Group 1 - Black & Decker Drill/PDR

Purpose

Gate 2 consists of two parts: cause for corrective action and a step-by-step disassembly of the drill. The cause for corrective action allows for the group to reflect on the first three weeks of the reverse engineering project and tweak the group's planned approach. The step-by-step disassembly process is meant to provide a person, that is unfamiliar with the drill, with a set plan that will allow him or her to break down the drill. To facilitate the disassembly process, a parts list, which provides part nomenclatures, quantities and photographs, along with end-step photographs are provided.

Causes for Corrective Action

As the group moves toward the dissection of the Black & Decker Power Drill, it is necessary to do an assessment of the work completed thus far as well as the management plan. Fortunately, the project has moved along smoothly with no major setbacks.

The group was able to communicate their strengths, weaknesses, and schedules effectively during the management proposal processes so that we could progress with very little deviation from the original plan. In fact, we have found only one aspect of our management proposal that needed editing. We had originally agreed that a group meeting would be necessary every Sunday afternoon to collaborate on group progress and to address any issues. However, it was quickly realized that this weekly meeting was not realistic when group members would have to commute 30 minutes one-way in order to attend a meeting that might last 15 minutes; our group sits together for lecture three times a week and any concerns can be brought forward in person during that time. Furthermore, the few questions group members have come up with that had to be immediately addressed, were effectively acknowledged and resolved via e-mail and phone conversations.

At this time, there are no unresolved challenges or potential problems therefor no other corrective actions need to be taken to complete the project as scheduled--the management plan was made flexible enough to account for any changes that may be necessary in the coming weeks.

Parts List

The "Parts List" table below provides a list of the components that will be observed during the disassembly process.

Diagram 6

Part List [1]
Item Number	Nomenclature	Quantity Required	Object Photograph		Item Number	Nomenclature	Quantity Required	Object Photograph
1	Housing and Cover	1			15	Reverse Ring	1
2	Spindle	1			16	Reverse Lever	1
3	Gear	1			17	VS Switch	1
4	Washer	1			18	Cord – 8ft	1
5	Front Bearing Plate	1			19	Cord Protector	1
6	Keyless Chuck	1			20	Clamp, Cord	1
7	Rear Bearing Plate	1			21	3/4" Screw with #15 Torx heads	11
8	Gear and Pinion	1			22	1 7/8" Screw with #15 Torx heads	2
9	Armature	1			23	Name Plate	1
10	Retaining Ring	1			24	Brush	2
11	Washer, Plain	1			25	Washer, Felt	1
12	Sink, Heat	1			26	Cap	1
13	Washer, Red	1			27	Level	1
14	Field	1			28	Bit Holder	1

Assembly Component List

The below "Assembly Component List" identifies assembly groups, as defined by the group, mentioned during the disassembly process.

Diagram 7

Assembly Component List
Assembly Number	Assembly Name	Assembly Components	Assembly Photograph
1	Internal Assembly	Motor Assembly Rear Bearing Plate Gear and Pinion Keyless Chuck Assembly
2	Motor Assembly	Field Reverse Ring (2)Brushes (2)1 7/8" Screw with #15 Torx heads Armature Assembly
3	Armature Assembly	Retaining Ring Heat Sink Plain Washer Red Washer
4	Keyless Chuck Assembly	Gear Front Bearing Plate Spindle Felt Washer Keyless Chuck

Product Dissection Plan

The "Product Dissection By Steps" table seen below details a step-by-step process for dissecting the drill. Special attention should be focused on:

The removal of the retaining ring: Its size, in combination with the required force to remove it, can launch the clip in an unexpected manner. A small box, about the size of a shoebox, is recommended during this process.

The orientation of the heat sink: The heat sink can be attached from either end. The wrong way will make the armature too short and it will no longer fit properly into the casing.

It is recommended that photographs of both parts and stages be used as aides during the disassembly process.

Tools required:

Torx #15 screw driver
(2) 0.5mm Flat-head screw driver

• The drill was in full working order prior to dissection and was unplugged.
  
