New heat shield design

Topics around mechanical design, controller and electronics. Mods & hacks welcome.
rimb05
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Joined: Thu Mar 09, 2017 2:05 pm

New heat shield design

Postby rimb05 » Fri Mar 17, 2017 1:39 pm

I just posted a heat shield and fan mount I designed (it's a remix of a nice fan mount design by Sylus).

http://www.thingiverse.com/thing:2183758

I basically got tired of having to remove my ceramic insulation blankets from the hotends, and the side fans, etc every time I wanted to change nozzles. So I combined a heat shield with a fan mount (similar to the way the Ultimaker design works). The only thing protruding from the shield are the nozzles and a fan duct, so my prints stay nice and cool while printing. I wrapped the entire thing in kapton and printed it with PC.

To change nozzles, I used a hotend stabilizing tool I modified that can be used from behind (because the fan blocks the front). I simply insert the tool, and use a socket wrench to remove the nozzle. Easy peasy.

I found that as long as I'm using the same nozzle type (Raise3D Micro Swiss from example), I don't see any significant height differences after changing nozzles. Just remember to unload all your old filament so there's nothing left in the isolation tube or nozzle when reinserting the new nozzle.

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walshlg
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Re: New heat shield design

Postby walshlg » Fri Mar 17, 2017 2:05 pm

nice design, but I imagine it'll melt if you print PC with it

rimb05
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Re: New heat shield design

Postby rimb05 » Fri Mar 17, 2017 3:31 pm

So far so good. I haven't seen any melting or softening yet when printing PC. I've coated it with kapton pretty well. There's an air gap between the hot ends and the shield, so in combination with the kapton, it seems to work well.

ABH
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Re: New heat shield design

Postby ABH » Fri Mar 17, 2017 6:31 pm

Good that this blower duct works for you, but I think your design is a little misunderstood. Why would you want to put kapton tap on the outside of you PC based blower duct?
Thin kapton tape is not an insulator by itself. The reason that some people like to use kapton tape on their hotends is that they might (?) obtain some insulation effect by trapping some still air in-between the metal hotend and the tape. Most insulation materials works by trapping still air in small air cavities. If the purpose of your design is to make a heat shield and protect your printed parts from the heat radiation from the hotend, then you should instead use aluminum tape.
In the infrared range, kapton has near 100% emissivity, like all other plastic materials. Aluminum, especially polished aluminum, has very low emissivity.

In general about hotend insulation:
Heat exchange between your hotend and the surroundings takes place partly by thermal radiation and partly by convection/conduction (almost 50% radiative loss I think, it's been some years since I did such calculations), so by wrapping kapton tape around your hotend you might reduce the surface temperature a little, because several layers of tape traps some air between the layers, and thereby obtain some insulation effect, but at the same time you increase the heat radiation from the hotend to your prints and the surroundings. You increase the radiative heat exchange because the native hotend is made of aluminum and natively has low emissivity whereas the kapton tape has 100% emissivity. So, if you want optimal insulation, use some good insulating material (ceramic fiber insulation, mineral wool etc.) towards the hotend and wrap it in aluminium foil/tape.

Jetguy
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Re: New heat shield design

Postby Jetguy » Fri Mar 17, 2017 6:45 pm

As I see it the tape is just a surface so that hot plastic has something smooth to slide off of VS the direct printed layers. In other words, worst case, you get that occasional blob of hot filament around the nozzle during purge or some other random little hot mess, and that keeps it from melting in and really sticking to the 3D printed housing.

Say what you want about the design- I'm just commenting on why I would use tape for the same reasons in that application or spot.

ABH
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Re: New heat shield design

Postby ABH » Fri Mar 17, 2017 8:34 pm

OK, maybe it would make sense to apply tape for protective reasons.
It might be easier to peel off melted plastic from the kapton than from the PC.
If this was the intention of the kapton tape, then I apologize to the OP for the accusations.
My general remarks are still valid though. There seems to be a general misconception in 3D communities that kapton tape makes wonders.
The only real benefit from using kapton tape is that it is a high temperature plastic and the tape has a high temperature adhesive.
The thermal characteristics of kapton is like any other plastic.

rimb05
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Joined: Thu Mar 09, 2017 2:05 pm

Re: New heat shield design

Postby rimb05 » Fri Mar 17, 2017 9:31 pm

Sorry for the confusion, the kapton tape is actually on both sides of the shield. It was just more convenient to wrap the tape all the way around instead of cutting it. While it serves no purpose in terms of heat deflection on the outside, it does provide some protection from blobs sticking to it, etc like Jetguy mentioned . But that was just a side benefit. The main reason for the kapton was to insulate the plastic from the hotend on the inside of the shield, so it wouldn't melt. I thought about aluminum tape but didn't have any on hand. The kapton works very well in this application.

I'm not using any kapton on the hotends - they are now completely bare. I used to have nice ceramic insulation "blankets", which worked great, but it made nozzle changes a pain, so that's why I designed this.

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walshlg
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Re: New heat shield design

Postby walshlg » Sun Mar 19, 2017 8:05 pm

I still think you will want to insulate the top of the heatblock since the isolation tube fan exhaust is blowing on that too.

rimb05
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Re: New heat shield design

Postby rimb05 » Mon Mar 20, 2017 11:41 am

My main reason for wanting to insulate the hotends was to prevent the tops of my parts from curling up, and other effects. I haven't really had an issue with the hotends not reaching temperature.

lami3d
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Location: Marseille - France

Re: New heat shield design

Postby lami3d » Fri Mar 24, 2017 5:24 pm

I don't understand why there are more and more fans to blow, bigger fan... because, i have these mods : 15mm fans +socke right fan duct and a good hot end insulation.

I set cooling to 50% max with PLA (100% for the bridge on S3D) and sometimes it's too much cooling (you see the upper surface is too dry) with speed around 60 to 80mm/s and i print in the high range temperature in general to get good layer adhesion and strong parts.
So, i'm wondering if i miss something? Or, you are printing at 200mm/s ?

On the picture, the kapton is just here to maintain the fan cover in place (printing ABS + CF + Aramid) because the new ones are cast and so soft that the cover can leave during the print :)

20170324_180153.jpg

rimb05
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Joined: Thu Mar 09, 2017 2:05 pm

Re: New heat shield design

Postby rimb05 » Fri Mar 24, 2017 9:31 pm

That fan I'm using isn't very powerful (I can barely feel the flow), but it's seems to be just enough for PLA. I like the Sylus design I'm using because the fan duct is right in between the nozzles, so I get good cooling distribution even when doing dual extrusion prints.


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