Group 12 - Black and Decker Drill

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Contents

Executive Summary

This page includes information on the disassembly and reassembly process of the screw gun. It includes a list of all the inner and outer components along with their importance to the function of the gun. There is a break down of how the gun actually works and a list of suggested improvements.


This page was created by Eric Sobczynski, Janelly Pineda, Stephen O’Hara, Shannon Orrange, and Erica Kerr. The group is a part of the University at Buffalo School of Engineering.

Introduction

The Black & Decker screw gun is an electrical powered device with a compact design that allows for the quick installation and removal of screws from drywall as well as several different materials. The screw gun costs a total of $37.50 and is advertised as the 5.0 Amp 3/8" VSR Drill with Overmolds, Model # DR202.

Each member of the group was responsible for different parts of the project but most of the project was a collaborated effort. Discussions took place for each section of the wirte up and the information included was decided upon before the write ups took place. Eric was the group leader and was in charge of the “Before Disassembly” write up, the photos, cad drawings of the individual components and the "Improvements" write up. Erica was in charge of the power point presentation. Janelly was in charge of the “Finish Disassembly” write up and the input of the data in the Parts Description Table. Shannon was in charge of the "Executive Summary” and the “Introduction” sections. Steve was in charged of the “After Assembly” and the “References/More Info” sections. The Acual disassembly and reassmbly of the product was completed by all the members.

Before Disassembly Section

The screw gun is a tool used in construction to fasten different types of screws for the purpose of securing a given object. This tool has other uses as it is capable of using different types of bits to perform some form of rotational operation. Other uses include using drill bits to drill holes in a given material.


This tool uses electricity from a normal 110 volt outlet. The electrical energy from the outlet is converted to mechanical energy in the motor of the screw gun. The motor does this operation by supplying the electrical power to the motor which it creates a magnetic field which is able to turn the shaft of the motor and outputs the necessary mechanical energy to fasten the screw.


The electric to mechanical energy is not a 100% efficient conversion. During the process Heat energy is formed by friction in the motor. The screw gun has an internal fan to help cool down the assembly. In addition to the loss of energy in the screw gun there is also a build up of heat in the work piece. This limits the available power which is needed to perform the tasked it is designed to do.


During initial operation the group noticed that sparks can be seen inside the drill, probably caused by the electric motor. Also the directional changer of the tool does not perform as expected. The problem might be some kind of interference or friction between parts inside the tool. The drill emits a high frequency noise generated by the motor fan and parts that are in a friction environment in the screw gun.


The group estimated that there is between 40 and 45 parts contained inside the drill. These include the outer casing screws motor and various other parts that the group assumes would be inside the screw gun


The materials the group believes the screw gun is made of are: steel, plastic, copper, and rubber. The internal motor and gears are assumed to be made of steel that is strong enough to withstand the power generated by the motor. The motor itself is assumed to be made using copper as this is how most motor are made. The outer case obviously is made out of plastic and rubber.

Disassembly Procedure

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  • Took first screw from the bottom
  • Took out the second bottom screw
  • Then took out the third screw, which was located on the handle
  • Next was the lower back screw
  • Took another screw out, located more to the top of the drill
  • Which led to another screw which was next to the warning sign
  • Took two screws out that were located on the tip of the drill
  • Took top cover off
  • Bit holder off
  • Took level holder out
  • There was two small screws holding the wires in the drill together, took those out
  • Took metal piece that was holding the screw in place
  • The forward reverse came off next
  • The whole inner component came off next, there were no screws holding that part together
  • Note: There was crease on the inside of the drill
  • Gear plate came off next
  • Then the rolling bearing inside
  • The two gears on the shaft came off
  • Next the piece with the chuck
  • The whole motor came off
  • Undid wires with small flat head
  • Pulled metal piece out of the plastic encasing the wires
  • The plastic encasing the wires was at the bottom of the handle
  • Spring clips of the back bracket came off (medium difficulty, needed to use pliers)
  • Slipped inside of motor out
  • Retainer clip off (medium difficulty, used a special retainer clip tool)
  • Took two more screws out that were located on the outside motor part (screw driver used)
  • Outside of the motor attached to copper wires
  • Then pulled out wires that were on the bottom bracket


All steps were easy to do, taking less than two minutes, unless other wise mentioned.

