In the world of manufacturing, every day can present new challenges. It’s up to innovators, like REGO-FIX and SolidCAM, to turn them into successes. In one such recent success, the REGO-FIX PowRgrip clamping system played a key role in helping SolidCAM, a leader in powerful integrated CAM systems, overcome a customer’s unique ceramic machining challenge.
In 2014, Ken Merritt, director of partner projects and senior applications engineer at SolidCAM, was contacted by a shop that was interested to see if his company’s software could handle a very hard sintered silicon nitride, a material where parameters for machining for extended axial depth and minimal radial engagement with a carbide tool would not work.
Merritt accepted the unprecedented challenge, collaborated with a partner from GW Schultz Tooling and began experimenting with finding a prototyped solution for this prospective client. That solution turned out to be mill grinding.
At the time, the typical material removal rate (MRR) for mill grinding pockets in fully hard sintered ceramics ranged anywhere from about 0.008” to 0.010” per cubic inch per minute up to 0.002” to 0.003” per cubic inch per minute. That meant that machining this prospect’s very small, 2” diameter part that included ribs in the middle would require a painfully slow 3.5 to 4 hours.
During the first test cut on a vertical machining center equipped with REGO-FIX tool holders, Merritt and team achieved 0.020 cubic inches per minute MRR with a tool that lasted an amazing 14 minutes. However, they learned from the test cut that they would need to create a CNC machine specifically designed for cutting ceramics because the extremely abrasive dross generated during machining such material would destroy a traditional machine tool within 18 months.
The first machine they designed protected all the moving components from the destructive buildup of ceramic material. Unfortunately though, it had an ER 25 spindle connector, so the team was unable to use the REGO-FIX PowRgrip toolholding system. When they tested the machine, the results were absolutely zero process predictability or repeatability, and there was significant tool runout because of the machine’s poorly ground spindle interface.
After truing up the spindle, the collet holders worked, but runout was still at an unacceptable level, as was vibration. Plus, a catastrophic failure of the tool that the team was unable to explain forced them to completely redesign the mill grind tool and conduct a second round of tests.
While the team did make significant progress – an hour of tool life at 0.035 MRR per cubic inches per minute – another unexplainable phenomenon occurred. Merritt termed it as a “mechanical piezo effect.” The manner in which the part was held in a brass vice caused vibration, and that vibration, in turn, generated an electrical charge that caused the inside of the tool to basically explode from its center out to its shank. What was occurring was that the collet clamping was acting as a vibrational dam blocking the tool frequencies.
After applying various damping materials to the prototype machine, including rubber and cardboard, and still unable to control the vibration, the team created its own CNC machine that would allow them to use the REGO-FIX PowRgrip tool holding, which uses a bimetal interface that automatically dampens vibrations. Plus, the tooling significantly reduced runout and eliminated vibration.
Equipped with REGO-FIX tooling, the performance of the new prototyped machine wowed attendees at a recent ceramics trade show as it machined fully sintered and hardened ceramics with a hardness of 75Rc. Experienced industry experts at the show estimated anywhere from 3.5 to 4.5 hours for cutting the ceramic parts, but Merritt’s team did it in about 7.5 minutes.
What the team recognized at the show is that they had to build their own machine at a much higher level than their successful prototype. Merritt looked for diverse yet interdependent technologies that blended together to make creating a new CNC machine a functional process. During their experimentation to create a stellar machine, the team realized that the tooling used in the machine needed to be held extremely precise and able to effectively dampen vibrations. REGO-FIX’s PowRgrip met and exceeded both requirements, while also providing much needed process predictability.