Inspection And Reporting System In CNC Machining

Quality control is absolutely essential in the manufacturing of complex and precision parts, often a significant expense in the manufacturing process. CNC machine quality control is daunting, no matter how much you know.  While you can’t just assume a shop’s CNC machining processes are everything you need them to be, there are ways you can rest assured they’re taking the proper steps to maintain accuracy on your products.

Few places outside of science labs have more metrology equipment than good CNC machine shops.  Touring a shop like MacFab Manufacturing, you’ll likely see micrometres, microscopes, dial test indicators, feeler gages, and maybe a big granite surface plate off to the side.  We have optical comparators, air gages, coordinate measuring machines, and wireless recording devices.  If you’re not well versed in metrology, we probably have the equipment you don’t even recognize, but don’t worry about that.  You need reassurances about how all that gear is used.

Testing the Testers

Almost all of those metrology devices are required to be tested for accuracy on a regular basis, and the results of those tests are kept on file.  The tighter the tolerances on your product, the more likely your product will be tested with more sensitive equipment, which carries higher inspection requirements.  If the shop is AS9100:D and ISO9001:2015 compliant like MacFab, they are required to recalibrate or verify the accuracy of most metrology equipment at standard intervals.  Any equipment -even “touchless” devices like laser scanners- can drift with time and use, and their performance must be evaluated to guarantee their accuracy.  This gives you a level of confidence that your products will perform as intended.  MacFab takes these recalibration and verification inspections seriously.  All of our equipment is maintained accordingly to give you the confidence of on-time delivery of a quality product.

Test Everything

CNC machine quality control touches on every aspect of the process.  That includes the testing instruments and your products, of course, but it also extends to the CNC machines themselves.  The beds your products are held by clamping and holding devices during machining also require periodic testing to maintain tolerances.  Then there are the raw materials for your product.  Does it match the minimum specifications for size?  Does it have the required hardness, corrosion resistance, thermal or electrical properties or other features you require?

All of this has to be tested properly -and routinely- to make sure your product comes out exactly as you need it to.  AS9100:D and ISO9001:2015 compliance requires our testing be done by people who have documented training.  It also requires testing to be traceable back to a known standard.  For instance, we can calibrate our dial test indicators using a surface plate, but that plate has to be tested periodically by an outside source.

Finally, it Begins

With all of that completed to satisfaction, the CNC machining process can begin in earnest.  The first part machined gets tested thoroughly, of course, to make sure the CNC machining process is set up properly.  MacFab’s system will create balloon drawings of your product and prepare a comprehensive inspection report that can be printed or emailed to your engineers.  That’s a large investment in quality control few machine shops have made.

As production ramps up, we continue to test according to a regimen that meets your standards.  Clearly inspections take time and cost money, but if a part is critical enough (such as medical devices, trace detection equipment, aircraft and satellite components), it may require full inspection on every unit.  More commonly, representative parts will be tested through the production run.  AS9100:D and ISO9001:2015 standards don’t try to designate precisely what is inspected or with what frequency.  Rather, it provides guidelines which can be incorporated as part of the CNC machining process.  Regardless, all inspection results are logged and provided with the finished product.

With tolerances routinely at .001” and sometimes as fine as .0001”, inspections and testing are more critical than ever.  Fortunately, CNC machine quality control has largely been standardized, and finding a shop like MacFab Manufacturing that works to meet and exceed the AS9100:D and ISO9001:2015 standards can help you rest assured your products will be right the first time.