Gate2: Product Dissection

From GICL Wiki
Jump to: navigation, search

Contents

Gate #2

Purpose

The purpose of Gate #2 is to acquire an understanding of the components within the Black and Decker Variable Speed Orbital Jigsaw and to assess the effectiveness of the original management plan proposed in the previous gate. This purpose is accomplished through the implementation of a detailed dissection process in conjunction with an analysis of the subsystem within the product. In addition, the initial management proposal will be analyzed in accordance to the issues the group faced since the prior gate.

Product Management: Preliminary Project Review

Cause for Corrective Action

Work and Management Plans:

The original management plan proposed in Gate#1 proved to be fairly successful. However, we did encounter a number of issues. Our initial attempt to designate a strict time schedule was later determined to be too rigid for several group members. As previously stated, we had planned to meet on the Monday and Thursday of every week. Yet, conflictions with employment scheduling and transportation issues prevented two group members from attending multiple meetings during the week. The meetings were thus rescheduled. However, the action of rescheduling ultimately proved to lead to miscommunications between group members. A few factors may have contributed to this problem. One issue would be that there was no single person who took charge of setting times, dates, and assignments for meetings. In addition, multiple individuals in the group attempted to pursue a leadership position. Hence, there was substantial confliction between members regarding the planned method to complete assignments. As such, the group has decided to permit additional room for meeting time fluctuation and has specifically assigned the role of proper scheduling and notification of team meetings to the communication liaison. Also, it has been decided, following a group discussion, that the project manager will provide the primarily role in deciding individual tasks for various assignments.

Challenges:

A couple challenges in our group have surfaced, and most have been addressed. There was an issue between two of the group members that was initiated during one of the group meetings. While everyone was trying to contribute to the task at hand, the group members who understood the task completely were taking over the work and were not communicating what they were doing very well with the rest of the group. This issue was resolved, however, by those members by setting a time to discuss the issue in private. It was agreed upon that more patience would be given in allowing the rest of the group the time and explanations needed for everyone to fully understand the material. An issue that has not been addressed within our group is the division of work. Although, as a whole, the group is attempting to split the work load evenly,short comings in abilities or quality of work have caused other group members to put more time and effort into the project than others. This will need to be addressed in a group discussion, and will be done so with each of the members contributing their own thoughts on the issue and their own ideas of what they believe should be done about the issue. Although a truly even distribution of work is not completely possible, we hope to make it as easy and pleasant as possibly for all members.

Product Archaeology

Product Parts:

The parts of the Variable Speed Orbital Jigsaw JS660 are detailed in Figure 1.

Figure 1: Parts List
Black and Decker JS660 Parts List
Part Number Part Designation Description Quantity Visual Representation
1

Power Cord

The power cord is the long, black length of wire that extends from the back of the tool and connects to an external power source.

1

Picture 10: power cord

Picture 1: Power Cord

2

Power Cord Clamp

The power cord clamp is a piece of metal which, when screwed into the body, restricts the movement of the power cord.

1

Picture 10: Blade Guard

Picture 2: Power Cord Clamp

3

Jigsaw body

The Jigsaw body is the plastic, black and orange exterior casing to the power tool. It consists of two halves.

1

Body.JPG

Picture 3: Jigsaw Body

4

Body Screw

The body screws attach the two halves of the Jigsaw body together. They have a 5/16 inch head diameter, and are 3/4 of an inch in length.

8

Shellscrew.JPG

Picture 4: Body screw

5

Reciprocating shaft Assembly

The Reciprocating shaft assembly is the metal extension connected to the blade holder.

1

Reciporcatingshaftassembly.jpg

Picture 5: Reciprocating Shaft Assembly

6

Carbon Brushes

The Carbon brushes are black rectangular boxes that complete the circuit to the electric motor. They are clipped into the Jigsaw body.

2

Carbonbrush.JPG

Picture 6: Carbon Brushes

7

Armature Assembly

The Armature Assembly is the inner portion of the electric motor.

1

Interior.JPG

Picture 7: Armature Assembly

8

Field Assembly

The Field Assembly is the exterior portion of the electric motor.

1

Exterior.JPG

Picture 8: Field Assembly

9

Blade Guard

The Blade Guard is the length of steel which blocks the blade.

