Group 39 - Black and Decker Drill

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Contents

Executive Summary

Description

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. Maintance only requiring a standard (flathead or #15 Torx) screwdriver.

The major functioning parts to this product were the housing, keyless chuck, gear 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 as well as to drive, 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 which is converted 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:

  1. Motor Assembly
  2. Cooling Fan
  3. Direction Switch
  4. Trigger
  5. Cord
  6. Level
  7. Chuck
  8. Gears
  9. Shell
  10. Trigger Lock
  11. Gear Assembly

Materials

We assumed that there are 5 different types of materials used in the drill. Some examples of materials we found are:

  1. Rubber
  2. Metal
  3. Plastic

Disassembly Procedures

Drill Disassembly Process Table

Dissasembly of the drill takes approxamately 30-40 minutes. The drill (not the trigger assembly) could be taken apart by anyone with basic tech knowledge and a flathead screwdriver.

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

Trigger Disassembly Process Table

Note** There are not many steps in the trigger dissasembly but they are very difficult and all pieces are very small. Pay close attention so no pieces get lost during this process. Dissasembly takes approxamately 5 minutes.

Step # Process Tool(s) Level of Difficulty
1 Remove the upper housing from the lower housing. At the bottom of a trigger there is a snap fit for these two pieces. Wedge a very thin flathead screwdriver under the upper half and pop it out of the grooves, do this with the other side as well and the top will come right off. The Metal Connection Piece will fall out during this step so make sure you do not lose it. Thin flathead screwdriver and hands Medium <30seconds
2 Remove the trigger from the upper housing by pulling it straigh out. Then remove the spring which fits snug to the upper housing. There is also a much smaller spring which fits into the bottom of the trigger. Hands Easy <30seconds
3 Remove the Rear plate by pulling it straight out of the back of the lower housing. Thin flathead screwdriver and Hands Easy <15seconds
4 Remove the slider and slider spacer by simply pulling them off of the chip. Hands Easy <20seconds
5 Remove the Chip by wiggling it lengthwise back and forth until it pulls straight out. A small flathead screwdriver can assist in the process. Thin flathead screwdriver and hands Medium <1minute

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.
Description
2 3/4" Screws with #15 Torx/Flathead heads 11 Metal Metal Casting Holds pieces of the drill together.
Description
3 1 7/8" Screws with #15 Torx/Flathead heads 2 Metal Metal Casting Holds the stator to the piece on the stator which holds the brushes.
Description
4 Level Holder 1 Plastic Injection Molding Holds the level in place.
Description
5 Level 1 Plastic and water(or liquid) Injection Molding For use to get the drill straight when driving screws or drilling holes.
Description
6 Bit Holder 1 Plastic Injection Molding Holds an extra screw driving bit, which is very handy when changing bits often.
Description
7 Double sided flathead/Phillips bit 1 Metal Metal Casting For use with flathead or phillips screws.
Description
8 Power Cord 1 Insulated Metal Extruded and Injection Molded Supplies power to the drill
Description
9 Wire Bracket 1 Metal Die Casting Holds the power cord sucurely onto the drill
Description
10 Trigger

(also see below)

1 Plastic Injection Molding Adjusts the speed of the drill by pressure applied to it.
Description
11 Wiring 2 (1 black, 1 white) Insulated Metal Extruded Makes power connections within the drill
Description
12 Directional Switch 1 Plastic Injection Molded Adjusts the direction in which the drill turns.
Description
13 Keyless Chuck 1 Plastic with a Metal core Metal Casting and Injection Molded Holds the bit tightly in place
Description
14 Motor 1 Metal, Plastic, Copper Wire Provides the electrical power for the drill Drives the drill due to current running through it.
Description
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.
Description
16 Commutator 1 Copper Metal Casting and sheet metal forming Creates an electric field
Description
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.
Description
18 Brush Holders 2 Metal Sheet Metal Forming Hold the brushes in place
Description
19 Brushes 2 Graphite Molded Makes contact with the commutator.
Description
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.
Description
21 Coil Springs 2 Metal Sheet Metal Forming Puts tension on the brushes so that they make contact with the commutator.
Description
22 Cooling Fan 1 Plastic Injection Molding Cools off the motor.
Description
23 Gearbox

