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Heatsink USA Extruded aluminum heatsinks, specializing in small custom cut orders

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Old 7th September 2009, 10:53 PM   #71
tms0425 is offline tms0425  United States
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Originally Posted by dcbingaman View Post
Hi, Russ - any updates on the big boys ??
I just bought four 8" lengths from him and they look very nice. Tom
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Old 28th November 2009, 07:40 PM   #72
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I just received some of this for a couple of projects. when they say "cut to size" they mean beautifully machined to size
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Old 19th May 2011, 01:20 AM   #73
Arick is offline Arick  Canada
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Hi everyone,
I just purchased some of these heat-sinks last month and the problem mentioned before on post 57 is still present. They are concave by 1/32nd of an inch or .8mm in the middle of the 10 inch with. It was not mentioned anywhere on their site, just tough some of you guy's might want to know.
Eric
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Old 19th May 2011, 12:55 PM   #74
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Originally Posted by Arick View Post
Hi everyone,
I just purchased some of these heat-sinks last month and the problem mentioned before on post 57 is still present. They are concave by 1/32nd of an inch or .8mm in the middle of the 10 inch with. It was not mentioned anywhere on their site, just tough some of you guy's might want to know.
Eric
In response to the 1/32" (0.03125) concave base on our 10.080" profile heatsinks; I would like to point out that the standard Aluminum Industry Standard for this width profile is .08064". So, providing you are measuring with a pin gauge on a flatness table, your measurment is well below the allowed tolerence for this profile. Quoting responses to this thread before, no extrusion (especially on a 10.080" wide and 2.875" tall) heatsink will ever be perfectly flat due to the very nature of the extrusion process itself. I do however agree with the poster about putting this information on the website, we will make this information available asap. If a person is not familiar with the Aluminum Industry, they would have no reason to be familiar with industry tolerences.
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Old 20th May 2011, 03:12 PM   #75
AndrewT is offline AndrewT  Scotland
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Hi,
30thou (=0.03" = 30mil = 0.762mm) of curvature in a 10.08" plate is roughly equivalent to a 35' radius on that plate. (actually, radius = 423.345")

If you take a 1" wide heat source, say a To264 device and calculate what effect that radius has on the out of flatness between the sink and the device you will find that over the 1" of contact width, the maximum gap to be filled with conductive paste is ~0.3thou.
Firstly the bolting of the device to the heatsink will pull in all of that gap (due to radius) to near zero.
Secondly, the aluminium plate can have much of this radius eliminated by clamping a bar across the backplate.

The force required and the stress set up in the aluminium can be derived from M/I = E/R = sigma/half thickness. sigma is the stress in the outer most fibre of the aluminium beam formed by the ~10mm thick plate.

The only effect of that radius is aesthetic and can easily be solved by gently bolting the backplate to a properly machined case that has been manufactured to meet the users required tolerances.
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Last edited by AndrewT; 20th May 2011 at 03:14 PM.
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Old 18th July 2011, 10:57 PM   #76
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Is the 10.125" extrusion still available (as it's not on the website)?

(Or is it now the "10.080"?)

Last edited by Andersonix; 18th July 2011 at 11:01 PM.
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Old 18th July 2011, 11:17 PM   #77
Arick is offline Arick  Canada
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Originally Posted by AndrewT View Post

Secondly, the aluminium plate can have much of this radius eliminated by clamping a bar across the backplate.
For your info, I bolted 3 L shaped aluminum bars of 6,35mm (0.25 inch) thickness , without bringing any of this radius out.
Eric

Last edited by Arick; 18th July 2011 at 11:19 PM. Reason: erasing the end of a sentence in the quote
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