Question

write 200 words (screw drivers )

To select materials based on properties, manufacturing, sustainability, available time, cost and performance.

Keywords:       properties, processing, performance, sustainability

Prerequisite Knowledge:          basic knowledge of general materials’ properties.

These factors can be broken down into the following areas.

Material Properties

The expected level of performance from the material

             Material Cost and Availability ?

             Processing - must consider how to make the part

Environment – the effect that the service environment has on the part The effect the part has on the environment. The effect that manufacturing/processing has on the environment.

Time available to make the component

Answer 1

As you mentioned the following parameters I am considering

1. Material Properties : Screw Driver consist of two parts one metal strip and plastic handle. The raw materials for most screwdrivers are very basic: Low carbon steel or medium carbon steel wire for the bar and plastic (usually cellulose acetate) for the handle. In addition, the steel tips are generally plated with nickel or chromium.
2. Properties are given below:

Expected level of Performance:

Low carbon steel or medium carbon steel wire is best suited material for Screwdriver. Carbon dominates the hardness but destroys theØ toughness. Torque value can be increased as the silicon content is higher. Nickel addition assists in compensating hard steel forØ toughness.

Chromium combined with molybdenum to form carbidesØ are beneficial for wear-resistance.

1. Manufacturing Process Processing and Environment :

                             First, coils of green wire (wire that has not yet been drawn to final size) are delivered to a factory in large coils, some as heavy as 3,000 pounds (1,362 kilograms). The wire is usually about. 375 inch (.95 centimeter) in diameter. The wire is then machine-drawn to the diameter necessary for the production run; one adjustable drawing machine can produce any required diameter. In drawing, wire is fed through a die with a reducing aperture until it assumes the proper size. After the wire is drawn, it is annealed (heat treated) to obtain the correct tensile strength in the metal. This process involves baking the wire at a temperature of about 1,350 degrees Fahrenheit (732 degrees Celsius) for 12 hours. Next, the wire is straightened by a string forge and then transferred to a cold forming press, which cuts the wire to the appropriate length and forms the tip of the screwdriver and the "wings" that will fit into the handle. These wings can be seen through a clear or semi-clear plastic handle. The newly formed "bar" (the actual screwdriver without Ats handle) is then heat treated in an in-line furnace at approximately 1,555 degrees Fahrenheit (846 degrees Celsius). This is a continuous flow process, and as the bars come through the furnace they fall into an oil quench for cooling. The bars are then placed in a draw back oven (450 to 500 degrees Fahrenheit or 232 to 259 degrees Celsius) and baked to a specified hardness.

The handles of a screwdriver are usually made of cellulose acetate; it is delivered to the factory in powder form (cellulose acetate rosin) and then mixed with a liquid plasticizer in a giant blender that holds approximately 1,000 pounds (454 kilograms) of the mixed material. If a colored handle is desired, pigments are added into the blender. The resulting paste, which has the consistency of thick cake batter, then goes to an extruder (a machine that forces a material out through an opening, the way a meat grinder forces out strings of meat), which extrudes a solid piece of cellulose acetate. The cellulose acetate is then cut into small pellets.

1. Time Availability to make the component:

The screwdrivers might be fitted with a special handle cover, depending on need. A rubber cap fitted over a screwdriver handle, for example, might be more comfortable for a professional using his tool five or six hours a day. A large handle with deep grooves might be ideal for some workers, while the home handyman who assembles a lamp or cabinet once every six months may not need or want to pay for the extra comfort.