Dr D-Flo's big build

Phaedrux

my print head weighs > 30 lbs (13.6 kg), which is likely 10x heavier than Modix

This may be the case. The Modix head is quite heavy as it is but probably not 30lbs.

At the meter scale everything becomes harder!

o_lampe

I will have to use a thicker belt and tensioning will be a concern because those c-beams are likely to buckle.

The cross section of the C-beam isn't very stiff. I'm surprised you use V-rollers for such weight? The rollers can pry open the V-shaped extrusion. Especially, when the unused V-slots aren't closed. (I hope, I made myself clear)

How much airflow does the vibrator on the extruder generate? Another source of turbulence and temp-drop, messing up ABS prints?
Extending the exhaust of the turbine is an easy fix, I guess.

DrDFlo

@o_lampe

@o_lampe said in Dr D-Flo's big build:

The cross section of the C-beam isn't very stiff. I'm surprised you use V-rollers for such weight? The rollers can pry open the V-shaped extrusion. Especially, when the unused V-slots aren't closed. (I hope, I made myself clear)

Do you have an example of the plastic v-wheels changing the geometry of c-beam or similar 20x20 extrusion? I have not seen this before, but I would be curious to see how heavy the payload was.

I could move to a more rigid C-beam: https://makerstore.cc/product/us-lr-chv-s/

However, I have been quite happy with the V-wheel system. Not only is it cheaper, but it also allows me to introduce some play on the print head by loosening the eccentric spacer so that if the pellet head runs into a Z-seam or another protruding artifact that it will move up slightly and keep printing.

@o_lampe said in Dr D-Flo's big build:

How much airflow does the vibrator on the extruder generate? Another source of turbulence and temp-drop, messing up ABS prints?
Extending the exhaust of the turbine is an easy fix, I guess.

I have the exhaust plumbed so that it exhaust away from the print. It generates 1 CFM but is only on for 3 seconds.

oliof

@DrDFlo said in Dr D-Flo's big build:

Do you have an example of the plastic v-wheels changing the geometry of c-beam or similar 20x20 extrusion? I have not seen this before, but I would be curious to see how heavy the payload was.

I've seen completely messed up 2020 x gantries from ender style i3 clones where overzealous tightening of the eccentric nut deformed the v slot channel. I will see if I can recover photo evidence.

o_lampe

@oliof
That's what I meant. The more weight you have to move around, the more you preload the wheels.
@DrDFlo I'm glad you didn't follow that usual route.

I also had chinese V-slot extrusions, where the angle of the V didn't match the roller contour.

sotpurk

@DrDFlo @o_lampe
"I am upgrading to a 12 mm high-helix lead screw for faster travels at lower RPMs, but I am limited here by the c-beam aluminum extrusion profile"

Why not go with a rack and pinion setup?
I am coincidentally making a very similar printer with the same extruder.
The differences are as follows:

Integrated servos instead of steppers for X and Y (Stepperonline iSV-T motors)
Using chains and custom sprockets for Z.
Modded the MDPH2 with a RTD pt1000 as a failsafe for the terrible grounded thermocouple on the extruder (Probably going to replace that too )
the X and Y motors use a 1:5 Planetary gearbox and connect to 1.5 module pinions that travel on racks. There's no backlash, it's smooth and it's really fast.
It's bigger.

DrDFlo

@sotpurk Woah this is an epic build! Sorry for the late reply, but is there any update on your build?

sotpurk

@DrDFlo I got a bit occupied with another project so it still roughly looks the same, but I've changed the Y and X printed mounts to CNC ones and doing the same for Z.
It's producing decent prints now apart from the entire frame oscillating at heights (which is expected since I'm going to support it externally later on)

Because the gantry is rather heavy, It's a lot of wasted energy to level/mesh the bed so I came up with remapping an actuator that has an end-stop at one end as Z when probing. That way only the actuator moves instead of the entire gantry moving in Z; but the 6HC doesn't allow the motors to remain energized when changing assignments so I'm waiting for a 6xd board to be delivered where I can do this externally. (there's no reseller in my country so importing takes too much time) (https://forum.duet3d.com/topic/31694/keep-motors-energised-when-changing-assignment?_=1680794473398)

Also installing a vacuum loop from the extruder for feeding pellets (the momentary exposure to moisture in the air isn't a big deal since the primary storage is isolated and it's only fed when being printed so no long-term exposure.)

Swapping the current worm gears as well, I was under the impression that worm gears can't be back-driven but seems like that's only the case when certain conditions are met. So have ordered new gearboxes with higher ratios (will use the old ones on another build) but man, imports.

Ideally, the extruder doesn't need to move beyond 120mm/s to achieve its maximum output but I've tested the machine to reliably move at 800mm/s which was scary fast.

Here's my most recent print:

sotpurk

@DrDFlo Hey, could you possibly also share your config file and the speeds at which you print? It would help a ton
I'm having trouble with the extruder since the motor is heating up a lot even while extruding PLA at relatively low speeds so a reference config would help a lot.
Thanks