CNC Lathe controlled with a PLC...

[JTracy38]

So here is the scoop...My company updates milling machines and lathes. We recently had one come to us that the customer wanted to have the linear actuator changed out with one that had a longer lead and add a gear reduction box. This is not a big deal except that it is a CNC machine being controlled by a PLC. I was able to add the new conversion constant for the axis but I am unable to find where in the logic the programmer was controlling the constant surface speed i.e. speeds and feeds.

If there is anyone who has used a PLC to control a CNC machine that may be able to give me a bread crumb to look for in order to verify that I will be able to maintain a consistent surface speed at different RPM's that would be great.

Thank you all in advance for any and all help on this.

Jay

 

[jstolaruk]

PLC model and make of the equipment would help.

 

[JTracy38]

The PLC is a 1756-L55 and the machine is a very old industrial lathe

 

[jstolaruk]

What kind of motion hardware is connected to the PLC?

 

[JTracy38]

There are 2 Ultra 3000 servo drives. 1) 2098-DSD-HV150-SE 2) 2098-DSD-HV220-SE

 

[jstolaruk]

There are 2 Ultra 3000 servo drives. 1) 2098-DSD-HV150-SE 2) 2098-DSD-HV220-SE

These are SERCOS controlled servos; in the rack that the CPU is in you should find a SERCOS module. Anything in the logic related to that module is related to controlling these drives. You'll probably need the Ultra s/w called Ultraware and I believe its free at the RA website.

 

[JTracy38]

I dug up the old computer that the original logic is on and found that the original programmer did not use the Ultraware s/w. It seems that the SERCOS module was configured through the RSLogix 5000 software.

Near as I can figure the coordinated motion system seems to take the information given to it via the recipes and multiplies it by a feed override factor. Then it moves those results into a series of feed rate tags based on the input tag which is then multiplied by the spindle rpm to give it the inches per minute.

With that information the question is, would it be safe to say that it is setup to self adjust the feed rate based on the spindle speed that it is registering?

Hopefully that makes sense...if not I will try to explain it better.

 

[jstolaruk]

With that information the question is, would it be safe to say that it is setup to self adjust the feed rate based on the spindle speed that it is registering?

If this question is not rhetorical, there hasn't been nearly enough information provided to answer it. Its going to take some close study of the code and some knowledge of the process.