How to configure Delta with 4 arms?

[o_lampe]

The guy in the video already said, that three arms would not allow the fourth arm to move in a wrong way. We have seen closed loop steppers, but they only control their own moves AFAIK. Reading in the encoder signals of four motors is sheer overload for the common RRF controller.
You would need servo motors instead of steppers. I'm wondering how good RRF is at controlling them?
And an overall closed loop printer would be a complete new story for RRF(5.0?)

Why not build a cartesian printer that big? Much easier to implement closed loop IMHO...

[dc42]

@kcmarine if you can overcome the build precision and calibration issues, then RRF already supports that kinematics. The delta support was expanded to support up to 6 towers a long time ago.

[KCMARINE]

@dc42 Thanks for all your input, do you know of any delta projects like this with more than 3 arms, I have searched the web and cannot find any examples in RRF. @o_lampe mentioned reading the encoder signals from four motors is sheer overload for a common RRF controller. If this is correct then am I understanding it is beyond the capabilities of the Duet 6HC - would that be correct statement? If so what direction should I redirect my focus - @zapta thanks for the links - I will dig deeper and get my head around how to implement this into the config - Cheers for your help guys

[dc42]

@kcmarine if you want to use motors with encoders for closed loop control then you will need to use either Duet 3 EXP1HCL boards to drive them (in which case a Duet 3 Mini main board should suffice), or external closed loop drivers and a Duet 3 MB6XD main board. Standard controller boards do not support encoders on stepper motors.

[zapta]

@o_lampe said in How to configure Delta with 4 arms?:

The guy in the video already said, that three arms would not allow the fourth arm to move in a wrong way.

What does this mean, that in case of misalignment, one or motor will skip steps? How does that work with close loop servo?

I would think that in case of a misalignment, something needs to give, e.g. slip, deform, or break.

[zapta]

@dc42 said in How to configure Delta with 4 arms?:

The delta support was expanded to support up to 6 towers a long time ago.

With a sufficient number of towers (5?), is it ok to have just one rod per tower instead of two?

[dc42]

@zapta said in How to configure Delta with 4 arms?:

@dc42 said in How to configure Delta with 4 arms?:

The delta support was expanded to support up to 6 towers a long time ago.

With a sufficient number of towers (5?), is it ok to have just one rod per tower instead of two?

With 6 towers you could have one rod per tower.

[KCMARINE]

@zapta I am assuming that this is what he refers to in the video as error checking, by having four arms, - if an issue like this would occur then the machine stops and throws an error to the operator - could be something like sensorless homing I am just guessing now ??

[KCMARINE]

@dc42 I have read all the docs on https://www.klipper3d.org/Kinematics.html referring to the kinamatics and I am failing to see where to make the changes in config files - can you point me in the right direction, please - I have 2 FLSun SR and going to give this a crack

[zapta]

Does this help?

"RRF 2.03 and later allow you to configure more than 3 towers (maximum 6 in total) on a delta machine. Typically, additional towers are used to carry extruders, allowing the Bowden tube to be shortened."

https://docs.duet3d.com/User_manual/Machine_configuration/Configuration_linear_delta

[KCMARINE]

@zapta Thanks,

Yes agreed we are on the right track - this config is adding a 4th tower to carry a flying extruder which is an excellent feature.

Further to this investigation, we would like to figure out what commands are required in the config file to combine the (4th Tower and Arm) - to the - (End Effector with the Hotend)

@dc42 can you share any thoughts on the direction of this investigation please would be greatly appreciated. Cheers

[o_lampe]

@kcmarine @zapta
You don't want to add another tower, but the angles of the three delta towers are also different: 90° instead of 120°.
How do you setup for this?

[KCMARINE]

@o_lampe @dc42 @fcwilt @zapta

This is an amazing video showing the operation.

https://www.facebook.com/StudioKiteAustralia/videos/2610252689056738

Great work by them and I can only hope to work towards something like this for RRF

Let me know what you guys think?

[dc42]

@kcmarine set up for 4 towers as if you were adding a powered flying extruder as described.in the documentation. In the M665 command use the XYZ parameters to specify that the first 3 towers are at intervals of 90deg instead of 120deg. Then use the M669 X and Y parameters to specify the position of the 4th tower.