Reusable mold for silicone boot for Wanhao D6 hotend

by Empiricus Mar 31, 2017
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Dude... this mold made me an absolutely perfect part.
I printed it at high rez then sanded pretty well.
Thank you very much.

Thanks. Glad it is useful.

Made this today. No sanding, and everything fit perfectly. Used an ultra thin layer of dialectic grease on the mold...then wiped off, the residual was enough to let the boot come off perfectly. For the boot I used Permatex high temp red rtv mixed 1:1 with corn starch. Solid but stretchy enough to get on block. After curing I did wash off excess grease ( not much ) with dish soap and water and let dry. Had to widen split on top a tiny bit, but no big deal. Thanks for the up!

Hello Everybody.

At first my english is not so good but i try my best.

I am very interesting about this silicone booth for my wanhao d6.

I printed the file on my d6 en it fits very good. Then i bouth a high temperature silicon and filled in.

After 24 houers i tried to open the form, but the whole form was together with this silicone. What was my mistake? Does everybody have some ideas??

Thank you very much.
Cheers Cyril

You need a few drops of liquid glycerin mixed into the silicone to help it cure. Silicone needs moisture to cure; the glycerin provides that moisture without ruining the consistency. Otherwise you'll have to wait a very long time to get it to cure on it's own. I've heard some people have had luck using corn starch instead but that does thicken the mixture quite a bit.

You can get liquid glycerin from a local drug store.

Please use the two component silicone from smooth-on I used. You know what the temperature stability is and there is no problem with curing.
Seriously, guys. Cost a little more but you are safe.

I'm sure that's a great product but it's a little out of my shoe-string budget price range. I used high temp Permatex Red RTV silicone gasket maker with a few drops of glycerin to help the cure. Material cost was ~$10 total. Came out great with no noticeable degradation after high temp prints. Gasket maker is made to withstand the heat and stress inside an engine; I'm comfortable using it on a hotend.

Yes that stuff is pricey but you can make quite few with amount you get. I also use it for metal casting. Cool if it works with gasket sealer. Glycerin is hygroscopic, I guess that is where the H2O comes from. I had people complain about gasket sealers breaking up after a short time or smoking. Maybe because of starch addition. Thanks for the tip.

That would make sense. I was skeptical, to say the least, of using a natural, flammable product like cornstarch in conjunction with a bit of metal whose purpose is to get very hot. But, I heard some people had success with it so I figured good for them - I just wasn't going to do it.

I recently found a copper RTV silicone that could be even better. Extremely high temp resistance and better chemical resistance: https://www.permatex.com/products/gasketing/ultra-series-gasket-makers/permatex-ultra-copper-maximum-temperature-rtv-silicone-gasket-maker/

If I ever need to make another boot that's what I'll probably use. It was listed on amazon for not too much more than the Red.

Also on a budget, I used the "Permatex Ultra Copper Maximum Temperature RTV Silicone Gasket Maker" that you linked. The result came out great. I didn't mix it with anything, but I did use Vegetable Glycerine as a mold release. I used a painbrush, dipped it in glycerine, used 1 coating on the reusable mold, then used printed "popsickle sticks" to coat the mold with the silicone gasket maker. After waiting for about a day for the cure just to be safe, I carefully removed the silicone from the mold and cut off the excess with scissors. I also wiped the inside of the silicone boot with tissue paper. Thank you for posting that link and sharing some knowledge! Cheers!

Also to note: it did smoke when I first used but went away by the time my 2 hour print was finished. Hasn't smoked since then.

I used the copper RTV silicone gasket maker with a little glycerin (not much, just dropped a bit in from the end of a popsicle stick and mixed in really well for a minute) and used dish soap diluted with water as a mold release 1:2 and it worked out perfectly. Cures in 24 hours, the glycerin is cheap and works amazing with this stuff. Thanks for the tip on the copper RTV silicone.

That's great! Glad I could help! Have you ever used red? I'm wondering if the cured copper is tougher than the red, which actually tears pretty easily.

One very cool thing about these homemade boots is they can EASILY be repaired. Just use a toothpick to dab a bit of fresh silicone in the crack or tear and leave it to cure. Works great because silicone bonds to silicone. The times I've done it the boot feels as good as new and it saved me from having to remake a new boot.

Of course you will have to make many more. The heat is no problem and they last for many months, but sometimes one gets ripped by a failed print or when changing the nozzle and the silicone boot is glued to the heat block by melted filament.

Yeah, I've had the boot get glued on by melted filament. I was worried when I tore it and figured I'd have to remake the boot but figured I'd attempt a repair first. I just used a toothpick and filled the cracks with fresh silicone. I didn't have high hopes going into it because the boot was torn nearly in two. It actually worked really, really well and I'm back up and running with my original boot. It saved me some money on silicone and time mixing and whatnot. I'll definitely do this again.

I started using high temp anti-seize lubricant as an interference layer between the heat block and the boot which so far has helped prevent the dreaded charred filament glue. It smokes a bit as the carrying oils burn off but it leaves behind a nice aluminum powder layer which does a good job of repelling molten filament. It may need to be reapplied every so often but I haven't reached that point yet.

You need some kind of mold release. If you used something different from the two component silicone and mold release I used it is hard for me to predict what would work. Have seen vaseline or soap but some material may prevent silicone from hardening. Look at instructables.com

In case anyone else reads through, I used high temp anti-seize lubricant as a mold release and it worked really well. The silicone popped right out.

It's possible that a thin layer of whatever you used as a mold release will be left on the boot and brought up to printing temps. That's why I went with anti-seize lubricant. It made my boot come out a nice shiny aluminum color which I thought would rub off but is apparently bonded superficially to the silicone. Looks extra fancy.

I've heard of people using clear shoe polish as a mold release. I've never done it but I think you just rub it on and buff it smooth. I was a little concerned with the smell so I opted for something I was more familiar with.

I had trouble printing the provided stl. The parts were not on the same reference plane so it tried to print some of the pieces into midair. The end cap that holds the plug also had some funkiness in the model so I fixed it. I will try and upload the stl's I used.

I also used high temp rtv mixed with cornstarch and soap as a mold release.


Thanks so much. I up loaded individual parts to avoid the problem,

Comments deleted.

When I made this on my Monoprice Maker Ultimate, for some reason the end caps were slightly small. With measurements from my micrometer and a quick calculation, I scaled them to 101.67% and then they fit. I uploaded the scaled caps in case anyone else is in the same situation. http://www.thingiverse.com/thing:2240781

Reusable mold for silicone boot - caps only- for Wanhao D6 hotend (monoprice maker ultimate)

by any chance was it an i3 styles printer im looking for a similar solution but so far all i have come across are solutions for e3d v6 style block non for the mk10 style blocks

I've had to use the top cap, bottom fit fine. The line that runs down the middle piece is too large for the top mold piece.

Cool have have fun. I usually just chamfer the inside edges of the top and bottom with an xacto knife and sand the mold halves a little also in the area were they go together for a perfect fit. Otherwise you can put tape around it. I usually print PLA at 90% extrusion but prefer PETG as it doesn't shrink and usually the print is spot on.

I could see PETG working better for this.