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Machine warm up

We've been having trouble with inconsistent parts throughout the day. The cuts vary within a range of about 0.003" on diameters. This is a Daewoo Puma 200MS lathe.

Today I started measuring temperatures using one of those guns with the laser pointer for non-contact measurement. Took measurements on the castings - near motors and away from motors, and the coolant tank.

The machine starts at about 55=BAF at 9:30am with the machine powered down (this would likely drop in February as it wasn't very cold as far as the end of January goes). It increases about 5=BAF/hr for 3hrs, then

5=BA every two hours until leveling off around 5pm at between 70=BA (areas of main casting not near motors) to 85=BA (near axis and spindle motors). Machine ran until 9pm today, though I left at 6pm so I don't know how it was doing after 11.5hrs on time.

The ambient temp in the shop drops to about 45=BAF over night, and we run at 65=BA-70=BAF during the day.

We're strongly considering tenting the machine over night and putting a space heater next to the main casting to keep it warm (perhaps a kiss goodnight, too). These diameter changes are pretty wonky and I'd prefer not to have to change offsets every 30-60min, especially when running some pickier parts.

Currently running a 30min warm up cycle from 9:30 to 10am, ramping the spindle from 1k to 5krpm over that time, cycling the turret, moving max X and Z (without crashing).

We did not see this kind of hourly change during warmer months. I remember changing the diameter offsets once or twice in the morning and holding 0.001" for the rest of the day.

Anyone doing similar or have suggestions? It'd be kinda slick to uncoil the hydraulic cooling coil and snake it through the casting so the machine warms up faster. Way too much work though.

Thanks for thoughts, as always.

Regards,

Robin

Reply to
Robin S.
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Mount 3KW worth of well insulated power resistors to the underside of the chip pan. Mount the thermistor inside the shields, away from coolant spray. Punch in a desired minimum temperature. Closed loop temperature control for practically No Money. Bob's your uncle.

--Winston

Reply to
Winston

Am Tue, 26 Jan 2010 20:25:07 -0800 schrieb Robin S.:

My first attempt'd be to maintain the 65°F (18°C) over night. From an ecological (economical) point of view it doesn't make much sense to let it cool down over night just to heat it up again in the morning - this requires a minimum of insulation of course.

Regards, Christof

Reply to
Christof Klaiber

I keep my shop at 60 deg F. Seems to be the best bet for $$$ and keeping my machines at the same temp all the time without getting condensation on them.

Who's the first guy in the shop? have that person start the warm up cycle.

Setting a thermostat back more than 5 deg costs more as I recall, heat needs to run too much to warm everything up.

Thank You, Randy

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Reply to
Randy

That's a nifty idea. Certainly a step above the space heater idea. Cheap too.

Thanks Winston.

Regards,

Robin

Reply to
Robin S.

I think our gas heater runs full tilt all day when it's really cold outside. I think it's undersized for our shop in the dead of winter.

Perhaps we should start measuring our gas consumption over the span of

2-3 days letting the ambient temp come down only 5=BA or so.

Thanks for the suggestion.

Regards,

Robin

Reply to
Robin S.

I've never seen condensation on the machine. I like the idea of keeping them ambient higher than it currently is though.

I'm the first guy in the shop. In the warmer months, 15-20min warmup is enough to stabilize the machine. Now that it's much cooler, the machine varies over the entire day, and its temp rises throughout the day too.

I'll look for some info on this subject on the web. I'd like to monitor our natural gas consumption during a tryout period and see if we're ahead/behind.

Regards,

Robin

Reply to
Robin S.

You're welcome.

Here is a suitable power resistor:

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It'd be a good idea to move the thermistor to the underside of the chip pan, to keep the temperature ceiling down to a reasonable number, overshoot and all.

--Winston

Reply to
Winston

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An immersed domestic water heater element that's controlled by a suitable thermostat would probably work better--If I recall these range up to ~4500 watts ( which seems like overkill at first) but it's better to err on the high side considering that (depending on coolant volume and casting mass) the coolant temp could very well drop off rather quickly during the initial morning warmup program.

Maintain your overnight tank warmth at just few degrees C below the highest temp that the coolant ordinary reaches during the typical workday.....and be sure to religiously run a morning warmup program every morning that sloshes liberal amounts of warm coolant onto the iron.

Reply to
Brother Lightfoot

"Robin S." wrote in news:122b7a98-69d3-47b0- snipped-for-privacy@o3g2000vbo.googlegroups.com:

I was going to suggest the tank heater but SVL beat me to it.

I was in a shop in MN that has over 100 CNC machines, a 24/7 operation. It was -5 F outside and the register above the machine we were installing was blowing cool air. So I said to one of the guys that the heater might be on the fritz. He laughed and told me that they run the AC year round due to the heat from all the equipment.

Anyway, I'd go with the tank heater and leave the machine dry cycling with the coolant running.

Reply to
D Murphy

Also only make up coolant volume at the end of the day--IOW if you suddenly add 2 buckets of cold water at midshift all bets are off.

Reply to
Brother Lightfoot

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