Gate 2 Group 27 2012

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Introduction

In Gate 2, we will first review how our team completed Gate 1, with attention to what worked well, as well as what areas need to be improved upon. Next, we will be dissecting the product, and recording each step of the disassembly. We will then identify and analyze each subsystem, and how each subsystem is related to the others. We will then review each subsystems' design and placement, and consider how the GSEE factors were taken into consideration.

Preliminary Project Review

Cause for Corrective Action

Our work and management methods from Gate One could use a fair amount of revision, although we did perform well in certain areas. One thing that worked out well was that one person set up the wiki page so that everything was organized, and all titles and links were set up so that the other group members would only have to copy and paste text from a word document into their allocated sections. Another thing that worked well was the fair allocation of different tasks to different people. This balanced the workload and made the project much more manageable for each person. Also, there was effective communication through email, as well as text messaging and phone calls. The group emails made sure that everyone had a record of what each person was responsible for. Also, some of us went to talk to the professors or the TAs, and it significantly improved the quality of our project. We will be continuing these processes for Gate Two.

Some of our work and management methods needed more revision and improvement in order to do better on Gate Two. The group’s time management needs the most improvement. In Gate One, we started very close to the deadline, and had to cram in order to get the project done, with no time for review, which was really needed. For Gate two, we immediately started on the project just after Gate One was due. Another aspect that needed improvement was that our group did not meet enough. For all future projects, we will try to meet at least every week, Wednesdays after class. Also, some members of the group are less experienced with technical writing, and tend to use things such as vague terms rather than exact values, and other such mistakes. Because of this, the group will use the meetings to review everyone’s work, and to help each other improve their technical writing.

Product Dissection

Difficulty Rating

An important part of understanding the product dissection is understanding the difficulty involved with each step of the disassembly process. The following rating system and tool chart is meant to inform the average homeowner who would be looking to disassemble the drill by letting them know how hard each step is going to be and any special tools needed to complete the task.

Difficulty Chart:

Table 4.1: Difficulty Chart

Rating	Description	Example
Easy	Tasks labeled as easy take from 10 seconds to a minute to complete. The action required is simple and easy for the average homeowner to understand and requires little physical force	Removing the housing screws
Medium	Tasks labeled as medium take from 1 to 5 minutes to complete. The action required is simple and easy for the average homeowner to understand but requires moderate physical force and the use of one or more tools	Removing the left hand thread star drive screw
Hard	Tasks labeled as hard take 5 to 10 minutes to complete. The action required is complex and hard for the average homeowner to understand. The action may require heavy physical force and the use of heavy tools or machinery	Removing the Chuck from the Clutch

Tool Chart:

Table 4.2: Tool Chart

Tool	Description	Picture
Flat Head Screwdriver	Screwdriver ment for screwing and unscrewing flathead screws. Also works as small pry-bar	Flat Head Screwdriver
Phillips Head Screwdriver	Screwdriver ment for screwing and unscrewing phillips head screws	Philips Screwdriver
Star Head Screwdriver	Screwdriver ment for screwing and unscrewing star head screws	Star Head Screwdriver
Allen Wrench Set	Set of allen wrenches ment for screwing and unscrewing allen head screws. Also good for removing E and C clips	Allen Wrench Set
Box-Cutter	Razor blade knife used for cutting various materials	Box Cutter
Combination Pliers	Pliers used for removal of uncommon threaded components	Pliers

Disassembly Process:

