In shell molding, a cast iron pattern is mounted in a mold machine and preheated to 500F. Te shell machine rolls as to fill resin-coated sand onto the hot pattern. Te sand grains are bonded by heat as an oven bakes the mold from the top. Te mold halves are removed from the pattern and glued together, ready to be poured. Shell molding provides better part-to-
part dimensional consistency than steel fabrications and avoids distortion caused by welding and the need for fixtures. In his example, Cook discussed the methods Eagle Alloy used to reduce cost in the conversion: • Freed up resources consisting of one welder, one machinist and the associated equipment.
• Improved appearance. • Provided machined part. Tree cylinder end sizes are now ma- chined from one common casting.
• Eliminated safety concerns. • Reduced components from two to one.
• Eliminated inventory. Total annual cost savings the
customer achieved by converting the fabricated cylinder end head to a steel casting was $46,000 after recouping the $11,000 tooling cost.
The 10-Step Program for Casting Defect Analysis
Kevin Fleischmann, associate direc- tor of education at the AFS Institute, provided an in-depth run-through of casting defect analysis to aid casting buyers in working with the supplier to solve problems found in their parts. Tis systematic approach addresses and solves the problem based on facts, not opinions and consists of root cause analysis and corrective action. Te 10 steps for defect analysis are: 1. Write the problem statement. 2. Collect process data. 3. Evaluate the data. 4. Classify and identify the defect. 5. Choose a corrective action plan. 6. Run a corrective action trial. 7. Evaluate corrective action trial. 8. Run a production test. 9. Evaluate the production test.
10.Solve? Final check-in.
May/Jun 2014 | METAL CASTING DESIGN & PURCHASING | 45
This sample casting used in the session on casting defect analysis exhibits sand inclusions. Using a real casting defect, Flei-
schmann walked through the steps of identifying the type of defect, running a corrective action plan and production test. One takeaway from
the session was if corrective actions have been exhausted without practi- cal, positive results, it may be time to revisit whether the defect had been identified correctly in Step 4.
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