How much heat sink is enough - G320X

[Bob La Londe]

I am getting ready to start connecting electrical parts on the Hurco, and I finally broke down and bought some Gekc Driver servo amps a while back. I know I need to heat sink them, but how much heat sink do they need?

I read one thread in searching where a guy had just polished the paint off the back plate in has cabinet. Slathered on some heat sink compound, and screwed down his drives. Is that enough. Its a big piece of metal, but its just a big flat piece of metal. I can make heat sinks easy enough if they need more than that. It just takes time away from other jobs.

The cabinet the 320s are going in is pretty large and it will get both a fresh air and an exhaust fan since I plan to put all the electronics except the VFDs in that cabinet, and put everything else in the other big cabinet. (Fresh air might get routed via duct from my office for a cooler source.)

[Bob La Londe]

Ok... lets try it this way. What heat sink did you use?

[Blind Squirrel]

1st. I think you should always go overkill when ti comes to heat sinking. You it might take some time to make some nice finned heat sinks, but then you have the extra piece of mind.

2nd. Not sure what is going on with you and Geckodrive, but I read where they posted something you sent in PM publicly. I doubt they are going to answer you. Somebody else might though. Looks like they will take your money though. LOL.

3rd. I think this might be regarding item 2 above. I checked out that power supply you sent me and I couldn't get it to put out anything that I could cause the problem you described either. I guess its one of those miraculous self clearing problems. I've been using it now for a while to drive some DM542s. Its a little under powered for the job, but I figured they would give it a good work out.

[Bob La Londe]

Got an email from Marcus. Said basically to use a minimum of 200 square inches of heat sink surface area. He misunderstood about mounting to back plate, but that's ok. I did get the answer I wanted.

The G320X can be thermally modeled as a 0.25 ohm resistor; assuming it will get up to full power (20A), this means you will have 100W to dissipate per drive. To dissipate this much heat you would need roughly 200 square inches of passive heatsink surface area. A fan used on the heatsink will help eliminate the excess heat and increase airflow to cut down the size of the required heatsink; unfortunately this is not as easily calculated because fans come in many different shapes, sizes, and CFM ratings.

I was suprised they didn't post that here. Its a good solid professional answer.

[brian257]

There is a build thread for a Bridgeport type machine I was looking at last week that shows the Gecko drives mounted on PC processor heat sinks with fans. It was a real slick design that was not very expensive. It gave part numbers and sources. Unfortunately I don't have the link to the thread handy.

My plan on the machine I am doing now was to just mount them to my aluminum back plane thinking that they did not need much in the way of a heat sink, but looks like Gecko recommends more than that. Since I have three drives and may expand in the future to five the PC fan/heatsink combo idea looks better and better.

[morestuff]

Hopefully this is not out of line here, but PMDX
offers a heatsink with over 250 square inches
of heatsink surface area. It is drilled, tapped,
and ready to go with full size Gecko drivers.

http://www.pmdx.com/Heatsink-01

Regards,
Steve Stallings
www.PMDX.com

[asuratman]

Hi Steve,
How do you install g320x on that heatsink?

[morestuff]

The G320X, or any other full size Gecko driver mounts to
flat side of the heatsink using the 4 screw holes that
align with the notches in the edge of the driver's base
plate. See this diagram:

http://www.pmdx.com/Doc/PMDX-Heatsink-01_Rev_11.pdf

While some of the pages on our web site show the heatsink
populated with stepper drivers and a PMDX-134 motherboard,
you can mount servo drivers also, but there is no equivalent
motherboard for servo drivers so you will have to use wires
as usual for the connections instead of a motherboard.

Regards,
Steve Stallings
www.PMDX.com

[Bob La Londe]

Hopefully that's enough... There is an exhaust fan to the left in line with the heat sink, and there is an intake fan at the top of the cabinet.