1

Picture 10: Blade Guard

Picture 9:Blade Guard

10

Trigger

The trigger regulates the flow of electrical energy. It is a black, rectangular box within the Jigsaw body.

1

Trigger.JPG

Picture 10: Trigger

11

Power Cord Clamp Screws

The Power Cord Clamp Screws attach the Power Cord Clamp to the jigsaw body.They have a 5/8 inch head diameter and are 1/4 inch in length.

2

Triggerscrew.JPG

Picture 11: Screw

12

Base Plate

The Base Plate is the steel plate the jigsaw body rests upon.

1

Bp.JPG

Picture 12: Base Plate

13

Angle Adjustment Lever

The Angle Adjustment Lever is the steel handle which adjusts the base plate angle.

1

Aal.JPG

Picture 13: Angle Adjustment Lever

14

Angle Adjustment Handle

The Angle Adjustment Handle is the black thumb tab attached to the end of the Angle Adjustment Lever.

1

Blackthumbtab.JPG

Picture 14: Angle Adjustment Handle

15

Handle Screw

The Handle screw secures the Angle Adjustment Handle to the Angle Adjustment Lever. This screw has a 3/16 inch head diameter and is 9/16 inches in length.

1

Tabscrew.JPG

Picture 15: Handle Screw

16

Detent Spring

The Detent spring is contained within the base plate assembly.

1

Bpspring.JPG

Picture 16: Detent Spring

17

Lock Plate

The Lock Plate is the metal plate within the base plate assembly.

1

Lockplate.JPG

Picture 17: Lock Plate

18

Base Plate Bolt

The Base Plate Bolt connects the base plate to the jigsaw body.

1

Bpbolt.JPG

Picture 18: Base Plate Bolt

19

Base Plate Washer

The Base Plate Washer is placed along the base plate bolt.

1

Bpwasher.JPG

Picture 19: Base Plate Washer

20

Insert

The Insert is the black, plastic piece within the base plate assembly.

1

Innsert.JPG

Picture 20: Insert

21

Angle Indicator

The Angle Indicator is the black, plastic dial which depicts the current base plate angle.

1

Bplateangleindicator.jpg

Picture 21: Angle Indicator

22

Blade Clamp

The Blade Clamp is the piece which holds the blade in place.

1

Bladeclamp2.JPG

Picture 22: Blade Clamp

23

Angle Plate

The Angle Plate is the white, plastic plate that rests on top of the base plate.

1

Angleplate.JPG

Picture 23: Angle Plate

24

Blade Support

The Blade Support is the black, steel piece which guides the blade during movement.

1

Bladesupport.jpg

Picture 23: Blade Support

25

Pivot Pin

The Pivot Pin is the steel pin within the blade support.

1

Pin.JPG

Picture 25: Pivot Pin

26

Roller

The Roller is the final gear within the gear train leading to the Reciprocating Shaft assembly.

1

Rollerr.JPG

Picture 26: Roller

27

Gear Train washer

The Gear Train washer is the small, steel washer within the gear train assembly.

1

Wassher.JPG

Picture 27: Washer

28

Dust Chute

It is the black, plastic tube that runs through the angle indicator and channels the material debris from the fan.

1

Dustchute.JPG

Picture 28: Dust Chute

29

Special lock plate bolt

The Special lock plate bolt is the long, black bolt within the lock plate.

1

Specialbbolt.JPG

Picture 29: Special Lock Plate Bolt(1)

30

Cam Gear

The Cam Gear is the primary gear within the gear train assembly. It is connected to the roller.

1

Gearr.JPG

Picture 30: Cam Gear

31

Counterweight plate

The Counterweight plate is the large, metal plate within the gear train assembly.

1

Counterweightg.JPG

Picture 31: Counterweight

32

Connecting Plate

The Connecting Plate is the metal piece which connects the armature assembly to the gear.

1

Connectingplate.JPG

Picture 32: Connecting Plate

33

Roller Needle Bearing

The Roller Needle Bearing is attached to the connecting plate.

1

Rollerneedlbearing.JPG

Picture 33: Roller Needle Bearing

34

Thrust Plate

The Thrust Plate is the metal plate between the connecting plate and the counterweight plate.

1

Thrustplatee.JPG

Picture 34: Thrust Plate

35

Snap Ring

The Snap Ring is the metal ring securing the gear to the gear train assembly.

