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FrozenGate by Avery

I want copper copper copper! (well... maybe not)

Wolfman29 said:
Just a point of input: all of this speculation is based on how long we can keep the laser on before we have to turn it off. That's all fine and dandy - maybe nickel really will help with the amount of time a laser can be kept on. However, we also know that it will drastically increase the amount of time it must be kept off before it can be turned on again for another full duty-cycle.

The question: is that what you want? For my builds, I prefer shortish duty-cycles (45 seconds-60 seconds on) with 30-45 seconds off. That's why I typically use copper when I can - it aids in transfer to the host a lot more than anything else (especially when getting a tight fit to the host), thus allowing it to dissipate that heat faster and be able to be turned on more quickly.
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Well...

That depends on whether there is more sink-to-air transfer going on than is being given credit.

I am working on this right now...


Awesome by tsteele93, on Flickr

It has the sink up front connected to a finned head (albeit stainless steel) that may dissipate more heat than we are giving the hostor credit for in this thread.

Here is my take, I think that copper is best. I'm curious about RHD's theory/questions. I think it would be intersting to see how nickel and stainless perform.

It isn't as complicated as some are trying to make it out to be. A simple test of identical sinks in a common host or two with binned diodes or the same diode in a copper module (which we all agree with offer a very good conduit to the various hosts - hopefully no one disagrees with this,) should show us if one metal stands out at keeping the diode cooler.
 
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Well, certainly the heat has to go somewhere and that somewhere is air. The ability of a metal to get the heat from its interior to the exterior where it can be removed from the host by air is controlled solely by its thermal conductivity. I don't think it can be argued that specific heat capacity will decrease the off time necessary, rather, just the opposite. Specific heat capacity means more heat will be stored in a lesser temperature gradient. Therefore, due to Newton's Law of Cooling, it will take longer for the entire object to reach room temperature than something with a higher initial temperature.

Further, because copper can transfer heat much more quickly to the outside of it, it will attempt to keep the temperature on the surface nearly exactly equal to that on the interior of the sink, whereas nickel and steel are perfectly content being warm in the core and cool to the outside for quite a while.
 
Yes, increased specific heat will increase the down time of the laser (off cycle). You can't get around that.

This is really about using small hosts or hosts with a very low surface area or a very low area of contact between the heatsink and the host. For example, in a truly tiny host you may only get 25sec before you must turn the laser off when using aluminium heatsink, but changing to a higher specific heat heatsink would let you run it for 45sec before it needs to cool. Yes, you would go from say a 25/10 to a 45/90 duty cycle, but some things are damn hard to do with only 25sec of on time.

Consider my Rigel-6.... it has a duty cycle of 45/15 from cold start and 30/15 there after. The laser takes approximately 20seconds to reach full output power, so you only get 10seconds of full on time during consecuitive runs. From a cold start the laser takes between 20 and 35 seconds tor each full output power, so going with a longer off portion doesn't increase the time at full power. After about 12 seconds at full power (a slightly extended on cycle) the power drops to half and then fluctuates more (it should be turned off now anyway). In such a build quickly wicking heat away from the laser will not yield increased time at full power, but having a higher heat capacity will yield a longer run time at full power as the thermal changes are smoothed out much like a parallel capacitor smooths out voltage changes.
 
I agree with all of the above.

However, I was under the impression that this discussion was essentially for all, non-finned handhelds, including C6 and up sized hosts?
 
I would think that it would scale up, but lose effectiveness as the build size increases. I could be wrong, this is just a gut feeling. But I think the effect would be more pronounced in smaller builds than in large ones. We're also not seeing a true need for innovation in large builds, we're already achieving continuous duty in ~1W large host/sink builds.

I think for true high power monster builds we need to move away from current host practices more than we need to innovate heatsink design, which mostly benefits smaller builds. I do consider the C6 to be a small build though.

For said high power builds we need to abandon the aixiz module and it's analogues and move to a one piece direct press heatsink/laser-host-head combo with a large mass and an even larger surface area to mass ratio made from highly thermal conductive metals; i.e. large deeply finned copper or aluminium.
 
Someone said:
Srry guys i dont know how to ask a new question but I found a 100% brand new fully metal and waterproof laser pointer for $66.99 at highpowerlasrepointer.com and I was wondering if it's trustworthy or not
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Someone said:
I found a 100% new all metal waterproof laser at highpowerlaserpointer.com for $66.99 and I was wondering if it's trustworthy or not :thanks:
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Someone said:
Oh and it 300mW and 532nm
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You are posting it in the wrong thread. Make a new thread in Green Lasers - Laser Pointer Forums - Discuss Lasers & Laser Pointers
 
Sigurthr said:
Yes, increased specific heat will increase the down time of the laser (off cycle). You can't get around that.

This is really about using small hosts or hosts with a very low surface area or a very low area of contact between the heatsink and the host. For example, in a truly tiny host you may only get 25sec before you must turn the laser off when using aluminium heatsink, but changing to a higher specific heat heatsink would let you run it for 45sec before it needs to cool. Yes, you would go from say a 25/10 to a 45/90 duty cycle, but some things are damn hard to do with only 25sec of on time.

