Beta testers for multiple motion system support

deckingman

@dc42 I don't know if my machine would fit your criteria but if you recal, the (6 input) hot end is on the XY gantry, and the 6 extruders run on the UV gantry. I currently use a python script to generate the UV moves such that the extruder gantry (UV) tracks the hot end (XY) but within a tollerance of +/-20mm so the UV moves are always shorter than the XY moves. It wouldn't be too difficult to slice the same part twice - once to generate the XY moves and then a scaled down version to generate the UV moves (although I'd likely have to run a python script to convert the G1 XY moves to G1 UV).
But if the goal is for the firmware to process two concurrent gcode streams, then I reckon I could test it.

kazolar

@dc42 my machine has 2 gantries with 2 independent heads on each. So as I called before a quad. 2 of the tools can be fully independent of each other, z is shared. If there is a way to synch z moves, this would be a cool project.

o_lampe

@dc42 I'd really like to be part of the test-team with my hashprinter. But it runs on @gloomyandy 's branch of RRF.
If he's part of the dev team or has access to your latest code (and is willing to colaborate) I'd love to test his branch.

A Duet3 setup with 11-12 stepper drivers is currently not affordable for me. (independent Z-axis would require 4 more steppers)
As a last straw I would sell the hashprinter (as-is) to someone in EU, who has the knowledge and funds to make it work.
PM me if you're interested...

JoergS5

@dc42 I will participate with two robot arms. Main focus will be collision detection and avoidance and I will help writing needed code.

gloomyandy

@o_lampe It looks like the code for this will be on the 3.5-dev repo. I will at some point be picking that code up and providing an STM32 version, so hopefully we will be able to contribute to the testing of this new feature. I usually try to track new developments reasonably closely so hopefully it will be possible to do that again.

oliof

@o_lampe I have an unused MB6HC and 3HC expansion board I can loan out to you. DM me for details.

o_lampe

@oliof That's very kind of you, but I'd need at least three 3HC boards or many other toolboards with 2 drivers per board. 15 drivers in total...

oliof

@o_lampe if one other kind soul finds they have a 6HC lying around you'd be set (-:

o_lampe

@oliof
Jepp, passing the hat is not my style. Unfortunately the shopping list would be alot longer (eg. hotends, direct drive extruders). That's why I proposed to sell my frame.
But it's over the top for a dual-motion system anyway. It would need 4 independent Z-axes and then it could work with two tools simultaneously. (then changing tools for perimeter and infill)
It's quite a challenge

oliof

@o_lampe you are not passing the hat if people propose giving, but I catch your drift. Unfortunately I have neither the funds nor the space for yet another machine, or I´d consider your offer.

breed

ive been working on this layout in the background while I finish other printers. should be what you are thinking correct?

o_lampe

@breed The critical thing about dual print heads and dual toolheads working simultaneously has always been the z-height. (mesh -leveling etc)
Idk if that's already in the scope of @dc42 project, but independent z-motion is the key for succesful multi tool systems.
Since you are still in the planning phase, you might consider adding an Z-adjustable toolholder. (I prefer dovetail sliders)

David, would you be so kind and tell us the options to drive the independent mini-z axes?
Geared DC-encoder motors would be small and strong, but they'd need a supporting toolboard.
Steppers would be huge and heavy. Remotely driven, it might be an option, if mesh leveling with backlash-compensation is available.

dc42

@o_lampe wouldn't a Nema 11 or Nema 8 stepper motor with leadscrews be suitable? Although the Nema 8 ones tend to be expensive. https://www.omc-stepperonline.com/linear-motor

breed

@o_lampe I haven't gotten near the point of adjustable z on one of the tool heads. I have 2 printers with makertech tilting hotend. They have grub screws for adjusting the heatbreaks, seems to work fine. I was hoping to get this one figured out and together by mrrf, but there are 4 other printers in the que in front of it. Maybe next year. Having automatic z adjustment would be awesome but the weight....I didn't want the common rail double x carriage because of carrying the second x carriage for all the y axis moves. I have an i3 style idex and basically never print mirror or duplicate mode. I def could see a path for simultaneous g code. Printing two different objects would be a useful time saver.