1

Snapring.JPG

Picture 35: Snap Ring

36

Cam

The cam is the black, plastic piece within the smart select assembly.

1

Sscam.JPG

Picture 36: Cam

37

Smart Select Casing

The Smart Select Casing is the black, plastic body that houses the components corresponding the Smart Select dial.

1

Smartselectcasing.JPG

Picture 36: Smart Select Casing

38

Pc Board

The Pc Board is the black, plastic piece which holds the cam in place in the Smart Select Housing.

1

Pcboard.JPG

Picture 37: Pc Board

38

Smart Select Plate

The Smart Select Plate is the metal piece within the Smart Select Casing.

1

Smartselectplate.JPG

Picture 38: Smart Select Plate

39

Duct

The Duct is the plastic, black piece which diverts the dust away from the blade.

1

Bduct.JPG

Picture 39: Duct

Ease of Disassembly

In an attempt to describe the difficulty of the product disassembly, we have defined a relative complexity scale. The ease of disassembly for this product will be rated on a scale between 1 through 5. Examples of this scale’s levels of difficulty are as follows:

[1]- No tools are required, simple to comprehend, little effort. The relative example is defined as the action of removing a gas cap from a automobile.

[2]- Requires the use of a tool, simple to comprehend, some effort. The relative example is defined as the action of removing a screw.

[3]- Requires the use of more than one tool, small amount of intellect, some effort . The relative example is defined as changing the oil in your car.

[4]- Requires multiple tools, intellect, moderate effort. The relative example is defined as changing brake pads on a car.

[5]- Requires specialized tools, high intellect, physically demanding. The relative example is defined as replacing a wheel bearing in a vehicle.

For the duration of the disassembly description, the ratings given to each step will be notated by the scaled number encapsulated in square brackets (e.g. [5] ).

Dissection Process

Tools Required The tools required for the dissection process are listed below.

  • Hands
  • T-10 Screwdriver
  • T-20 Screwdriver
  • Phillips flat head screwdriver
  • 1/4 inch flat head screwdriver
  • Needle nose pliers
  • Snap Ring Pliers
Table 2: Dissection Process
Dissection Process
Step Description Tool Required Difficulty level Visual Representation
1

Remove all 8 screws ( part #4) from the body. Unscrew these screws in a counterclockwise motion.

T-20 Screwdriver

[2]

This step was rated to be a 2 because it requires the implementation of the correct screwdriver and its proper usage.

Screwsideofshell.JPG

Picture 40: External Screws

2

Pull the two plastic sides of the body (part #3)apart, there were no clasps or retainers fastening it.

Hands

[1]

This step was rated to be a 1 due to the fact the body separated very easily with almost no effort.

Step 2jigsaw.JPG

Picture 41: Separated shell

3

Remove the blade guard (part #9).

Hands

[1]

This step was rated to be a 1, since the guard practically falls out.

Bladeguard.jpg

Picture 42: Bladeguard

4

Remove the dust chute (part #28) and base plate angle indicator (part #21), there are no restraints.

Hands

[1]

This step was rated to be a 1, these components are not secured in any way and lift right out.

Exhaustandbpangleseparated.JPG

Picture 43: exhaust port and base plate angle indicator

5

Remove the base plate by removing the screw (part #15) from the black thumb tab on the angle adjustment lever; unscrew counterclockwise. The lever can now pass through the slot in the body allowing the base plate to be removed.

T-10 Screwdriver

[2]

This step was rated to be a 2, you need the correct screwdriver and to know how to use it properly.

Thumbtab.JPG

Picture 44: black thumb tab

6

Remove the entire base plate assembly, with its attached components, by separating it from the body and sliding the angle adjustment lever (part #13) through the body. Unscrew inner retaining screw using a torx bit. This screw is of equal size to the screws that held the body together.

Hands

[1]

This step was rated to be a 1, there was no need for any specific position for the lever to pull through the body, so the base plate assembly detached very easily.

Baseplate.JPG

Picture 45: base plate assembly

7

From the base plate assembly, rotate the angle adjustment lever clockwise to allow the assembly to separate from the other pieces.The screw connected to the lever is a left-handed thread (part #29).

Hands

[2]

This step was rated to be a 2 because it took minimum effort to unscrew the lever and you had to realize it was a left-handed thread.

