VDE "Schnekenstruder" goes for a spin

Finally all together. Marlin 2.0.9.3, platinum PT1000 hot end sensor with linearized OPA388 amplifier, modified mother board, pure silver heat block, DIY tri-metal heat break (titanium at hot end, OFHC copper at the heat sink end, 12.5 gauge 316SS hypodermic tubing through), Diamondback 0.4mm diamond nozzle, and of course, the VDE Schnekenstruder.

Steps per millimeter tuned to 2360, but didn't change anything else. Retractions seem fine, and printing a 25.4mm test cube as I type.

I need to clean up the wiring, and make a new part cooling duct. This assembly is 4.5mm shorter than the original, so the cooling ducts were too big.

I also need to make a more elegant drive motor attachment for the Schnekenstruder, but that's trivial.

EDIT: Printed another heat sink adapter that is 2mm shorter, and also started getting intermittents on the extruder motor connector. So I clipped off the connectors and soldered the wires directly together. I've also decided that a screw mounted anti-torque roller is the simplest solution, so printed one of those, too. Clips, magnets, etc, are just too much of a pain. The Schnekenstruder works frighteningly well, but there is a small learning curve, especially for unloading filament. After doing several filament changes, I believe I need to reduce the retractions to something on the order of 0.5mm. Otherwise it's damn near impossible to do a cold pull. I attribute this to the tri-metal heatbreak.

Edited 2 time(s). Last edit at 01/28/2022 06:08PM by rq3.

Well, this is unexpected. It turns out that the "anti-torque" mechanism for the filament is not needed. At least with PLA. The filament melting in the hot end is sufficient.

Edited 1 time(s). Last edit at 01/31/2022 12:36PM by rq3.

Quote
rq3
Well, this is unexpected. It turns out that the "anti-torque" mechanism for the filament is not needed. At least with PLA. The filament melting in the hot end is sufficient.

Since I can't edit, I'll commit the sin of quoting myself. PETG doesn't need any anti-torque mechanism either. And I've ordered a NEMA 11 pancake stepper that weighs only 28 grams, which should bring the all-up weight of the entire extruder and hot end to about 70 grams. Calculations indicate that this motor should work, barely, but it will be interesting to see.

... there are even NEMA8 steppers - maybe with 1:3 gearing or something else?

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Quote
VDX
... there are even NEMA8 steppers - maybe with 1:3 gearing or something else?

I've looked at NEMA 8 steppers, BLDC, brushed printed pancakes, even pneumatic and hydraulic motors. Once you get into gearing the weight gain is a no-go for any motor. It looks like the NEMA 11 is kind of the minimum weight "sweet spot", given other constraints like shaft diameter, torque, speed, etc.

The NEMA 17 I'm using weighs 70 grams. The NEMA 11 on order weighs 28 grams. It will be interesting, and requires only a shaft adapter and a NEMA 17 to 11 adapter plate (aluminum, printed, carbon fiber). An easy days work.

Edited 1 time(s). Last edit at 02/04/2022 09:10PM by rq3.