Calibration Required for CNC Machines?


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Hi All,

We are re-writing our maintenance and infrastructure SOP and we currently have in there that the CNC machines are calibrated when first installed and additionally when determined necessary. I am trying to find any resources that say calibration for production machines is required for ISO. We just want to cover our bases and make sure that the only requirement for production machines is validation through IQ/OQ/PQ and documenting FAI and SPCs that conform to customer requirements, and that calibration strictly refers to monitoring and measuring equipment. Thanks!


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In General, calibration is required for monitoring and measuring equipment. No requirement of calibration of Production machines. Suppose if we have any gauges installed in the machines which affects product / process quality then the particular gauges need to be calibrated.
Most machines like this have some built in calibration checks, most others can be programmed to produce a cube or sphere for manual verification. Our waterjets cut a cube or square (depending on the thickness of the material), for an axis runout check you can cut an "L" shape at each corner of a large plate (4x8 ft or 5x10ft) to measure diagonals and sides. Then I record the validation in my calibration records.


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You will be sampling and measuring the products from the CMM. If you are using calibrated equipment then that will link measurement traceability to the performance of the CMM in place of a "calibration".


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On some CNC's they might have a probe system that measures and adjusts offsets during the run or just measures the part for acceptance. If this is the case, the probe system will need to be calibrated as that measurement is used to determine acceptance of final product. If you are just running parts and then using calibrated instruments for final acceptance, the machine does not need to be calibrated. Maintained yes, calibrated no.
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