One of the principle design goals of any successful production equipment is to keep it as simple as possible. A piece of manufacturing equipment that has to be relied upon 24/7 has not only to be simple to use but also simple to maintain and repair. This is not an easy task for engineering as new technical possibilities and ambitious customer requirements drive us in the opposite direction. But the old and over used saying of "what's not there, cannot go wrong" is still as valid as ever.
If you are fighting with small tolerances then 0.0012 mm per 100 mm and °C change of temperature may be significant or even catastrophic (example steel).
So what about temperature compensation - it often only requires one sensor, it is not rocket science but there is no free lunch. The sensor will have to be calibrated, mechanically fixed or positioned, interfaced and programmed. In some machines it is unavoidable and others manage without any negative consequences.
Measuring systems can avoid the use of a temperature sensor if the following is true:
- The measurement system uses a setting master - a relative measurement principle
- The part and the setting master are manufactured from the same material or have the same temperature coefficient or both are known and the measuring system can adjust accordingly
- Temperature changes of the part are slow enough to allow the use of a setting master cycle to "realign" measurements
- The part and setting master have the same temperature
- The relative changes measured are "small" compared to the dimension measured
This works because the setting master has been measured and certified in the metrology laboratory at 20°C and this value is recorded in the measuring system. The probes attached only measure differences between the setting master and the part. Changes in temperature are registered by the system during the setting master cycle as probe value changes on the setting master. Because of rule number five, the fact that the measured differences are "uncompensated" is not significant.
Be careful when comparing values to other systems - if the above method is used the values displayed are "temperature compensated" to 20°C - no sensor required.