60.2 PRACTICE PROBLEMS

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1.

a) ECM is used to remove metal from an iron workpiece. The feature being cut is a square hole 1cm by 0.5 cm. To cut down 1cm/min, what current is generally required?

b) How would the current change if the part was 3% carbon?

c) What advantages does ECM have over EDM?

2. We have a metal alloy that is a combination of Zinc and Silicon, but we are unsure what the ratio of the metals is. But an ECM machine can cut a 5mm square hole 2mm deep at a current of ___________ in one minute. What percentage of the alloy is zinc?

3. Describe good applications for EDM.

4. Explain how EDM is best suited to producing complex internal features, such as sharp inside corners.

5. Wire EDM produces parts with a profile that is vertical. What types of applications is this well suited to? Are there particular dies that benefit from this technique?

6. A hole that is 70mm deep and 10mm in diameter. What is the machining time using a) EDM, b) ECM?

7. Which of the following materials are suitable for EDM, EBM, ECM? State Why? a) stainless steel, b) ceramics, c) quartz, d) thermoset plastic, d) copper, e) diamond.

8. Describe the ability of EDM, EBM, ECM to produce sharp corners.

9. Describe the basic operation of an EDM machine using figures. Show why corners are rounded and why flushing is important.