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…