Got ABS? You need a MakerGear 50 cal. Nozzle and Longer Barrel!

[calinb 11]

Some time ago, Joergen suggested that I try a larger nozzle. I finally got around to it and I'm very happy! My best ABS setup to date has been a "V1/V2 hybrid" (V1 setup with the V2 Teflon anti-jam coupling/tube). The V2 exhibited a few more problems related to poor flow and layer bonding than my hybrid when printing ABS. I also made a 20 mm long V2-compatible tube out of stainless steel and it was even worse than the V2 brass tube. For SS, I will will need a lot more length, which I'm planning to implement someday by extending a SS tube to the top of the extruder head wood box but it will involve a complete redesign of all the plumbing and associated hardware from the Bowden tube down. It will not use a PEEK and it will feature an aluminum mount to replace the PEEK and act as a heatsink that alsol conducts heat to the aluminum plate. There's no reason not to use that big plate that UM provided to to more than just hold the hot end up! I'll tap some airflow from the fan to cool the aluminum plate and custom holder / heatsink too with a custom fan shroud too.

 

For now, I installed a Maker Gear BigHead 0.50 mm nozzle and 36 mm MakerGear brass "barrel," which offers considerably more brass mass and length then the UM design. While I was at it, I made a few mods that resulted in a total loss of only 3 mm in Z travel, compared to the UM V1 or V2 hotend. My changes also make maintenance easier and reduce the likelihood of plastic leakage. I didn't shorten my PEEK, as I've often considered doing, but I installed a custom aluminum locking nut/spacing shoulder under the peek, which also acts like the shoulder on the V2 brass tube. I have 1mm of space between the Al heater block and my 2 mm thick custom Al locking nut, which is enough to eliminate heat conduction from the aluminum heater block to the PEEK. I made a micro boring bar and turned a 2 mm deep internal recess in the end of the V2 Teflon part to accept the standard turned down end of the MakerGear brass barrel. The Teflon is a nice tight fit, sandwiched between the brass barrel and the wall of the PEEK. Molten plastic will have a hard time getting past two ninety degree turns and the 2 mm of tight fitting overlap. So far I have no leakage there or inside the aluminum heater block bore, because the brass barrel goes all the way though the block--like the V1, but the MakerGear barrels are turned down on both ends, which really seems to help them seal well at both ends.

 

 

 

Hopefully these photos will last longer than the dozens of photos I posted to the old forum that were lost. :(

Assembly is only 3 mm longer than stock

 

Note that turned down end of MakerGear brass barrel extends 2 mm more upward than standard UM brass tube when positioned correctly. (Trial fit with Teflon piece and calipers before locking aluminum lock nut.)

 

Teflon tube hot end bored on hobby lathe with custom micro boring bar to fit turned-down end of MakerGear barrel. A numbered drill bit will get you close, but will not produce as close of a fit nor will it produce a matching squared internal corner in the Teflon part.

 

2 mm long turned down shoulder on MakerGear barrel fits perfectly in bore of Teflon tube.

 

I think this is a much better setup for ABS than the original UM nozzle. Now that I have the extrusion calibration (extrusion multiplier or "flow tweak") dialed-into netfabb very well, I can even print 0.40 wide perimeter lines on 0.080 layers at 40 mm/sec travel, which is the narrowest width I ever used with the 0.40 mm nozzle. I'm sure a good 0.40 mm nozzle can extrude even thinner but that's plenty good and works out to less than 4 mm / sec filament extrusion rate. On the top end, I had no trouble extruding close to 30 mm/sec fill (~90 rpm), which was giving me problems before.

 

-Cal

 

[joergen 2]

hi cal,

thanks so much for documenting this... this is also my current setup, since I had problems with the V2 0.4mm nozzle and ABS... the difference of Cal's setup to mine is I have shortened my PEEK by about 2mm, and instead of a flat alu counter nut, I am using a 20x25mm alu cooling piece (I think it was used for a mosfet or transistor before, kind of a butterfly style) under the PEEK for even more cooling of the upper end of the tube, in addition to aggressive silicone foam insulation around the alu heater block (front, sides and bottom, no foam on the back and top)

 

[calinb 11]

hi cal,

thanks so much for documenting this...

 

Sure--thanks to you for suggesting it, Joergen! It's like having a new A-B-asS-kicking machine! The difference is incredible. I've had no more extrusion "stickiness" developing with the resulting slowdowns and under-extrusion, plus I get better first layer line (wider) adhesion to bare warm glass and lower extrusion temperatures for the same end results.

For now, I'm just wrapping the heater block and top part of the nozzle with fiberglass bid tape (a bare, non-sticky-backed fiberglass weave cloth used in fiberglass resin fabrication). After wrapping as much as I can reasonably fit around the hot end (while trying to keep the aluminum nut and PEEK uncovered) I just hold it with a square knot at the end. Eventually I will design a new molded or machined insulator to fit over the aluminum block from above in my full box length stainless barrel design, but this is working so well, I probably won't be motivated to do so for awhile. This setup will probably print Taulman 618 nylon just fine and only the high temps required by polycarbonate or other high temp materials will likely motivate me to continue further development.

>I am using a 20x25mm alu cooling piece (I think it was used for a mosfet or

>transistor before, kind of a butterfly style) under the PEEK for even more

>cooling of the upper end of the tube,

I'll add that I thought about using something providing more cooling, but I wanted to limit the diameter of my aluminum locking nut to 14 mm so it could remain attached to the barrel/PEEK assembly during removal through the 14 mm hole in the aluminum plate, thus retaining its barrel position indexing. I also wanted to keep it thin to retain as much Z-height as possible (yeah--I know...I'll probably never use it all anyway). Despite having flats for a 10 mm wrench, the aluminum nut is only thick enough for two internal threads so it cannot be tightened super tight, but it does the job when tightened moderately and my aluminum heater block is nice and clean inside (and there's no source of leaks inside the aluminum block bore so it will remain clean). If the barrel became stuck in the aluminum block and posed significant resistance to removal, it would be necessary to use heat during disassembly to keep the moderately tight lock nut from turning and losing index (or maybe stripping). Once the aluminum nut is indexed and locked correctly, there is really no reason to every disassemble it unless something becomes damaged (like overheating the PEEK).