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Drawing Fundamentals:
- To design a mold, the mold design should be easier to
understand and easy to interpret.
- The bill of material should be accurate.
- The type of lines used in the
mold drawing should be standard and distinctive.
- Use standard sizes of
sheet sizes for drafting purposes.
- The details of the mold should be entered in the title block,
i.e. company name and address, mould/part name, mould/ part
number, material used, drawn by, checked by, drawn date, revision
date, sheet number, scale, drawing number, size of drawing.
- Bill of Material should contain the rough size of components,
qty of items, material type, sheet no where detailed component
drawing can be found.
- Special instruction should be added on drawing as per
required.
- In dimensioning use
- To define the location of the centre of a hole, use Centre
line dimensioning.
- To provide the dimensions from a reference plane, use Base
line or Datum dimensioning.
- Different types of tolerance
- Unilateral System: In this method, tolerance is given in
only one direction. It is used in interchangeable
manufacturing where precision fits are required. Tolerance can
be revised without effecting type of fit.
- Bilateral System: In this method, tolerance is given in
both directions. It is not possible to retain the same fit
when the tolerance is varied. Bilateral tolerances are used in
large scale manufacturing.
- Tolerances for the mold:
- Standard tolerances: In this method, dimension is given
from one reference. This avoids stack up problems when all
dimensions are added
- Cumulative tolerances: In this method, dimension if
referenced from adjacent dimension. This method causes stack
up problem when the dimensions are added.
- Different Holes and Shaft sizes
- Holes: H6, H7, H8, H9, H11
- Shafts: c10, d10, e9, f7, g6, h6, k6, n6, p6, s6.
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