Concentricity if cylindrical surfaces is affected by the design of the diecasting, Factors involved include the size, wall thickness, shape and complexity of the diecasting.
Concentricity of Die Cast Surfaces
Concentricity of diecast surfaces is affected by the type of die casting elements involved. These include surfaces in fixed relationship (formed by one die member) by opposite die sections, by auxiliary die members such as slides and cores, or combinations of these.
1. Basic tolerance - fixed surface in die relationship
Cylindrical surfaces A and B are formed by the same die section. If diameter A is 178 mm and diameter B is 102mm, diameter A will be concentric with diameter B within 0.25mm T.I.R. [0.10mm + (4 x 0.04)] = 0.26mm.
2. Surfaces formed by opposite die sections
Diameters A and B are formed by opposite die halves. If the projected area C of the die casting is 250 x 380 (950cm2), cylindrical surface A is 200mm in diameter and cylindrical surface B is 150mm in diameter , diameter A will be concentric with B within 1.06mm T.I.R.
3. Surfaces formed by two moving die members
Diameter A and B are formed by moving die members. If diameter A is 125mm and diameter B is 50mm, projected area of die member C is 160cm2 and projected area of die member D is 77cm2, diameter A will be concentric with diameter B within 0.93mm
|Basic tolerance for 125mm diameter - 0.10+ (2x 0.04)
|Projected area allowance for member C (160cm2)
|Projected area allowance for member D (77cm2)