Maintaining spindle temperature

[3d_danny]

I know there has been discussions about warming up Columbo spindles but now that winter is here ( northern hemisphere at least) and the temperature in the shop is rather cold(no heat), keeping the spindle warm is becoming time-consuming.

I typically leave the computer, control box, and Bot powered-up all day. Setup between jobs can be as little as 15 minutes. Since the VFD is powered, the spindle fan is running and within 10-15 minutes the spindle is stone cold again. Bringing it back up to operating temp can be as long as an additional 15-20 minutes, running at no load. My jobs typically run from 1-2 hours so say if I run 8 jobs a day, it adds an additional 2 hours to the BOT time.

I take a rag and cover the spindle fan inlet between jobs (if I happen to be standing there when the job completes) but if I am not there, it cools right back down.

I would be curious to know how this is handled in other shops. Time is precious and lost time is lost money....

On a side note, I happened to be in a Shopbot powered shop with a 5 HP Columbo a couple of weeks ago and they never warm up the spindle.

Dan...

[olecrafty]

The fan can be wired to shut down at the end of a file. I don't have the info readily available to give you, but I know it can be done.

The spindle should be warmed before cutting. The shaft clearances are too close not to do so. Premature bearing failure and possible shaft damage is the price for not doing so.

[3d_danny]

Ideally, controlling it with the Shopbot software would be the best way. A relay wired to an output switch that would control the fan. A SO command could be inserted into the cut file to kill the fan at the end of the file. It would also allow easy control of the fan during its cool down routine at the end of the day. Colombo also recommends a cool-down to prevent condensation in the bearings. With the SO command used, it could be easily disabled during the summer when shop temperature reach 100

I think I will look at the fan circuit to see how it is connected.

[ron brown]

I wonder if it would make sense to have a preheat for the spindle. Surly a heating element would be more efficient than the motor windings for heating a spindle. It could be inner-connected to a fan. I think it would only take a comparitor chip and a thermister and minor elctronics.

Ron

[gerald_d]

Don't you cold-weather guys have things like heat trace cable to stop water-pipes from icing........

Ron, motor windings make a brilliant heater if the voltage is turned down. When we had water-logged motors in the mines, we connected a welding tranformer to them for a day to dry them them out. The approx 30-50V supply was good for heating them, but not high enough to flash across the wet insulation.

[richards]

Right now my shop is 24-degrees F. Not a pleasant place to be. After warming up the spindle (and leaving the door between the house and the shop open long enough to get the temperature at least to 40-degrees), I partially cover the fan on the spindle with a piece of cardboard between cuts. (The cardboard has a piece of string attached to it and the wall so that I can't leave the shop with the fan covered.) It's not a very elegant idea, but it does work.