After Disassembly

Part Description Table

Part Name Quantity Model Number Description Function Material Reason for Material Selection Reason for Appearance Manufacturing Process
Outside Cover 2 2005 22-47 Contains air vents. Has a rubber grip and is red and black in color. Covers drill mechanism. Plastic It is inexpensive, durable, and light weight. While also providing insulation. It is highly visible, with and attractive color scheme. It's ergonomically designed for support use. Injection Molding
Power Cord 1 18AWG-2C Has two springs and is black in color. The cord is 1/4 in thick. Allows drill to get power from electric sockets. Cooper, plastic, and steel IT insulated the inner working of the cord, while also being flexible and a good conductor of electricity. It is standard design to fit into electrical socket outlets and is black in color to decrease the appearance of dirt. Extrusion
Trigger 1 17-99 It is black in color and contains a small trigger lock. Allows operator to turn the drill on and off and provides speed control. Consists of plastic and metal components It is cheap, durable, provides insulation, and it is light weight. It is ergonomically designed for comfort and use. Injection Molding
Short Screws 11 Black in color, torque style head and course thread. Holds various components together. Steel High strength Functionality Machined
Long Screws 2 Black in color, torque style head and course thread. Fastens motor bracket together. Steel High Strength Functionality Machined
Springs 2 Coil Holds brushes against motor Steel Ductile and high strength It is an efficient compact design Extrusion, Sheet Metal Forming
Brushes 2 It is black, rectangular in shape with grooves. Helps complete motor's circuit Carbon It is soft material to reduce damage, also conducts electricity. Efficient wear design Extrusion
Motor End Piece 1 It is beige in color and has 12 fins Immobilizes shaft Plastic It is economical, durable, provides insulation and it is light weight Functional Injection Molding
Washers 1 It is 1/16 of an inch thick, with a 15/35 outer diameter, and a 9/32 inner diameter Separates motor components Steel Easy to produce Standard design Sheet Metal Forming
Bushing 1 It is red in color, 1/16 inch thick, it has a 9/16 inch outer diameter,9/32 inner diameter It separates motor components from each other and reduces friction and wear Plastic It is inexpensive and reduces friction and wear It is functional and shows wear in order to know when to replace Injection Molding
Retainer Clip 1 It is black in color, 1/32 inch think with an outer diameter of 13/32. It is 'c' shaped with indentions on the side. Holds components on to motor shaft Steel High strength and rigid Effective design Sheet Metal Forming
Level 1 It is clear plastic with inner green liquid It allows for even drilling Plastic and alcohol It is inexpensive and visually enhancing Easy to see, visually attractive Injection Molding,
Level Mount 1 3612596 Black in color, rubber and has air vents Holds level Plastic It is inexpensive and durable Fits in with color scheme,and it is visually attractive Injection Molding
Rotational Changer 1 1 It is black in color with texture grip Changes direction of the drill Plastic Durable and inexpensive Fits in with color scheme and visually prominent Injection Molding
Bit Holder 1 1 It is black in color Holds bit to the top of the drill Rubber Flexible and molds better to the bit A cognate design and fits color scheme Injection Molding
Fastener 1 Silver in color Holds power cord to frame Steel Cheap and easy to produce Functional Sheet Metal Forming
Trigger Insert 1 Silver in color Connects medium for wires Steel Good conductor Functional and fits into trigger Sheet Metal Forming
Outer Motor 1 385849-00 051705-XP Round cylinder, steel banded outside, copper coils inside, plastic frame Helps convert electrical to mechanical power Copper, plastic, steel,and laminate High conductivity,and easy to produce plastic mold Efficient design for a rotating motor Sheet Metal Forming, Extrusion, Machining
Motor End Bracket 1 2B Round cylinder, terminals spring holders,black, rotates to reverse motor Holds motor together and reverse motor rotational direction Brass, plastic,and copper High conductivity, easy to produce plastic mold, prevents corrosion Fits with outer motor Injection Molding, Sheet Metal Forming
Inner Motor Component 1 385537-02 052105-XP, KG16 shaft with cooling fan,plastic insulation under ball of copper wire with metal plates, green resin insulation, copper cylinder over a plastic cylinder, holes in end of shaft, gear teeth at one end Fan to cool motor, helps to convert the electrical to mechanical power , connects to gear assembly Copper, steel , laminate, plastic,and resin high conductivity, high strength, cheap easy to produce,and holds everything together Design to fit into outer motor, balanced design, generates air flow Sheet Metal Forming, Extrusion, Machining
Gear Bracket 1 HKOBIO ZT Puzzle shaped, bearing for main shaft, slot in side with no purpose, holes to hold different gears Holds gears together, provides bearing for shaft to spin Aluminum, steel cased bearings Light weight, high strength Holds all components in alignment Metal Casting
Gear Assembly 1 P 41 tooth gear, 12 tooth gear, on a shaft, has end stopper Ratios down rotational speed,provides more torque Metal, and steel High strength, durable changes rotation speed, increases torque Metal Casting
Chuck 1 XD200503231-1-7 Gear on one side, bracket, bit holder, felt bushing, shaft Bushing to prevent debris from entering case, and hold bit Plastic, steel, felt Doesn't wear on case, cheap, user comfort, high strength, durable Matches color scheme, to hold bit, ergonomically designed Machining, Injection Molding
Bit 1 P2 * SL8 Hexagonal shaft, phi lips and straight head Connects screws to drill Steel High strength, durable,and rigid Universal designed Machining


