Still having over-heating problems with control box

[yobot]

I added the heat sink fins to my PRTAlpha control box a while back, and they don't help much. Even when the box is only warm to the touch, internal temps of the drivers are too hot to more that lightly touch. That heat does not seem to be transfered to the outside of the box.

Day before yesterday, I ran all day without incident.

First thing yesterday morning, I had my first ever "communication issue", even though I had just started up the system. I rebooted everything and worked most of the day.

Toward late afternoon, I had another "communication failure" while moving the Y axis by keyboard when the bot stopped responding, then shortly thereafter, decided to head off in the X axis on its own. I powered it off before it hit the stops.

I felt the box, it was only slightly warm. I opened it up and it was like an oven. I am honestly amazed that the electronics worked at all. The temperature levels far exceeded even commercial rated components.

So, last night, I ordered 5 nice size peltier devices (thermoelectric coolers) with heat sinks, that I am going to mount on the outside of the case. Obviously, the case isn't conducting heat very well, but I still intend to turn it into a refrigerator (non-condensing). The devices are 13 volts at 5 amps each, and I happen to have a nice unused 45 amp metered, adjustable, highly regulated 0-15 volt power supply I can use for them.

If that doesn't work, I will add more. For now, I have no choice but to operate with the door open on the enclosure.

Anyone with similar experiences, please share your solution(s).

David

[brucehiggins]

I was hsving problems with one of my controllers overheating causing one of the x-axis motors to stop working. I hsve left the cover off my control box for the past 2 months and haven't had a problem since. I blow the dust out regularly with compressed air.
Bruce

[bcammack]

On our Omag and Northwood CNCs, there is a small A/C unit on the electrical/electronic cabinet. I don't see why a person couldn't graft a very small window A/C unit into the door of the PRTalpha box and refrigerate the livin' whee out the circuitry within.

[yobot]

That would work, Brett. I will do it if I have to. I am curious though to find out if others aren't having similar issues.

I roughly figured the peltier devices provided about 1075 BTU total. Maybe that will be enough to keep things cool.

David

[bcammack]

To be honest, I sort of wonder if you don't have some component that is marginal from a thermal perspective.

Our PRTalpha is running dual steppers on both X and Y and pushing a half-inch compression spiral bit through 3cm of really dense acrylic-modified polyester solid surface material (it's also 65% alumina trihydrate powder). IOW: the steppers have to put some muscle into pushing the bit through this stuff.

The machine sits in the middle of a warehouse about two miles from the Atlantic ocean near Daytona Beach, Florida. It's usually in the 90s back there from July to October. We keep a simple box fan blowing on the heatsink side of the control box (mounted under the table) and experience zero overheat issues.

[yobot]

Maybe it is a single component.

What I do know for sure, is that ALL the stepper drivers are blistering hot (literally) and they are not making a good thermal connection to the box. Don't know if it isn't flat or what.

Until I have some time to really mess with it, I will just make an ice chest out of the enclosure.

It has run this hot at times all the way back to when I purchased it in 2004. The heat sinks where added recently. I think that SB started including them on the boxes somewhere back in 2005. As I recall, others have had similar problems.

All the best,
David

[davidp]

David,

We had that problem some time ago with internal temps in the box exceeding 70C.

We removed all of the drivers from the board and mounted them onto a 25mm thick slab of Aluminium and then mounted that directly to the back of the board, using heat sink compound. We then installed three banks of heat sinks and 6 cooling fans mounted on the heat sinks.

So far this has maintained the temp inside of the control box to a maximum of 10C above ambient temperature, and in four years we have not lost a driver, only one contactor.

I would not recommend running the Bot with the door of the control box open. It will attract dust, the dust will clog up the ventilation and hold more heat and just exacerbate the problem. Fix it now and be done with it.

My 2 bobs worth

David

[yobot]

Thanks for the response, David.

The temps inside the box have been a bit hotter than 160 degrees. In fact, the heat sink compound itself has run down the inside of the box in a half inch wide streak below three of the drivers.

I think adding the blocks for some rigidity and additional contact area to the box is a great idea. I will do that. I still plan to proceed on refrigerating the box as well. I should be getting the thermoelectrics in today. I hope to get them mounted late this evening in order to buy myself some time to get my current orders filled.

On your aluminum, did you purchase it locally? Do you recall what grade it was (assuming it was pretty hard), and was it pre-surfaced, or did you do that yourself?

Thanks,
David

[tree]

I was having the same trouble in the beginning with our BOT. We have a 2 spindle standard and therefor... no heat sink. The second spindle doesnt get used as much and when thoses driver are in idle lock they produce more heat. Therefore the driver above it (Y) would thermal out and turn off. I removed the side panel, placed a 10" panel fan on the cabinet the control box is in right beside the drivers, and tilted the control box on its side as much as I could to let the heat rise clear of the driver above it. So far so good. However I dont have AC in the shop where I am at so if the ambeint temp in the encloser reaches over 90F I start to have trouble. I bet tilting it completely on its side would help alot as well.

[hespj]

I had overheating problems. First thing I did was install a couple of computer fans inside the box to better distribute the hot air to the box sides. This helped, but I finally fixed the problem by putting a bank of computer fans (4 I think) blowing upwards over the cooling fins on the back of the box. No problems since.