1. An important sheet metal sizes should be complete, correct, clear;
2. Size baseline choice should not only consider the design requirements, but also consider the processing of positioning and measurement of test requirements;
3. Has assembly required with the size of the two parts should be tolerance requirements;
4. With the choice should be reasonable, preference-based hole system, as far as possible with the selection of priorities and common areas;
5. Tolerance level should be chosen to be appropriate;
6. Geometric tolerance selection should be reasonable and appropriate;
7. Did not note Tolerance and non-injection use of geometric tolerances according to information platform / design specifications / technical specification "not note size of the public
Poor technical specifications "and" did not note form and position tolerance specifications, "the implementation.