The ultimate success of the casting design depends on the communication between the designer and foundry engineers. When the foundry is properly informed of part requirements, there is usually a compromise of specifications that will allow for maximum compliance to print specifications and finish part design.
1. Standard Linear Tolerance(mm) As-cast tolerances of angles is mainly a function of the part design and their ocation in casting. They range from +/- 1/2 degree (considered minimum) for well supported positions to +/- 2 degree where existing distortion could be expected. Inclusion of gussets and ribs normally minimizes distortion and many sections can be mechanically straightened. 2. Flatness, Strengteness and Roundness
Possible Thickness Section Sink per Face of Casting
Up to 25
25 to 50
50 to 100
100 to 150
Straightening adds cost, but sometimes cannot be avoided. The actual straightening costs are often dependent on the tightness of the tolerance specified, so do not specify tighter flatness, straightness, roundness, or other requirements than you actually require. (WOTECH typically straightens parts using die sets that will be included in your tooling price.) 3. Size and Weight Range Size and Weight. Part size and weight are the most critical factors in determining part cost because mold capacity is limited by both size and weight. The more pieces that can run on a mold, the lower the part cost. Unnecessary mass should always be removed by correct engineering practices to reduce part weight.