Heatsink bows archim
Open, Needs TriagePublic

Description

The heatsink is not a good fit under the Archim, you can see the board bow as the fasteners are tightened.

logan created this task.Fri, Nov 30, 7:14 AM
logan created this object with edit policy "LulzBot Hardware Products (Project)".

@logan how much are they bowing? i think a little bit of bow is normal as we want the heatsink/thermal gap filler to be sandwiched between the board and chassis for good thermal conductivity.

logan added a comment.Fri, Nov 30, 7:35 AM

@tutley I don't know how much is to be considered normal, but you can visibly see the bow looking against the power supply and hear the board bowing as the fasteners are tightened. Seems excessive to me.
One measurement taken near each of the bottom fasteners for the Archim from top of power supply to PCB: 28.75/28.86mm
One measurement taken from top of the PSU to the PCB behind the Z-motor connectors: 27.75

@mjpelletier is ~1mm of bow acceptable for sandwiching the heatsink?

After looking at @logan 's machine, it does seem that the bow on the archim is a bit excessive. There is some concern because once the drivers heat up this will potentially bow worse due to thermal expansion.

The heatsinks we are using on alphas are slightly thicker than the ones that were milled for the prototypes. I believe the prototype heatsinks were 9mm tall. The drawing was changed to use standard bar stock at 9.53mm tall. The piece i measured that logan had was closer to 9.75mm tall. Which is still in spec according to the drawing.

oliver added a subscriber: oliver.Fri, Nov 30, 12:02 PM

I completed the spc control charts for the heatsinks. The folder is in the T3537 branch of the quiver repo but here is the html files for each dimension.

west added a comment.Mon, Dec 3, 7:38 AM

I'm going to contact the supplier and see how much more it would be to knock it down to the original size, @kent mentioned looking into if the heatsink actually works. We may not even need it

west added a comment.Mon, Dec 3, 8:08 AM

@logan I'm going to rev the drawing and have the thickness @8.5mm, that should allow compression on the thermal gap filler

west added a comment.Mon, Dec 3, 8:18 AM

(I would like to get some heatsinks in before setting this as "needs review"

logan added a comment.Tue, Dec 4, 7:26 AM

@west Are you saying you'd like to get some heat sinks ordered to the new drawing first? or you'd like to know the results of installing the ones @kent milled to 8.2mm?

west added a comment.Tue, Dec 4, 9:28 AM

We can use the ones kent milled, they are technically in tolerance of the ones that are on order

logan added a comment.Tue, Dec 4, 10:20 AM

Install of all 20 milled heat sinks went smooth, a slight bit of compression but not bowing the archim that I could see.
All of the archims that were previously installed with heat sinks that were too large have been marked with a "B" on the USB housing.