The necessity of a clean air supply for air bearing machines has already been covered. This problem is nonexistent with mechanical bearing units.
Some people are concerned about chips. Our latest designs enclose all ways under covers or bellows to protect them against dirt, dust, oil and chips. The economical Checkmaster is equipped with wipers. Should a chip find its way in and cling to the bearing or way, it will make itself known immediately and can be removed quickly. That same chip can find its way just as well between the air pad and way of an air bearing machine, and is much more likely to do serious and costly damage there than to our machine.
As traditional QC decentralizes, CMMs are migrating to the shop floor where some regular preventive maintenance is important. The simplicity and reliability of mechanical bearings becomes even more advantageous here. Mechanical bearings are extremely accessible and can easily be cleaned or oiled when necessary. Air pads are less accessible, require more caution and skill and take longer to perform preventive maintenance.
The Helmel CMM construction is an elegantly simple and uncluttered concept designed for ease of assembly and therefore ease of service.
figure 1, V and Flat Bearing Design
An example is the gravity loaded V-and-Flat design, see figure 1, employed in the X-axis of all models and certain Y-axes. This approach has been used successfully in machine tools for over 100 years. It never needs adjusting.
Again: improved reliability and less service!
Please compare this to a typical air bearing system as shown in figure 2.
Imagine adjusting all those pads by means of a threaded stem and a jam nut, keeping an eye on the delicate air gap and squareness at the same time.
Operating costs should also be considered.
An air bearing CMM will consume $500.00 to $2,000.00 worth of compressed air each and every year, over and above the installation cost of the air supply line and filter system.
This cost is non-existent with Helmel machines.