Lhscrew.JPG

Picture 46: left hand threaded screw

8

The base plate assembly can now be separated into 6 pieces.

  • The steel base plate (part #12)
  • The white plastic clamp/indexer (part #23)
  • The steel lever (part #13)
  • The left-hand threaded clamping stud (part #18)
  • Little black spring (part #16)
  • Black half indexing gear (part #20)(pops out of base plate using hands, no tools required)

Hands

[2]

This step was rated to be a 2, the parts separate with minimal effort.

Bplayout.JPG

Picture 47: Base Plate Layout

9

The blade support (part #25) is now removable by removing the steel pin that is securing it. Pliers may be necessary because of the pin being a little snug.

Needle nose Pliers

[2]

This step was rated to be a 2 due to the pin requiring a slight effort to come out.

Pin.JPG

Picture 48: Blade support and Pin

10

Remove the blade support (part #24).

Hands

[1]

This step was rated to be a 1 because the pin is the only item holding the support in place.

Bladesupport.JPG

Picture 49: Blade Support

11

Orient the Cam gear (part #30) to the 9:00 position on the gear-train by hand spinning the white plastic fan. Remove the saw blade holder assembly (part #5) by sliding the piece towards yourself away from the body, and then to the front of the body allowing the assembly to clear the cam and gear-train to be removed.

Hands

[4]

This step was rated to be a 4 because of the specific orientation and maneuvering to remove the component.

Reciporcatingshaftassembly.jpg

Picture 50: Reciprocating Shaft Assembly

12

Remove the 2 screws approximately 6 cm from the right hand side of the tool; they are 1 1/2 inches in length with a 1/4 inch head diameter.

Screwdriver

[2]

This step was rated to be a 2 for the use of a screwdriver.

Longscrew2.JPG

Picture 51: 3/8 inch screws

13

Remove the two black Carbon Bushings (part #6) from the rear of the tool that rub against the back portion of the motors shaft. These boxes are spring loaded and appear to have a one way snap design, meaning they are meant to be put together and not taken apart.

Small flat headed screwdriver

[3]

This step was rated to be a 3, because the process of prying out the boxes is slightly more unconventional than the straight forward use of removing a screw, and the components were seated tightly.

Electricalboxes.JPG

Picture 52: Black Electrical Boxes

14

Remove the two black screws (part #11) from the steel plate securing the power chord.

(#1) Philips head screwdriver

[2]

This step was rated to be a 2 because of the use of a screwdriver.

Triggerscrew.JPG

Picture 53: 5/8 inch screws and Steel Plate

15

Remove the steel plate (part #2) that was securing the power chord from body.

Hands

[1]

This step was rated to be a 1; clamp lifts right off.

Steelplate.JPG

Picture 54: 5/8 inch screws and Steel Plate

16

Gently grip the motor (part #8) in the center of the tool with one hand and the metal plate (part #31) with the other hand that is approximately 5.5 cm from the right hand side of the tool and lift the entire assembly straight up from the plastic body. This May require the assistance of another person to hold the body.

Hands

[4]

This step was rated to be a 4; the step requires an additional person and it is difficult to remove the motor without damaging it or other components.

Motorremoval.JPG

Picture 55: Motor Removal

17

Remove the metal plate and CAM by hand from the inner assembly, there are no restrictions.

Hands

[1]

This step was rated to be a 1, these components lift right out.

CAM.JPG

Picture 56: Metal Plate and CAM

18

Remove the trigger assembly (part #10) from the body, there are no restrictions.

Hands

[2]

This step was rated to be a 2, the trigger assembly pops right out of place.

Trigger.JPG

Picture 57: Trigger Assembly

19

The drive shaft of the motor (part #7) is removable by gripping the white plastic fan and steel outer portion (part #8) and moving the components to the left and out. This is the simplest state of the motor, it cannot be broken down any further due to the copper winding and magnets being molded onto the motor shaft. Also, the fan and bearings on either end are pressed onto the shaft and are not designed for separation or removal from the shaft. The wires use soldered connections and while they could be un-soldered, there is no need due to the wires not running through any holes and not restricting the removal of any components.

Hands

[1]

This step was rated to be a 1; there is no contact between the drive-shaft and another component. It simply comes right out of the motor coil.

Separatedmotor.JPG

Picture 58: Separated Motor

20

Flip the remaining portion of the body over to expose the smart select dial.

