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PM 25MV excessive spindle heat?

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JBuckley13f

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#1
First let me say that I've been very happy with this machine. It's a very capable small mill. Anyhow I was machining some 1/4 uhmw plastic today about 2200 rpm with a 3/8 HSS cutter taking light cuts .025 or less. My spindle got pretty warm, sure you could put your hand on the head but it was much warmer than Id like. When I went to remove the collet and endmill the collet itself was almost too hot to touch. Any thoughts? I've had this machine since I believe Feb so it's definitely broken in I'd say.
 

T Bredehoft

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#2
I have a temp gage on mine, after two hrs of intermittent cutting at abut 2200, it reached 126º f. It felt too hot to touch, but it takes almost 140º to burn. I was cutting 1018 steel with carbide. feeding 8 inches per minute)
 

mikey

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#3
I'm going to guess your spindle bearings are the source, possibly due to excessive preload or perhaps too much grease in the bearings.

My RF-31 runs FAG sealed angular contact bearings and run at a consistent 107 degrees F as measured directly at the bearing, even after running for fairly long periods of time at high speeds. This is about what the factory says to expect. My collets do not get hot at all.
 

mksj

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#4
My last bench top mill (BF-30) which was quite a bit bigger, with a 3 speed variable speed motor which had a top end of 3000 RPM and the spindle would get very hot running it for extended periods. To the point where you couldn't touch the spindle bottom. Also the collets became uncomfortably hot. No doubt the bearings were good but not great. Getting the preload just dialed in perfectly and you also have clearance changes with temperature, no doubt contribute to the increased heat. Still I used the mill for about 7 years and never had an issue, but if it was in continuous operation (CNC) then I would have torn it down and put in higher quality bearings. Everything to a price point. I think you should be ok, seems more common in bench top mills, as I have seen oter similar mills also who's spindle also got very hot.
 

aliva

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#5
What is too hot?. Take a temp reading and then go from there. You maybe surprized that it's running a normal temp.
 

Cadillac

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#6
Sounds like a lubrication problem. Spindle and collets getting hot is no good. I might be wrong but I thought they don’t like anything over 120-140?? A proper spindle lubed would not run 120 no matter how long you run it.
 
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