Heatsink

Progress is slow, delays in the fabrication of this part.  I had moved the CNC control to a laptop machine, and neglected to disable some power saving functions.  When the computer turned the display off after 15 minutes of inactivity, it also was somehow able to put a hiccup (or perhaps shut down completely) the USB port driving the CNC.  The mill would then freeze, lose all of it's offsets (these tell the machine where the part it's working on is located)  and need to be rebooted.  15 Minutes into a 45 minute program.  Several times before I figured out the problem and corrected it.

Cutting the fins of a heatsink is generally a tricky one.  You want a lot of surface area, and that means deep slots, and thin fins.  There are a couple ways to do it, none of them fast.  It would be simpler to mount pre-made extrusions to the sides of an aluminum block, but I like machining things so I came up with this design.  It is sized to fit a 40mm DC fan directly.

 

To start the process of cutting the fins, it's best to remove as much material as possible.  Deep, narrow slots have issues with chip clearance, and the less material there the better.  I drilled these holes, the same pattern from both sides.  While I could have packed things a little closer together, I didn't want to risk busting through a wall, and messing things up.  Both sides were used because again, at much over 8-10 times the drills diameter deep, things start to get tricky.  These did do a good job for their intended purpose.

The depth of the part again poses a problem when trying to mill something like this.  The slots are .095" wide, so the most generally available "deep" endmill is .0625".  That will cut to ~.4625" deep, almost enough to get halfway through the block.  A shallow pocket on the face allowed just enough clearance to get the end mill halfway through.  A little more could be removed, but if this doesn't provide enough cooling as is, it's time for a totally new design.  

The rear of the block is slotted for clamping action on the stainless thermal barrier tube.  You can see the counterbored holes on the side which will facilitate the clamping action.  A little breakthrough into the fins was unavoidable with the size of these parts.

The last op was to put this hole pattern into the top.  The mount for this extruder will be of a 3 pointed design.  The tripod will provide equal contact, positive location, allow the head to move in case of a crash, and even electrically indicate such a crash.  It also could serve as a 3D probe, more on this later.

These holes match the pattern in this mount arrangement.