Group 6 - Black and Decker Power Drill - Gate 2

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Contents

Purpose

The purpose of this gate is to perform an initial group assessment to evaluate group dynamics and functioning. The assessment critiques the work and management proposals developed in the first gate of this project to determine the effectiveness of our group. The Black & Decker DR202 Power Drill must also be dissected, documented and reassembled. This will allow us to gain further knowledge of the interactions between the components inside the drill, and how the sub-systems come together to perform the overall task. This gate provides a plan for the dissection of the drill so that someone who has no prior knowledge or experience can follow the steps and take the drill apart with ease.

Cause for Corrective Action

Up until this point, group dynamics and functioning have been successful. Due to this fact, we have had little conflict with our original plans. We are all responsible people who want to make sure the work is completed in a timely manner and to the best of our ability. Each of us has been consistently attending group meetings and has been communicating effectively via emails and phone calls.
We have made only one change to our original management proposal. Initially, we planned to meet every Thursday afternoon following a class that we all share. We also planned to have tentative meetings on Tuesday evenings. At the time, this proposal was sound, but we neglected to take into account other schoolwork and outside activities that our group members participate in. This led to some mutually canceled meetings on Thursdays in order to accommodate for other work. We have decided to just meet one day a week on either Tuesday or Thursday. Despite this cutback in meetings, we have still been able to work efficiently individually and bring the information together to turn it in on time.
For the most part, we have followed the work proposal we initially created. Our groups members have fulfilled their duties and have effectively delegated tasks. One change that we have made to our proposal is that our initial assessment of weaknesses was slightly inaccurate. We realized through the last couple of weeks that a major weakness in our group lies in proofreading of our written assignments. We have checked our work for grammatical errors, but have failed to check for completeness. As a result, some of our assignments have been lacking in content and specificity. We plan to correct this issue by looking over the work done by other group members. This way we will have a fresh set of eyes reading over the responses to questions. This will assure that the question is actually being answered, and it will be clear where the response is located.
Strong communication between group members is key to avoiding future challenges. If we continue to talk after our MAE 204 and MAE 277 classes, we will all be aware of assignment due dates and who is responsible for completing each portion of the assignment. This way there will be no confusion that might result in missed deadlines or incomplete work. We will also check our group Google account regularly to review work that the other members have posted.

Product Dissection

Parts List

Table 4 lists the parts that comprise the DR202 drill. The images presented were taken during the dissection of the drill.
Table 4 Parts List
Component Number Component Name Number Required Image Component Number Component Name Number Required Image
1 Drill Housing 2 (Right Side and Left Side)
Right Side Drill Housing
Left Side Drill Housing
14 Field 1
Field
2 Spindle 1
Spindle
15 Reverse Ring 2*
Stationary Reverse Ring
Movable Reverse Ring
3 Gear 1
Gear
16 Reverse Lever 1
Reverse Lever
4 Washer 1
Washer
17 VS Switch 1
Trigger
5 Front Bearing Plate 1
Front Bearing Plate
18 8 Foot Electric Cord 1
Power Cord
6 Keyless Chuck 1
Keyless Chuck
19 Cord Clamp 1
Cord Clamp
7 Rear Bearing Plate 1
Rear Bearing Plate
20 3/4" Screw 11
Shorter Screw
8 Gear and Pinion 1
Gear and Pinion
21 1 7/8" Screw 2
Longer Screw
9 Armature 1
Armature
22 Cord Protector 1
Power Cord
10 Retaining Ring 1
Retaining Ring
23 Felt Washer 1
Felt Washer
11 Plain Washer 1
Plain Washer
24 Level Holder 1
Level Holder
12 Heat Sink 1
Heat Sink
25 Level 1
Level
13 Red Washer 1
Red Washer
26 Bit Holder 1
Bit Holder


  • Take note that the reversal ring is actually two separate parts. One part stays stationary on the field, and the other is moved by the reverse lever.

Steps for Product Dissection

Tools Used

  • Screwdriver with TORX T10 bit
  • Flat head screwdriver
  • Hands

Difficulty Scale

We also developed a difficulty scale for the individual steps is based on how taxing each step was to complete as well as the tools required and the amount of time needed:

  • 1 Requiring minimal effort: A step requiring minimal effort would required little physical input on behalf of the dissector. The only tool required for the step would be your hands. The components would easily slide apart and would be quick to complete.
  • 2 Requiring moderate effort: A step requiring moderate effort would require some physical input on behalf of the dissector. A screwdriver or hands would be required to complete this step. Human force would be required to separate the components, requiring more time on behalf of the dissector.
  • 3 Requiring maximum effort: A step requiring maximum effort would require the most physical input on behalf of the dissector. The components would not separate without significant force. A screwdriver and hands would be required to separate these components. This step would take the longest amount of time and should be completed with caution.


