Articulated Arm Machinery

Guys

Following on from blog posts by Brian Koresedal [builders.reprap.org]

And a suggestion by Jonathon to look into SCARA articulated arms.

I felt it worth sparking up a discussion on articulated arms in general.

Personally I like Brian's idea and direction of exploration but can see the benefits of the SCARA model in ensuring that the Z axis is always vertical with respect to the work bed/plane.

I was left wondering if there was some way to combine the two. IE the simplicity, low component count and versatility of Brians design with the inherently constrained Z of the SCARA.

It took a while but the answer was staring me in the face on my work bench.

I have a spring counter balanced angle poise lamp that where ever you position it the lamp/head is always in the orientation you last put it.

The lamp has two struts per arm section that are linked by a fixed bracket. The two struts and the bracket at each end form a parallelogram. This makes sure that whatever the angle of the struts are moved to the end links move acordingly but stay parallel also.

This technique could be used to make an arm like brians that keeps the extruder on the end vertical with respect to the bed and work-piece no matter where you move it and without needing to perform tricky kinematics to achieve it.

Thoughts for what they are worth.

aka47

Edited 1 time(s). Last edit at 10/07/2009 07:03AM by aka47.

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Necessity hopefully becomes the absentee parent of successfully invented children.

... go through the links in this thread: [forums.reprap.org] - the link to the high-accuracy parallel-scara-concept in the harmonic-drive-paper in the last post is gone, but i should have the file somewhere in my backups ...

Viktor

Viktor

Thanks for that but the hypertext link doesn't seem to have worked. I would like to see it though and the paper too.

Cheers

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.