Co-ordinate measuring machines (CMMs) are expensive instruments, costing both time and money. Therefore, it is strategic to dedicate only the most important, delicate inspections to the CMM. All remaining controls should be performed on alternative equipment. By Guillaume Bull, Technical Product Manager at Creaform.
CMMs are complex metrology instruments and must be handled by experienced operators. Acquiring the necessary technical expertise takes significant time, and advanced technicians in quality control and inspection are in high demand. Programming often requires extra time for changes and adjustments, particularly when the program is made for a one-off inspection, such as dye stamping. Moreover, rigid measurement set-ups are essential to get accurate measurements on CMMs. Parts must be carefully fixed and positioned to enable operators to make measurements and ensure quality.
CMMs are the no.1 choice for measuring complex parts. Any measurement of complex parts also requires a lot of time to measure all of the features, control the different angles, and inspect the complete shape. In the automotive and aerospace industries quality control regularly involves large parts. Inspecting those parts means several trips back and forth from the production floor to the laboratory, which requires time and may cause delays.
Acquiring a CMM is a major capital investment – purchase costs can vary from $50,000 to $200,000 depending on the measurement volume and the required functionalities. Installation represents the major part of the total acquisition cost. A CMM must be installed in an air-conditioned room, be positioned on a vibration slab, and have access to compressed air. All these building properties must be carefully planned, which can easily increase the invoice to $1m.
To ensure the CMM remains fully functional, a maintenance budget must be created for calibration, hardware upgrades, and replacement parts. Annual maintenance costs can represent 15%-20% of the original purchase cost. In contrast to portable metrology tools, CMMs are fixed laboratory equipment of huge dimensions that cannot be stored. They will permanently occupy many square feet in a room that must be controlled for temperature, humidity, and vibration. Up-to-date software must also be maintained to take full advantage of all the functions available. Software upgrades are regularly available, and an annual fee might be required to access new features, reports, and functionalities.
CMMs require highly skilled operators. They key is to optimise this know-how and assign these operators only to critical tasks. Those with less experience could then use other metrology tools like portable CMMs that require a lower level of expertise.
Metrology performed at intermediate steps on the production floor, with portable, less expensive equipment by less skilled operators can reduce the burden on the CMM. By choosing which quality controls to perform on CMMs, and redirecting other inspections to alternative solutions, quality managers will save time and money.