Grind or grind? This is a radial grooving problem. Stuart Cleary, Head of Aviation Business Development at Cranden Diamond Products, gives his take on the latter.
Well, I say grind every time, but I’ll do it, we make grinding wheels. But when people ask me why I think this approach is the best, I have a list of good reasons. I’m not saying you shouldn’t grooving, just better – that’s my reasoning.
When machining aerospace alloy parts, CBN-coated wheels can cut at least twice as fast as milling, resulting in real cycle time savings of about 50 percent. If manufacturers switch to CBN grinding wheels and stop buying carbide cutters, their tool cost savings will be around 70-80%.
We’ve been making precision wheels with diamond coated and electroplated CBN profiles for many years, so we know what works and what doesn’t. Aircraft engine manufacturers keep us on our toes by inventing harder and harder materials that create endless problems because they are difficult to turn into precise, aesthetically designed aircraft engine parts. Tolerances, hardness, brittleness, and thermal stress exacerbate the problem, not to mention anchoring.
If the profile is symmetrical, and if you can afford it, the VIPER grinding method to restore the profile to a standard wheel will do – and be prepared to wait for a back coated dresser. But VIPER grinding isn’t everything, and places where you can buy standard grinding wheels and dressers have become a seller’s market, to say the least. Naturally, you will look for alternatives, there are only two of them: milling and galvanized grinding wheels with diamond/CBN.
The good news is that electroplated diamond grinding wheels are suitable for all machines donated to VIPER such as Blohm, Mägerle, Makino and Starrag, just to name a few. The bad news is that few people dare to make any “adjustments”, so the work is shifted to CNC vertical machining centers. I say “bad news” because, as an experienced grinding wheel supplier, I find that milling grooves is very difficult, especially radial grooves, and expensive tools won’t do the job. Tiny diameters, short life and thermal damage issues mean it’s not right. That’s why.
Parts: Aircraft engine castings are often complex, to say the least. Workpiece retention is a big problem for VIPER Grinding; designing a thrust mount or packing a part is not easy at all, and transferring it to a milling machine is expensive and difficult to handle. Imagine programming your 5-axis machining center offline to do all of this (using the Crandon wheel, of course).
Machine: Really the same as above, but if money isn’t an issue and cycle times and timing don’t matter, then it’s ok. If you have the space and a spare technician who can really make it work, go for it. If you are using lean or monobloc processes, minimizing operations by focusing on doing everything possible on one machine can have a big impact on your iterative strategy. Our advice: contact us and use your existing machine, as many others do.
Design and tolerance. Don’t you love designers? Geometry, tolerances, finishing requirements? Yes, these are very complex heat-resistant alloy parts for aircraft engines, but I didn’t think how the shop operators were going to make them. You can then measure and check the part for thermal issues by milling. Of course, many of these issues are related to grinding and milling, but there are also important differences.
So why switch to grinding instead of milling? Mainly due to the high thermal conductivity of coated CBN. It dissipates heat better than anything other than diamond, which means lower wear resistance and very long wheel life. Grinding outperforms milling every time and leaves a better finished shape.
Profile wheels are checked at Crandon by grinding samples, which are then checked to ensure that the shape is within micron tolerances.
Best of all, CBN wheels already have groove profiles on the rim, so no trimming is required! The wheels are real so tuning is important, but after that it goes until it wears out. Then you put on another one. It’s really easy to work with and we have products for many big companies.
In short, you can control the shape with the geometry of the circle, you can control the finish with the grain size, diamond or CBN are available for various materials, the wheels can be delivered within three weeks of ordering, the profile wheels are quality controlled and made Comes with ground sample for ease of installation; there are practically no problems with the material of the wheel. Nickel, diamond and steel case only; full support from Cranden Diamond Products; we offer full after-sales support, including problem solving.
Once the connection is established, Cranden will request a part/wheel profile drawing and some machine details/specs. We will visit and inspect your setup, design your grinding wheel and assist you with programming CNC parts, speeds and feed rates. We were assisted by a leading aeronautical engineering firm that we hired for a larger installation. After you have tried our wheels, we have delighted you with the new manufacturing process and hold your hand with us for your next large order for electroplated ultra-abrasive wheels. This is your move.
Post time: Sep-30-2022