Part Improvements

Black and Decker is labeled as the largest manufacturer of power tools in the World. Even though it has dominated the world power tool market there are still places where Black and Decker can improve their products. In our Black and Decker screw gun our group found multiple places where improvements can be made. The first suggestion we had was to increase the number of bits that the operator can store on the tool. This suggestion was made for a couple reasons, first the operator may loose the bit and may not have any extra replacements for it. Also with more options of bit sizes and types of bits in general; the screw gun will result in a more versatile product for different tasks. If more bits are actually added onto the drill there are convenient places were the bits can be stored. These places include the back of the gun and the open spaces on the handle.


The drill did show some problems in the user interface. First the directional changer is in a inconvenient place if being used with one hand. Our group recommends that the direction changer switch be moved closer to the operator's hand. Also the directional changer is rough to operate. The components of the switch do not operate smoothly which needs to be improved. Along with user interface issues the trigger lock which allows the trigger to be locked in the on position needs to be larger. Which leads to another control feature that is hard to operate with one hand. The problems with this part is that it is too small to use and it is in the wrong place for easy one handed operation.


The last set of improvements that our group suggests are based on the comfort for the operator. First the screw gun can be made lighter and have a more compact design. As we had the tool apart we observed that there is extra room in the case that can be eliminated. Another problem that can be improved is that the handle can be made more comfortable by incorporating a gel embedded handle. This will allow less vibrations to be transfered through the handle onto to the operator.


There are many other improvements that can be made such as adding a battery or a more powerful motor but these improvements would change the class of the tool which Black and Decker has already filled with other products.

Parts

Screw Gun Parts
Part Name Picture 3D model 2D model
Inside Armature
armature
File:Armature1color.tif File:Drwarmature.tif
Outside Armature
outside armature
File:Outermotorcolor.tif File:Drwoutermotor.tif
Bushing
bushing
File:Bushing.tif File:Drwbushing.tif
End Bracket
end bracket
File:Endbracketcolor.tif File:Drwendbraket.tif
Washer
washer
File:Washercolor.tif File:Drwwasher.tif
Retainer clip
retaining clip
File:Retainerclipcolor.tif File:Drwreteiner.tif
Gear Plate
gear plate
File:Gearplate.tif File:Drwgearplate.tif
Gear Set
gear set
File:Gearsetcolor.tif File:Drwgearset2.tif
Chuck
chuck
File:Chuckcolor.tif File:Drwchuck.tif
Drill Assembly File:Drill2.tif File:Drill2.tif
Drill Assembly
assembly
File:Drill.tif
Exploded Drill Assembly
assembly
File:Drillexplode.tif


