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BadMouth:

--- Quote from: RandyT on June 03, 2022, 12:44:43 pm ---Very nice!   But man, those extruder swaps definitely need to be moving in tandem.  I would think that two motors on the same axis, with the same feed rate and direction with differing destination points, should never result in a conflict.  Or is this just a safe test?

--- End quote ---
Hmmm.... It's just the order of operations in the tool swap macro which I copied and pasted from the Klipper documentation.  The only other Klipper based IDEX system I saw behaves the same way.

What you say makes sense. I will see if I can get them moving simultaneously.  If nothing else, I can crank the travel speed.

BadMouth:

--- Quote from: BadMouth on June 03, 2022, 04:41:58 pm ---
--- Quote from: RandyT on June 03, 2022, 12:44:43 pm ---Very nice!   But man, those extruder swaps definitely need to be moving in tandem.  I would think that two motors on the same axis, with the same feed rate and direction with differing destination points, should never result in a conflict.  Or is this just a safe test?

--- End quote ---
Hmmm.... It's just the order of operations in the tool swap macro which I copied and pasted from the Klipper documentation.  The only other Klipper based IDEX system I saw behaves the same way.

What you say makes sense. I will see if I can get them moving simultaneously.  If nothing else, I can crank the travel speed.

--- End quote ---

Not only was I not able to get both carriages moving at the same time, the switch got even slower once I attempted to print larger objects.
To prevent oozing, Cura drops the hotend temperature of the inactive toolhead to whatever holding temperature is specified in filament properties.
The next time the toolhead is called up, it doesn't move until it comes back up to filament melting temperature.
Easy enough to tweak the holding temperature, but it is one of many things I did not see coming.
Eventually I plan to have some type of plate over the nozzle while it is parked.

Printing seemed to work fine in my short test last week, but now I keep getting layer shifts.  All the belts are tight, but at some point in the print where the toolhead is performing extremely harsh and quick movements, I can hear belts jump teeth and the layer shifts diagonally.  Everything seems tight.  The Y drive motors don't have a flat spot for the pulley's grub screw, but if that were slipping I don't think the belt would make noise.  It's a similar sound to when one of the motors is backwards and fighting the others.  If I slow the print down to 30mm/s with 60mm/s infill, it doesn't happen.  Everything keeps getting slower.  :(  I am going to grind flats on the Y drives and look for mechanical causes.  I will also also swap the drivers around.  Already tried cranking up the current and it made no difference.

The one thing that has worked out well is using HIPS filament as support material.  ABS and ASA hardly stick to it.  It holds well enough to stay in place, but peels right off when pulled.
I wasn't looking forward to buying expensive solvent to dissolve it.  It turns out that solvent will only be necessary in cases where there are internal supports that can't be reached.

RandyT:
I get the feeling that a gcode post-processor is in your future.  Filament drool is always going to be an issue with a dual hot-end setup, which means cool-downs, heat-ups, primes and maybe even nozzle wipes.  All of which introduce slow-downs. The X1 Carbon (coming soon) actually swaps filaments on the fly, with purging and wiping steps between.  It's a very fast Core X-Y printer, so the swaps tend to be absorbed somewhat into the overall print time, but at the cost of wasted material.  I'd suspect that leaving the hot-ends up to temp, with a short purge/prime and wiping blade might be the best bet for swaps.  If the gcode interpreter sees the extruder assembly motion as X1 and X2, one would think that substituting something like G0 F<feedrate> X1<park position> X2<print position> would get them moving in tandem.  The PP would need to be able to identify a swap, and set the positions accordingly, depending on which head was doing the printing. 

The bright side of this is that the world would be your oyster once you had a framework for doing this, as any custom actions (wiping, priming, etc.) could be wedged into the same space.

As for your other issue, be careful of stepper motor resonance.  Not saying that this is your issue, but if you are operating in the resonance band for the motors, it could cause problems.  Decreasing or even increasing the speeds could help in this case.  Honestly though, it sort of sounds like an acceleration/jerk problem.  Unfortunately, if that's what's going on, the only way other than reducing the overall speed of the movements is to reduce the weight and/or stiffen some of your components.  While I like the idea of these massive, heavy duty machines, I think they start to get so large and heavy that some of the pitfalls of CNC routers start to appear on them.

BadMouth:
I followed a couple people trying to use filament swaps for dissolvable supports, but they claimed that the parts turned out weak due to contamination from the support material no matter how much they purged.
They were engineers so I assume then knew what they were talking about, which is why I went down the IDEX path.
The Qidi iFast looks to have what I want, but I can't spend that much on another printer after building the Vorons.

I ground flats on the Y motors and added a shim behind where the belts are attached to make them tighter.
Just did a test print and had a shift and a shift back!  :lol

I think it is something to do with the Y motors.  It just dawned on me that both are running off the same driver, so they may be starving for power.
That and they are unknown scrap motors pulled out of an original monoprice mini select.
I upped the vref voltage to what the driver board can handle and am giving it another go.

If that doesn't work, I'll put them on separate drivers.

RandyT:

--- Quote from: BadMouth on June 09, 2022, 01:24:45 pm ---I followed a couple people trying to use filament swaps for dissolvable supports, but they claimed that the parts turned out weak due to contamination from the support material no matter how much they purged.
They were engineers so I assume then knew what they were talking about, which is why I went down the IDEX path.

--- End quote ---

This is where a wiper comes in (guessing they didn't add one).  A thin piece of silicone at the edge of the print volume and over which the nozzle must pass would go a long way to counteract drool contamination.


--- Quote ---I think it is something to do with the Y motors.  It just dawned on me that both are running off the same driver, so they may be starving for power.

--- End quote ---

Believe it or not, that makes resonance even more likely the culprit.  Even though it is done often on the Z-axis, it's considered bad practice to connect two motors to a single driver.  With small and seldom moves it can be gotten away with, but when the motors resonate they can fight each other as they will not be resonating in sync with one another.

Or it could be a power issue :)  Either way, giving each motor it's own driver would be a good step to take.

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