Question

Discuss the requirements for each of the following components and discuss which of the processes you would choose to make the product. Please provide references where possible.

1. Screwdriver.

An example is shown below:

Example: An ashtray

Select all materials possible in making ashtray e.g. stainless steel and explain the properties of stainless steel. Hence choose the best material based on production purposes.

Explain briefly all the process involved (e.g. casting, forging, etc) in making the product for the selected materials. Explain in detail the best process that your group had chosen for making of the product. (Eg: Molding, include diagram.)

Conclusion to why your group had chosen the materials and process for every item above.

Overall conclusion to the above case study e.g teamwork, what you had gained from the case study, etc.

Answer 1

The raw materials steel wire (SAE6150 (Cr-V), SAE (Si-Cr) and S2 (Mo-V))., plastic, nickel, and chromium are used to produce screwdrivers. The steel wire is used to make the screwdriver bar, plastic is used to make the handle, and either nickel or chromium is used to plate the steel tips of the screwdriver.

Manufacturing process-

Making the steel wire-

1.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.

2.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.

3.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.

4.If the screwdriver is designated for professional use, it is transferred to a hand-grinding department, where the tip is ground to size. The shank is chemically milled and then polished. The screwdriver then goes to a nickel flash bath and is electrically chrome plated.

Handles-5.he 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.

6.Next, the pellets are fed into another extruder that extrudes the materials for the handles in bars that are 8 to 10 feet (2.4 to 3 meters) in length. If a two-color handle is desired, a second extruding machine can be attached to the first to extrude a single, two-color rod. The rods are then put into an automatic turning machine, which shapes the handles and cuts them to the final length. A hole is then drilled in the handle where the bar will be inserted.

7.The handles are machine washed and dried to remove grease, oil, and excess scraps from the turning machine and the extruder. Next, the handles are immersed in an acetone vapor bath, which melts and smooths the outside of the handle. The acetone vapor is highly flammable, and this process takes place inside an explosion-proof room.

Assembly-

8.The method of final assembly depends on the quality of the tool being produced. Professional models are assembled individually on a horizontal assembly machine that hydraulically forces the bar into the plastic handle. The handles are branded by a hot stamp immediately before going into the assembly machine. This assembly process requires one skilled operator for each machine.

Other models might be assembled on hydraulic presses, three at a time. The least expensive models are assembled six at a time on one machine and placed by robot on a skin card machine that packages the screwdrivers for mass-market sale.

Figure-The plastic handles are made by mixing cellulose acetate with a plasticizer and then extruding the mixture into bar form. After further shaping, the bars are drilled so that the rods can be inserted, cleaned to remove dirt, and dipped in an acetone vapor bath, which melts and smooths the outside of the handle.

Composition of steel-

1. Carbon-Carbon is an element that is effective for enhancing the hardness of steel

2.Silicon-Silicon is an element that is effective in improving the strength of steel and the sag (relaxation) resistance of the spring as a solid solution element in ferrite. In this study, these effects were used for the design of the newly developed screwdriver bit steel not only to increase the hardness but also dramatically prevent the plastic deformation under torsion application.

3.Nickel-Nickel is an element that is effective in improving the toughness of steel after the quenching hardening and tempering treating, In addition, nickel is also added to reduce the decarburizing layer. The latter effect is beneficial to reduce the drawback.

4.Vanadium-Vanadium is significant in the effect of refining crystal grains in the low temperature rolling and austenitization condition.

Property of celeose acetate-

Good toughness

Deep gloss

High transparency

A feel that can be described as ‘natural’.