Table 4.3: Disassembly Process

Step	Description	Difficulty	Tool Used*	Pictures
1	Remove the seven right sole housing screws with a phillips head screw driver	Easy	Phillips Head Screwdriver
2	Create cardboard layout of drill	Easy	N/A
3	Place corresponding screws in diagram	Easy	N/A
4	Remove metal crimp on battery port	Easy	Flat Head Screwdriver
5	Cut battery port sticker along shell seam	Easy	Box-Cutter
6	Remove plastic shell piece with flathead screwdriver	Easy	Flat Head Screwdriver
7	Take connected subsystems out of plastic shell using plyers	Easy	Combination Pliers
8	Remove motor connections with a flathead screwdriver	Easy	Flat Head Screwdriver
9	Remove motor/gear assembly form clutch/chuck assembly by rotating and then pulling	Medium	N/A
10	Remove planetary gearbox form motor	Easy	N/A
11	Pull off motor washer	Easy	N/A
12	Remove motor mount screws with phillips head screwdriver	Easy	Phillips Head Screwdriver
13	Remove motor cover	Easy	Flat Head Screwdriver
14	Remove eight ball bearings from gearbox	Easy	N/A
15	Remove planetary gears	Easy	N/A
16	Remove secondary planetary gears from gearbox	Easy	N/A
17	Remove star drive bit in drill chuck (left hand thread)	Medium	Star Head Screwdriver
18	Remove chuck from clutch with allen wrench	Hard	Allen Wrench
19	Pry off grip ring from chuck	Medium	Flat Head Screwdriver
20	Remove c-clip from clutch head	Medium	Allen Wrench and Combination Pliers
21	Remove metal position ring	Easy	N/A
22	Take off position collar	Medium	N/A
23	Remove spring tensioner, spring and washer	Medium	N/A
24	Remove tape from trigger box	Easy	N/A
25	Remove tabs surrounding trigger box with small knife	Easy	Box-Cutter
26	Remove trigger spring	Easy	N/A

(*N/A denotes step can be done by hand)

Intent For Disassembly

After the disassembly of the drill we determined that although most of the drill is intended for disassembly, there are a few components that are not ment to be taken apart. Due to the nature of the drill and the warranty informations provided in the box it can be assumed that most of the drill's subsystems need to be easily accesible both for the initial assembly and to perform maintenance on the drill. First, the plastic housing that contains the drill's major subsystems can easily be removed using a single common size phillips head screwdriver. This signals that the drill's subsystems are ment to be easily accesible. The next part of the drill that is ment to be taken apart is the drill's trigger system. It can be accessed be removing a series of plastic tabs from the trigger housing and allows direct access to the trigger circuitry. Again, the easy access can be explained by the need for drill maintenance. The clutch and chuck are easily removed from the the motor by unscrewing 4 screws. This along with the fact that the motor input wires are also easily detachable signals that the motor of the drill is ment to be easily replaced. The difficulty we had separating the the clutch from the chuck infers that the although they are ment to be disassembled, it may only be done by someone with the right tools and experience such as a company maintenance technician or a tool repair man. The clutch itself can be further disassembled be easily removing a few more screw which signals that the it is ment to be disassembled, either to add lubricant or replace cracked ball bearings. The chuck itself is not ment to be disassembled. It is sealed together by a factory made bond which can not be reversed. This is because of the design of the chuck, if taken apart the chuck does not easily go back together and if broken, requires a replacement chuck; it is essentially unfixable if broken.

Connection of Subsystems

The drill contains several subsystems which work together, transmitting energy and signals across systems boundaries. Each system was optimized to maximize its function, and to work with its corresponding subsystems. Image 5.2.1

Battery to Trigger Box

Image 5.1.1

• Physical: The battery is connected to the trigger box via a plug and wires. The plug is permanently housed inside the base of the drill, and is positioned so that it will contact the metal connections of the battery when the battery is placed in the drill. The two metal prongs of the plug fit into the metal-lined slots of the battery, forming a metal-to-metal physical contact. The metal prongs are each connected to a separate wire, which leads to connections on the circuit board of the trigger box.
• Energy: The battery supplies electrical energy, with an electric potential of 12 volts. The electrons flow through the wire connected to the negative polarity battery connection, then through the circuit and back to the battery again into the positive polarity terminal.
• Signal: The trigger box signals the amount of current to be drawn from the battery by limiting the amount of electricity that can flow through the circuit.
• Reason for connection: The trigger box is connected to the battery so that it can limit the amount of electricity going through the rest of the circuit. Without this connection there would be no control over the energy flowing through the system.
• GSEE Influence:
• Connection's influence on performance:

