Emerging ultra-porous, fine-grain bonding matrix technology
helps deliver angstrom finishes on extremely hard materials
North Kingstown, RI— Meister Abrasives, USA is partnering with a number of users seeking to produce ultra-smooth surface finishes (measured in angstroms) on an efficient production basis. The new wheels rely on an extension of the HPB high-porosity bonding matrix technology developed by Meister as it introduced new lines of free-cutting CBN and Diamond abrasive wheels and dressers over the past five years.
Bruce Northrup, Vice President and General Manager of Meister USA said, “some manufacturers of precision components in aerospace, semiconductor, medical device and other industries are seeking to achieve exceptionally fine surface finishes – – often measured in angstroms – – not only on hard alloys but also on materials like sapphire, silicon carbide and gallium arsenide. These ultra-finishes call for the use of extremely fine superabrasives many times smaller than those used in grinding automotive components like fuel injectors.”
Northrup said, “the only way to achieve ultra-fine finishes on components like these has been to send them through a series of lapping processes. This approach is very time consuming and requires an investment in a number of lapping machines. We have seen as many as 5 lapping machines being used sequentially in this manner. If you can grind these pieces instead of lapping them, you can become far more productive and eliminate the huge capital equipment cost. Unfortunately, superfine grinding of hard materials has not been an option, because abrasives manufacturers have not been able to manufacture ultra-fine grit wheels that were both highly porous and durable, while still being able to cut.
“Ultra-fine superabrasive particles tend to pack together tightly in the bonding matrix. As a result, these wheels are generally not free cutting. There is not enough porosity in the structure of the bonding matrix to effectively expose the abrasives or allow the coolant to efficiently flush away ground workpiece material. The conventional approach to making wheels more porous is to introduce porosity additives into the bonding matrix. These additives burn away during the wheel’s firing process to make it more porous. This porosity exposes more superabrasive particles to the material for more aggressive cutting; while the larger pores left behind in the matrix allow the coolant to flush away ground material faster. Unfortunately, the use of porosity additives creates other problems because the structure in-between the induced pores is still dense. Furthermore, these induced pores tend to weaken the wheel’s structure. So the wheels tend to break down faster and have to be replaced frequently.”
Northrup said the new technology developed by Meister Abrasives’ R&D in Switzerland takes an entirely different, engineered approach to imparting porosity. He said, “in the most recent iteration of this ongoing R&D effort, our Swiss engineers found a way to evenly disperse fine diamond particles so they are firmly supported as nodes within a naturally porous and open-structured bond matrix. No porosity agents are needed. The pore structure is similar to what we see with our HPB wheels but the diamond grains are many times smaller. These wheels break down slowly, in a controlled fashion to provide efficient fine-finish cutting, along with prolonged wheel life.”
Dr. Peter Beyer, CEO and Chief Technologist of Meister Abrasives AG commented on the difficulties of creating an ultra-porous bonding matrix to stage fine diamond for effective material removal. He said, “the smallest diameter of diamond grains used in standard superabrasive grinding wheels is approximately 15 microns. With these new ultrafine products we are talking about diamond particles that can be 100 times smaller. This is very expensive “dust”. You might imagine how difficult it is to homogeneously blend five different components with this grit size. To manage these processes, we have developed a completely new manufacturing technology. The resulting fine grain, high porosity wheels are already being used by a significant number of early adapters in critical applications. Visitors to IMTS 2014 will have an opportunity to see some samples.”
Visit Meister at IMTS Booth N-7351.