What are the limits to inspection by CMM?
While a CMM machine can certainly play a crucial role in the process of qualifying parts manufactured in production, there are a few drawbacks that need to be considered to save time and money.
What are the requirements for setting up and maintaining a metrology room including a CMM as equipment?
The environment must be controlled.
To ensure accuracy and repeatability of results, it is important to ensure that the room in which the CMM is located is controlled. Temperature and humidity are parameters controlled as a priority and sometimes a positive pressure to limit dust can be integrated into the room. Indeed, temperature differences can influence the parts measured and create nonconformities that would otherwise be good. The costs of fitting out and maintaining a metrology room are significant and must be taken into account.
Qualified personnel, a key issue.
During dimensional qualification, it is crucial that personnel are fully trained to operate and program a CMM. It is not enough to simply know the use of a CMM, but to understand the use and operations linked to the tolerances of the parts indicated on the plan in order to create the program that meets the requested requirements. It is therefore important to understand:
- Reading plans
- Geometric tolerancing
- The CMM operation
- Use the machine programming software
Soft parts can cause defects.
If you need to inspect a part with soft materials, such as rubbers or elastomers, the probe may cause the surface to sag when it hits the object, causing defects in the digital analysis.
Tools adapted to the use.
There are different types of probes that can be used with a CMM machine depending on the part that will be measured. The probe must touch the object. This must establish physical contact with an object in order to perform a measurement. Although this is not generally a problem, this process could potentially damage delicate surfaces or even deviate due to a part that is too soft. Several instruments can therefore be integrated into the CMM inspection head. Probes (different sizes), 3D scanner, profile probe, etc.