Trigger Box to Motor

Image 5.2.1

• Physical: The connection between the motor and trigger box is composed of two wires, leading from the trigger box to the connection tabs on the back of the motor. The wires are soldered to the trigger box. The other end of the wire is soldered to a metal clip, which fits on the tab of the motor.
• Mass: There is no flow of mass other than the flow of electrons, which is negligible.
• Energy: The trigger box sends a regulated amount of electricity through it, originally coming from the battery. This then gives power to the motor.
• Signal: The signal is the regulated amount of electricity coming from the trigger box.
• Reason for connection: This connection exists because the motor needs a regulated amount of electrical energy so that the user may have the proper mechanical energy for the application.
• GSEE Influence:
• Connections influence on performance:

Motor to Clutch

Image 5.3.1

• Physical:The motor is connected to the clutch by a planetary gear box. The planetary gear box cosists of six gears, three of which are plastic and three of which are metal. There is also a drive gear in the center that spins the three gears around it. The clutch regulates the torque of the motor. The clutch is operated by turning the plastic piece to the setting of the desired torque.
• Mass:No mass is transfered.
• Energy:The power from the motor is regulated by the clutch.
• Signal:The motor will only work if there is a signal received from the trigger, and the clutch needs to manually be turned inorder for it to use the desired torque.
• Reason for connection:The reason the motor and clutch are connected is to ensure that the right amount of torque is used. Too much torque could damage what is being worked on and not enough torque prevents the task from being accomplished.
• GSEE Influence:
• Connections influence on performance:

Clutch to Chuck

Image 5.4.1

• Physical:The clutch is attached to the chuck by a threaded screw, which required a lot of torque to unscrew.
• Mass:No mass is transfered.
• Energy:The Clutch takes mechanical rotational energy and transfers it directly to the Chuck. The clutch limits the amount of torque that can be put on the system by letting the system slip at a certain torque.
• Signal:The clutch can only be signaled by the operator. The chuck is signaled by the drill and the operator in a joint effort to tighten the chuck keys around the drill bit.
• Reason for connection:The clutch and chuck are connected to ensure that the correct bit and torque and used during the task.
• GSEE Influence:
• Connections influence on performance:

Arrangement of Subsystems

The subsystems arrangement is quite complex as most of the subsystem connections are mechanical. The outer housing is held together using simple Philip head screws. The housing holds the trigger switch, electronic circuit, led, the direction changing switch, the motor. The battery latches on to the housing at the bottom. The torque controller is connected to the motor and is latched onto the housing to hold it into place. The chuck is connected to the torque connector.

The whole product is can be broke down into different subsystems as follows:

Battery

Switch and control unit

The motor

The torque control unit

Chuck

The subsystems are arranged very methodically and in a simple way, which makes understanding the function and the of transfer of energy of each component very easy and this intern makes the product repairability high.

The battery transfers energy to the motor by converting chemical energy to electrical energy. This energy then passes through the control system which houses the trigger and the direction knob. The signal form the user to the machine is processed through the trigger and direction switch which is connected to the electronic unit housed right adjacent to it and this unit transfers the energy to the motor for either clockwise or counterclockwise movement based on the user signal input. The motor then transfers the energy mechanically to the Torque control unit which houses a few axels that is connected to the torque control knob. This torque control know is connected to the chuck using a screw which is connected through the center of the chuck by a star screw bit and a grip ring connected to the torque control unit. The speed of the drill is changed by the user signal input through the torque control unit.

Each subsystem is well designed and is placed in the appropriate place in order of hierarchical transfer of energy and usability. Thought the torque control unit can be moved and added to the switch and control unit by manipulating the integrated circuit to process the user signal, it is better to the placed just as the product is designed, as this is the most comfortable for the user. Adding the torque control to the housing unit makes it hard to control the many switches on one single hand. But with control units distributed and placed in such a way that it can be controlled using two hands makes the product a much better and well designed one, and easily accepted by the consumers for its usability.