Question
Download Solution PDFA taper provided on the pattern for its easy and clean withdrawal from the mould is known
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFConcept:
Draft Allowance:
Pattern draft is the taper placed on the pattern surfaces that are parallel to the direction in which the pattern is withdrawn from the mould (that is perpendicular to the parting plane), to allow removal of the pattern without damaging the mould cavity.
Shrinkage Allowance
- During cooling of the material in the Casting process, the molten metal tries to shrink in size because of the increase in density, in all the three stages, the material is getting shrunk (reducing its dimensions or volume).
- But shrinkage allowance taking place in 1st two stages is called Liquid Shrinkage.
- Shrinkage in 3rd – the stage is called Solid shrinkage.
- Liquid shrinkages are always compensated by providing a riser in the casting process.
- Solid shrinkage is compensated by the giving shrinkage allowance.
- It is expressed as mm/m.
Machining Allowance
The extra dimension provided on the casting and it will be removed by machining after the casting has been completed is called Machining Allowance.
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