Converting a Boxford 250B

Please look at this video: Y axis jogging.

1. It sounds like it's stuttering. I thought the Universal Stepper Controller would not do that. Also this PC have quite good latency numbers.

The axis also stalls out at quite a bit lower speed than the old Boxford controller. I assume this is caused by the stuttering.
How do I fix this?

2. At the end of each move it sounds like a chicken. I played around with the PID settings and is above 100 for the I term! From previous experiences this is extremely high! But it seems to help kill the "chicken" somewhat earlier. It could go on for a minute before. What are sensible numbers for this.

One problem I have is simply understanding the concept of a stepper being a servo and needing a PID. Since the ecoder readback is just a copy of the step generator there should always be no error. But it seems this is not the case.

I got some very prompt support from Jon Elson at Pico Systems, and now the stuttering and chicken is gone! :lol:

Now X and Z is behaving well as far as I can judge. Have to tune speed and accel though.
I will share the configuration and document connections when all (or most) things are level here, in case someone else come across one of these fine lathes.

Next one up is to connect up the VFD inputs to get the spindle running. The VFD did spread copious amounts of HF noise, so I routed more GND through the machine using thick fine stranded wire.

Status now is it moves in Z and X. It does not have a steady note while stepping, but it seems not to loose steps. I'll hook up the logic analyzer to the step inputs later to check this. It could be mechanical.

Also the spindle reacts to speed commands, although running the opposite direction. I'll have to look for how to invert motion.spindle-reverse. Probably just swapping 2 phase leads to the motor is the easiest way.

I started trying to control the tool changer using the Boxford Lathe ATC toolchanger component. But it causes a following error. I connected it's output to a PID input and it seems the PID does not like a step input. I tried to pipe the output through limit3, but could not see any difference. Maybe just not understanding how to set the max values in limit3.
If I just run it as A axis I can G1 A<number> or jog and it moves as commanded.

I started trying to control the tool changer using the Boxford Lathe ATC toolchanger component. But it causes a following error. I connected it's output to a PID input and it seems the PID does not like a step input. I tried to pipe the output through limit3, but could not see any difference. Maybe just not understanding how to set the max values in limit3.
If I just run it as A axis I can G1 A<number> or jog and it moves as commanded.

Are you are using the component I wrote as per below?
wiki.linuxcnc.org/cgi-bin/wiki.pl?Contri...oolchanger_component

If so, what output are you connecting to a PID, and why?

It is designed to take over the stepgen for the ATC and output commands directly via a similar link to this
net apos-cmd toolchanger.0.position-cmd => stepgen.3.position-cmd

The hal line
net apos-fb stepgen.3.position-fb => axis.3.motor-pos-fb
has to be commented out or you will get following errors.
Because axis.3.motor-pos-cmd is not connected to anything it will be 0. Therefore it will see any value other than 0 in axis.3.motor-pos-fb as an error

A specimen set of hal connections are in the header of the comp file

regards

Yes, that's what I'm using. And I connect it to a PID. sjaavik.no/linuxcnc-dev/univstep/BoxfordHAL.pdf
The connection marked with question marks is connected so it replaces axis.3.motor-pos-cmd.

This is the connections when I gave up yesterday: sjaavik.no/linuxcnc-dev/univstep/halshow.txt

Since I'm using the USC my understanding is it has to go through a PID.

My understanding is that the toolchanger code issue the full move immediately, so the PID sees a step to the target position.
But of course much of my problem is I don't know much about the internals of LinuxCNC. I pretty much have to find that out by observing the pins. The stepgen component will do the accel/run/decel as far as I understand it.

If I connect it as A axis (as the .PDF shows) I can change to next tool position by G1 A<current pos+distance to next tool+fudge> F2000. Then go back <fudge> to engage the pawl using a new G1. So although I don't fully understand the existing code, it should be close if the output can be made to act like the G1 output.

Hi

The toolchanger outputs moves in a manner similar to using a MDI command.
However the axis is defined as linear, because the ATC will only rotate in one direction and if you leave it as rotary, linuxcnc will try to take a shortcut backwards when that is a distance less than 180 degrees.

It monitors the progress of the command and does not do anything until the actual position equals the commanded one.
Linuxcnc will take care of acceleration and deceleration within the settings in the ini file for the axis.

If you have a stepper powered ATC I do not see what having a PID component connected is supposed to do, the toolchanger takes care of all the required movement at the velocity and acceleration set for that axis

regards