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45.7 PRACTICE PROBLEMS
1. TRUE / FALSE - Investment casting is well suited to producing many parts at once.
2. The part below will be referred to in a number of questions. The drawings are not to scale but they do show an axisymmetric part (i.e., round) with a hollow internal core. The drawing is not to scale, but the rough dimensions are given. You are free to make assumptions (they must be stated) where necessary.
a) Describe in details the steps required to make this part using sand casting.
b) List the steps in detailed to make this part with investment casting.
c) List other casting processes that could be used to make this part. Provide your opinion of relative ranking (e.g., 1 to 5) with a general reason for each.
d) List other casting processes that should not be used to cast this part. Provide a reason why not.
e) If the part is to be made with injection molding, what special considerations would be required?
f) List appropriate techniques for making this part using thermoplastics. Give a relative ranking (e.g., 1 to 5) with reasons.
g) List types of composite manufacturing techniques that are, and are not suitable for making this part. Give reasons why.
3. a) Design a sand casting mold for the jar shaped part below. Include risers, gates, runners, etc., Indicate the parting line between the cope and drag. It will be filled from the side as drawn.
b) List and explain why 2 features of this part would be hard to cast.
4. Suggest parts that are best suited to produce with the following casting techniques. You must briefly state why is best suited to the method.
a) Centrifugal lost wax investment casting
5. Describe the procedures that would be involved in making a bronze statue. Which casting processes would be suitable? Why?
6. Why are castings normally cooled slowly?
7. How does the microstructure of a casting relate to the cooling rate?
8. What factors will result in a cast part not matching the pre casting mold shape?
9. Suggest two casting methods that would be suitable for making small toy cars? Indicate which would be better and why.
10. Suggest two casting processes would be well suited to making a large casting of a 4 foot tall ornament? Indicate the benefits and limitations of each.
11. How can hot tearing be avoided in castings?
12. Why should risers be located near large masses in cast parts?
13. How can chills help deal with large masses in a mold?
14. List and describe 8 different casting applications.
15. Identify design features that will cause problems when casting.
16. What are the major advantages and disadvantages of casting over other manufacturing processes.
17. Why is a complex runner/gate system used in sand casting. Why is it important to pour slowly and continuously?
18. Why is it important to allow gases to escape? Are there any processes where this would be more important? Which processes eliminate this problem.
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