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  1. Mike's SCARA Robot

    Hi All,

    I don't post here often but thought some might enjoy the project I've been working on since the beginning of COVID. I am an engineer, amateur machinist, and robotics enthusiast. I was fortunate enough to happen across a '99 Seiko D-Tran TT8800 SCARA robot at an industrial surplus supply store. It did not have a controller or have any guarantee to not be broken, but at $200 I couldn't say no.

    Over the last year and a half, I've been researching about the robot, figuring out wiring, proprietary AC servo feedback, homing sensors, and building a custom controls system for the robot. Through work, I have access to some Allen Bradley PLC and servo drive equipment that I can mess around with for home projects.

    Click image for larger version. 

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    At 130 lbs and a 35" reach, this robot is one of the largest SCARA robots I've seen available. I don't yet have plans for it other than messing around, but it could become a tool changer for my CNC mill, or maybe a 3D printer.

    The most challenging part of this project has been developing a custom interface board to sit between the Yaskawa AC servo motors on the robot and my Allen Bradley servo drives. The motors use a Yaskawa proprietary protocol which they refer to as incremental "multiplexed" feedback forcing you to use Yaskawa drives. My custom PCB (based on clocked sequential logic in 74AC series CMOS chips) decodes their protocol and presents a standard incremental TTL with hall effect commutation feedback signal to the servo drives. I am very proud of this design as I was never taught digital logic and just figured it out as I went.

    Click image for larger version. 

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    I am fairly finished with the mechanical and electrical side of this project and I was working hard at developing an interface to the robot using G-Code through a totally custom designed interface programmed on an Allen Bradley PLC. There are certainly some G-Code programs out there that could do what I want, but the interface to the PLC allows for some very powerful implementations of kinematics and real-time control rather than just pre-programmed motion.

    The full project log can be found here:

    And here are a few videos of it running:

    I'm happy to answer any questions you have or share more photos and videos!

    Last edited by mcardoso; 08-12-2021 at 01:27 PM.

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