Most coordinate measuring machines (CMMs) are manufactured using air bearings to provide precision movement, hence they are often referred to as air bearing CMMs, as opposed to mechanical bearing machines that might be called "air bearingless CMMs".
Air bearings are often preferred because they can be very repeatable, and they allow a machine design that is more economical to build because any hard, flat surface is suited as a bearing waypath. However, because they actually float, they are more sensitive to variations in motion and require more settling time for precision. For this reason many higher speed and more rugged plant floor CMMs are air bearingless.
Air bearings also require clean, dry compressed air, and most industrial compressors manage to let oils and water accumulate, causing severe and expensive damage to the bearings, and requiring multistage filtration in-line to protect against oils, water, and particulates that might reach the bearings.
Air bearingless CMMs, i.e. mechanical bearing designs, are capable of greater acceleration, and are favored for production demands. They are also better suited for manual CMMs because they are non-floating so the moving CMM structure maintains its geometric rigidity and integrity even when manually handled during measurements.
Filed under Air Bearingless CMM by Helmel CMM