Z Crawling?

[Dave_C]

I was making a part today that required facing and I started running the Intercon program, noting fancy, just 2.25" X 5.5" and .020" off the top.

As I was running the part I could see that my Z depth was getting deeper and deeper. My first thought was that I did not get the end mill tight enough, so I checked it, very tight. Not the issue! Then I thought, maybe a drive pulley was slipping but I have mine keyed so nope, not the issue.

So I returned my Z to the home position but it did not return to home. It was about .200" lower that where I had set it.

So after lunch I loaded up the Intercon program, looked it over, no problems there so I opened the CNC code, no problems there the Z was the same on every pass.

SOOO I ran the program as an "air cut" and sure enough, I could see the Z had moved down by the end of the program. It did so slow enough that my eye could not detect it. So I removed my Z axis belt cover, ran the program again and I could see the Servo (NOT A STEPPER) but a Clearpath Servo [the high end 6400 step one] was creeping ever so slowly.


I ended the program and went to spinlde manual mode. I ran the spindle using the 100% button which is actually half speed, and no problems. So I upped the speed to full throttle and sure enough, the Z started to creep!


So now I have to figure out how to solve that issue! Cables are not routed close to the motor but I may have a clue as to where the problem lies.


I'll isolate my power supply away from the 240V that supplies the drive and use a separate 120 volt receptacle to power the acorn and see if that helps.

I'll let you know what I find out.

Dave C.

[DICKEYBIRD]

Try slowing the acceleration rate way down. If that fixes it, start speeding it up until it starts "crawling" again then back it down to a happy medium. Sounds like skipping steps to me.

[DICKEYBIRD]

I ended the program and went to spinlde manual mode. I ran the spindle using the 100% button which is actually half speed, and no problems. So I upped the speed to full throttle and sure enough, the Z started to creep!

Oops, missed that one Dave, sorry.

[Dave_C]

Solved! (I think)

I tried a couple of isolation things but they changed nothing, then it hit me, I had changed the wizard setting in tab 5 from 400,000 to 200,000. I'm not sure what my old noggin was thinking but I changed it back to 400,000 ramped up to full speed and no crawl.

I'm not smart enough to tell you why that solved the issue but I do know I did not have it until I removed the software and did a re-install which at that time I set the 400,00 to 200,00. (I think I thought that was the setting in the old setup) I should have looked at my screen shots!

Anyway, it isn't crawling anymore!

One thing you don't know is my top speed is @ 150Hz on the motor!

Dave C.

[Dave_C]

Anyway, it isn't crawling anymore!

Oh if that were only true!

I just thought it was solved. I booted up this morning and thought I'd run a retest at full RPM and as soon as I did the problem came back!

So I spent all morning doing things like:

1. I ran a 120 volt circuit to the Acorn power supply (isolated circuit) NO Change!
2. I shortened my drive motor cable from about 11 feet down to 4 feet, which is as short as I can make it. No more loop down to the floor and back up to the motor. Now it is straight out of the control cabinet and horizontal over to the motor. NO Change after all this work either!

It is obvious that the Drive is causing the Clearpath Servo to "creep" even when there is no program running but only when I get above 73 Hz! But why?

3. So what I did was retune the Clearpath Servo on the Z axis and retest. Problem is gone for now! I ran it full speed for at least a minute with the belt cover off the Z axis so I could detect even the smallest movement and it did not move.

So tomorrow when I restart everything will it work or not? Will it ever be reliable? I'm starting to have my doubts but I don't know where the Ghost is. Wherever it is I'm thinking it is also why I can not get the Quadrature errors to stop even though I've bought 3 new encoders.

Related issue or not? I have no idea.

Dave C.

[ScotY]

The DRO for Z is not moving, just the motor? I would assume noise but I haven’t made any parts yet so don’t know if I will have the same problem. I have wires all over the place!

[Dave_C]

Just the motor! I ran it this afternoon and it ran just fine. Stay tuned!

[bilorn]

I am having a similar problem. Just getting machine going. DMM DM4 servos.
Ran one intercon program 12 circular pockets 1/2 inch deep 1 inch apart moving only the Y axis. This ran okay.
However, I cannot get a repeat of this.
Z axis goes deeper on each hole, looks as if z is going faster down than up.
Auto tune on servo went okay.
Z home position is changing downward when this happens. The program calls of a tool change, the home position on
the first run of program is about .050 away from switch on successive runs of the program home position keeps going down.
Motion is smooth on all axis. This error will also occur on dry runs with spindle control not powered.
Acorn recommended wiring used.
Mechanically everything is solid.
This has me stumped!

[Dave_C]

You just duplicayed my issue exactly!

[Dave_C]

This error will also occur on dry runs with spindle control not powered.

Ok, we may have different issue after all as my Z crawl was only when I ran my spindle at high speed! (I have to think on these issue sometimes)

Let's start seeing what we have in common and see if there are similarities that we might trace this back to.

1. I'm running a version 2 Acron board
2. CNC 12 V 4.12
3. Clearpath servos, and my Z axis servo is a NEMA 23 while the X and Y are NEMA 34's.
4. 6,400 steps per rev, not the 800 ones!
5. Using all Clearpath power cables as well as step and directon cables from Clearpath.
6. Yaskawa VFD and a 1.5 HP drive rated motor.
7. Top speed is obtained at 150 Hz.

Let's start with that and see where we are!

Dave C.