cast your own heat sink!

And... what are you trying to say? You have a crappy 700 degrees pot oven that you probably used to make war hammer figures. You might as well have been making rice crispy treats. Buy a heat sink they are relatively cheap and will save you the trouble of going to the hospital.

I've posted this before but i just gave my fab guys a rough sketch of a heatsink
approx 100 x 25mm with a 11.95 hole drilled ( ill fine tap ream it when needed)
with heat fins on it and a set screw i can make a lot of these cheap  hopefully he'll get this done quickly so i can post a pic or two

299792458_ms said:

And... what are you trying to say?  You have a crappy 700 degrees pot oven that you probably used to make war hammer figures.  You might as well have been making rice crispy treats.  Buy a heat sink they are relatively cheap and will save you the trouble of going to the hospital.

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! ! ! TROLL ! ! !

lasersbee said:

[quote author=299792458_ms link=1227164847/0#16 date=1227212365]And... what are you trying to say?  You have a crappy 700 degrees pot oven that you probably used to make war hammer figures.  You might as well have been making rice crispy treats.  Buy a heat sink they are relatively cheap and will save you the trouble of going to the hospital.

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! ! ! TROLL ! ! ![/quote]

He needs to go crawl back underneath his bridge.

Ted

I have cast a lot of aluminum, both industrially and in smaller home-based shops. Here are some things to consider:
Is it possible?- Yes, we see cast-aluminum products all around us.
Is it practical for the casual DIY to accomplish?,- in nearly all cases, no, but look at some of the things that we do here, it is possible, but not practical.

The Molds:
The molds are usually made from "packed-sand", you pack the sand into the proper-shape using a pattern, usually made of wood to produce a void in the sand, into which the molten aluminum is poured and allowed to cool. A steel-mold may also be used, but you will need to preheat the mold and likely use more than gravity to push the molten-metal into the steel-mold, (injection-molding). Even industry uses "sand-casting" for nearly all of the aluminum-casting that is done.

The Temperature:
Aluminum melts at over twice the heat required for lead, or gold, jeweler's equipment will likely not be rated for high enough temperature, but I can ask my jeweler-friend to see what he thinks. The temperature will also require a fairly serious kiln, or oven, while in contrast lead may be melted over a hot-plate, the tempertaure-difference between the two are worlds apart.

The Results:
1).Density-The cast aluminum will be less-dense than "milled" aluminum, which I would think would be a disadvantage for use as a heat-sink, but I would leave this to the physics-experts here to determine.

2) Accuracy/finish-Your part, out of the mold, will have a fairly rough-surface, check out an engine-block, or cast-aluminum-wheel surface to get an idea of what it will look like. Cast-parts are almost always finish-machined to improve finish, at least on any of the critical-dimensions/finish surfaces. Even when machined, cast-aluminum will not be as nice as milled-aluminum. Another reason cast-parts are finish-machined is that because of shrinkage of the cast-material, (alum. is one of the worst for this), you would have to finish-machine just to get decent accuracy of your dimensions. For a heatsink in a pointer, all dimensions are fairly critical, as is the surface-finish, so you will most likely be machining the whole-thing when you are done anyway.

3) Your shape- The desired-shape for most host's would be a cylinder with a hole through it, You will not likely be able to "cast" the hole into the part, due to limitations of the molding-process (draft-angle is required on all surfaces to get you pattern out of the sand), so you will be machining the ID-features, casting will not help you here, unless you are injection-molding, so really you would be casting a solid-cylider, and then machining everything, including the OD of the cast-part. You would be better-served just starting with an aircraft-grade milled-aluminum bar-stock at this point.

Summary:
It would seam to me, that this would be an impracticle-idea from start to finish, however that being said, anyone one who tries something new, will learn a great-deal regardless of the success in the end. You may not end up with a heastink-casting process, but you will learn a hell of a lot, which is really the point, right? You may even somehow be able to overcome all of the above obstacles and come up with something new, [highlight]let's remember, it would seam impractical for most people to buy a DVD-burner and make a high-powered laser from it's harvested-diode, but we all share a passion for doing just this.[/highlight] The above information is not meant to discourage, rather it is meant to prepare anyone wishing to pursue aluminum-casting, with some starting information of what you will be up against.
Good luck to all. If there is anything I can do to help, just let me know

DH

Wow, very helpful reply. Thanks a lot. I was thinking that because I will be using such a small amount of aluminum, I could heat it with a torch and a thick metal cup to hold the molten metal in, rather than the oven or kiln. Is this not feasible?

