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Machined Copper+Aluminium Labby / Beam Combinining

691175002

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For my second attempt at a lab laser I stepped it up a notch.  This lab style heatsink is huge and looks the part.  Every surface has been machined and the centerpiece is a 3/4" copper block which fits the aixiz module and provides extra cooling.

Some basic progress pictures:

Surfaces all machined square and painted with layout dye.


Cutting...


Machining the fins...


Onwards to the copper, its harder to machine than aluminum but nothing too troublesome.


The finished heatsink:



All parts loosely press fit and are held together by a single set screw.


Assembled.


I put it together with a blu-ray diode and some artic silver.  Only running at 140mA since I want to keep this diode for a while with 100% duty cycle.  I would stress test it but I only have a few diodes and is there really a question about the performance of a solid copper/aluminum block?


One of the modules is a 5mW red, two are blu-rays and one is empty.  :'( I better buy more sleds before I go through withdrawal.

The following experiment doesn't really deserve a full thread of its own IMO so I will tack it on the bottom here.  Playing around with a beamsplitter just to see how hard it really is to combine two different lasers.

The setup, a beam splitter from a leftover sled on top of a pile of post-it notes (perfect for adjusting height) and a pair of lasers. (Excuse the blue layout dye, I don't like working with lacquer remover when I can avoid it).


The path of the green laser.  Because the green is unpolarized it splits approximately 50-50.


Blu-ray, polarized so it transmits almost completely.  The beam diameter is a touch larger than the cube though.


And together.  If you look closely you can see the thin green beam right in the center of the violet beam.  The camera is far more discerning than the eye, this was not noticeable in person.


Getting a good beamshot was hard because the camera weighs violet so much more heavily than our eyes.  The beam was a nice blue/aqua color, however unlike a pure blue the dot color changes significantly depending on the fluorescence of the material in question.

This experiment wasn't that hard to set up and was a lot of fun, if I had a high powered red I would have done yellow as well.  My next project will be to build a small self contained module with screws to align two modules a mirror and a beam splitter.  I've drawn up a plan but I need to pick up some screws and taps before I can begin.



And that's all for today. I will probbably end up selling/trading some stuff for other laser related gear since I need my hobbies to be at least somewhat self-supporting.  I am also working on picking up the tooling required to make a solid copper direct-contact heatsink.  I'm sure there will be interest in solid copper modules with the same dimensions as the aixiz module.
 

Benm

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Re: Machined Copper+Aluminium Labby / Beam Combini

Wow, that's very nice machining on those modules, looks like they will do their cooling job very well.

One thing that slightly concerns me is the use of both aluminium in close contact, which might not be ideal (oxidation and all).
 

L@z3r

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Re: Machined Copper+Aluminium Labby / Beam Combini

Quote from 691175002
"All parts loosely press fit and are held together by a single set screw "
The parts are loose ? That's not good for heatsinking if that is so.
 
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Re: Machined Copper+Aluminium Labby / Beam Combini

L@z3r said:
Quote from 691175002
"All parts loosely press fit and are held together by a single set screw "
The parts are loose ? That's not good for heatsinking if that is so.
umm by loosely press fit, that means that you have to shove them in there but not as hard as a REALLY tight press fit, everything is in contact but the inside dia and the ouside of the copper heatsink are near the same, with the copper one being slightly larger.
 

691175002

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Re: Machined Copper+Aluminium Labby / Beam Combini

L@z3r said:
Quote from 691175002
"All parts loosely press fit and are held together by a single set screw "
The parts are loose ? That's not good for heatsinking if that is so.
If they aren't loose enough to slide with minor force then there would be substantial problems removing/inserting the parts.  I made sure that it was as close as practical, I figure that the aixiz module is likely to be by far the weakest link when it comes to cooling anyways (And they vary so much in size a tight fit would be impossible without locking yourself to using only a single module).

I never even thought of oxidization being a problem, most heat sinks are made of aluminum and Wikipedia gives aluminum oxide a high thermal conductivity but I'll see what happens over time.
 
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Re: Machined Copper+Aluminium Labby / Beam Combini

One question, why are you using a 4 flute endmill with on aluminum? You would get a much better finish. I can also tell you that you that your mill is out of tram because the tip marks are only going one direction.

Other then the maching, very nice work! I like the CNI style heads and I like the copper usage!

Ben
 

691175002

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Re: Machined Copper+Aluminium Labby / Beam Combini

Laser Ben said:
One question, why are you using a 4 flute endmill with on aluminum? You would get a much better finish. I can also tell you that you that your mill is out of tram because the tip marks are only going one direction.

Other then the maching, very nice work! I like the CNI style heads and I like the copper usage!

Ben
I had broken my 2 flute endmill a while back, the small endmills break really easily (that's my excuse, I was feeding too fast) and I haven't gone out of my way to pick up a new one.  I should probbably be using a slitting saw but I'm not sure if I have the courage for that.

I don't have much experience with machining, mostly what I can read online.  There are only marks one direction because when using the 2.5" facing tool I try to avoid cranking the knob 5+" worth of turn and if the piece is shorter than 2.5" I can just stop.  I'm not sure if that is bad practice, some people intentionally mess up the alignment to avoid cross-hatching when machining but I wouldn't go that far...

I did the full travel on the leftmost heatsink (the one with the layout dye), you can see the marks on the top of it:
 

Benm

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Re: Machined Copper+Aluminium Labby / Beam Combini

For the loose/tight fit situation: There really is no good solution using metal alone. To ensure perfect thermal contact, it has to be so tight you'd need a vise to get the copper tube into the block (i.e. deforming the metal so you -make- the perfect fit).

The most practical solution would be to use to thermally conductive compound. This also aids in filling out any machine marks on the contact surfaces.

Also, the aixisz modules arent neccesarily the weakest link in the thermal chain: the diode is press fit in there with quite a lot of force ensuring proper contact, and they are a few mm of solid metal from diode to outer edge.

That said, there is only so much you can do with passive cooling. Machining the heatsinks to take a TEC between module and ambient would probably be an easier way out, and allow sub-ambient operation of your lasers if need be.
 

691175002

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Re: Machined Copper+Aluminium Labby / Beam Combini

I'm not sure what kind of metal the aixiz modules are made of and it is very difficult to get a perfect fit between the module and the heatsink since they vary so much in size. I do put thermal paste between all the parts anyways.

I will probably make a peltier heatsink at some point in the future (preferably after I pick up a set of M9x0.5 taps so I can machine a direct contact heatsink as well) just to round out the set, after a point one starts getting diminishing returns on power output.
 

Kenom

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Re: Machined Copper+Aluminium Labby / Beam Combini

Very nicely done. I cheated and purchased a setup specifically designed for this. hehe


 
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Re: Machined Copper+Aluminium Labby / Beam Combini

Kenom said:
Very nicely done.  I cheated and purchased a setup specifically designed for this.  hehe



Nice Kenom

When can we expact some beam shots ;)

btw i can top that one ;)

 

691175002

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Re: Machined Copper+Aluminium Labby / Beam Combini

Kenom said:
Very nicely done.  I cheated and purchased a setup specifically designed for this.  hehe
I'm interested, where can you find these kinds of things?
 

Kenom

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Re: Machined Copper+Aluminium Labby / Beam Combini

it came from a laser printer.
 




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