Introduction To Casting Processes by Stead Fast Engineers Pvt Ltd –
part 2
one of the leading Induction heating system manufactures
Design, Materials and Economics
Design Considerations in Casting• Design of the part
• Casting process and material
• Locate parting line• Locate design gates• Locate mold features
such as sprue, screens and risers
Design Consideration of Cast Parts
• Corners, angles, section thickness– Avoid sharp
corners angles and fillets
– Stress raisers, cracking, and tearing
– Sections should be blended smoothly
Design Consideration of Cast Parts
Design Consideration of Cast Parts• Flat Areas
– Large flat areas may warp during cooling
– Poor surface finish from uneven flow in pouring
– Resolve with ribs, and serrations
• Circles and Rounds– Lower cooling rate in
circles induces hot spots– Shrinkage cavities and
porosity
Design Consideration of Cast Parts• Shrinkage
– to avoid cracking during the cooling process there should be shrinkage allowance
– Staggered ribs, change the intersection geometry
• Patternmaker’s Shrinkage Allowance– 10-20 mm/m
Design Consideration of Cast Parts• Draft
– Used to enable easy removal of pattern without damage to mold
– Range from 5 to 15mm/m
– Angles of 0.5° to 2°• Dimensional Tolerances
– As wide as possible within limits of good performance
– Letters and markings
Locating the Part Line• Part line – separates upper
and lower mold– Flat plane, along
corners or edges– This will avoid
flash at the parting lines
Locating and Designing Gates• Gates
– Connections between runners and the part
– Multiple gates preferred
– Feed into thick sections of the castings
• Runners– Distribution channel
for molten metal from the sprue into the gates
Casting Alloys• Nonferrous Alloys– Aluminum,
magnesium, copper, zinc, tin, lead
– Good electrical conductivity and resistant to corrosion
– Most of these alloys share characteristics of good machinability and can all be welded
Casting Alloys• Ferrous alloys
– Cast irons• Largest quantity of all
metals cast• Good wear resistance,
hardness and machinability
– Cast Steels • Material used under
extreme heat conditions
• Railroad, mining and construction
Casting Economics• Cost– Depends on materials,
equipment, and labor– Preparations require raw
materials, time and effort– Melting, pouring, heating,
cleaning, inspections– Equipment cost lowers
with large # of castings– Solutions to alleviate
unneeded cost are being looked into• Rapid prototyping
Molten Metal Pour
Solidification
Solidification Temperatures
Dimensional Change
Pinholes
Blowhole
Scab
Pinholes
Rough Surface
Thank you…
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