Related Terms
1. Nominal Weight of Castings This includes the machining allowance and other process allowances, serving as the reference weight to measure the weight of the inspected casting.
2. Weight Tolerance of Castings The allowable range of variation in the weight of the casting, expressed as a percentage of the nominal weight.
3. Weight Tolerance Grade of Castings The classification that determines the degree of the casting weight tolerance. The national standard GB/T 11351-1989 “Casting Weight Tolerance” specifies the weight tolerance grade, represented by the letter “MT,” and there are 16 grades, from MT1 to MT16.
4. Weight Deviation of Castings The difference between the actual measured weight of the casting and the nominal weight, expressed as a percentage of the nominal weight.
Determination of Nominal Weight of Castings
1. For mass or large-scale production, the nominal weight is determined by randomly selecting at least 10 castings from the first batch of qualified castings, with the average measured weight being used as the nominal weight.
2. For small batch or single-piece production, the nominal weight is determined by the calculated weight or the actual weight of any qualified casting mutually recognized by both the supplier and the customer.
3. The nominal weight is determined by the actual weight of a standard sample.
Detection and Evaluation Procedure of Casting Weight Deviation
1. The nominal weight of the casting and the weight of the inspected casting should be measured using a scale with the same accuracy grade, which has been verified by a metrology department. In investment casting, X-ray or CT scanning, as well as coordinate measuring machine (CMM) methods, are sometimes used for weight deviation detection.
2. The inspected casting should be cleaned before weighing. The remaining runner and riser should meet the specified technical requirements. Castings with defects should be repaired and qualified before weighing.
3. The casting weight deviation will be considered acceptable in the following two cases:
• When the casting weight is greater than the nominal weight, the weight deviation must not exceed the upper tolerance of the weight tolerance.
• When the casting weight is not greater than the nominal weight, the weight deviation must not exceed the lower tolerance of the weight tolerance.
If the inspection results do not meet these conditions, the casting weight deviation will be considered unacceptable.
4. For castings with weight tolerance requirements, the nominal weight and weight tolerance grade must be indicated on the casting drawing or technical documents according to the specified annotation method.
Post time: Feb-14-2025