Hands

[1]

This step was rated to be a 1.

Shellwithdial.JPG

Picture 59: Outer shell with the Smart Select Dial

21

Gently pry under the smart select dial alternating sides, and the dial will pop off. Corresponding components to the dial are removable by hand and will come right out; this is approximately 6 cm from the right hand side of the body.

1/4 inch flat head screwdriver

[3]

This step was rated to be a 3 because you need to be careful not to break the dial and have to pry around the dial in different locations in order to do so.

Smartdial.JPG

Picture 60: Smart Select Dial

22

If snap ring pliers are available, use them to remove the snap ring (part #35). If not, take the following steps. Take small needle nose pliers and insert the nose of the pliers between the snap ring tabs. Place the 1/4 in flat screwdriver between the cam gear and the counter-weight plate. Apply slight pressure with the screwdriver my twisting or prying. Separate the pliers to expand the snap ring while applying pressure with the screwdriver. The cam gear will push the snap ring off of the stud and allow the gear-train to be disassembled. Pull off the cam gear first, then remove the counter-weight plate, then the thrust plate, and finally the needle roller bearing.

Snap Ring Pliers

Needle Nose Pliers

Hands

1/4 in flat screwdriver

[4]

The step possibly requires the use of multiple tools. The snap ring can be difficult to remove from the cam gear.

Sgeartrain.JPG

Picture 61: Gear Train

23

From the smart select assembly, remove the selector cam retainer by hand. Remove the smart select plate (part #38) by simply lifting it out. Remove the selector cam by hand as well.

Hands

[1]

The assembly does not possess any securing mechanisms.

Smartselectassembly.JPG

Picture 62: Smart Select Assembly


Difficulties During the Dissection Process

There were two primary difficulties encountered within the dissection process. The original method of dissection, detailed in Gate#1, specified that the process would begin with the removal of the base plate assembly from the jigsaw body. Despite repeated attempts and multiple tools, we were unable to remove the base plate special bolt from the lock plate. Ultimately, our repeated attempts proved to actually strip the bolt. However, the persistence of our efforts eventually gave way to the bolt's removal. We discovered that this bolt was a retaining bolt, which means it is designed to not be removed. The other challenge during the dissection process was the gear train assembly. The primary gear within the assembly implemented a snap ring in order to secure itself to the assembly. In consideration of the rigorous motion of the gear train while the jigsaw is being used, the snap ring must securely hold the components together. Thus, it proved to be difficult to pry the snap ring from the assembly. However, our group was able to overcome this challenge through the implementation of needle-nose pliers.

Was the Product Intended to be Disassembled?

In consideration of the intended recipient of the product, household consumers, one must conclude that the product was not intended to be dissembled by the customer. However, in the interest of product repair one must also consider whether the specific assemblies within the tool are intended to be dissembled by a verified technician or, rather, simply replaced. From our challenges during the dissection process we may conclude that the lock plate and bolt contained within it were not intended for disassembly. Our dissection process also determined that the lock plate assembly may be removed from the base plate assembly as a whole without effecting blade performance. Therefore, it is a reasonable assumption to conclude that the lock plate was not intended to be disassembled for the decreased likely hood that it requires repair. The material of the plate, i.e. steel, also confirms the durability of the plate. The armature and field assemblies would, in all likelihood, also be replaced rather than disassembled and repaired. Therefore it is logical to assume that the motor was not intended to be completely disassembled. The remaining assemblies of the tool, however, possessed minimal restrictions during the dissection process. For instance, the carbon brushes were simply clipped into the jigsaw body and the wires were free fed through channels. The evidence of minimal restrictions presents the likely possibly that the remaining components (i.e. trigger, base plate assembly, reciprocating blade assembly) were intended to be easily disassembled by a technician.

