I am going to attempt to build a SCARA platform for testing various tool configurations. I will be using Arduinos, RAMPS 1.4, Kollmorgen N4MT ServoDisc DC motors for X & Y, Nema 17 steppers for Z & E (when testing 3d printing module). I am running Marlin FW for the Mega/RAMPS and some custom code for outboard Arduino Nanos used to feed H-bridges to replace Pololu drivers on X,Y axis'. Rotary encoders are from Robogaia, H-Bridges are dual LM-298 from OSEPP, custom motor mounts and gears to drive encoders are my first step so far. Feel free to chime in as you see fit, I know little to none about SCARA systems so far but I have some ideas and have done some research already on the design I want to achieve, all comments are welcome! Cheers!
Edited 2 time(s). Last edit at 05/17/2016 07:53PM by MarkBot. Just an Artist, Musician, Designer, Programmer, Maker
Hi! I am also interested on SCARA with servos and encoders, I am going to start the project in two weeks. This guy has posted his printer running on servos so you could use his code/experience [fightpc.blogspot.com.es] Most people running printed gears have had problem with backlash, I was thinking on using belts and printed gears on top of the arm, also the encoders will be on top of that gear to reduce backlash to (almost) zero. The structure will be similar to this one [www.thingiverse.com] but with some big improvements over tip dropping (in that design, tip drops around 3 mm)
Thanks for replying! These Kollmorgen motors are DC brushed motors, they are not servos (proper) with integrated controls. Although they do have built in tachometers that may prove to be useful at some point. The gears are designed from the same tooth pattern and the ratio is tall so backlash should be minimal. As far as tip drop goes, my aim of this design is to use the motor body itself as part of the arm length, so the linear flex will be minimal. The gears do not drive the arms just the encoder for shaft rotation measurement, the arms are direct drive off the motor shafts. These motors are so powerful and efficient, and they accelerate to full speed in less than 1 rpm under a load greater than the weight of the motor itself. Way overkill for what is really necessary for the robots size, but they are what is laying around in the bin for free. Harnessing the speed into useful control may be a challenge, but nothing that hasn't been done before. The final version after a few updates should be able to mill soft metal or engrave with rotary/laser, as well as pick-n-place for wave soldering and painting. I am still working on some code changes in the Arduino conversion driver, but in the next week or so I should have some new pics of the progress of the build.
Again thanks for your interest!
Edited 1 time(s). Last edit at 06/06/2016 10:10AM by MarkBot. Just an Artist, Musician, Designer, Programmer, Maker