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printing small nylon features with a large delta?

Posted by shadowphile 
printing small nylon features with a large delta?
November 20, 2017 07:51PM
I've been playing with Taulman 910 Alloy and discovered that it still has too much water (makes steam puffs, snapping sounds, frothy or bubbly extrude) even after sitting in my drying bin for 24 hours. My bin is powered with a 75 watt heater and sits at about 90 deg F and 22% humidity. (if it was insulated I could probably drop that wattage lower to save electricity)
I have not discovered yet whether 24 hrs at 22% is just not long enough, or whether it needs to be baked at a higher temp. It's rather inconvenient to come home after work and bake my nylon in the stove for four hours!

It does print clear more often than not though so I played with the settings the last few days.
I'm trying to print some tiny (1.8 centimeters longest dimension) blower ducts that have some walls only two extrudes wide. They came out quite crappy. I get over-oozing at sharp corners where the nozzle direction changes 90 degrees, which is clear to see while printing. The same issue is probably to blame for all the other crappy results. If this indicates built up pressure that shoots out when the nozzles slows down for corners I'm not sure what to do. I use Slic3r but the Pressure Advance (which should be for just this occasion) is apparently not very finished and no development any more.

I have a 300mm print zone so about 800mm of bowden tubing. Also, nylon is not particularly stiff. I am thinking that maybe there is too much sponginess to compensate when trying to print 0.2 layers, 0.3 wide, at 20 mps. Right now I'm retracting 4 mm, printing at 255 C. Dropping the speed even lower might do the trick but only for very short jobs.

Thoughts, ideas, experience? Am I pushing the limits of performance with a large delta?
Re: printing small nylon features with a large delta?
November 21, 2017 02:55AM
Where's your extruder mounted? If it's on top, you can shorten the Bowden tube by placing it roughly mid height. ( and use a rotating extruder bracket )

90°F sounds pretty low? I can imagine 90°C would work much better ( 10° below boiling point of water ), but I haven't digged into filament drying theory before.
Re: printing small nylon features with a large delta?
November 21, 2017 04:58PM
The 90 deg F in my bin is very long-term storage of everything. PLA starts warping if I go much higher.
I did try drying the 910 filament for 4 hours last night at about 200 F (just below the glass-transition point).
At rare moments there might be a crackle but otherwise it flowed smoothly.
We will see how it performs after sitting back in my dryer/storage box for several days where it might reabsorb too much water again.

I"m still having lot of problems. I've gotten pretty good at dialing in PLA but nylon is thicker and harder to predict. Even a 10mm cube is difficult.

Oh..my cold extruder is half way up cocked at an angle. It is the shortest Bowden tube path I can find while minimizing sharp curvatures.

Edited 2 time(s). Last edit at 11/21/2017 05:48PM by shadowphile.
Re: printing small nylon features with a large delta?
November 24, 2017 03:07AM
By reading the headline again, I got a crazy idea: Why not built a smaller plugin delta inside the big delta?

Say, you have a big delta with dual shaft steppers and the bed is removable.
Wouldn't it be nice to use the rear stepper shaft to drive a smaller Delta with it? ( given, that the smaller Delta is more accurate than the big one )
You would have to remove the bed, plugin the bottom-less frame of the small delta ( with it's own rods, effector, bed, endstop and hotend ) and go on from there.
Both printers share the bottom frame with electronics and steppers. You just have to design some inner corners to plugin the small towers.

As I said, it's crazy, but fun to think about it winking smiley
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