Connection of the Subsystems:

Table 3: Subsytems
Sub Categories Components Picture
Electrical
  • Carbon Brushes
  • Trigger
  • Wire
  • Field Assembly
  • Armature Assembly
  • Power Chord

Trigger.JPG Separatedmotor.JPG

Picture: 63 Tigger Picture: 64 Motor Ensemble

Powercord.JPG

Picture: 65 Power Cord

Mechanical
  • Gear-Train Assembly
  • Blade holder assembly
  • Smart Select Dial
  • Base Plate
  • Lock Plate
  • Angle Adjustment Lever
  • Angle Adjustment Handle
  • Handle Screw
  • Detent Spring
  • Base Plate Bolt
  • Base Plate Washer
  • Insert
  • Angle Indicator

Geartrain2.JPG Bladeclamp2.JPG

Picture 66 Gear Train Picture 67 Blade Clamp

Shellwithdial.JPG Bplayout.JPG

Picture 68 Dial Picture 69 Base Plate Layout

Cooling System
  • Fan
  • Dust Chute
  • Duct

Duelfan.JPG

Picture 70 Fan


Sub System Description of Connections

Electrical:

  • Energy- Electrical energy is transferred from an external source to the trigger by means of the power cord. The trigger is then attached to the motor by the two red wires as shown in the picture, which carries the electrical energy. In this case the trigger limits the amount of electricity flowing into the motor, thus adjusting the mechanical energy produced by the motor. The two components of the motor are depicted in Table 3. The outer section is the motors coil which produces the magnetic field. This encases the armature assembly which has permanent magnets attached to it. When an electric current is running through the motors coil, the inner component will rotate rapidly and produce rotational mechanical energy. The carbon brushes also carry electrical energy. These brushes ride on a copper ring that is broken up into segments. These segments allow the circuit to be completed as well as the phase angle of the magnetic field to constantly adjust in a manner so it can continuously "pull" the armature assembly. If this did not occur, then the motor would not spin but rather be stuck in one position.
  • Physical- The wires are physically connected to the components. The carbon brushes are also physically connected to the motors drive shaft.
  • Signal- The trigger sends a signal to the motor


-These components are all connected in order to allow the electrical energy to be transfer to the motor where the energy will be converted to rotational energy. The order of these connections must also be followed because each component must come before the other in order for the system to operate.


Mechanical:

  • Energy- The the fans rotating motion causes a difference in pressure creating pneumatic energy. One use of this energy is it allows the debris to be blown away from your cutting path so you are able to see your line you may be following. The other use is discussed in the next subsystem. The gear-train is another component of the mechanical system that utilizes energy. The main purpose of the gear-train is to convert the rotational mechanical energy to a mechanical linear oscillating energy.
  • Physical- The armature assembly of the motor is physically connected to a couple of components. The first of these components are the brushes which were mentioned above. Another component that is attached to the motor is the fan. Proceeding the connection of the fan, the armature assembly is physically connected to the gear-train. The gear train is subsequently attached physically to the blade holder, which is what grips the blade. The "Smart Select" dial is connected to the blade support apparatus physically as well. Rotating the dial by hand controls the recommended setting type for a material by changing the angle of the blade support, subsequently changing the angle of the blade.
  • Mass- Other functions of the gear-train assembly include reducing vibration and increasing blade momentum from a steel counter-weight plate that oscillates opposite of the blade. The gear-train also reduce's the speed of the motor while increasing the torque due to the gear ratio implemented.


- Ultimately, the mechanical components are connected to convert rotational energy into translational oscillating energy. Without the electrical sub system feeding this system, it would be unable to do any of this. Each subsystem works with the next to accomplish the end task.


Cooling System:

  • Energy- The other operation for the fan, which is its main function, is to remove thermal energy (heat) from the motor, by pneumatic energy. Because of the many windings of the coil, there is much heat built up due mainly to the current flow and some from friction. Without this cooling process, the coil would likely heat up enough to melt the copper causing a short within the windings and ceasing the operation of the motor.
  • Physical- The fan is physically connected to the motor armature.


- The Cooling system needs to be connected to the mechanical system to utilize its rotational energy. It would be illogical to have a separate system to rotate the fan when the motor already exists to create rotational energy, so the fan is made as part of the armature.

Influence on factors

• We have concluded there are multiple factors that are primarily responsible for this tools configuration. The first being economic; The mechanical and cooling systems could have been made separately and not connected. However, it is more conventional and cost effective to build the saw with a single motor and convert the rotational energy it produces to suit each part. The same idea can be applied to the fan itself. Fans have been used in electronic power tools for years, but until recently, none have used the fan as a means of blowing debris away from your cutting path. Black and Decker saw the opportunity to utilize the use of the cooling system for more than just cooling the motor. So they were able to create a second function for a component that was already in use. One downfall of this type of connection, is that the motor performance is decreased because of the extra load it now has to burden besides the gear-train. This could effect the motor by decreasing the life span slightly, but is still a more efficient setup. Another connection that considered was the smart select dial. This operates from the physical connection to the blade support. This could have been accomplished by other means, such as a small motor and lead screw, but that would be a waste of money,weight and space for such a simple function.


