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Drawing Fundamentals:

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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