Posts by Darius Grigaliunas

Till now we did standard ABB robot arm joint calibration and TCP position calibration as described in RoboDK docs. TCP orientation is just rotated 90 degrees relative to robot flange.

Seems like angle errors comes from joint inaccuracies, as angle error changes when moving tool along single axis.

We also did some custom calibration where we used laser distance sensor and collected real distances to the blade surface and theoretical distances using virtual environment. Did some optimization on that and got orientation offset which improved angles but not as much as we would like. Initially angle error could go up to 1.3 degree, now getting up to 0.7 degree error depending on joint configuration and where tool is pointing to. Preferred error is up to 0.2 degree (based on saw blade diameter).

Accidentally missed SkyeFire first comment. Thanks for the idea, will give that a try.

There are various cuts based on material design. And robot might need to cut with different edge of the blade depending on cut position and robot reachability.
Besides, I don't think moving TCP to the edge, would solve this. Right now main issues is that when cutting along a line, saw blade moves sideways. And on longer and/or deeper cuts that increases friction between the side of a blade and material, resulting in stopping the blade completely.

How it should move along a line. Saw blade moves from right to left in this image (top view, yellow part is the material):

How it actually moves (exaggerated):

One idea we are thinking of is to put Inclinometer (or multiple for different axis) sensor (for example) on spindle motor to see angle errors and make corrections. Haven't used them before so wondering what is your opinion about that.

Hello everyone,

Have a robot arm with attach spindle motor and saw blade (see attached image). Having issues with tool angles. Because saw blade has radius of 26 cm, small angle error (~1 degree) in TCP (center of saw blade), results in significant position, angle errors on saw blade edges where the actual cutting is happening.

Most tool calibration techniques only calculates TCP position and disregards orientation error. Maybe someone has experience with similar tools and can share ideas/techniques how tool orientation can be calibrated?

Thanks in advance!

Hey,

First question, do you need CAD model in your simulated environment? For collision detection or other reasons.
If yes, you can't really go around it and you will need to get CAD model or create your own CAD model (it can be simplified CAD model).

No matter you have CAD or not, you will need to make a mechanism to define how your lathe works. That is not that hard and you can read documentation how to do that:
Create a Mechanism or a Robot - RoboDK Documentation

Hey, I had similar issue but in the end failed to achieve having single mechanism for all axes.

This might help you:
How to make a mechanism with 2 colinear axis?  

In my case, in the ended up with separate mechanisms for each axis and stacked them in appropriate way to achieve desired movements.