate #1 | 1 | Stainless Steel | Metal Casting | Holds the Motor Shaft securely to the gear assembly. |  |
|
| 23c | Rubber Spacer | 1 | Rubber | Injection Molding | Provides a small gap to reduce friction. |  |
|
| 23d | Fabric Spacer | 1 | Felt? | Sheer Cut | Prodived a gap to reduce friction. |  |
|
| 23e | Plate #2 | 1 | Stainless Steel | Metal Casting | File:Plate Description |
||
| 23f | Large Gear | 1 | Stainless Steel | Metal Casting | Produces more power when in conjunction with other gears. |  |
|
| 23g | Gear and Pinion | 1 | Stainless Steel | Metal Casting | Produces more power when in conjunction with other gears, pinion creates spacing and alignment. |  |
3D Computer Aided Design
3D Cad Drawings were done of the gearbox. We had noticed that this was one of the most important and intricate parts of the entire drill and used CAD to better analyze these key components. Shown in the CAD drawning of the gearbox to the right are the following parts:
Keyless Chuck
Plate A
Plate B
Rubber Spacer
Fabric Spacer
Large Gear
Gear and Pinion
Assembly
| Step # | Process | Tool(s) | Level of Difficulty |
|---|---|---|---|
| 1 | Start with right side drill housing | none | Easy |
| 2 | Put power cord and trigger on the grip and fasten them by (2) 3/4" screws with a power cord bracket. | # 15 Torx or flathead screwdriver | Easy <1minute |
| 3 | Put together outside motor and power cord. When we connected them, we had to pay attention which wire was going to which hole. We put the black wire through the hole named as B and the white one through the other side. The other side was not named. | Hand | Medium <2minutes |
| 4 | Connect the end of the stator which holds the brushes to the stator using (2) 1 7/8" screws | # 15 Torx or flathead screwdriver | Easy <1minute |
| 5 | Put the two brushes back in their housings whose colors were gold. When we put them back , we had to pay attention the shape of surface of magnets. One side was flat but the other side was rounded. Put the magnets in their housing with the rounded side touching the comutator. | Hands | Medium <3minutes |
| 6 | Put the armature rotor back into the motor. At this step, the rounded sides of the brushes touch the copper on the commutator(part of inner motor). Tension had to be put on the brushes at this step in order for the commutator to fit back into place. | Flathead Screwdriver to assist in putting tension on the brushes | Medium <3minutes |
| 7 | now combine the three pieces of the gear assembly | Hands | Easy <30seconds |
| 8 | Combine the chuck and the gear assembly by putting the rotor into the gear assembly through the first plate. | Hands | Easy <30seconds |
| 9 | Put the level and the spare bit holder back into place on the housing of the drill. | Hands | Easy <1minute |
| 10 | Put the right side of the drill on top of the side with all the pieces now assembled into it. Use (9) 3/4" screws to fasten it back together. | # 15 Torx or flathead screwdriver | Easy <3minutes |
| 11 | Plug it in and see if it works. It works!!! | Hands | Easy <10seconds |
After Assembly
Working Operation
After plugging in the drill and pulling the trigger, electricity flows through the drill. This flow coming from the cord goes into the motor, which then turns the gears. The gears then cause the chuck to spin either clockwise or counter clockwise based on which side the switch above the trigger is on. When you release the trigger, the motor deceases it output power and stops spinning which causes the gears and the chuck to stop. If one were to pull the trigger and press in the triangular button on the left side of the handle, the trigger locks in the pulled position and the drill continues to spin until the trigger is released, which then disengages the lock. Our product works the same after the dis/re-Assembly process.
Analysis
To design and test our product, there are a few different types of analysis that could be used. These include ergonomic analysis to design a comfortable and easy to use handle and trigger, proper distribution of weight and center of mass, and the proper length of the power cord needed for average use. Furthermore, an energy analysis could be used for the power needed in the drill to work effectively on different types of materials doing different jobs (i.e. how much power the drill would need to output to screw a wood screw into a two-by-four, or drill a ½ inch diameter hole in a piece of steel ½ inch thick).
Models
A basic engineering model that could be used to determine the best ergonomically positioned grip and trigger would be to use the basic setup of a pistol, which is essentially the same setup as a drill. Also, to find how much power would be needed to screw a wood screw into a two-by-four would be to measure the power it takes to use a non-electrically powered screwdriver and screw a wood screw into a two-by-four.
You could use estimates for these models because the style/setup of each model can vary. For example, different styles of pistols have different grip and trigger setups, and it will take varying amounts of power to screw a screw into different materials.
Disassembly/Assembly
The disassembly and reassembly processes were reverse of one another, the way the drill was designed, one would have to work from inside out to put the drill back together after working from the outside in to take it apart.
The same tools were used to take the drill apart and put it back together. These included a flathead and phillip screwdriver.
We were able to reassemble the drill because the parts were not assembled in the beginning in such a way that it made them impossible to put back together. They came apart in groups of pieces, and each group broke down into its individual parts which were easy to put back together.
Possible design changes
Our group would recommend a few design changes, which include putting the center of mass of the drill directly over the handle so it is easier to balance in your hand and moving the spare bit holder to the back of the drill and fashioning it out of the same piece of plastic that the black cap on the back is made of. This would reduce the cost of having to mold a whole separate piece for the holder where it is now.
Some new features that we would recommend would be a battery instead of the wire for power, a perpendicular handle on the side of the drill to help press on the drill during use, and a wrist strap that would pull a key out of the drill and turn it off if it were dropped from the user’s hands.
We would not recommend a new shape or layout because the shape and layout of the drill now have been tried and tested for years and have remained the standard for power drills. It is a stylish drill, and we would not recommend changing it in that manner. As for the configuration, its setup is well thought out and easy to use except for the issue with the center of mass.
Recommendations
Our group would recommend that the company could reevaluate their design in the field regarding centers of mass and bit holder placement. If the bit holder were made out of the same material plastic that the end cap is made of, the company would not have to mold a whole separate piece, thus saving time and money.
Its use is straight forward, and our group feels no additional recommendation would be required in this area. The few maintenance requirements may be changing the bit occasionally and keeping the mechanical components lubricated. Unless it’s used improperly or abused, it should never stop working.
There are many models a customer could get from this company depending on the job requirements. Since our product is a corded drill I could recommend replacing the cord for a cordless but Black and Decker already sells a different drill with this option so the suggestion would become redundant. This company started in 1917 and since then has become a muti-billion dollar distributing industry. Thousands of intelligent people from multiple generations have worked to improve this product, so it would be arrogent at best to presume that I could solve all possible design improvement this drill may need.
References
Group analysis and discussions with all members of team
Multiple hardware store employee interviews (i.e. - Home depot, Lowe's, True Value)
www.blackanddecker.com/ProductGuide