o_lampe

@dc42
It would work, but the weight penalty isn't worth the +/-1mm movement we need for Z-hop and mesh leveling.
Even a small hobby servo with excenter could do this, but their speed isn't controlable. That makes it difficult to move them in sync with XY motion.
So IMHO a dc motor with encoder would be the best option.
A mockup picture of a modified PTFE dovetail slider with dc motor/leadscrew

In a perfect world we'd have access to the heightmap(s)-data and route the z-correction to a device of our choice.

bot

What about shims to adjust hot end Z height? On my printer, I'm able to add shims to the top of the hot end to lower its nozzle's Z height.

dc42

Thanks for all who have responded. I may be able to provide a first build of RRF with dual motion system by this Friday. This version will have some limitations:

The two motion systems must share a common Z axis
Standalone mode only (not SBC mode)
Resume-after-power fail will not be supported
Simulation mode may not be supported
Pause/resume may not be fully implemented
There will be no attempt to predict collisions between the two print heads, so the GCode commands must avoid potential collisions
There will be no checking that commands for different motion systems don't attempt to drive the same axis simultaneously
No mesh bed compensation

It's time to think about preparing GCode files that case use both motion systems. There is some documentation at https://docs.duet3d.com/en/User_manual/RepRapFirmware/Multiple_motion_systems on how the different motion systems are addressed in GCode.

The simplest way to use the two motion systems is probably to load two objects on the build plate in your slicer and space them far enough apart so that they can be printed independently by your two motion systems without collisions. Then change the GCode file produced by the slicer so that the commands for one object are assigned to motion system 0 (by using the M596 P0 command before a block of commands for that motion system) and commands for motion system 1 are assigned to motion system 1 (using M596 P1 before a block of commands for that motion system).

You will need to add a M400 command to sync the motion systems before and after each G1 Z command that does a layer change. Obviously you cannot use Z hop on travel moves. Don't let the blocks of contiguous commands for one motion system get too long, or the other motion system might pause for a short while as it skips the block.

You will need to select one tool for each motion system at the start. One of those tools should map the X and Y axes to the corresponding axes of your second motion system, for example U and V.

In the future I hope we will be able to do the splitting of objects into multiple motion systems either in the slicer, or in a standard post-processing script.

o_lampe

@dc42
That'll be exciting to try!
You should also mention that mesh leveling must not be enabled.

I wonder, how a waiting tool behaves when layer times are way different? Will it go in parking position or just sit and wait for the other tool to finish the layer? Will it automatically retract/unretract?

o_lampe

@dc42 said in Beta testers for multiple motion system support:

There will be no checking that commands for different motion systems don't attempt to drive the same axis simultaneously

How do we address layer changes then? Isn't Z-axis a common axis of both systems? Do we need to define a third tool just for the z-axis and switch to that tool before layer change?
Putting M400 before a layer change will only wait for the other tool to empty the print queue, but it's not guaranteed to be finished with the layer...

dc42

@o_lampe said in Beta testers for multiple motion system support:

@dc42 said in Beta testers for multiple motion system support:

There will be no checking that commands for different motion systems don't attempt to drive the same axis simultaneously

How do we address layer changes then? Isn't Z-axis a common axis of both systems? Do we need to define a third tool just for the z-axis and switch to that tool before layer change?
Putting M400 before a layer change will only wait for the other tool to empty the print queue, but it's not guaranteed to be finished with the layer...

When multiple motion systems are in use, M400 causes them to synchronise at that point, i.e. no motion system proceeds past that M400 until all motion systems have finished executing it.

Only one motion system needs to move the Z axis to do the layer change. Another M400 command after that Z move will ensure that the other motion system waits for it to complete.

@o_lampe said in Beta testers for multiple motion system support:

I wonder, how a waiting tool behaves when layer times are way different? Will it go in parking position or just sit and wait for the other tool to finish the layer? Will it automatically retract/unretract?

Currently it will just sit there. In the future I will add an option to park waiting tools, probably by using an extra parameter on M400. Meanwhile you could call a parking macro just before the M400.