Great information Dark_Horse. Thank you for sharing your knowledge here. BTW, i purchased 2 of your "full length Dorcy Jr heatsinks" , and i absolutely love them. They make the Dorcy Jr laser mod even easier since i dont have to figure out how to keep your other Dorcy Jr heatsink in place!

Ted

a great way to melt the aluminum is to build a small blast furince that burns charcoal or wood. i used 3 coleman propane tanks that were empty. i purged them with argon and cut the ends off. then rig up a way to blow air in the bottem. i use a high flow air mattres inflaiter. it blows out a lot of low pressure air. a vaccum cleaner that blows will also work great.

for the cursible, i have used a tin can, but the skinner propane tanks with its top cut off works the best.

also, rock salt makes a good flux

Dark Horse, stop trolling the forums. ;D Just kidding, excellent post. +1 [smiley=thumbsup.gif]


stupid trolls, what the hell do they get out of it thats so amazing? Knowledge? Experiance in how to pester people? I just don't get it.

Nice, I never really put much thought into casting a heat sync, but as I have said before...all you really need is a drill press and some taps and dies and a belt sander. seriously, please do the cast, I am actually really anxious to see how it turns out---> maybe it will be an easier solution.

Troll- someone who posts controversial and usually irrelevant or off-topic messages in an online community.

I'm just trying to rid the ignorance out of thebucketmouse that's all. He must realize the dangers faced when dealing with liquid aluminum, and just go out and buy a heat sink. You guys need to chill out with the internet slang your sounding like geeks.

299792458_ms said:

Troll- someone who posts controversial and usually irrelevant or off-topic messages in an online community.

I'm just trying to rid the ignorance out of thebucketmouse that's all.  He must realize the dangers faced when dealing with liquid aluminum, and just go out and buy a heat sink.  You guys need to chill out with the internet slang your sounding like geeks.

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I'd say a 200mW laser is a lot more dangerous than molten aluminum- i'd rather have a burnt hand then a lost eye due to a stray reflection any day of the week. So the topics discussed on this forum have, by default, some level of danger. You should stop trolling around here.

charleytown55il said:

a great way to melt the aluminum is to build a small blast furince that burns charcoal or wood. i used 3 coleman propane tanks that were empty. i purged them with argon and cut the ends off.  then rig up a way to blow air in the bottem. i use a high flow air mattres inflaiter. it blows out a lot of low pressure air. a vaccum cleaner that blows will also work great.

for the cursible, i have used a tin can, but the skinner propane tanks with its top cut off works the best.

also, rock salt makes a good flux

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This seams like a pretty good way to build a small-furnace, and some really good practical advise.
You may be able to melt the small-amount you need with a torch, already in a crucible/mold, (ceramic works really-good, but I have used steel as well). You will want to have some control over the temp, if you over-heat it, it will "burn". I am not sure what really happens chemically to the over-heated aluminum, but you won't like it, (similar to a soda-can melted in a bonfire).
I have melted small amounts of silver in just a crucible with a torch, and a very long-handle. The idea with the long-handle was to heat the material to a molten state, and then swing it in large circles in order to force the material deep into the mold/crucible to eliminate voids, (like a jeweler's set-up). I was ironically trying to produce a silver "bar-stock" that I could in-turn machine into my wedding-ring, ( a couple of decades ago). This process turned out to be pretty dangerous and did not work very well. I escaped without injury, but it was not one of my better ideas.

One last comment about casting heatsinks that just occured to me- what if you didn't use aluminum? There are a few other materials that would actually be better for a heatsink, and a few of those are certainly easier to cast, like gold. Of course gold is a little cost-prohibitive to use for this. Material-selection might just be the trick, maybe the secret to your success is not to compete with machined aluminum-heatsinks for cost, but rather performance, maybe a different material would make this easier and more effective. Silver is much cheaper than gold, and can be cast in a jewelers set-up, (of course). Lost-wax casting produces a much better finish and has less shrinkage. If you were interested, I can have my jeweler-friend cast whatever you want, he would probably only charge for the material. Some "post-cast" sanding/machining would always be needed.This would certainly cost more than our current heatsinks but it could produce a superior heatsink to anything available to us right-now.

Damn, now you have me wanting to cast a silver-heatsink.....how the hell did that happen??? LOL
+1 for the topic!

DH

PS-Thanks for the support and compliments on my heatsinks, I really appreciate it!

Correction: 299792458_ms = speed of light

299792458_ms said:

You guys need to chill out with the internet slang your sounding like geeks.

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Um....It's a laser forum. I for one am a geek, which has served me well in fact. Hell, I even use my geekiness to earn a very comfortable living if you can imagine that. Being as how this is a laser forum, I have a feeling that there may be one or two other geeks out there as well..