  

Diagram 8

Product Dissection By Steps
Step	Description	Tool Required	Time Required	Difficulty (1-3)	End-Step Photograph
1	Removed the (9) screws from the drill housing that secure it shut	Torx 15 screw driver	2:15	1	Exterior
2	Separated each external component from drill housing: the exterior cover was lifted away allowing for easy access to the level and bit holder located on the top of the drill housing	Hands	1:45	1	Exterior Cover and Parts Interior
3	Removed the metallic cord clamp which secures power cord	Torx 15 screw driver	0:54	1	Power Clamp Removed
4	Removed VS switch from drill housing by lifting it out	Hands	0:10	1	Trigger Housing Removed
5	Slid reverse lever from its grove in the drill housing	Hands	0:10	1	Direction Switch Removed
6	Lifted internal assembly from the drill housing where it was held in place by groves Take special note of the orientation of all internal parts. When replacing internal assembly notice that the white power cord is on top and that the smooth side of the heat sink is away from the motor	Hands	0:45	1	Internal Assembly Removed
7	Separated internal assembly into motor assembly, keyless chuck assembly, gear and pinion, and the rear bridge plate assembly by sliding each component apart	Hands	1:23	1	Exploded Internal Assembly
8	Removed power wires from the rear of the motor assembly by pulling out on the wires, noting that the black wire entered the motor near the hole marked with a "B". Removed the armature by compressing the retaining brushes with a flat-head screwdriver, which secured the armature inside of the motor assembly by clamping down on it near the heat sink. Disassembled motor assembly into field and reverse ring by removing (2) field screws.	Torx 15 to remove (2) flat-head screwdrivers	4:39	3	Exploded Motor
9	Carefully removed retaining ring from rear of armature by applying pressure with two flat-head screwdrivers on the tails of the "C" shaped clamp--two screwdrivers are required to prevent the retaining ring from rotating as the clamp is slid off. The armature should be placed inside of a box in order to maintain control of the retaining ring when it is forced off. Removal of the ring allowed for the separation of a washer and the heat sink.	(2) flat-head screwdrivers small box (6" x 4")	3:27	3	Exploded Motor Shaft

Total dissection time: 14 minutes, 12 seconds.
*Note: the break down for the difficulty levels are as follows:

1 = easy; requiring little effort.
2 = medium; some prior thinking required.
3 = hard; required multiple attempts; two people recommended.

Post-Dissection Analysis

Below are a few sample questions that address the purpose and methodology behind the drills design:

- Is the product intended to be taken apart easily?

Based upon the disassembly described above and the fasteners used, which can be easily removed and replaced, this product could be intended to be taken apart. All but two steps were rated as a 1 out of 3 on the difficulty scale and the whole dissection process took two people a little over fourteen minutes. Step 8 received a difficulty rating of 3 because the group failed to take specific note of which wire went in which hole on the reverse ring and because the removal of the armature was not immediately apparent and was best accomplished by two people: one person compressing the brushes while the second slides the armature out. Step 9 received a difficulty rating of 3 due to the retaining ring: the removal of the ring requires two people to push it off and the group underestimated the effect of the force and the resulting acceleration of the ring once it was released from its position. Luckily, the floor was white and the ring showed up easily on the linoleum. The rest of the steps consisted of either removing some screws or lifting components held in place by molded plastic.

The ease of disassembly is a benefit of the drill such that it allows for broken or worn pieces to be easily replaced by the user as opposed to a more complex drill where someone would have to be paid to fix it. On the other hand, the initial investment of the user might not be worth the effort to trouble shoot a broken drill and replace parts.

- What fasteners are used and why?

The fasteners used are:

(11) 3/4" Screws with #15 Torx heads: These metallic screws are a non-permanent, inexpensive and effective way to secure lightweight materials while minimizing assembly/disassembly time.
(2) 1 7/8" Screws with #15 Torx heads: These metallic screws are a non-permanent, inexpensive and effective way to secure lightweight materials while minimizing assembly/disassembly time.

The manufacturer, by using all the same Torx head screws, can keep production time and costs down by reducing the number of different tools required to assemble the product. Additionally, by securing the screws into the drill housing, nuts are not needed reducing production steps and materials required.

- Are special tools required?

The only special tool required was the Torx #15, but pictures taken from a digital camera during disassembly will provide a visual aid that can be relied upon for reassembly. Additionally, having snap ring pliers on hand would provide an increase in control and dissection speed while removing the need for the two screwdrivers.

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Reference

[1] "DeWalt Service Technical Information" dewaltservicenet.com. 12 OCT 2009 <http://www.dewaltservicenet.com/Products/DocumentViewPDF.aspx?productid=33258&typeId=8795&documentId=21976&AspxAutoDetectCookieSupport=1>