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Topics - hunserv

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1
Feature Requests / Mechanical corrections from software
« on: November 21, 2009, 06:58:28 AM »
Hello,

The recent days I was wondering about a few features which have been mentioned earlier, but I do not know if it is possible to realize them.

Background story:
I have a High speed CNC machine with precision linear guides and ballscrew, integrated cooling for thermal stability, etc... However, this is not new.
Screws are renewed, accuracy is as it is... (Not the highest grade)
Linear guides are OK, but it had once a crash, and by measuring axis perpendicularity, at one point one axis has a small bend at a certain range.

I'd like to get some answers on 2 of them:

1. Screw mapping.
How is it nowadays? How well does it work?
Can I do the followings:
I mount an accurate measuring device on the axis, and go through the whole range of the axis. By comparing actaul and theoretical positions, and making a deailed screw map for each axis fore each "step" I could make it more accurate without mounting expensive glass scales...

2. Axis "linearization"
This one is for the bent axis...
Solution 1:  I change the wrong axis's components (quite expensive solution)
Solution 2: make comepnsation from software... Is it possible to somehow do this?
e.g give offset values for axis X when axis Y is at the range of 200-300... even different at different Z levels...
The offset equation is quite easy to define, I can make measurements to know the exact amount of deflections...
If Mach keeps track of absolute positions, then it should not be too difficult, no?

Thanks in advance!

2
Feature Requests / Automatic feedrate override
« on: July 31, 2008, 03:44:19 PM »
I am working on a servo project (very slowly) and wondered, if an additional feature could be realised:

By feeding back MACH the servo loads of each axis, a feedrate override could be utilised, if any of the axis load goes beyond a certain percentage...
Now could someone tell me how to realize this feedback? e.g. modbus analog inputs? (no high resolution is needed) or even a digital input would be OK, saying any of axes are above x% load, so override feedrate by y%.... or something like that...

This way even steppers could be made unstallable (encoder feedback, and PID control on servo - this would work only with high-rate microstepping, the "stepper-servo" is quite nicely working, but of course similar control is needed as for DC servos)

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