Ceramic Hot-end Mount Seeks To Improve Extrude Performace


Take a gander at the part of this extruder head which looks like a chess pawn. It’s the mounting bracket for the hot end and it’s made out of ceramic. [Ed] came up with the idea to use ceramic to mount the hot end when trying to improve the design while keeping it rather simple and easy to assemble. The concept uses the thermal properties of the ceramic to insulate well enough to operate the extruder at higher temperatures without causing other problems.

Where does one get a custom ceramic part anyway? Turns out you can get low volume runs from China much like PCBs. The minimum order was ten units, which was still a leap of faith since he had no way of testing the design in advance. The first run with the new part went quite well, but only for the first layer and then the filament jammed. He’s still not sure why, but overcame the issue by lining the inside of the ceramic with a PTFE tube. This means he now has to use a smaller filament to fit through it. But the quality of the prints he’s getting with 1.75mm stock and the ceramic head are superb.

It may even be possible to print this ceramic part some day. We remember seeing another extruder that can deposit ceramic clay.

26 thoughts on “Ceramic Hot-end Mount Seeks To Improve Extrude Performace

  1. This doesn’t make sense to me. Generally, hot-ends are insulated by PTFE, which starts off-gassing at about 220C. The whole point of using a ceramic hot-end would be to remove the PTFE from the mix, so using a PTFE sleeve doesn’t improve matters much. Why not go to a potter and ask them to glaze the inside of the ceramic, That would smooth it out and, hopefully, fix the jamming problem.

    1. I wonder if a potter could make the whole thing. Many towns have a local ceramics class with a shared kiln. I think if I wanted a small part like this I’d consider starting there.

    2. Well, my initial thought was “what about teflon” only to learn that teflon == PTFE.

      I wonder if you could use a glass tip or glass lining. I’m not sure if it is possible but it seems like it should be able to take the heat.

      1. Electroplate or CVD with just about any kind of metal you want: if thin enough it won’t conduct heat very well. If you could press or spin in a thin tube liner that would also work.

        Maybe check out the suppliers that make tubing for scientific purposes: Upchurch, Vici, and SGE produce a wide range of polymer and metallic tubing. http://webstore.idex-hs.com/TechInfo/polymerInfo.asp.

        Just looking at it, PEEK (which I use a lot of) has double the temperature rating of teflon. It’s also much more rigid.

        Various steel tubing is available with ID ~2mm, and it can be purchased already electropolished to have very smooth entry/exit points. I know nothing about extruder design, but it’s also trivial to get adapters, step-down etc, so maybe nozzle design could be simplified? http://www.vici.com/tube/cust-met.php

      2. Borosilicate glass (pyrex = doesn’t expand much when heated) softens at a little over 800’C so it should withstand the temperature. Regular glass (= soda-lime glass) is roughly the same temperature-wise, but the thermal expansion with temperature will make it more difficult to work with. It will most likely shatter for various reasons.

        Teflon is slippery; glass, not so much.

        Drill bits have a titanium coating, largely (I’m told) because titanium is slippery and presents less friction at the cutting surface.

        Perhaps a thin coating of titanium on the inside of the shaft?

    3. I’d also imagine that ceramics make terrible thermal breaks as they’re good conductors of heat. The point of the barrel is to reduce the volume that’s being liquified and prevent that heat from traveling up the tube and melting, causing jams and melting the mount.

        1. There are different kinds of ceramics. Shuttle tiles are made of porous silica. This part was made of dense, metal loaded ceramic, so it will conduct more heat than a shuttle tile, but much less than something really conductive, e.g. metal. I also think a glass or quartz tube might be better.

  2. Details for the Shapeways ceramic option can be found at http://www.shapeways.com/materials/ceramics-design-guidelines

    The main gotcha is that “holes must be at least 5mm in diameter”. That said, there is the caveat that glazing can add up to 1mm in certain areas. It could work to your advantage if the bore were designed for 5.5mm diameter and shrank by 1mm radius to give a 3.5mm diameter manufactured diameter for 3mm filament.

    Looks like i.materialise has similar design constraints: http://i.materialise.com/materials/ceramics/designGuide

  3. You can get High Temp PTFE tubing that would work just as well. The problem with ceramic is that it is a rough and porous surface when not glazed which means that once the filament was heated it would have a tendency to ad hear to the inner walls of the chamber.

    In theory you could get a tube made of ABS or PLA that is the interior diameter that you want then insert that into the hole with the glaze around it. Once the glaze has dried and you fire (bake) the part the plastic should evaporate out leaving a hole the correct diameter.

  4. Find a local dentist that knows what a CEREC or E4D is (CADCAM system for milling crowns). Buy an e.max block from them (material cost is $25-30, but every machine comes with a color sample pack that includes shades they will never, ever use) or have him hand you a used block with a few mm of material left on it (free, they get trashed). You now have a small piece of funky purple ceramic that can take several hundred degrees like it was nothing. Not certain what the thermal properties are, but it’s less conductive than metal.

    Cut with diamond bits, low speed and extremely low force. Tons of water. e.max wears out diamond bits extremely quickly and is a bit of a pain to cut through, but if all you want is one small hole, I don’t see you having too big a problem.

    Note: There’s other ceramics, but I specified e.max because it starts life purple. This’ll stop them from handing you a composite (read: plastic) block that will react badly to being heated. Also, mention that you can 3d print custom sized plastic parts and you may have some new best friends. Medical equipment aside, the tool holders, cabinets, and everything else in a dentist’s office seems to be made of cheap as possible garbage that breaks every other tuesday. Make them a replacement plastic foot for something and you probably just saved them about $300 just counting repair technician time.

  5. Nice tip about e-max, thats handy.
    I know a dentist here, might ask them nicely if they can spare a piece.

    Another thought, make “water glass” coated ceramic as this stuff once set melts at 800C or so and is already in liquid form.
    Doesen’t like moisture though so the hot end will need to be bagged with silica gel when not actually printing anything.

  6. umm, Couldn’t you glaze an entire opening, then drill a hole through the glaze?

    Then drill again with a sanding buffing bit, and make any size hole through glaze as a tube that is surrounded by ceramic.

    I don’t know the properties of the glaze, but if it is high heat, and could have variable depth and still radiate heat, wouldn’t that work?

  7. As a dentist myself, I believe that it would’ve been easier for the man to make the part himself. firing porcelain is very well documented in dental literature. he could get the porcelain from any dental lab supplies vendor.

    if all-ceramic fails, it would be wise to construct a metal framework onto which he fires the porcelain.

  8. I’m working on finding a supplyer of ceramic hotends. Zirconium looks like it has the temperatures I need. Metal is pretty much unusable since the temperatures will exceed their melting point.

    1. The Porcelain used in spark plugs has high thermal conductivity. That’s why he wenr with Zirconia. The trouble with Zirconia is that it has a firing temperature of 1800C plus can form some nasty crystalline structures if it’s fired too slowly.

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