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Single Arm Scara

Posted by vitaminrad 
Single Arm Scara
February 26, 2015 10:00AM

I've been working on a SCARA arm prototype and reworking the kinematics in Marlin firmware to support it.

At the moment I've got a working build of Marlin and most of the forward / inverse kinematics solved - there are issues with my design that necessitate a re-design in respect to using physical end-stops. I'm looking to use Hall Effect sensors in place of mechanical switches.

Calibration should be relatively simple. Firmware expects initial cartesian coordinates relating to endstop positions, so that it may deduce the initial angles. From there, cartesian X / Y coordinates are translated into the proper angle rotations for each joint (of which there are only two.)

The additions of the Morgan kinematics added to Marlin by Quentin Harley where instrumental in allowing me to see how best to go about modifying the translations. The Morgan kinematics are very similar to a Delta / Rostock configuration. The kinematics for a single arm are very similar to the Morgan transformations.

I have a lot to learn, and still a lot to sort out. If anyone has questions or is interested in using the firmware I'd love feedback.

Here's a video I made for a friend showing some of the first moves:

SCARA Single Arm Kinematics Test YouTube Video

Here are a couple renderings of the build in it's current state:

Re: Single Arm Scara
February 26, 2015 04:34PM
I'd also like to say I've gotten a lot of feedback from Nicholas Seward. I haven't implemented much of what he's suggested yet, but will soon.

Edited 1 time(s). Last edit at 02/26/2015 06:32PM by vitaminrad.
Re: Single Arm Scara
February 26, 2015 05:32PM
That machine is great! I would love to see the firmware

Re: Single Arm Scara
February 26, 2015 09:18PM
Thank you.

(Marlin for SCARA Arm)

Edited 1 time(s). Last edit at 02/26/2015 09:19PM by vitaminrad.
Re: Single Arm Scara
March 04, 2015 12:47PM
Hi there,

great machine! Thanks so much for showing and sharing the firmware!!!
What are the specs of it (arm lengths, bearings, steppers, µ-stepping,...) ??

Could you please also tell us which Marlin files you have modified ?
Just in case somebody wants to implement a slightly different geometry .... cool smiley

I´m completely lost when looking into Marlin for finding the Morgan implementation...mainly because there are so many files whose function I do not understand.

Best regards
Re: Single Arm Scara
March 04, 2015 08:11PM
Hey Mike,

Thanks for the kind words and your interest.

I'm re-designing the arm to be much more flexible in terms of calibration and reach. I'll post an update if you are interested. Not complaining, but I've been in a really dark space lately and haven't felt like communicating much. I'll try and post some new shots soon.

I tried printing something the other day and it worked pretty darn amazing without being calibrated at all. You can barely hear it move. The motors I'm using are Sanyo something or other with 400 steps per revolution and a Printrboard limited to 16x micro stepping. I'm using a belt reduction to drive the arms but I can't recall the ratio right now. Sorry I'm being so vague. I'll respond soon. I wanted to say thanks for asking though.
Re: Single Arm Scara
March 05, 2015 12:58AM
... my experience with scara style mechanics shows, that a serial scara lacks of stability and resolution, while a parallel scara is much more rigid and superior in accuracy across the complete building area ... and much simpler to assemble too winking smiley

Re: Single Arm Scara
April 03, 2015 10:04AM
Any news on this one ?

Is it correct, that you only modified "Marlin_main.cpp" beginning in row 4343 to fit your single arm geometry?
Is there another file needed to be modified?

Edited 1 time(s). Last edit at 04/03/2015 10:40AM by theothermike.
Re: Single Arm Scara
October 21, 2016 10:04AM
Hi there,

I am trying to make single arm scara 3d printer too.
Is this firmware working?

Re: Single Arm Scara
March 07, 2017 02:35AM
Hi vitaminrad,

I'm working on the same configuration of scara arm as yours. I've make my firmware run based on repetier firmware & make easy calibration route. You can download the firmware here www.wangsamas.com
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