Aditional Carterian Z axis on delta printer

sga

Hello all,

This is a follow up of an old request I think:
https://forum.duet3d.com/topic/424/delta-tool-support-axis
Sorry to come back after so long time with this issue, but I understood at the time that you were about to rewrite the firmware to make this possible/easier.
My goal is currently to turn my 3d printer into a 3d clay/paste extruder.
The problem is that the clay is pretty heavy, too heavy to be mounted as in a flying extruder on the 3 delta axis.
As you say hinted homming is an issue.
My current idea would be to attach the container with a fastconnector after homing and offsetting the effector down by a couple of centimeters.
And to reply to tony, the tube between extruder and clay will be 3/4 of an inch so pretty stiff.

My first idea (might be a bad one) was to have the clay hanging and thus could follow the x-y movement a bit. Tube would act as a leash.
The printer is pretty high so I think it could follow.
Also adding an elastic element could potentially address the constant lenght issue if tuned well and still prevent the "whole" weight to be on the effector.
Essencially to start experimenting though I would need at least a Z motor to follow the Z of the delta.

Thank you in advance.

p.s. Sorry I realise this might not be the right forum category, I posted here because I just read 2 articles on similar subjects.

dc42

Modifying the firmware to support this would be a lot easier now because the support for different kinematics has been rewritten. There is a brief overview of how to do it at https://github.com/dc42/RepRapFirmware/blob/dev/AddingNewKinematics.md. To support an extra Z axis on a delta, the easiest approach would be to derive the new kinematics class from LinearDeltaKinematics and override the CartesianToMotorSteps function.

sga

Dear Dc42,

Well, I guess after reading through the link I am a still a bit confused.
But I will start exploring and hopefully things will clear up if I dig in the code.
According to step 1. I shall first ask you for a kinematic type number after having suggested a name:

LinearDeltaWithExtraCartZ.

And then implement what you suggested for step2.

Cheers,

dc42

I have allocated you kinematics type number 9 with enumeration name linearDeltaPlusZ.

sga

@dc42 Thanks