Light Machine Corp. Benchman XTr (retrofit)

andypugh wrote:

Halscope might help.
Moving smoothly until a following error can be an indication that the machine is pegged against the physical speed limit. That will be very smooth, right until the setpoint is too far ahead of the actual.

You _could_ consider cascaded control loops, with a PID that takes a velocity input to convert the drives to velocity mode and a second PID driving the velocity PID to do the position control.

But I would only suggest that if you really enjoy PID tuning
 

I agree with every thing Andy said except the tuning.  I thought my duel PID loop config was much easier to tune than tuning the torque commanded drives using only a single PID.  And it seems to perform much better under varying loads.

I guess there are a few comments and questions. The last time the machine had a working .ini file and conducted several operations. Since then, the machine was changed to the standard Debian wheezy 2.7 and upgraded to 2.8. Upon initially opening Linuxcnc, a command prompt came up with an .ini file conversion for the new build. At this point, after enabling the machine, the spindle drops and creates a following error. What is strange is that the .ini files are identical, so not sure what the problem might be or what exactly changed when "updating". Anyone more familiar with the change have an idea for a quicker solution to get back to the last working point?

This question is perhaps the more important. Can anyone recommend a more user friendly drive that allows an easier way to tune the existing motors on all 4 axes? At this point, I am ready to throw some money at this machine to start reliably making chips.

Mesa 7i25+7i77+7i84
Dc Brushed motors
High resolution encoders
67.5V

After upgrading to 2.8 then running a configuration for the first time it checks for a "VERSION =" line in the ini file and if it doesn't exist or is too small then runs the conversion script on it. If you did not let the conversion script run when prompted the config files will not be converted and they will not work with 2.8. The majority of the changes have to do with the Joints-Axis change that happened with 2.8. Before 2.8 the terms joint and axis were used interchangeably and meant the same thing. After 2.8 there is a distinct difference between them in the code, where a "joint" number only refers to a motor and may or may not correspond to a Cartesian axis letter. An "Axis" letter only refers to a Cartesian axis in space. This change makes setting up non trivial kinematics machines more straight forward and machine configs less ambiguous. There were a few other minor changes to some other pin names as well. The conversion script will usually automatically make all the the nessisary changes to a config, but there are always exceptions. For this reason the conversion script will also save the original files to a backup directory within the config dir.

(I believe Andy wrote the conversion script.)

Hi Guys,

I am listing two Benchman XTs for sale in Grand Rapids, Michigan. Both are operational and under power now but one is in need of some y-axis work as it seems like it's got a pretty gnarly groan to it. Would love to hand them off to an enthusiast like the folks are on here. Asking $3k but they will require pickup in Michigan from a residential address.

Ryan

[url] grandrapids.craigslist.org/tls/d/grand-r...ning/7475023151.html [/url]

 

I wish I lived closer.