Centroid Community CNC Support Forum

Thanks for that Cncsnw
I'll try it in the morning. (It's 8:30pm here).

cncsnw wrote: ↑Mon Feb 15, 2021 2:37 am The end position for G28 moves is on the "Return Points" table: F1/Setup -> F1/Part -> F9/WCS -> F1/Return.

It is entered as machine coordinates (distance from machine home).

Despite following these instructions, cncsw, I am unable to see any change in the machine's behavior.

In the wizard options I turned on "display machine co-ordinates", so that I could see the controller's position.

I then followed your instructions and set the "Return Points" for both the Z axis and the X axis to a value of 5.00 (the value before my change was 0). I saved the settings, restarted Cnc12 lathe and checked that G29, G30, G30P3 and G30P4 were all still set to 5.00 for axis Z and X.
I then rehomed the machine and the machine co-ordinates still displayed as 0. From a physical look at the distance the axis were from the home switch, confirmed that they were still the same distance as they were before I changed the settings as well.

I proceeded to run the pawn-mm file, and had the same error at the same time as before. I feel that nothing has changed.

I realize that 5mm is probably a bit an excessive reduction in axis travel, but I thought I could refine the setting later if it worked.

I thought you wanted to change the point that a G28 code moves to.

Did you instead want to change where your machine homes to?

cncsnw wrote: ↑Mon Feb 15, 2021 8:31 pm I thought you wanted to change the point that a G28 code moves to.

Did you instead want to change where your machine homes to?

I thought that the changes you had suggested would change where my machine homes to, but out of curiosity, I tried a G28 command in the MDI after reading your reply. When the G28 command was run from the MDI, the machine moved and triggered the X limit switch rather than stopping 5mm away.
It seems as if I am not understanding you?

What I really would like to do, is make the machine use it's homing cycle to read the limit switches, then instead of setting the machine co-ordinate of 0.0 only 0.025mm away from the limit switch, to set machine 0.0 to be 2.0mm away from the limit switches. This would help me greatly

It appears you are currently homing both axes of your lathe to the plus limits (which is generally the best choice).

You can probably accomplish what you want, by setting the G28 position to X-5.0 and Z-5.0.

Machine zero would then (still) be immediately in front of the switches, but any G28 move would stop 5mm short of machine zero.

When you set the G28 position to X+5.0 and Z+5.0, you were asking it to return to a position on the plus side of machine zero. That is why it ran into the limit switch.

Incidentally, you should also measure and set your software travel limits. Since you are homing both axes to the plus end, your software travel limits should both be negative distances: how many mm of actual travel the axis can move away from home, without running out of mechanical travel.

With the software travel limits set, the control will check the moves in your CNC program when you graph it with F8, and also when you press Start to run it. If any move would go outside the machine's travel envelope, the control will give you a "907 _ axis travel exceeded, line __" error message.

To address your most recent inquiry, yes, it is possible to find the switches, then move farther away from them before setting machine zero. But that makes your homing sequence non-standard and more complicated, and does not gain you anything that you could not already get by changing the G28 position in the appropriate direction.

Thank you very much for a clear explanation, cscsnw,
In desperation I have totally uninstalled my CNC12 Ver4.5 software and upgraded via a "clean" install to version 4.62. I restored a ver 4.5 backup report made in November last year, when all was working as expected.

This did not resolve my limit switch issue, but at least any problems that I now have should be "clean" addressable problems.

I carried out the settings you suggested, as per the screenshot below, but no joy. Things are still the same.

Can you elaborate on "things are still the same"?

Try composing a short step-by-step description of the simplest possible sequence that illustrates the current problem or problems.

Also, set your software travel limits, and make use of the F8/Graph preview.

cncsnw wrote: ↑Tue Feb 16, 2021 1:32 pm Can you elaborate on "things are still the same"?

Try composing a short step-by-step description of the simplest possible sequence that illustrates the current problem or problems.

Also, set your software travel limits, and make use of the F8/Graph preview.

I thought, when I typed "things are still the same", that it was fairly broad and assumed the same knowledge of the sequence of events that I had - sorry.

Here is the story:
In about 2001 I converted my, then manual, lathe to Mach3, using a VFD and steppers. I also changed the standard single phase 240v 1.5 hp spindle motor to a 3 hp 3 phase motor.
The machine then became an occasionally used device to help with my vintage motorbike hobby etc. I learned to use M3, mainly using "wizards" and was quite happy.
In 2020, whilst browsing the internet, I thought it's about time I upgraded the lathe. This led me to a new and exciting cycle of raised and dashed hopes, and eventually to a working V4.5 Acorn system.
Late last week, I needed to do a simple turning job in order to make a spindle for a device to true up motorbike wheels. I noticed that a new version of Acorn had been released and proceeded to upgrade.
The upgrade to V4.62 seemed to go quite well at first, but when I tried to create a job in the CAM section of the CNC12 program, my lathe behaved inconsistently, acting as if it was not getting the dir signal for the Z axis, and eventually hitting the tailstock with the carriage, instead of the Z axis being no where near the tailstock, which is where it should have been.

This led to several (5 so far) days of trying to work out what's happening and to fix the machine. I completely uninstalled V4.62 and re-installed V4.5, restoring a backup report from earlier this year, which seemed to restore my, then working, settings.
I have now re-upgraded via clean install, to 4.62 and restored a V4.5 backup report from late last year. This is the current situation.

The current symptoms seem strange. When I set part 0 for the Z and the X axis to the middle of the bed and run the pawn-mm gcode, my X axis hits the limit switch, aborting the job just after the spindle starts and while G28 command is running. This is despite what we have done.

Also I discovered, yesterday, before I gave it up for the day, that the Z axis is behaving strangely.

Here is an example:
For this scenario, part Z0 is at the spindle. Z200 is 200mm up the bed of the lathe.

1/ Starting at Z200 I move the Z axis, using the MPG, at 100X to Z0. All works as expected.
2/ Still using the MPG, I move the Z axis back to Z200.
3/ Using the MDI, I command "G0 Z0" and press cycle start, the Z axis then doesn't move, there is no error from the servo drive, but the Z axis DRO updates from 200.00 to 0.000 almost instantly.

This is in addition to the tripping of the X axis limit switch, when running the pawn-mm. There seems to be something fundamentally wrong, but, I'm not sure how to find the error. The only good thing is that the symptoms are repeatable. I have a "feeling" that it is hardware related, but that's just a feeling and the symptoms are more like software.