Following error monitoring on stepper machines

I have searched the forum and can't seem to find what I am looking for. Probably using the wrong search terms or something because I don't think my idea is in any way revolutionary or has not been done or tried before.

I have a 3 axis CNC milling machine that I converted using open loop steppers for the axis drives and it works very well. However, I am wondering is it possible on a stepper driven machine using the parallel port to set up following error detection that could halt the machine. I am not looking for on they fly correction of a following error essentially closing the loop, but just detection and then a machine halt. I realize that with a standard stepper system that if a following error happens that steps have been lost and that the maximum available torque has been exceeded so you can't really get back the lost steps with a standard stepper system.

So, I am not looking to make a closed loop stepper system, or change to a closed loop servo or stepper system. I envision the stepper still operating in open loop and I only want to detect if a following error/missed steps has happened.

For example, lets say I have a part program that pushes the machine beyond what the steppers can handle. What I would like is to detect the following error with a rotary encoder mounted on the stepper and if detected, just stop all operation to prevent something bad happening.

My main concern is not saving a part, but preventing the following error from resulting in a crash that damages the machine itself.

Thanks in advance.

John Brannen

Thank you for the response.

I realize that I could go with servos or closed loop stepper systems, and mentioned them in my post, but do not want to do this for various reasons, one being cost.

The encoders are not costly, and my steppers are dual shaft with a stub shaft sticking out the back end, so mounting encoders is a not a problem.

What I am looking for is some help on how this would wire up to the parallel port and how the HAL file would need to be modified to accomplish it.

Thank you. It may be a few days before I can get all that together as I have to got out of town for work. I will post those things when I can. I do want to try this and if successful put together kind of a guide to what is done for others who may want to go down the same road. I will probably start with just the X axis and go from there.

thanks again.

As a start, the link below is to one encoder option that I am looking at. It is advertised as 5V-24V, so hoping it works well on 5V. It is 600 pulses per rev, which is enough for the following error detection I desire. At 600 P/R, the encoders should be good for about 0.0003" resolution but I only want to check for following errors greater than about 0.002" to 0.004". My mill has 200 step/rev steppers and I run at 1/8 microstepping, and each motor revolution equals an axis movement of 0.200"

Given the above, does the encoder P/R need to equal the microstepping, which would be 1600 /rev? I wouldn't think so, but if it does I need to look further for an encoder.

The mill is a typical benchtop mill and is a Grizzly G0704 model. Below is a picture of the mill I found on my PC from when I was building it. The picture shows the motor attachment which is typical and the extended shaft can be seen.

As for my "files", what will you need? The ini file for my LinuxCNC setup?

Thanks again

www.aliexpress.com/item/1pc-New-Encoder-...ing/32669741048.html

Thanks again. Those links will give me something to chew on while cooling my heels in the hotel room.

Wow. Great assistance. A quick look at those 2 links and I think I may be able to muddle through this.

Thank you very much for the great and fast support.