New Way Air Bearings ® is no stranger to the world of ultra precise metrology, manufacturing and inspection systems. Our products formed the basis for the modern coordinate measurement system, control observatories with sub arcsecond precision, and operate for years on end while only requiring simple and infrequent maintenance procedures. Today we want to discuss the critical capabilities that our air bearings, built on proprietary Porous Media Technology ™, offer to the diamond turning industry.
Thermal Stability
The most common motion solutions employed for diamond turning systems are fluidic hydrostatic slide bearings and spindle bearings, which require a constant loop of oil being fed into the bearing to supply the hydrostatic fluid layer. As our industry partners at General Electric’s Research Center have identified, oil based bearings are susceptible to temperature spikes, which in turn affects viscosity, and thus fluid thickness. Due to this connection between fluid temperature and thus performance, hydrostatic bearing systems often require accompanying chillers to extract the heat generated by turning operations which can exceed 18,000 RPM. Even with this infrastructure, the tooling base underlying your workpiece can grow, subtracting from your ultimate tolerancing and requiring greater compensations from the part designer and machine operator.
For the major players in the diamond turning industry, such as Kern, Moore Nanotechnology Systems, Precitech, DAC International and others, the challenge of thermal stability within the rotary or linear motion assembly of the lathe or mill is a known challenge. In fact, back in 1967 it was shown that air bearing based spindles dramatically reduce thermal spindle growth. Nuclear weapon engineers at Oak Ridge switched from oil hydrostatic bearings to air bearings, retrofitting them onto a boring machine spindle. The heat generated by oil shear in the hydrostatic bearings at high speeds induced thermal growth in the system, which was completely removed by their novel air bearing solution. This has been a well understood solution for over 50 years, and solves the source of thermal growth rather than attempting to compensate for its effects.
Reduced Complexity
Switching to a porous media based system can seem daunting, but it is actually a simpler motion solution than hydrostatic bearings for diamond turning. Porous media bearings use clean dry gas supplied by your own internal air supply that meets New Way standards for solid articulates, water, and oil. Unlike hydrostatic bearings, there is no need for chillers or other forms or refrigerants to keep the bearings cool, and since there is no recirculation, there is no oil to change.
Increased Cleanliness
Hydrostatic bearings are prone to leakages, which can send oil flying out both within your manufacturing facility or even worse, within the tooling space of your machines themselves. Porous media air bearings do require plumbed air lines, but the air flow itself is surprisingly low. For example, a 25x50mm flat rectangular air bearing only requires 60 psi input to achieve 60lb of load capacity and the total flow is very low, at 2 Standard Cubic Feet per Hour. As a result, there is no concern for securing high pressure lines, or any potential safety concerns regarding the air supply.
Bonded Bearings for Diamond Turning
Our bonded bearings are the ideal solution for any OEM who’s considering retrofitting their diamond turning system. Our bonded bearings are available in a wide array of sizes from 12mm up to 147mm, and with custom sizing available. They are thin, varying from 1-4in to 1/2in thickness, and require no modification to an existing system’s guideway. Modular bonded bearings can easily be integrated thanks to our vacuum replication process. Instead of positive pressure, vacuum is pulled through the bearing, securing it to the guideway. the motion carriage or stage is then slid over, and epoxy is injected into the space between the bearing and the stage. This approach completely eliminates the need for match machining, providing relief from thermal growth while reducing cost and complexity.
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If you’d like to learn more about our products, speak to an engineer for a technical discussion on the merits of porous media, or request a quote for your application, please contact us, and our dedicated engineering sales team will be in touch!
