(andy pugh):
/... 3,000 to 10,000 seems to be a somewhat awkward range, being rather
faster than a standard induction motor and rather slower than the
generic high speed spindles. /Yes, it is an awkward range. As we are tying to correlate SFM to the grinding wheel SFM, a potential way to deal with this is to go with a bigger diamond dressing wheel on a slower spindle, or a smaller one on a faster one.
/ If you look at the ER32 eBay spindles those seem to top-put at 18K.
The listings generally say "0 to 18,000" but I suspect that isn't quite
true. /Exactly what I hope to find out here.../I have used my 24k spindle at 6k. That leads me to think that an 18k
one might be OK at 4K. Is your application high or low torque? Maybe the
answer is a standard induction motor and belt drive? /Great information, and I do not think our torque demands are going to be high as we are planning to continue to use a narrow rim of diamonds, albeit at larger diameter. I have a couple other belt driven stations in this workcell, and I was kinda hoping to stay compact and direct with this one given space constraints. Thank you!
/Danny Miller: /
/Have used a cheap Chinese air cooled 18krpm 3kw spindle for years.? You
must drive them off a VFD anyways. /
~$350 vs $12K means that we could burn a few to find out, and makes sense at this point to try it for ourselves./At 3000 rpm you have much less power.? Well the torque is probably the
same but power=torque * rpm. The air cooled is cooled by a shaft-driven
impeller, so fan rpm drops to 3000 rpm too.? At high torque, low-rpm
loads, it will still generate a lot of heat but get very little fan
cooling.? You can swap with a DC computer fan or go with water cooled. /Apparently there are different schemes for the air cooling, and they seem to add size. We can do liquid and use filtered coolant. Also, the duty cycle is rather low, currently about 40 seconds every 15 minutes. Thank you!
//
Andy//
--
Andy Evans
Evans Precision Tooling Incorporated
541.990.2122
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