Saturday, May 26, 2018

UMMD Gets an XCR3D Hot-End

During some recent hunting for the source of a print quality problem with UMMD, someone posted something about a new hot-end on the Rep-Rap forums.  It looked interesting, and I've started seeing problems with the E3D V6 that was on UMMD, so I decided to check it out.

I ordered an XCR3D hot-end via Ali-express for a whopping $16 shipped and installed it in UMMD and found a few interesting things.

XCR3D Hot-End mounted on the Titan extruder in UMMD.  The heater block started out the same black color as the heatsink.

First, the Good:


It fits tightly into the Titan extruder, much tighter than the E3D V6 did, so it's very secure, no wobble, and no unwanted rotation caused by the heater cartridge wires pulling on it.  It doesn't feel over-sized - it feels like it fits properly.

The fan is absolutely silent- I put my ear within a few cm of it and couldn't hear it running.  We'll see if it lasts...

The fan bracket is metal and screws securely to the heatsink.  No more melted plastic, no more rotating fan.

The stainless steel heat-break is a bit more robust than the E3D part and the Teflon tubing doesn't go as deep into it.

The heatsink end of the heat-break is not threaded- it is held into the heatsink using set screws.  I like that!  I've had the heat-break come loose in the E3D V6 a few times.  Also, if you were setting up a multiple extruder machine, having the heat-breaks held in with set screws would allow you to set the nozzles at exactly the same height.  It also means you can take a jammed heat-break/nozzle assembly out without having to take apart the whole extruder- two thumbs way up!  It also means you can swap in a different heat-break/nozzle assembly without taking the extruder apart.

It comes with a 50 W heater cartridge that heats up quickly- it gets to 240°C in 60 seconds!

It has options for temperature sensors- I got the cartridge thermistor and it seems to be a direct and accurate replacement for the E3D part.

The heater block, heatsink, and fan bracket all have a black coating (anodized?) that looks nice.

You can order the kit with 1 m or 2 m long leads.  I just cut them off and put connectors on to fit UMMD's extruder carriage cable.

The brass 0.4 mm nozzle that comes on the unit appears to be well machined.

It comes with some little, stiff wire tools to clear a jammed nozzle.  I have not tried to use them.

There is a standard lock ring to hold the tubing into the hot-end for Bowden set-up, and inside the heatsink there's a phosphor-bronze (?) part with fingers that are angled downward.  You can slide in the Teflon tube and the fingers grab it and won't let it slide upward.

Now the Less Good:


The black coating on the heater block quickly burns and turns brown.  It doesn't seem to affect operation, just appearance.

The overall length is a few mm longer than the E3DV6 so you lose a little of your Z axis print capacity.  It is actually about the same length as a V6 with a volcano heater block.

The heater and temperature sensor cartridges are held into the heater block with set screws.  E3D's split block and clamp design holds the cartridges without crushing them.  You can always change the heater block.  One concern is that the set screws will fill up with plastic and I won't be able to get a wrench into them if I need to replace either of the cartridges.  We'll see...

Even though photos on the manufacturer's page at Ali-Express show Teflon tubing, none is supplied with the hot-end.  For direct extrusion you need 65-75 mm of tubing (I didn't measure it).  For Bowden you need whatever length your printer needs.

Installation:


It was pretty easy.

I took the heat-break and nozzle out of the heater block, applied anti-seize compound to their threads, and screwed them back into the heater block.

I put a little thermal compound on the heat-break and slid it into the heatsink and tightened the set screws.

Next I pried the black plastic Bowden tube lock ring out of the top of the heatsink,  pushed a piece of Teflon tubing into the heatsink until it stopped at the bottom of the heat-break, then cut it so there were 16 mm of tubing standing above the top of the heatsink.  That extra tubing fits up inside the Titan extruder's guide piece.

I applied anti-seize compound to the heater and thermistor cartridges and their set screws and mounted them in the heater block.

I cut the cables to appropriate lengths and installed connectors to mate with the extruder carriage cable.

I heated it up to print temperature and tightened the extruder nozzle against the heat-break with two wrenches, one on the heater block and one on the nozzle, then let it all cool back to room temperature.

Finally I ran a PID auto-tune on the hot-end and updated the firmware configuration with the constants returned by the controller.  When I heat it up to print it overshoots the set temperature by about 5°C then quickly settles to the set temperature and doesn't move after that.  It gets to 240°C in 60 seconds flat.

Printing:


I have printed both ABS and PLA with it and it seems to work fine.  At some point I may try the volcano hot-end again.


6 comments:

  1. Any particular reason why this hotend?

    Wondering if in future, for faster printing, we are going to want more controlled airflow near the nozzle. The large rectangular block at the end of the hotend is a problem.

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    1. This hot-end had some features that made it look better than the V6- the fan mounting bracket, the larger diameter heat-break tube, and the set screws holding the heat break in the heatsink. The price was right, too.

      For now I can live with the heater block as it is. There are other configurations that might be neater and allow better print cooling air flow.

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  2. Both of mine came with the teflon tubing as shown on the purchase site. Haven't unwound it yet to see if it's any good; they just showed up.

    I got two for dual extrusion capability, and part of the reason I went with this particular unit was the use of the set screw to set the height.

    I would prefer the slot for the heater cartridge and having the thermistor cartridge opposite the heater cartridge of the original, but at least the set screws in these blocks are oriented to push the cartridges against the filament melt path. I plan to wrap the block in kapton tape which should keep the set screw socket clean.

    The change in color is normal; color anodizing aluminum is done with organic dyes which denature when heated regardless of the color. This is not related to the pretty colors from anodizing some other metals like titanium, which are essentially iridescence. It would have looked nicer if they hadn't color-anodized it, just plain anodized; they must have gotten a deal on black anodizing and cheaper to throw all the parts in the bin than sort them out, I suppose.

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  3. I don't know if the adhesive on Kapton tape can tolerate the hot-end temperature.

    I've been using this hot-end since May and it's still working fine. The fan makes a bit of noise and vibration now- I don't think it was able to handle 50C in the enclosure. I haven't had any filament jams and it just keeps going. The nozzle seems to be pretty well made, too.

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  4. I have typically wrapped my heater blocks in kapton tape and it hasn't come off yet. I wrap the ends around the wires going into the heater block so the adhesive doesn't have to hold strongly to stay in place. I have mostly printed PLA and PET variants so not quite as hot as printing ABS, but I doubt it matters since I originally got the kapton tape as temporary solder mask and it never failed while soldering at the edge. ☺

    I couldn't get the lock ring out of the top easily. I was hoping I could experiment with bowden vs. direct by going back and forth, but I'm guessing that prying it out destroyed it when you did it?

    I haven't tested with them yet because I'm waiting for other bits for putting together the printer they will go on...

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    Replies
    1. I didn't have much trouble getting the lock ring out. I have since redesigned the extruder carriage and moved the motor above the bearing block with a short 75mm Bowden tube to the hot-end. That allowed me to center the extruder nozzle which in turn allowed me to shift the bed assembly mid way between the Z axis guide rails.

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Leave comments or a questions here and I'll try to post a response as soon as I can, if I can figure out how to get it working...