How do you seal your heat block?

@Digital Dentist: Yes, I do understand that, and it is what I was trying for. When I tightened the nozzle against the throat, I was aiming for the point where there might have been enough room for a sheet of paper between the head of the nozzle and the heat block, and that's about where it is. I can't tell now, because it's full of plastic, but I don't think that it's backed out. It might have been possible for about another 1/8 of a turn for the nozzle to go into the block without the throat there, but not more. If the nozzle were tightened hard against the block, I'd expect the leaking to be coming out the top of the heat block, next to the throat/heat break.

I believe that the fact that it was good for a while, and is definitely not now must have to do with heat cycles and dissimilar metals. (Stainless steel throat, brass nozzle, aluminum block) Something must be deforming under heat, and not coming back to the same position the next time.

@MKSA: Yep. That's how I'm going to do it.

As it happens, I was about to be changing the heat block anyway, since I now have some PT1000 sensors, and I need a different heat block that can fit the cartridges.

Thanks for being patient with me. I do a LOT of DIY type projects, and I'm generally (If I do say so myself) pretty good at it.

To me though this method of tightening the nozzle and heat break together to form a seal is something that I would just never see in other applications.

In anything automotive related, there would be a flange and gasket system, particularly if there needed to be a temperature range tolerance. that would mean a flange on the nozzle and another on the heat break, and both would be gasketed against the surface of the heat block. Alternately, the threads could be tapered to force a sealed fit under torque, like BSPT or NPT threading. It seems to me that with the need for good thermal contact would make this a superior solution.

I'll start going through my assorted collection of crush washers to see if I can find one that will work inside the 6mm thread of the heat block. I have some aluminum and copper ones, meant for a fuel system, and some fibre ones meant for oil systems. Either one should be fine to for any temperatures that I'm ever going to print at. I also have some sealant meant for metal head gaskets which might just do the trick, which also doubles as an anti-sieze compound.

---

MBot3D Printer
MakerBot clone Kit from Amazon
Added heated bed.

Leadscrew self-built printer (in progress)
Duet Wifi, Precision Piezo parts

Indeed not seen in the industry as many things in the 3D printer community !
Fact is, most hobbyists who recently started "designing" 3D printers have no clue about mechanic, or just theoretical but not practical !
Thingiverse gives a pretty good timeline how things went down the drain overs the years.
Chinese copiers try hard to make bad designs worse and the few good ones, really bad. Their success rate in doing so is amazing.

---

"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Maybe that's my problem. I don't BELIEVE in it enough. I expect the system to leak and therefore it does.

I do have a tube of this in the garage: [www.permatex.com]

I'd almost forgotten that it was there, I bought it to seal an oil cooler line, but ended up replacing the oil cooler with something that used BSPT threads instead. This stuff is supposed to be good to 371°C so it should certainly stand up to 3D printing temperatures.

---

MBot3D Printer
MakerBot clone Kit from Amazon
Added heated bed.

Leadscrew self-built printer (in progress)
Duet Wifi, Precision Piezo parts

The problem with these sealants is that thy may end up sealing the nozzle ! Very good brand Permatex and BEWARE don't mix BSPT i and NPT BTW

Heatbreaks should not be threaded but conical , flared like high pressure hydraulic coupling. It is the way I make my own.

Edited 1 time(s). Last edit at 11/01/2018 06:38PM by MKSA.

---

"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Heh. I drive a Japanese car that has BSPT threads in the block for oil and coolant fittings, and live in Canada, where everything that it's possible to buy is NPT. Or any kind of aftermarket sender for oil pressure or temperature is NPT. I have a numch of BSPT to JIC adapters for that kind of stuff.

I'll be very sparing with the sealant, and I have some of those nozzle cleaners. I'll probably assemble it with the cleaner in place, and just cold-torque the nozzle into place with a light layer of sealant on the mating surface, and since it's copper based, maybe cover one thread or so on the nozzle and heat break. the last thing that I want is extra sealant going into the melting chamber of the nozzle or obstructing the filament in the heat break.

---

MBot3D Printer
MakerBot clone Kit from Amazon
Added heated bed.

Leadscrew self-built printer (in progress)
Duet Wifi, Precision Piezo parts

Maybe I'm just lucky. I just tighten the nozzle against the heat break when the heater is at 250C and get no leaks.
I've successfully assembled (I think) 10 hot ends. One thing that helps perhaps is that I have a zero tolerance for problems. If I have any trouble whatsoever I replace the heat break. If possible, I replace it with an "all metal" one. I have one that ended up with an interesting configuration of parts that were not quite factory stock.

I did have one massive heater block that always leaked out the top (next to the heat sink). A couple of wraps around the thread with plumbers tape solved that problem.

DLC

---

Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

Not much point in using an all metal heatbreak if you'll wrap the threads with plumbers tape (teflon).

Quote
Trakyan
Not much point in using an all metal heatbreak if you'll wrap the threads with plumbers tape (teflon).

Nope. That one still used a PTFE core. Totally a Frankenstein's monster hot end in that printer. Built with "sorta fits" and "what I have in the junkbox" parts.
I have a full replacement for it when I rebuild the entire thing. At the moment it works for creating large test prototype parts with a "fire hose" nozzle.

DLC

So far Permatex Copper gasket seems to be good. I coated about 2-3 threads of the heatbreak with a very thin smear on the end that mates to the nozzle. I did not put any on the nozzle at all. I hot-torqued the nozzle in to 30 in-lbs (Slightly higher than the 26.5 in-lbs/3Nm that E3D recommends, but still in a close range.) I ran a shortish print which seemed to go well. It certainly would have been leaking before this.

I still need a new heat block anyway, since I'm still not using the PT1000 sensors that I bought, but there's a mail strike on now, so I haven't got a new block yet. I want to see if this method is good first anyway.

And yeah... I kind of thought that teflon tape wouldn't be a good idea if the idea is to want to be able to have the higher hot-end temperatures.

I was considering a paper gasket. These get used in automotive applications for service up to about 300 deg C, even though the combustion temperature for paper is 233°C (Or as made famous by Ray Bradbury, 451 degrees Fahrenheit.) The paper won't burn if it's not exposed to enough oxygen, but I've always considered it to be risky.

I don't have any aluminum or copper crush washers small enough to use in a hot-end like this. Most of these that I have are for larger fittings, 12mm ID or larger, or else I'd have used one. I have some head gasket sealant that is, so far as I can tell copper dust with just enough of some volatile petroleum product to make it stick together. I might use this on the nozzle, since it should also have excellent thermal conduction properties. I'm not sure what the thermal conduction of the Permatex stuff is, since it also has silicone, but it's rated to 371°C, so it's more than good enough for the heat break, but I'm not sure that I want it between the nozzle threads and the heat block. I'm okay with it between the nozzle and the heat break though, so that's how I arranged it. It still seems to work well for running the plastic through, doesn't seem to have hurt extrusions at all.

---

MBot3D Printer
MakerBot clone Kit from Amazon
Added heated bed.

Leadscrew self-built printer (in progress)
Duet Wifi, Precision Piezo parts