Hybrid direct bowden, how to set up?

solo3d

Hello,
I'd like to use 2 different extruders, with 2 motors and 2 drivers and one hotend.
The point is to use a very small stepper, for the direct extruder and a larger one, for the bowden. The extruders have 3:1 and 4:1 ratio, so I will be using 2 drivers. I understand people questioning such an idea, but I have some reasons for that.
My question is, is there any simple solution, to map 2 motors to 1 tool, to work simultaneously.
Thank you.

alankilian

@solo3d See in the GCODE page:

zapta

@solo3d said in Hybrid direct bowden, how to set up?:

is there any simple solution, to map 2 motors to 1 tool, to work simultaneously

Do you plan to extrude with both of them simultaneously or sometimes with one and other times with the other?

solo3d

@zapta both always on.

o_lampe

@solo3d said in Hybrid direct bowden, how to set up?:

The point is to use a very small stepper, for the direct extruder and a larger one, for the bowden. The extruders have 3:1 and 4:1 ratio,

What is the mixing ratio between the two motors?
In mixing mode it can happen, that the stronger motor pushes molten filament up in the other path. They are actually fighting against each other. Both motors small wouldn't be enough torque?

solo3d

@o_lampe Don't think I made it clear. The dual extruder set up is to drive the single filament line. The purpose is, that the light motor used with the direct extruder is helped by the other extruder, at the other end of the bowden. Basically they are working as a single unit, just helping each other. The problem is, the extruders have the different ratiosand will require different steps per mm values, so I can't just connect the motors in series.

dragonn

@solo3d I am doing something like that and using mixing hotends but they is a big problem with that - it is almost impossible to setup the steps/per mm or mixing ration perfectly right.
I think the only solution would be that the bowden extruder uses rubber wheels some kind and pushes a litte bit faster then the direct extruder. When setup right it would just slip over the filament when they is no space to push it.

o_lampe

@solo3d said in Hybrid direct bowden, how to set up?:

The extruders have 3:1 and 4:1 ratio,
@solo3d said in Hybrid direct bowden, how to set up?:
The dual extruder set up is to drive the single filament line.

OK, understood.
What are the diameters of the drive wheels? Are they same or does it get really wicked with different diameters?

solo3d

@o_lampe both are mbg gears, one is belt driven 4:1, the other is the regular 3:1

o_lampe

@solo3d said in Hybrid direct bowden, how to set up?:

the other is the regular 3:1

If only it was 3:1, but AFAIK it's 50:17 (2.95:1) or 50:16 (3.125:1)

solo3d

Ok thanks. Sounds like it will be much easier to get another extruder, with the matching ratio.

MaxGyver

@solo3d

Hey, I have tried exactly what you are describing with some success. I have switched back to just using a single extruder because I had some printing artifacts and needed to make sure that this is not caused by the hybrid extruder setup.

So I have to recall my setup steps from memory here:

setup two separate extruder motors in your config.g with their respective driver assignments, voltages, acceleration, jerk and e-steps depending on the gear ratio of each extruder.
create your tool and tell it to use extruder drive 1 and 2

; tool 0 
M563 P0 D0:1 H1 F1 ; tool 0 uses extruder drive 1 and 2 , heater1 and fan1
M568 P0 R0 S0 ; Set active and standby temperatures

Set tool mix ratios to 100% so that both extruders are used.

M567 P0 E1.00:1.00 ; Set tool mix ratios of tool1 to 100% for extruder 1 and 2

-Max

zapta

@solo3d said in Hybrid direct bowden, how to set up?:

@zapta both always on.

For mixing, the resident expert is @deckingman.

His blog is here, may give you some ideas. Also on youtube with same username. https://somei3deas.wordpress.com/author/deckingman/

deckingman

@solo3d I saw my name mentioned so I'll jump in here. As I understand it, you want to use the extruders in a "push pull" arrangement yes? To be clear, your hot end has a single filament input and a single nozzle output yes? If those assumptions are correct, then the method that @MaxGyver posted above is correct.

That is to say, you define the steps per mm for each extruder which will take care of the fact that they have different gear ratios. You do this in one single M92 command using a colon separator. So for example, if the first extruder has 400 steps per mm and the second has 500 steps per mm then the command would be M92 E400:500.

From this point on, the first extruder will be D0 and the second extruder will be D1. So then you define the tool to use both extruders and the single heater i.e (assuming you want to use tool 0) M563 P0 D0:1 H1. Then you set the mixing ratio to use 100% of each extruder so M567 P0 E1.00:1.00.

solo3d

Thanks to all who responded!
All working now!