Casting
Upcoming SlideShare
Loading in...5
×
 

Casting

on

  • 280 views

My News

My News

Statistics

Views

Total Views
280
Views on SlideShare
280
Embed Views
0

Actions

Likes
0
Downloads
12
Comments
0

0 Embeds 0

No embeds

Accessibility

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

Casting Casting Presentation Transcript

  • Fundamentals of Casting Casting, one of the oldest manufacturing processes, dates back to 4000 B.C. when copper arrowheads were made. Casting processes basically involve the introduction of a molten metal into a mold cavity, where upon solidification, the metal takes on the shape of the mold cavity. Simple and complicated shapes can be made from any metal that can be melted. Example of cast parts: frames, structural parts, machine components, engine blocks, valves, pipes, statues, ornamental artifacts….. Casting sizes range form few mm (teeth of a zipper) to 10 m (propellers of ocean liners). Ken Youssefi Mechanical Engineering Dept., SJSU 1
  • Casting Processes • Preparing a mold cavity of the desired shape with proper allowance for shrinkage. • Melting the metal with acceptable quality and temp. • Pouring the metal into the cavity and providing means for the escape of air or gases. • Solidification process, must be properly designed and controlled to avoid defects. • Mold removal. • Finishing, cleaning and inspection operations. Ken Youssefi Mechanical Engineering Dept., SJSU 2
  • Sand Casting Terminology Ken Youssefi Mechanical Engineering Dept., SJSU 3
  • Sand Casting Process Ken Youssefi Mechanical Engineering Dept., SJSU 4
  • Solidification Time Solidification time = C(volume/surface area)2 Where C is a constant that depends on mold material and thickness, metal characteristics and temperature. Ken Youssefi Mechanical Engineering Dept., SJSU 5
  • Solidification Time Sphere, cube and a cylinder with the same volume Ken Youssefi Mechanical Engineering Dept., SJSU 6
  • Casting Defects Hot tearing – hot tearing, cracking, occurs if casting is restrained from shrinking, during solidification. Ken Youssefi Mechanical Engineering Dept., SJSU 7
  • Casting Defects These defects can be eliminated by proper mold preparation, casting design and pouring process. Ken Youssefi Mechanical Engineering Dept., SJSU 8
  • Casting Defects Hot spots – thick sections cool slower than other sections causing abnormal shrinkage. Defects such as voids, cracks and porosity are created. Ken Youssefi Mechanical Engineering Dept., SJSU 9
  • Casting Defects and Design Consideration Ken Youssefi Mechanical Engineering Dept., SJSU 10
  • Design Consideration Ken Youssefi Mechanical Engineering Dept., SJSU 11
  • Die Casting Hot chamber, low-melting alloys; tin, zinc, lead. Cold chamber, high-melting alloys; aluminum, copper. Higher pressure needed High production rates, good strength, good dimensional accuracy and surface finish, and good quality parts. Ken Youssefi Mechanical Engineering Dept., SJSU 12
  • Centrifugal Casting True centrifugal casting Centrifuging Ken Youssefi Mechanical Engineering Dept., SJSU 13
  • Squeeze Casting Cast parts have good mechanical properties, good dimensional accuracy, fine microstructure, good surface finish. Ken Youssefi Mechanical Engineering Dept., SJSU 14
  • Precision Casting Plaster Molding Plaster of Paris (gypsum) is used as the mold material, other components are added to improve the strength and reduce the setting time. The pattern is dried at 400 oF and the two halves are assembled and molten metal is poured into the cavity. The process produces fine detail with good dimensional accuracy and surface finish. Used to cast aluminum, zinc and copper-based alloys (low-melting temp.) Ceramic Molding Similar to plaster molding, except it uses ceramic as a mold which is suitable for high temp. applications. Mixture of zircon (ZrSiO4), aluminum oxide (Al2O3), silica (SiO2) and other bounding agents. Ken Youssefi Mechanical Engineering Dept., SJSU 15
  • Fabrication of Plastics Injection Molding Ken Youssefi Mechanical Engineering Dept., SJSU 16
  • Fabrication of Plastics Hot-Compression Molding Vacuum Forming Ken Youssefi Mechanical Engineering Dept., SJSU 17
  • Design Considerations • Wall thickness should be kept uniform if possible. Non uniform wall thickness could lead to warpage and dimensional variations. Minimum recommended; .025 in or .65 mm, up to .125 for large parts. • Round interior and exterior corners to .01-.015 in radius (min.), prevents an edge from chipping. Ken Youssefi Mechanical Engineering Dept., SJSU 18