workpiece touchoff getting lost (v2.6.4)

Hi All

I'm running linuxcnc 2.6.4 on a cnc router i recently built. It's a manual toolchange machine. I have no tool holders and I touch off to a workpiece, the table or a fixture generally.

I am using fusion 360 to do the cam programming for the router. I have been noticing that depending on the order in which i load my program in linuxcnc and touch off, that it will ignore the touch off i did when i run the program - for example, suddenly there is a 2mm offset in the z axis.

What i normally do is have different operations in different g code files (one per tool since i have to manually change tools and touch off) - so i load a g code file, touch off xyz, then press run, it asks for the tool and i press continue since the tool is already loaded and then when done, i might load another file, same tool or not, touch off if necessary and run, and press continue, etc.

In my tool table i have nothing filled in for x/y/z since i don't have a tool offset (i'm touching off to the workpiece, fixture or whatever). I only have the diameters of the tools in the tool table.

Here is an example of a program where i noticed the x/y touch off shifted by 2mm so it doesn't seem to be an issue only related to z touch off - pastebin.com/Ep0gJMXJ

I've been starting and stopping my program shortly after i hit continue on the dialog popup asking for the tool, to verify and confirm the touch off is still correct. However, this is very time consuming and annoying. I just want to touch off once and then keep loading and running programs and I want the tool touch offs to stay in effect until i put in a new tool and touch off.

I originally downloaded linuxcnc image and put it on a flash drive, i've been running that and haven't installed any upgrades.

@gregcnc on #linuxcnc already mentioned this behaviour might be due to having stopped programs halfway, and that a touch off would be required if that happened, and that this would have been eliminated in 2.7. But he said he isn't 100% sure. Can anyone confirm or does anyone have any other ideas where this is coming from?

Thanks!
B

andypugh wrote:

Are you running from the actual flash drive?
Are you 100% certain that there are no offsets in the tool table?
Can you describe the exact sequence you use for touching-off?

1) yes, I am running from the flash drive directly, the PC has no hard drive. I could use an SSD and move to that if necessary.
2) when i open the tool table in axis (edit tool table) and look at it there the data fields for the tools are empty, nothing is filled in. do you recommend putting 0 in every field instead? I didn't actually go on the command line and open the file to inspect it.
3) here it is:

I) start axis and home machine
II) load g code file, jog spindle to where i can reach it, put in new tool
III) touch off to fixture (x or y first, then z)
IV) start machine, popup asks for tool, i click continue
V) mill, and stop machine halfway if i'm using only one of two pockets in the fixture
VI) load new g code program for other tool
VII) jog spindle and load new tool
VIII) touch of Z again to fixture
VIV) go to IV)

this is how i mostly do it, sometimes i might have loaded the tool first, touched off Z and then loaded the program, started and clicked continue on the popup. it should not make a difference?

andypugh wrote:

Does Linux have write-access to the USB drive? And are you running a config specific to your machine?
I am surprised that there isn't a problem at step IV if the tool-table is blank and the G-code asks for Tool 1.
The fact that it doesn't complain makes me wonder if there is another tool-table somewhere that is being used.
If the CAM-created G-code is asking for a tool-change then it can save a lot of confusion if you make sure that you do your touch-off with the tool pre-loaded. (M6 T1 G43). ie, at Point 11a, tellthe system that you have loaded a tool.

I created a config for my machine using stepconf and then edited the config further to add a probe panel for the touch probe i recently bought from tormach. I've been putting g code in my home dir on this flash drive without a problem so permissions should be no problem? if you tell me what to check specifically i can do that.

the tool table is not blank, i've filled in all the tools but there are no offsets for any of the axis since i don't need any. i just put in new tools as I go, and all i do is enter the diameter of the tool and a comment. if i get an error that a tool doesn't exist i will add the tool and then reload my g code.

I always load my tool manually and touch off before i start my program. so when i get the dialog popup asking to load a tool, i just click continue since I've already loaded the tool at that point.

andypugh wrote:

bschiett wrote:

I always load my tool manually and touch off before i start my program. so when i get the dialog popup asking to load a tool, i just click continue since I've already loaded the tool at that point.

And that _should_ be OK, except that the CAM system is inserting toolchanges and G43 commands.
Even then, it _should_ be OK if the offsets in the tool table are all zero. But the spurious G43 and M6 commands do create scope for trouble.

are you saying it would be a better idea to config the post processor / cam software such that it doesn't output these commands?

andypugh wrote:

bschiett wrote:

are you saying it would be a better idea to config the post processor / cam software such that it doesn't output these commands?

In your situation, I think that would be best, yes.

thanks, do you know if this is a bug with 2.6 and if upgrading to 2.7 would fix it?
any other g codes in the beginning of my program which should be removed?