The drill was not working before we took it apart. We also found that the reverse ring was broken into three pieces and the inner wires were not attached to the motor.


Table 5 shows the step-by-step instructions to dissect the DR202 Drill. It includes the actions required as well as the necessary tool for each step. An estimated time for completion is also provided.

Table 5 Step-By-Step Dissection
Step Instructions Tools Required for Step Estimated Time for Step (minute:seconds) Difficulty (Scale of 1 to 3) Photograph of Step
1 Remove the nine screws from the right side drill housing that holds the housing together using a flat head screwdriver. Flat Head Screwdriver 2:10 2
Drill Without Screws
Click Here to View Removal of Screws Video
2 Lift off the right side drill housing to reveal the inside components. This allows access to the bit holder, reverse lever, level holder, and level located on the top of the drill. Slide these components out of the housing. Hands 0:30 1
Removed Level, Bit Holder, and Level Holder
Click Here to View Removal of Casing, Level Housing, and Bit Holder
3 Remove the internal assembly from the left side housing. Slide the gear system from the armature shaft and slide the stator off of the armature. Hands 0:15 1
Removed Internal Assembly and Cord
Click Here to See Removal of Internal Assembly Video
4 Unscrew the two screws holding the cord clamp down, and remove the cord clamp, VS switch, and power cord from the housing. Flat Head Screwdriver
Hands
0:45 2
Internal View: Removed VS Switch, Cord Clamp, and Reverse Lever
Click Here to View Removal of VS Switch and Cord Clamp Video
5 Separate the removable reverse ring from the field and unscrew the two long screws holding the stationary reverse ring to the stator. Flat Head Screwdriver
Hands
2:10 2
Exploded Internal Assembly Without Gear System
Click Here to View Removal of Screws From Stator Video
6 Slide the rear bearing plate, the gear and pinion, and front bearing plate from the keyless chuck. Hands 0:20 1
Exploded Gear System
Click Here to View Separation of Gears Video
7 A c-shaped clamp called the retaining ring is located at the end of the armature assembly by the heat sink. This clamp must be removed in order to remove the washers and heat sink on this end of the assembly. To do this, take two small flat head screw drivers and apply a force on the endpoints of the retaining ring. This force will cause the retaining ring to be ejected from the shaft. Take caution because the retaining ring may shoot off farther than intended and the piece may be lost. To prevent this from occurring, direct the piece toward a wall or other object that will be able to absorb the force and stop the projectile. (When we removed this piece, we were not expecting it to shoot off too far, but it was luckily caught in the shirt of a group member.) Then remove the plain washer, heat sink, and the red washer from the shaft. Small flat head screwdriver 1:30 3
Armature Assembly
Click Here to View Armature Disassembly Video

Total Dissection Time: 5:45

Product Dissection Assessment

Challenges During Disassembly

The first challenge we faced during disassembly was in the removal of the nine screws from the drill housing. We noticed that a number of the screw heads were stripped which made them harder to remove. We had to take extra caution when removing them to prevent them from further damage. We also realized that we needed to minimize the amount of times we opened and closed the drill. The major challenge we faced during this process was with the removal of the retaining ring from the armature shaft. The retaining ring had to be pried off using a screwdriver with a force applied by the thumb behind the screwdriver head. This required a great deal of physical effort and precision because of the small size of the retaining ring. In addition, the retaining ring had a tendency to shoot off the shaft. This means extra care had to be taken to assure that the retaining ring was not lost. We solved this issue by catching the ring in the shirt of one of our group members. Another challenge that we faced dealt with the quality of one of the components. The movable reversal ring was broken into three parts in our drill. This was an issue because the drill could not work in its current state.

Ease of Disassembly

During the disassembly process, we found that most of the inner components are designed to be taken apart easily so the user can perform repairs on the drill without much effort. For example, the gears are accessible and can slide apart with ease so they can be replaced if worn. Some of the more complex interactions, such as the keyless chuck assembly, are not intended to be disassembled easily. When we attempted to dissect the keyless chuck assembly for the first time, we realized that more effort was needed than most of the other tasks, and that the gear could not be removed by human means. Therefore, we concluded that this part was not intended to be disassembled. If the system had been taken apart, a sufficient amount of mechanical force would be required to do so, and the part would not be able to be replaced easily. Since we cannot disassemble this sub-system, we do not know for sure how the components are connected, but we suspect they are glued or welded.

