Random tabs issue

[Leadscrew]

Hi All,

First post on this forum, recently upgraded to 10.5 from 8.5 and all was well until I updated the software to 10.514, now without any tabs being set I am getting very thin about 0.2mm tabs left randomly at the start point of the cut, we are mainly cutting acrylic and I was able to fine tune the cut so that the protective film was cut without going into the sacrificial layer underneath, but because of the tabs issue I now have to sand off the razor sharp tab left behind or set the "Z" axis height slightly below the surface of the sacrificial layer.
With a vacuum bed I try to preserve the sacrificial layer for as long as possible since the more you cut into it the lower the available vacuum becomes.
Is this a known issue, I can't see mention of it anywhere on here, any help gratefully received.

Thanks David

[Adrian]

Are you using the same post processor as before?

[Leadscrew]

Hi,
Yes nothing has changed but the software update to .514

Thanks

[martin54]

I haven't noticed any difference & there haven't been any other posts on the forum about issues as far as I know. How do you set your z zero? Material surface or machine bed? Guessing machine bed if you don't want to cut into your vac bed. What do you mean by randomly leaving tabs?

[Leadscrew]

Hi,

Yes on the machine bed (sacrificial layer / spoil board). By randomly leaving tabs I mean just as if tabs are intentionally incorporated in the cut except for the very thin nature of them 0.2mm ish, for instance I have just cut a job using a 2.5mm bit and the cut was perfect with no phantom tabs, yesterday I cut 116 480mm dia. discs with a 5mm bit and tabs were present on all of them, to get round the problem I had to cut into the sacrificial board which as mentioned I don't like to do for reasons of preserving maximum vacuum.

This happens when the tabs box is un checked of course and when the tabs window hasn't even been accessed on the job.

Thanks David

[Adrian]

If it doesn't show on the preview then it's outside of VCarve as an issue in my experience. Have you looked at the code or run through the code through a simulator?

Always best to attach files when possible with issues like this as pictures only show a tiny part of the story.

[Leadscrew]

Nothing shows up in the preview and just cut another job with no problem, tab when it does occur is always at the start point and if I move the start point the fault moves with it, the tab is centred on the start point meaning that as the end of the cut approaches the Z axis lifts during cutting before it lifts for traverse clearance at the end of the cut.
All I know is I didn't have this problem and now I do, don't know if it's as a result of the software update or a windows update causing the issue but it's causing problems for me.

Included is one of the problem files if anyone can spot anything wrong with it.

Is there a way to go back to the earlier version without rolling windows back.

Thanks

[GEdward]

I'm sure someone with more experience will jump in but from what I see, there is no problem with the software or the tool path. I looked at the Mach 2/3 arcs (inch) g code and I do not see Z being commanded to do what you see happening. In my experience, if the machine is doing something it is not being told to do, the problem lies in the machine or it's controls. My initial thought is that you have some Z axis backlash. There really is no good way to compensate backlash out of Z axis since the weight of the assembly will usually push the axis assembly down to end up loading the top side of the lead screw, ball nut or timing belt assembly. If this is the problem then I'd suggest that you make sure the Z guides and screw assembly are clean and well lubed and see if that helps. Otherwise, check the machine for looseness or wear. I believe the timing of your issue relative to the upgrade is reason to be suspicious but it is unrelated imho.

Ed

[rig gap]

I would check for backlash in the "Z" axis. Maybe connectors at the motor pulley or lead screw are loose and allowing erratic movement.

[Leadscrew]

On the Z axis is a 120mm dia. water cooled 4kw spindle motor and with the fixing clamp and rest of the vertical carriage it's very heavy, because of all this weight if there were any backlash it simply would not come into play, and especially not when using small bits like 5mm dia.
The machine is free in all axis and is piped up with auto lubrication so there is no fault there.
If it could be put down to such problems with the machine then the error would manifest its self in different ways, but it does not all the phantom tabs are all the same length and depth, and as previously stated the end of the cut finishes at the centre of the tab and to do that the Z axis has had to be lifted and that positively rules out backlash in the Z axis.

I've still got version 8.5 on the computer so I will try that on the same file and if that works ok then it would mean there is version 10.514 / windows issue.

Cheers

[sharkcutup]

If you have saved the file in a later version you will not be able to use that same file in an earlier version of the software. Files are not backwards compatible.

Sharkcutup

[Leadscrew]

Yep forgot the reason for moving to version 10.5 was Windows 10, DXF and DWG files saved in a windows 10 program can't be opened by version 8.5 either. Bugger.

[mtylerfl]

You should be able to import the DXF or dwg vectors into any version of the software. They are just vectors.

[sharkcutup]

Yes Michael that is true but that does not solve the repeatability issue of the same file.

Sharkcutup

[mtylerfl]

Yes Michael that is true but that does not solve the repeatability issue of the same file.

Sharkcutup

That’s right.