Difference between revisions of "Electric Razor"

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[[Image:MECH DESIGN LAB 1B 3D VIEW.jpg|left|thumb|400px|Isometric View]]

Revision as of 15:00, 7 February 2008

Bucknell Mechanical Design Home


Group Members

Jerec Ricci

Chris Slavin

Brian Walker

Electric Razor

Figure 1: Conair Electric Razor Before Disassembly
Figure 2: Conair Electric Razor Primary Housing


This electric razor was manufactured by Conair. It is used for personal grooming, such as shaving or trimming of facial hair. It is able to provide a close shave or cut longer hair with included attachments.

How It Shaves

The motor is powered by two AA batteries and turns an offset shaft. The rotation of the offset shaft is translated into only horizontal motion by allowing the offset shaft to move freely within a vertical slit on the blade base mount. This in turn moves the moving blade against a stationary blade to cut hair.

User Requirements

-Shaver is able to cut hair

-Will not cut face

-Long battery life

-Fits into a human hand

-Can trim beards/sideburns


Engineering Specifications

-Hairs cut per pass (%)

-Angle of blade (degrees)

-Motor Efficiency (%) or Battery life (time)

-Fits users grip (% of population)

-Adjustable length (mm)

-Vibration (amplitude)

-Users like it (%)


The table belows lists the components for the Conair Electric Razor:

Table 1: Conair Electric Razor Component List
Part # Part Name Category Function Material Picture
1 Primary Housing Structural Component Provides a mount for all other parts, user holds this part Plastic
2 Electric Motor Input Moves the blade Metal
3 Battery Door Structural Component Covers and holds batteries in place plastic
4 Upper Housing Structural Component Holds taper control switch and serves as a mount for cutting heads Plastic
5 Blade Base Mount Motion Conversion Element Serves as a mount for both blades and converts the motion of the motor output shaft to the side to side motion of the blade Plastic with metal springs
6 Stationary Blade Structural Element Guides hairs to be cut and serves as an anvil for the moving blade Metal
7 Moving Blade Output Cuts the hairs that have been guided by the stationary blade Metal
8 Snap Mount Structural Element The blade base mount or nosehair trimmer snaps into the tabs on this part Metal
9 Screws Structural Holds device together Metal

Computer Rendered Components

Electric Motor

Isometric View
Isometric View
Isometric View

Analysis of Rendered Components

Electric Motor

The decisions that had to be made in the design of this component include the size of the motor for it to fit within the primary housing, the weight of the motor to meet the goals of a low weight shaver, the power produced by the motor in order for it to be able to cut hair efficiently, and the amount of power needed to be supplied to the motor for it to run properly.

The critical features of this motor are the offset bar to generate only side to side motion of the razor blade and the links going to the motor that connect the offset bar. The critical dimensions of this motor are its overall size compared to the primary housing and the size of the offset bar to give the right amount of side to side motion for cutting hair.

The loading that will be placed on the motor will be cyclic loading as it completes every revolution. There will also be cyclic loading on the components connecting to the motor.

To evaluate the performance of the motor it could be hooked up to a power source and tested to see how long it would run. The shaft could also be hooked to different weights for different trials to determine how much work or power the motor is able to produce.

Moving Blade

The decisions that had to be made in the design of the moving blade were how it could be mounted to the blade base mount, how many teeth it should have. The blade snaps onto the blade base mount using 2 circular holes that fit over the two circular protrusions on the blade base mount. The number of teeth the moving blade can have is limited by the stationary blade. Since the moving blade had to be narrower than the stationary blade, it was limited to 20 teeth.

The teeth on the moving blade are what actually cut hair. They work similarly to scissors, shearing hairs off using the stationary blade as an anvil. The moving blade was also limited in width by the stationary blade. If the moving blade was wider than the stationary blade, it would move its teeth beyond the teeth of the stationary blade, but no hairs would be cut by the moving blade teeth alone.

There should only be minimal loading on this component since it will pressed against someone's face. The rapid side to side motion of the the moving blade may stress the plastic on the blade base mount where it snaps together.

The most important thing for the blades to do is to cut hair. To evaluate their performance, one could measure how much hair is cut per pass as a percentage.

Stationary Blade

One decision that had to be made with this component was the size of the two circular holes at the bottom which lock the blade in place via screws. The number of prongs at the top (27), their shape, and the cut out angle that cuts into them were all decisions as well. Finally the thickness, length, and width were all decided upon.

The individual prongs/blades have two purposes. The first is to elevate/separate individual hairs. The second is to act as one end of the wedge between the moving blade and itself to actually lop off the hairs. There are 27 such prongs, each 0.025 inches wide and 0.142 inches long. The entire stationary blade is 1.122 inches tall and 1.103 inches wide. The two screw holes are 0.184 inches in diameter. The angled tip is 0.258 inches long and descends the entire thickness of the blade, or 0.092 inches, which gives it a slope of -0.3565 from the pointy tip of the blade if the sideways slot is at the top.

Loading on this component will come from pressure from the user's face or fingers. Some of this loading will be transferred to the screws holding it in place and some will be transferred to the moving blade behind it. These loadings will in most cases be minor.

User tests in which only the stationary blade is variable can measure performance. By varying the design of the stationary blade only, its performance can be compared to other stationary blades, and its relative performance would thus be evaluated. Since stress on this component would most likely be minor, stress tests would not be necessary.