Sub-Systems

Table 6 lists the various sub-systems that perform the different functions of the DR202 Drill.
Table 6 Sub-Systems
Sub-System Number Sub-System Name Components in Sub-System Image
1 Drill Housing Right Side Housing
Left Side Housing
Power Cord
Trigger
2 Wiring Cord 8ft
Inner Wiring
Power Cord
Trigger
3 Direction of Output Reverse Ring
Reverse Switch
Movable Reverse Ring
Reverse Lever
4 Motor Armature Assembly
Field
Reverse Ring
Two 1 7/8" Screws
Motor Assembly
5 Gears Gear
Front Bearing Plate
Rear Bearing Plate
Gear and Pinion
Spindle
Gear Assembly
6 Keyless Chuck Felt Washer
Keyless Chuck
Keyless Chuck

Sub-Systems Interaction and Arrangement

There are six sub-systems for the Black and Decker DR202 Drill as shown in Table 6. The first sub-system is the electrical wiring; this systems main function is to transport electrical energy into and throughout the drill to power the other subsystems. Electrical energy is first brought to the drill from its energy source by the power cord where it is then transported through the bottom half of the grip to the trigger. The trigger is an essential part of the electrical wiring subsystem that acts to complete the drills electrical circuit enabling the drill to operate. The trigger requires an input signal from the user upon which it closes the circuit allowing the electrical energy to flow from the trigger to the next subsystem of the drill, the reversal system. The reversal system is made up of three components, the reversal ring, the stationary reversal ring and the reverse lever. When an input signal is provide to the reverse lever it physically pushes the bottom reversal ring left or right which makes the ring spin clock/counterclockwise on the stationary reversal ring. This connects one of two sets of electrical nodes on the stationary reversal ring, which allows the electrical energy to flow into the electric motor, our third subsystem. The motor is made up of two components, the stator and the armature and is responsible for converting electrical energy to electromagnetic energy to rotational energy. The electrical energy flows into the coils of the stator creating a magnetic field within it. This magnetic field then induces a current on the coils of the armature forcing it to spin about its axis. The armature of the electric motor lies on the armature shaft, the first component of the next subsystem. The job of the gear system is to reduce the RPM and increase the torque of the fast spinning armature to make the rotational energy provided by the electric motor usable for drilling holes and driving screws. The gear system accepts the rotational energy of the motor through the armature shaft, which spins the gear and pinion, the first gear of the gear reduction system. The gear and pinion rotates the front gear which is physically attached to the spindle which drives the chuck. The keyless chuck is the next subsystem of the drill and its task is to hold and drive the bit, which is completed by a combination of human and rotational energy. Human energy is used to lock the bit in place by rotating the two halves of the chuck opposite each other to open/close the jaws of the chuck. The rotational energy transmitted from the gear system’s spindle drives the chuck which spins the bit completing the overall function of the drill. The final subsystem of the drill is its casing. The housing provides the drill with its structural integrity, a grip, the bit holder, level, and overall organization of the individual subsystems in an ergonomic and usable fashion.
The subsystems are arranged as described above and as shown in Table 6. The subsystems are arranged this way because the drill has a very specific overall function that it performs and because there are only a few subsystems that act to create this overall function so there are very few ways to arrange them differently if any at all. The energy has to be brought into the drill first because it is needed to power the motor and if the motor is not powered then the gear system can not perform their function. The only subsystems that can possibly be adjacent are the reversal system and the keyless chuck because they do not affect the overall function of the drill. And the only subsystem that can be moved to a different spot in their current arrangement is the reversal system but this would create a less ergonomic feel of using the drill and would benefit it in no way.


Outside Influencing Factors

The connections between the different sub-systems of the drill were each affected by global, environmental, economic, and societal factors. The connection between the power system and the motor system are very cheep. They are joined by two wires to deliver the electrical energy to the motor. This type of connection is inexpensive. It is also a safe connection because of the rubber housing the wire is inside of. Environmentally, the wires can be recycled or used again in another product to reduce pollution. Wires are also a universal connection type for electricity around the world. The connection between the reversal system and the motor system is cheep economically. The reversal ring is held on by two screws and moves by a lever. The connection is made by two small strips of steel. This cheep type of connection is great to connect these two sub-systems. The connection between the motor and reversal system is also situated in a way to make the reversal ergonomic and intuitive for the user. Environmentally, the connection between these two systems can be reused in a different system, reducing the pollution factor of the connection. The connection is also a universal connection because of the way the connection is set up. The reversal ring slides from one set of connectors to another to switch the direction of the electricity flow. The connection from the motor to the gear system and keyless chuck is cheep because gears are made quick and cheep due to machining processes. The gears that connect the systems are cheep to make, but are also safe because of the way they are situated inside the drill housing. The steel used to make the gears can also be recycled to be used on other projects, and they are also globally known to reduce or increase the rotations of a certain component.

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