Group 39 - Black and Decker Drill

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Latest revision as of 22:15, 9 December 2006

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:

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

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