Consider my Rigel-6.... it has a duty cycle of 45/15 from cold start and 30/15 there after. The laser takes approximately 20seconds to reach full output power, so you only get 10seconds of full on time during consecuitive runs. From a cold start the laser takes between 20 and 35 seconds tor each full output power, so going with a longer off portion doesn't increase the time at full power. After about 12 seconds at full power (a slightly extended on cycle) the power drops to half and then fluctuates more (it should be turned off now anyway). In such a build quickly wicking heat away from the laser will not yield increased time at full power, but having a higher heat capacity will yield a longer run time at full power as the thermal changes are smoothed out much like a parallel capacitor smooths out voltage changes.
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And another question is whether it is the diode or the driver that is getting too hot?
 
Well it's just an example but I would guess in my case it's the diode, and not the driver, though I'm not convinced the driver is constant current so... who knows. I'm not about to dissassemble my $500 laser to find out. If I ever get a high power 589 or 593.5 I'll be rebuilding my Rigel into a larger host though.
 
rhd said:
In other words, given a choice between a heatsink that can conduct the heat to the host walls more quickly, and a heatsink that can absorb a whole lot more heat, in most builds you would prioritize the heatsink that could absorb more heat ...While copper is known to a fantastic choice for finned heatsinks (for CPUs, etc)...
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I thought the general consensus was that Cu "absorbs" heat more efficiently and Al transfers heat more efficiently.... :thinking:

My CPU HS is actually based on a lapped Cu core welded to Al fins.

I do agree with you that chip-cooling applications and LED / Diode cooling are apples & oranges. For one thing, you can cover a major surface area when working with chips and heatsinks - most of which are lapped flat and mated with an ultra-thin layer of thermal compound with the sole purpose of filling in the pores and gaps between the two lapped surfaces.

You have none of these advantages when buliding hosts and thus may indeed need to consider alternative solutions.

Regardless of the numbers, steel as a heatsink is going to be a hard sell...


BShanahan14rulz said:
I still say doing away with modules would net more gains...
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Agreed. Ken's Kryton host had the right idea by fitting the diode directly into the head of the host which is one large piece of Al. Since you can't really manage tolerances equivalent to a CPU's lapped die and a lapped HS, you're much better off doing away with a "module" if at all possible.
 
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Traveller said:
I thought the general consensus was that Cu "absorbs" heat more efficiently and Al transfers heat more efficiently.... :thinking:

My CPU HS is actually based on a lapped Cu core welded to Al fins.

I do agree with you that chip-cooling applications and LED / Diode cooling are apples & oranges. For one thing, you can cover a major surface area when working with chips and heatsinks - most of which are lapped flat and mated with an ultra-thin layer of thermal compound with the sole purpose of filling in the pores and gaps between the two lapped surfaces.

You have none of these advantages when buliding hosts and thus may indeed need to consider alternative solutions.

Regardless of the numbers, steel as a heatsink is going to be a hard sell...
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No, Al doesn't "transfer" the heat as efficient as copper. That's why CPU heatsinks have copper pipes but Al fins. Al fins = for dissipation. Al dissipates heat faster than copper. Copper holds to more heat and transfers heat better.
 
Ryan, that's not true either. There's no physical constant that effects how well something "dissipates" heat. The only thing that matters is the thermal conductivity of the two interacting materials. Copper is always a better choice if your other choice is aluminum (except cost, obviously).
 
Ryanrenesis said:
Al fins = for dissipation. Al dissipates heat faster than copper.
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Agreed - I used the wrong terms (absorb & transfer vs. transfer and dissipate). Thanks for pointing that out :thanks:

Wolfman29 said:
...There's no physical constant that effects how well something "dissipates" heat. The only thing that matters is the thermal conductivity of the two interacting materials...
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I was under the impression that Cu absorbs heat more efficiently but is "slow to release" said heat... but I think I'm under-qualified in this group so I will just go sit in the corner and listen in a bit longer... :beer:
 
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That's not the case whatsoever. Al has a lower specific heat capacity, so it stores less heat per unit volume. That implies that it will reach a lower temperature sooner, but it is still giving up energy as heat more slowly.

It seems that Al cools off faster because it reaches a lower temperature faster, but copper just stores a lot more heat for a smaller temperature, so it has more heat to give off per degree Kelvin.
 
RHD's experiments will probably have an effect on what material heatsink we recommend for users who already have a stainless steel host. I think it will also be valuable for creating mass-produced, multi-host compatible heatsinks, as these will not have that glove fitment that a custom designed heatsink will, and thus will have an insulating pocket of air around the heatsink.

I think most of us use aluminum hosts, though, because they are better at providing more quickly usable mass that can be added to the heatsink if properly made, instead of impeding the movement of heat. Not to mention, you can anodize aluminum hosts to further increase its radiative emission, and it is easier to machine deep fins into than steel. The biggest downside, IMO, is that polished stainless steel looks and feels so much better.
 
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