Group 3 - Black and Decker Drill

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 the component was. We also produced CAD drawings and pictures of each component. After all this information was gathered we reassembled the drill.

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

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

Introduction

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

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

Lazarus,Shawn ()

Sendlak,Christopher ()

Davis,Angela ()

Tewes,Jennifer ()

Theresanathan,Jerry()

Before Disassembly

Purpose

The Black and Decker Drill is used to drill holes into various materials (ie. wood, sheetrock). The drill uses an AC current from a wall and directs electricty 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

Step Number	Process	Tool	Level of Difficulty
1	Unscrewed screws to remove plastic casing (housing)	Phillips Head Screwdriver	Easy
2	Removed electrical cord by unscrewing screws	Phillips Head Screwdriver	Easy
3	Removed reverse switch that fits into hole at the base of the motor	Hands	Very Easy
4	Removed circuit box and its parts (two springs, metal strips, wires, silicon chip)	Pliers and Alan Key	Hard
5	Separated drill bit, motor, gears, and magnetic field	Hands	Easy
6	Separated and removed small magnets	Hands	Easy
7	Unsnapped plastic casing around magnetic field	Hands	Medium
8	Unscrewed large screws on magnetic field	Phillips Head Screwdriver	Easy
9	Unlocked the wire locks	Hands	Easy
10	Removed plastic ring that included two wires	Hands	Easy

After Disassembly

Part Table

Part Number	Part Name	Number of Parts of This Type	Part Material & Reason for Material	Function	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	Injection Molding
2	Screws	11 (Casing Screws) 2(Long Screws)	Metal Strength and longivity of part	Holds separate components together	Machined
3	Level	1	Plastic (externally) Strengh and durability Liquid (internally) To allow for the bubble to balance in the liquid	Shows the user if the drill is being held horizontally	Injection Molding
4	Keyless Chuck	1	Plastic (externally) Comfort of use for user Steel (internally) Stenght and longevity	Place for the bit to be held	Injection Molding and Machined
5	Wiring	1	Copper Conductor of electricity Plastic (insulation) Shield other components from electricity	Supplies power to components	Extruded
6	Cord	1	Plastic (externally) Shield user from electrcity Copper wiring (internally) Conductor of electricity	Supplies power to the whole drill	Extruded
7	Trigger	1	Plastic Sheild user from electricity on the inside	Contolls the speed	Injection Molding
8	Chip	1	Silicon Condutor of electricity and computational power	Controls the power supply	Silicon dipping Implantation
9	Armature Coil	1	Copper Conductor of electricity	Allows for the generation of power	Copper wire wound around central axel(Insulated)
10	Commucator	3	Metal Strength and durability	Allows tranfer of electricity in the coil of the central axis
11	Reverse Switch	1	Plastic Strength and comfort for user	Changes the direction that the chuck rotates in	Injection Molding
12	Armature Axel	1	Metal Strength and durability	Allows for motor rotation	Machined
13	Cooling Fan	1	Plastic Light weight and durability	Draws air into the drill to cool down the motor	Injection Molding
14	Field	1	Copper Conductor of electricity	Allows for power genetration from the motor	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 dissapation of heat	Die Cast
16	Armature	1	Metal Conductor of electrcity	Facilitates transfer of power from the coil
17	Cord Clamp	1	Metal(Aluminum) Durability	Holds the cord in place	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	Injection molding
19	Brushes	2	Carbon Longevity to withstand repeated friction	Contact commuter determines drive direction	Machined
20	Brush Holders	2	Metal(Brass) Strength and longevity to withstand friction	Hold the brushes stationary	Sheet metal forming
21	Coil Springs	2	Metal Conductor of electricity	Regulates power supply to the brushes	Sheet meatl forming
22	Gear and Pinion	3	Metal Strength and Durability	Transfers motion to the chuck	Extruded
23	Plate	2	Metal Strength and longevity	Holds the gears in place	Die Cast
24	Cloth Washer	1	Cloth Good cushion to prevent parts from rubbing together	Reduces friction due to the rotating gears and chuck	--
25	Magnetic Insultator	1	Cardboard Insolator	Insulates the copper coil from outside interference	--
26	Circuit Box	1	Plastic Insulator of electrcity	Controlls the speed of motor	--

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 off setting 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 advantagous because these pieces would not be able to slide around in their current slots. Unfortunatly there are no components on the inside of the drill that could be combined because most of the parts need to rotate seperatly to allow the drill to function.

Assembly

Assembly Process Table

Step Number	Process	Tool	Level of Difficulty
1	Connect Chuck to Gears and Plate. Place in Housing	Hands	Easy. Just place parts together and set into housing
2	Attach Brushes into Brush holders	Needle nose pliers	Hard. Needed to pull springs back to attach brushes
3	Connect wires to straiter and armature	Hands	Medium. Make sure wires are correctly aligned and attached to the field
4	Using the long screws, connect motor and commuter together	# 15 Torque Driver/Phillips Screwdriver	Hard. Needed to make sure all parts were aligned, which was difficult due to the lack of visability in these parts
5	Attach trigger to the housing	Hands	Easy. Just place in the hole in the housing
6	Connect wires from straiter and armature to the trigger	Hands	Easy. Make sure that the wires are connected into the corrent holes
7	Connect cord to wires	Hands	Easy. Make sure that like wires are connected to each other and simply twist ends together
8	Screw wire clamp over the wires from the cord	# 15 Torque Driver/Phillips Screwdriver	Easy. Screws are easy to attach becasue of the high visability of the parts
9	Attach reverse switch to housing	Hands	Easy. Slides into hole
10	Attach level to housing	Hands	Easy. Simply place in slot on top of housing
11	Attach level to housing	Hands	Easy. Slide into the hole in the housing
12	Attach bit holder to housing	Hands	Easy. Slide into hole on the housing
13	Fit top half of housing on top and screw two halves together	# 15 Torque Driver/Phillips Screwdriver	Easy but time consuming to screw in all the individual screws into the casing; also to properly align housing make sure that the wires are out of the way

After Assembly

Disassembly vs. Reassembly Discussion

The disassembly and reassembly process were basically the reverse of each other. It took less time to dissasemble 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 seperated. 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 power from the AC power cord and changes it to mechanical energy to rotate the spindle and motor. This allows for mechanical energy to be produced to rotate the chuck to allows 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 controll allows for the variable speeds of the drill. The commutator allows the drill to run on direnct 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 transfored along the spindle to the chuck. The reverse switch allows for the change in direction of the current which in turn changes the direction that the chuck rotates in. 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 agin could be a working prototype or actual drill. Another type of analysis that could be is strenth 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 can be used to model this test.