Delta robot photos

Yesterday I took some photos with the details.

Platform

Platform joints

Actuator and home sensor

Upper joints

LinuxCNC delta robot

I considered building a delta robot for a long time. It's well known, but I was interested how rotary actuators work and how fast the robot can actually move. The main problem is rotary actuators stiff enough with high torque.
Recently I had a chance to purchase a few small harmonic reducers size 14 with 50W Yaskawa servo motors for a decent price. The reducers have cross roller bearing incorporated, so I just needed to install the reducers to the plate and screw the robot arms to their output plates. Robot arms and parallelograms were made of light aluminium tubes. The joints consist of steel balls and aluminium sockets.
Delta robot control is definitely a job for LinuxCNC. I used MESA 7i43 and 7i48 boards to control Yaskawa SGDH-A5 servo drives in analog velocity mode. Tuning PID and servo drives setting is the most difficult part. It's hard to get oscillation-free positioning with high acceleration. S-curve acceleration would be extremely useful for delta robots, but LinuxCNC does not support it (yet, I hope).

More photos and videos coming.

Yet another video of hexapod (must be the last)

Video with hexapod parallel robot 6 axis rapid moves from summer 2011. Way faster than the first video, but still not enough. Could be faster with better PSU for DMM servos, or with more advanced and more powerful servos. By the way, DMM already has Dyn-3 servos more suitable for closed loop, pity that it's too late for the hexapod.

Done (or almost done) with this machine, I'll probably cut one more final complete video and that's all.
But new machines and robots coming soon.

Another video of hexapod

I just found a video of hexapod parallel robot milling wood 5 axis from summer 2011, with improved velocity and acceleration. It should be MESA 7i43 that increased the step rate. And LinuxCNC is much more stable with hardware stepper than software.

The acceleration must be near 10m/s2, max velocity 10-12m/min.

Update: config files for 7i43 hexapod7i43.ini and hexapod7i43.hal.

LinuxCNC hexapod machine tool

As I promised, here's a bit more. Since EMC2 name has changed recently, now the machine becomes LinuxCNC hexapod.

The machine was assembled without ballscrews, servo drives connected to breakout boards and motors, and proved to rotate. Then the ballscrews were connected to the platform joints, and the nuts bolted to the actuators. Till the last moment there were doubts, that the platform would be rigid enough. But it proved rigid as planned! The very first moves were luckily captured on the video. Not much spectacular, but really exciting for me.

CNC touch probes review

Looking for a simple inexpensive touch probe for parts measuring and hexapod calibration, during last two months I became a kind of market expert in touch probes. So, here's a summary of my investigations.

There are many top-quality industrial probes with 1um and better precision, based on kinematic, optical or strain gauge technologies. The most popular industrial probes are Renishaw.