Centroid Community CNC Support Forum

I'm having serious issues with CNC12 V4.5. It started last night during a profile operation where the Z-axis will head at max speed straight through the limit switch and into the motor mount. Now tonight it's doing it with the same part from last night, the new part I created plus a simple example part that came with the software. The X-axis is also doing the same, crashing through the limit switch. I checked the IO page and limit switches are operating properly as are all the other inputs. I've attached the report for reference. Everything was working properly before last night so I'm not sure what happened.

You do not have any limit switch inputs defined. A home switch is not a limit switch unless you choose one of the "HomeLimit..." options.

That said, it does appear you have software travel limits defined, so it is surprising that, once you have homed the machine and are running a job, you are able to run past your home switches. That suggests loss of position (i.e. dropped steps or false steps).

Run the job again, but be prepared to pause it (e.g. with Feed Hold), and watch your DRO positions.

After you have done your part zero, what should the DRO positions read when you are right in front of the home switches?

When you run the job and it is about to plow through the home switch unexpectedly, pause it. What does the DRO position show then?

It seems I do have the limits defined under the inputs section of the Wizard (see attached). I have them wired in series to input one. They have worked correctly for the last week or so, including up to 2 nights ago. The report I generated occured after the crashes. It doesn't seem right that the Z-axis should head toward home during the middle of the operation especially at max speed. Two nights ago I ran the program successfully with several operations such as facing, turning, drilling, boring, threading but once it reached the Profile section, it went haywire. So it had to be homed correctly to run the 1st several operations.

At Home position, the Z-axis should read +3.2800. However, it was reading -4.8258 after crashing through the limit switch. That seems to be the culprit but I don't know what's causing the DRO to flip +/- in the middle of the part. I've attached a sample part that's doing the same thing. I have a feeling I'm doing something wrong in the profile section.

need more info, what motors and drives are you using? photos etc?
photos of your machine and the home switch locations and the directions you have defined?
please post the intercon file in addition to the g code. intercon is .lth located in the intercon directory

I was curious about how HomeAll and LimitAll work. It looks like you're using HomeAll but I can't see LimitAll.

On my test bench, where the servos can move freely without limits, I installed a single N/O switch for HomeAll and used Wizard to set the homing routine to sequence through the three axes, one at a time to set my home position. I installed another N/O switch for LimitAll. Then, I ran Cycle Start and pushed the switch three times to mimic each axis sensing home. The DRO showed 0.0000 for each axis. Next, I used MDI to command each axis to move 10 inches at 10 inches per minute, slow enough so that I could easily test the HomeAll and LimitAll switches. After the axes started moving, I repeatedly pressed the HomeAll switch. Nothing happened. Then I pressed the LimitAll switch. Axis movement stopped immediately. That's what I expected to happen, but I've never tested HomeAll and LimitAll to verify how HomeAll and LimitAll actually work. From my test, I don't think that using HomeAll has any effect for sensing axis limits. It seems to be used exclusively to home the machine. For limit sensing, it looks like you either need to install limit switches or use soft limits.

HOMEALL is not a LIMIT Switch input.
It uses one input along with the cncm.hom file to home each axis of the machine.
When you use HOMEALL, it is critically important that you set your SOFT LIMITS or Travel limits correctly. (And this is also assuming your Steps/Rev and Overall Turns Ratios correctly)
If you are overrunning your travels, you likely do not have your Travel limits set correctly.
As a test, you should be able to power up the machine, home it. Then jog the machine to the opposite travel end and it should stop shy of hitting a hard stop.
Press Alt D before you test this so you can see the MACHINE POSITION as you do this. It should start out at ZERO for all three axis until you move. The DROs will tell you the distance traveled, you should take note of the values just before each axis hit a hard stop. THOSE should be your Travel Limit Values.

Report back. Show pictures of the machine as well. Video would be helpful too.

Marty

If your travel limits are set correctly on your lathe, then the other possible issue is you have open loop steppers? and your are loosing steps.
Please take the time to follow this post: http://centroidcncforum.com/viewtopic.php?f=20&t=383

Your position-loss problem might be related to attempting to do feedrate moves at 6" and 8" per revolution.

If you meant to use feedrates in inches per minute, then you need to change the feedrate mode to inches per minute.

If you mean to use feedrates in inches per revolution, then you need to use much smaller numbers (or keep the spindle speed to 20RPM or less).

Guys, thanks for all the input so far. This machine has been homing out correctly for a week until this incident occured even with the HomeAll on Input 1. The Z axis would hit the limit switch and settle just prior to it and then the X-axis would do the same afterward just like I have it set up in the Wizard. Both would read Machine 0's. The steps per revolution for each axis were dead on to .0000. I think it's more of the feedrate issue where I meant to say 8" per minute NOT revolution. I thought I had changed that back to in/min in my sample...The motors are closed loop ClearPaths with decent res encoders. Even if the Z-motor lost steps, it shouldn't head in the positive direction at the start of the Profile cycle since all the cuts would have gone from right to left (as viewed standing in front of the lathe).

Do I need to set my soft limits in the positive direction (tailstock side) if I already set them in the negative (spindle side)? FYI, they worked flawlessly in the negative direction.

The hardware I'm using is:
Lathe: Grizzly G0752
Motors: Teknic ClearPath CPM-SDSK-2321S-ELN
Centroid Acorn board
CNC4PC C86ACCP ClearPath connector board

I will have to get the Intercon file when I get home from work.

You should change out those limit switches to those with a short throw roller, not the long leaf switches you have. I don't think you'd be repeatable with those. You should be able to find them on ebay.
5 pc TEMCo Micro Limit Switch Short Roller Lever Arm SPDT Snap Action home LOT https://ebay.us/ikOhWE

Since you have a lathe, you home to the positive direction, so your limits would be entered in the Travel Limit (-) fields as - numbers (-5, -15) and that's it.
DO try what I suggested, Power up the machine. Home it. Machine should move to each switch and back off.
Press Alt d (Machine coordinates)
The DROs should be 0
Jog each axis of the machine in the negative direction. The control should stop you at the -value you set in travel limits.
Let us know how this goes when you can run this test.



Marty