Your company received an order to machine a batch of 150 steel parts that are 73.0 mm in diameter and 250 mm in length. One of the processes is a finish turning operation. Where the feed is 0.30 mm/rev, and depth of cut is 3.5 mm. You were assigned to select the cutting tools for this operation. There are three tool materials available: high speed steel, cemented carbide, and ceramic. Your manager asked you to compare these tool materials. You found that for the high speed steel tool, the Taylor equation parameters are: n = 0.130 and C = 80 m/min. The price of the HSS tool is $20.00 and it is estimated that it can be ground and reground 15 times at a cost of $2.00 per grind. Tool change time is 3 minutes. Both carbide and ceramic tools are in insert form and can be held in the same mechanical toolholder. The Taylor equation parameters for the cemented carbide are: n = 0.30 and C = 650 m/min; and for the ceramic: n = 0.6 and C = 3,500 m/min. The cost per insert for the carbide is $8.00 and for the ceramic is $10.00. There are 6 cutting edges per insert in both cases. Tool change time is 1.0 min for both tools. The time to change a part is 2.5 min. The cost of machine time is $40/hr. The setup time for the batch is 2.50 hrs. The manager asked you to compare the three tooling cases, from the following points of view: (a) cutting speeds for minimum cost, (b) tool lives, (c) cycle time, (d) cost per production unit, (e) total time to complete the batch and production rate and (f) the proportion of time spent actually cutting metal for each tooling? (f) Which tool material would you recommend for the process? State other factors related to the workpiece specification that could influence your decision.
You were assigned to design the process a cold upset forge for cylindrical part that has 30 mm diameter and 30 mm height. You found that the shop has a hydraulic forging press that is capable of exerting a maximum force = 1,000,000 N. You have conducted the proper test to determine the flow curve of the metal. You have found that K = 400 MPa and n = 0.2. In order to go ahead with the process design, you needed to determine The maximum reduction in height to which the part can be compressed with this forging press. You have consulted a colleague about the value of the coefficient of friction for such a process, he advised you to use a coefficient of friction = 0.1.
When you presented the results to your manager, he asked you the following questions:
1. How did you determine K and n for this material?
2. What are the values of the yield strength and ultimate tensile strength of this material?
3. What is the maximum reduction in height to which the part can be compressed with this forging press?