(also see below)

1 Metal Metal Casting Creates the mechanical power for the drill.
Description

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.
Description
10b Housing (Lower) 1 Plastic Injection Molding Holds all components of the trigger.
Description
10c Double Finger Trigger 1 Plastic Injection Molding Fits the fingers of the user for comfort.
Description
10d Trigger Spring 1 Metal Extruded Pushes the trigger back to stop the drill when pressure is no longer applied to the trigger.
Description
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.
Description
10f Electrical Connection Piece 1 Metal Metal Casting or Sheer Cut Makes an electrical connection within the trigger.
Description
10g Electrical Connection Piece Spring 1 Metal Extruded Puts pressure on the Electrical Connection Piece to get a good electrical connection.
Description
10h Slider 1 Silicone and Copper Silicone Dipping Makes connections with the Chip.
Description
10i Slider Spacer 1 Silicone Sheer Cut Provides space between the Slider and the Chip.
Description
10j Rear Plate 1 Metal Sheer Cut and Bent Covers up the rear of the trigger housing.
Description

Gearbox Parts Table

Part # Part Quantity Material Manufacturing Process Purpose Picture CAD Diagram
23a Motor Shaft 1 Stainless Steel Metal Casting Drives the gears.
Description
N/A
23b Plate #1 1 Stainless Steel Metal Casting Holds the Motor Shaft securely to the gear assembly, as well as provides stability withing the housing of the drill (knotches into the housing).
Description
See Below
23c Rubber Spacer 1 Rubber Injection Molding Provides a small gap to reduce friction.
Description
See Below
23d Fabric Spacer 1 Felt? Sheer Cut Prodived a gap to reduce friction.
Description
See Below
23e Plate #2 1 Stainless Steel Metal Casting Provides stability withing the housing of the drill (knotches into the housing).
Description
See Below
23f Large Gear 1 Stainless Steel Metal Casting Produces more power when in conjunction with other gears.
Description
See Below
23g Gear and Pinion 1 Stainless Steel Metal Casting Produces more power when in conjunction with other gears, pinion creates spacing and alignment.
Description
See Below

3D Computer Aided Design

Description


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 #1

Plate #2

Rubber Spacer

Fabric Spacer

Large Gear

Gear and Pinion

Assembly

Assembly is very basic and takes approxamately 20-30 minutes.

Step # Process Tool(s) Level of Difficulty
1 Start with left side (looking down the drill) 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

Trigger Assembly Process Table

Note** There are not many steps in assembling the trigger but they are very difficult and all pieces are very small. Pay close attention so no pieces get lost during this process. Assembly takes approxamately 15-20 minutes because of all the small pieces and extreme difficulty of step #5.

Step # Process Tool(s) Level of Difficulty
1 Start off with the lower housing and insert the chip into its slot. Hands Medium <30seconds
2 Place the slider spacer and slider on top of the chip. Hands Easy <30seconds
3 Now move to the trigger. Insert the small spring into the botom of it. Hands Easy <15seconds
4 Insert the large spring into the upper housing. Put the trigger into the upper housing as well and press the lock down on the trigger to hold it in place. This can be very tricky due to the tension on the spring. Hands Medium <20seconds
5 Holding the upper housing upside down, place the electrical connection piece, upside down, on top of the small spring in the trigger. On the bottom of the housing place the slider all the way to the back of the chip. While holding the top housing upside down place the bottom housing onto it. This process is extremely trickey and may take several attemps. Hands Difficult <5-8minutes
6 Slide the rear plate into the slot at the rear of the housing. 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 its 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 #15 torx 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 multi-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