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.