Power Scissors

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Contents

Power Scissors Dissection

Overall.jpg

Function

The primary function of the Power Scissors is to cut through different materials. There are two blades, the bottom one stays stationary, and the top blade moves rapidly, opening and closing. This action allows the tool to cut through different materials.


Parts

The table belows lists the components for the Black & Decker Power Scissors.

Table 1: Power Scissors Component List
Part # Part Name Category Function Material Picture
1 Motor Input Serves as Power Supply for blades
Motor.jpg
2 External Casing Structural Component Protects internal components and holds them together Plastic
Complete open.JPG
3 Jaws Ouput The bottom blade remains stationary, while the top blade moves continually up and down Steel
Jaws.JPG
4 Battery Input Provide power to motor Wrapped in cardboard
Battery.JPG
5 Cam Motion Conversion This forces the bracket to move by translating rotation motion of the motor, to translational movement in the bracket. The bracket then causes the upper blade to open and close Plastic
Yoke.JPG
6 Screws Structural Holds Casing Together Metal
Screws.JPG
7 Bracket Support element Ball and socket joint limits movement of jaws. The socket is ovular so it allows some movement of the jaws. Plastic
Blade housing.JPG
8 Button (spring) Motion Conversion Closes switch to start motor by closing circuit. Button – plastic

Spring – metal Switch - metal

Customer Requirements

  • Blades are sharp enough to cut different materials (1)
    • Have a sharpening function
    • Changeable blades for different materials to cut
  • Easy to use (2)
    • Has a low weight
    • Has a small size
    • comfortable to hold
    • Wireless
    • Easily accessible buttom to start
  • Aestheically Pleasing (3)
    • More likely to be bought
  • Long battery life, chargeable (4)
  • Doesn’t break if dropped (5)

Engineering Specifications

  • Material for jaws is sharper than the intended material to cut
    • Corresponds to blade sharpness (1)
  • Batteries last for 4 hours of continuous use
    • Corresponds to long battery life (4)
  • Force of scissors is greater than 5N
    • Corresponds to ability to cut through material (1)
  • Weight is less than 5 lbs
    • Corresponds to easy to use (2)
  • Scissors retain sharpness for 40 hours of use
    • Corresponds to blade sharpness (1)
  • Torque on motor is great
    • Corresponds to ability to cut through material (1)
  • External casing can withstand force from being dropped
    • Corresponds to long-lasting (5)
  • 90% of people surveyed found the scissors pleasing
    • Corresponds to Aesthetically pleasing. (3)

Scissor Jaws

Scissors.jpg

1. What decisions were made in the design of this component/module?

    • In making this component it was important to find a way to create jaws for cutting that moved rapidly. It order to solve this problem the jaws were made so that only the top jaw moved, while the bottom remained stationary.

2. What are the critical features and dimensions? (It may help to annotate the screenshot of the CAD rendering.)

    • Critical features of this component are the dimensions that correspond to the shape of each jaw. The angle of the blades could also be measured, as well as the thickness to the part. The angle of the blade affects the sharpness of the tool, and the thickness affects the load that can be withstood. Another important feature was the angle that the jaws could open to, an attribute that is important to ensure that the tool is safe.

3. What kind of loading do we expect to be on the component?

    • Loading can be expected from the material trying to be cut. The force of the cutting, and the resistance of the material to be cut will create stress on the component.

4. What measures can we use to evaluate performance?

    • To evaluate the performance of the jaws they should be tested regularly for sharpness. It is important that the jaws retain sharpness so that the tool can perform its function to cut through material. This can be tested by determining the forces necessary to cut through various materials. It is likewise important that the jaw is functioning properly and not opening at too large of an angle, as this will deter from the safety of the tool. This can be measured by determining the angle at which the jaws open.

Slider Mechanism

Sliderfront2.jpg

1. What decisions were made in the design of this component/module?

  • It is clear that the decision was made to make the slider mechanism as simple as possible. Essentially it seeks to turn the rotating motion of the engine shaft into reciprocation motion perpendicular to the shaft with as little parts as possible, most likely to improve weight, cost, and packaging properties of the product.

2. What are the critical features and dimensions? (It may help to annotate the screen shot of the CAD rendering.)

  • It is important that the slider is long enough to provide adequate clearance on either sides of its receivers. This ensures that as the slider moves back and forth between its holding brackets, that the receivers (which protrude from the slider), so no contact the brackets and disrupt ro jam the oscillation. Also, is is necessary that the grove cut into the back of the slider, which acts as a receiver for the shaft coming from the motor, fits the guide on the end of the shaft perfectly in the lateral direction, but has ample vertical clearance on either side. As the shaft on the motor spins, the guide piece on the end of the shaft moves up and down, and left to right. By making the with of the receiver equal to the width of the guide, then all left/right motion of the shaft is transfered into the motion of the blades. By leaving clearance in the height, the guide can move up and down in the receiver without disrupting the motion of the slider (which should only move left to right).

3. What kind of loading do we expect to be on the component?

  • The slider is expected to be subjected to cyclical forces in the lateral direction, switching back and forth from left to right. These forces will create compressive loading on the insides of the sliders receivers.

4. What measures can we use to evaluate performance?

  • The efficiency of the slider can be evaluated by determining how much of the power generated by the motor shaft is transfered to the cutting blades. Also, the consistency of its motion can be analyzed as well to determine how smooth its operation is.

Slider.jpg

Motor

1. What decisions were made in the design of this component/module?

  • When choosing a motor the first decision would have to be what size motor, power wise, do we need to cut through our desired material.

2. What are the critical features and dimensions? (It may help to annotate the screenshot of the CAD rendering.)

  • It is critical that the motor fits inside the sized casing for the scissors. It is also important that we have a motor that is not to heavy. We do not want the product to be uncomfortable to hold.

3. What kind of loading do we expect to be on the component?

  • There will be a torque applied to the motor depending on the force applied to the blades or jaws of the scissors.

4. What measures can we use to evaluate performance?

  • We can measure the amount of torque the motor can produce and how long the motor can run on its charge.

Motor1 pro.jpg