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Author Topic: LED heat and 3D prints  (Read 1491 times)

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Offline SirRawThunderMan

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LED heat and 3D prints
« on: October 17, 2019, 10:39:42 AM »
So, I've been thinking about this for a while now, and haven't really found much in the way of data, or been able to parse the question in a way that google can understand it. LEDs generate heat when they operate. Most common/cheap FDM filaments have a relatively low melting point (I've mostly used PLA, which is anywhere around 180-200C). Is there ever any risk that "standard" high power, tri/quad-cree, li-ion battery powered setup could generate enough heat to damage FDM 3D printed internals?

I'm thinking, say, a scenario when you'd butt a printed part right up against a heat sink because of cram-fu needs. Would that print be at any risk?
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Offline K-2SO

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Re: LED heat and 3D prints
« Reply #1 on: October 17, 2019, 04:23:25 PM »
Yes, it would. If real copper and Aluminum can get hot, that would become a gooey mess.

I find your arguments vague and unconvincing.

Quiet! *Slap* And thereís a fresh one if you mouth off again.

Offline jbkuma

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Re: LED heat and 3D prints
« Reply #2 on: October 17, 2019, 05:46:43 PM »
The melting point is less important here than the glass temp. The LED won't get close to 180C, but it will get into the range that the PLA can soften.  Of concern also is that your LED would ideally be dissipating into the saber as well.

When I make printed sabers I always use an aluminum core to handle the torque of swinging the saber around, but it will also help with the heat.

The design of your saber will determine how the heat affects it. Some geometries are more resilient, the number of walls and infill density will also be a factor.

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Offline SirRawThunderMan

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Re: LED heat and 3D prints
« Reply #3 on: October 18, 2019, 03:39:43 AM »
Yes, it would. If real copper and Aluminum can get hot, that would become a gooey mess.

Yes, but can an 18650-powered LED ever get them that hot in the first place? I honestly have my doubts about that. I figure that much heat would at least melt the solder off the pads first. Although, if that happens, in theory, the loose wires could fall back and short through the heat sink. assuming that didn't hit the 18650's discharge PCB, that could heat up the heat sink enough, but that's a million to one chance.

The melting point is less important here than the glass temp. The LED won't get close to 180C, but it will get into the range that the PLA can soften.  Of concern also is that your LED would ideally be dissipating into the saber as well.

The design of your saber will determine how the heat affects it.

Yeah, this is more my concern. Specifically design. The way I see it, a saber using MHS parts should have little to worry about. MHS LED holders and emitters are machined to fit together perfectly, and then lock into MHS parts. the extra mass of aluminium in the emitter should offer an ideal additional heat sink that should dissipate the heat well.

But, what about a saber with a MHS 1" or 7/8" led holder+heat sink, and a scratchbuilt, layered aluminium tube hilt (the kind I like to build)? There's plenty of gaps in between the various layers that would impede dissipation, and the 1" heat sinks are usually loose in tubing with a nominal ID of 1", so there's little contact between it and the walls of the hilt? Could that, in theory, leat to heat welling up around the heat sink, and damaging any 3D printed parts around it?

All that is nice and theoretical, though, and based around the assumption that a li-ion battery can actually supply enough power for an LED to overheat. I used a tri-cree as an example earlier, and those are usually made of three Cree XP-E2 LEDs. According to their datasheet (https://www.cree.com/led-components/media/documents/XLampXPE2.pdf) at 1A, they will fail when they reach a temperature of 150C, but have an ideal operating temperature of 85C. So, well below melting point of PLA, but firmly within PLA's glass transition temperature.

I'm no expert on batteries. however, given that in the last few years, we've seen a shift from 18650s to larger battery sizes and capacities (21700s, 26650s, etc.) Could theoretical glass transition temperature damage occur as those batteries enable a longer operating time for LEDs?

I mean, technically, all this is rather moot, given that any damaged printed parts have the advantage of being replaceable by another print. It'd suck in the heat of the moment (while duelling, or at a con, or something) but it'd be fixable, at least.
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Offline K-2SO

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Re: LED heat and 3D prints
« Reply #4 on: October 18, 2019, 04:49:31 AM »
If youíre using a copper heat sink, as long as your printed parts arenít directly attached to it, you will probably be fine, though a little space would be helpful. I personally wouldnít recommend connecting the two, and would recommend some space between the heatsink and the PLA. It can get very hot, even with a copper heat sink (which prevents solder from melting) but hey, I guess the best way for you to find out is to just do it, and see what will happen for yourself.

I find your arguments vague and unconvincing.

Quiet! *Slap* And thereís a fresh one if you mouth off again.