• Another contributing factor is societal. It was decided to use an electrical system to connect to the mechanical system for convenience and to keep it light weight. It could be possible to use a small gas IC engine to power the jig saw, but it would not be very appealing to the consumers. A small IC would create emissions and be heavier due to the components needed as well as having to store fuel. It is just logical to use an electrical system to connect to the mechanical system. Also, alternatively, they could have made the product cordless. While this does give the consumer more mobility, it increases the weight and cost as well which many people may not be willing to spend. On top of that, batteries have a shelf life and must be replaced at some point adding to the consumers ultimate cost. Because of this type of connection, it allows for many characteristics that are needed. The operation of the jigsaw creates a lot of vibration. Since the motor armature is not connected to the field assembly, it is capable of handling the vibrations and not inflict damage on the other components.


• Globally, the type of connection the smart select dial utilizes makes if extremely easy and simple for all users. This connection is also well suited because of the forces and vibrations from operation, allow this simple physical connection to last for the life of the saw.


• The final factor is environmental. The connection between the motor and gear-train is an efficient way of converting rotational energy into translational oscillating energy. This is mainly due to the gear ratio, allowing for a lot of torque but relatively low speeds for the blade itself. Also, electric motors generally tend to be more efficient at constant high speeds.

Arrangement Reasoning

• The subsystems are most likely arranged in the most cost effective manner possible; although there was a limited amount of leniency for the placement of most of the parts for the fact that there is just a basic order of components that must be followed. This is also a contributing factor for there being only one motor and fan used in the tool. This would allow for the tool to be more compact and in a shape that can easily be manipulated and utilized by the user. The fan was placed such that it could perform two specific separate tasks: cool the motor and clear debris. Since there is only one fan being used for both of these functions, there was a limited number of places that it could be placed to ideally utilize its performance due to the shape and style of the fan. The air intake is located at the rear of the product to reduce the amount of dust/debris that is taken into the system, to draw in cool air, and to channel the air through the entire motor.
• The adjustment angle lever is located farther back on the product as well, which prevents some hazardous issues. With the lever being placed so far back, if something were to interfere, such as shirt sleeve getting caught on the lever causing it to release/change the positioning of the base plate, the user would be a safe distance away from the harm of the blade. Also, at this position, it doesn't force the user to place his hand near the blade. Usually an operator will have the tool plugged in and want to adjust the angle "on the fly". Correspondingly, the user will most likely still be holding onto the saw's handle, where the trigger could accidentally be squeezed causing the blade to move. So the position of this lever helps to reduce that potential hazard.
• A blade guard is also provided to aid as a safety feature for the user, seeing as there is a higher chance of a finger or hand approaching the blade due to a slip or carelessness. The guard also further aids on the placement of the lever.
• Lastly, the power cord, although able to be placed anywhere, is placed in the back of the saw so as to be out of the way of the user while sawing. If it was in the front or side or just at a higher location, there would be a higher chance of it getting caught, cut, tangled, or plainly and annoyance to the user.
• With the simplicity of the systems with the jigsaw, there are very many limiting factors on placement of components and adjacent subsystems. This is mostly due to the simple fact that some components have to be placed in a certain location in order for the operation to occur, such as the cooling system cannot be adjacent to the electrical system because the motor needs to be able to rotate the fan. Also, since there is no presence of chemical hazards, there is no danger of a spark igniting anything. For the components that do have some free range, the only issue to keep in mind is the rotating components, so wires need to be placed accordingly. Another factor for components to be adjacent is just space. The jigsaw body would have to be enlarged in order to place any components next to another, so even though it may be possible, it is not logical. In its entirety, there really are not many components or subsystem that could be adjacent just based on how the systems work and each system has to come before or after the other.

Citations

(1) Special bolt. (2011). Retrieved from http://www.ereplacementparts.com/special-bolt-p-431614.html?osCsid=nsaqks8s22bchns08chbc823t0