casting 101 C
Reducing Casting Costs in the Cleaning Room
Steve Robison, AFS Senior Technical Director D
esigners often assess the capability of their casting supplier by re- viewing the metalcast- ing facility’s melting,
pouring and casting production processes. But post casting process- ing also can be a major contributor to the fi nal selling price of the casting. Gate removal, grinding and fi nish- ing processes are the most common cost contributors. Past studies have indicated that cleaning room labor and processing can comprise 20% or more of the casting selling price. Casting buyers who want to control costs should consider the effi ciency of a metalcasting facility’s cleaning room opera- tion and post casting processes when reviewing a potential partner. T e following checklist raises some basic questions to consider. Where does the metalcaster place
Is the cleaning room being used
to correct casting related problems? While casting issues such as rough surface fi nishes and other defects can be improved in the grinding room, this additional work greatly increases costs. Check castings for issues such as: • Excessive fl ashing on the parting line.
• Rough surface due to metal pen- etration into the sand mold.
• Broken molds that leave excess metal on the casting.
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gates and risers? Post casting effi - ciency begins with the casting design and engineering stage of development. Runners, gates and risers should be lo- cated where they will be easy to remove in the cleaning room. Reduced time per casting increases effi ciency and mini- mizes costs. Other issues include: • Can the gates be connected to a section of the casting that will be machined in a later operation? If the surface will be machined, perhaps some of the gate connec- tions can be left on the casting and grinding time can be reduced.
• Are the gates and risers attached to an area of the casting with restrict- ed access by grinding and cutting equipment? If the connections are diffi cult to cut off , the operator may not be able to cut them as close to the casting, which leaves more metal to remove in grinding room.
Has the foundry incorporated any
automation in the cleaning room? Does your supplier use any form of au- tomation in cleaning room processes? Automation reduces labor (a major cost factor) and improves consistency in cutting and grinding operations. Beyond robots, automation includes such things as trim presses, pressure assisted grinding and fi xtures. Does the supplier follow best
Casting buyers who want to control costs should consider the effi ciency of a metalcasting facility’s cleaning room operation.”
• Other casting defects that aff ect surface fi nish. Does the facility use computer
simulation to optimize the gating system? How does the metalcaster determine gating and riser design? Are there too many gate connections? Are the risers too large? Computer simulation can optimize the gating and risering system to reduce excessive gates and risers. It also can predict po- tential casting defects that will aff ect the cleaning room. What is the casting yield? For each individual mold, yield is defi ned as the percent of metal poured that becomes part of the fi nal component. Gates and risers are not part of the fi nal cast- ing component and are removed and recycled. T is material is recycled at a signifi cant cost, so if the volume of gating and risers can be reduced, then less metal is poured and the cost per pour will be reduced. Properly engineered gating systems and computer simulation should help improve yield.
safety practices? All equipment also must have appropriate guarding and work tool stands. For best productivity and safety, training is critical for all cleaning room personnel, and workers should be fi tted with appropri- ate personal protective equipment. All work- ers are recommended to go through both regular in-house
training and professional training, often provided through the abrasive manu- facturer. Clear, written procedures for safe operation are essential. While the casting purchaser may not be able to determine the details, part of the audit- ing process might include a conversa- tion to determine the foundry’s safety procedures and processes. Has the facility’s cleaning room
maximized abrasive technology and equipment? T ere have been many advances in abrasive technology. Has the supplier recently evaluated its grinding wheels and abrasive material to maximize productivity? Grinding materials should be customized to fi t depending on the alloy, amount of metal removed and the equipment being used. For optimum productiv- ity, equipment must be maintained properly and operated at maximum capability. Purchasers might ask about maintenance procedures and inquire if the metalcaster has considered new technologies and material choices.
Jan/Feb 2014 | METAL CASTING DESIGN & PURCHASING | 47
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