Assembly

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  • Put plastic bushing onto armiture
  • Put heat sink fan onto armiture
  • Put washer onto heat sink fan
  • Put retainer clip onto heat sink fan
  • Put end bracket into the out motor
  • Screw in two long torque head screws into end bracket and outer motor
  • Put inner engine into outer engine
  • Put brushes back into bracket
  • Put springs into place to hold brushes to motor (very difficult)
  • Put gear plate into gear shaft
  • Put gear into gear plate
  • Put chuck into gear plate
  • Put drill mechanics into drill cover
  • Put switch into cover and connected it to the end bracket
  • Took drill mechanics out of drill cover
  • Connected black and white wires to end bracket
  • Put drill mechanics into case again (difficult)
  • Put metal case into trigger
  • Put trigger into cover
  • Put wire holder into cover
  • Put two torque head screws wire holder
  • Put bit holder into case cover
  • Put level holder into case cover
  • Put level into level holder
  • Tried to put case covers together (did not fit together)
  • Found out heat sink fan was on backwards (putting the heat sink fan on we consider a medium step)
  • Remove inner mechanics
  • Remove holder piece
  • Remove heat sink fan
  • Put heat sink fan on properly
  • Put inner mechanics back into cover
  • Put covers together
  • Screw in torque head screws into cover
  • Test the screwdriver to see if it works, find that the directional switch is not moving right
  • Remove screws from cover
  • Take off cover
  • Discover that the wires are getting in the way of the directional changer
  • Move the wires out of the way
  • Put cover back on
  • Put screws into cover
  • Test screwdriver again (works)

All steps were easy, taking no more than two minutes, unless otherwise mentioned

After Assembly

The screw gun worked as we predicted it would before disassembling it. We did learn that the motor causes the gears to turn at such a high rate of speed that gear reduction is used to lower the that speed and increase the torque. We discovered how the directional changer works. The switch causes the wires to touch different brass connections which will cause the rotation of the drill bit to change. The parts were made of steel, plastic, and copper which we had predicted. Two parts, the brushes, which were made with carbon. They were made with carbon so they would not become magnetized.

During the reassembly we had some difficulty getting the components back in the case. The wires would get in the way and we spent some time moving them around so that we were able to put the components in the case properly. There was only one metal piece to hold the wires down and that was down in the handle section of the drill. Up near the motor there was not anything to hold the wires down, so they kept getting in the way. We also had some difficulty getting the retainer clip and the springs back on. The heat sink fan was also put on backwards. These obstacles took some time to overcome but we were able to successfully put the screw gun back together. The steps to reassemble the screw gun were not the exact opposite of the steps that we took when disassembled it.

The all the parts could be modeled using ProE. The measurements of the part sizes had to be accurate since the components all had to fit together. This made the modeling of the gears a little difficult, but still possible to do. How the drill works can even be modeled using mathematical models. Since the components of the drill are made of durable materials designed to handle heat, friction, and vibrations estimates can be used for the mathematical modeling of how the drill works.

References

Armature (electrical engineering). (2007, October 18). From Wikipedia, The Free Encyclopedia. Retrieved 24:32, November 07, 2007, from http://en.wikipedia.org/wiki/Armature_%28electrical_engineering%29

Additional Information

http://www.blackanddecker.com/ProductGuide/CategoryOverview.aspx?cPath=1496.2050

http://en.wikipedia.org/wiki/Die_casting

http://en.wikipedia.org/wiki/Injection_molding

http://en.wikipedia.org/wiki/Metal_casting

http://en.wikipedia.org/wiki/Electric_motor