More G code issues

[jcatcmc]

Hi ,
I am having problems with a simple V Carve job ( see attached image ) I have confirmed all the vectors to be carved are exactly 2 mm apart, when I leave the flat depth unchecked the carving below the oval carves at 1.428 mm depth ( about right ) and above the oval it varies all over the place up to 2.3 mm deep ,consequently the lines are approaching 3 mm wide.
If I set the flat depth at 1.5 mm deep it really looses it , carves multiple small sections, moves a bit, plunges up and down in the one spot for 5 or so seconds , moves on, runs a 40 mm line 5 to 6 times ect, at that point I gave up. The material is uniform thickness , I am using a 0.5" 60 degree cutter. I have started from scratch and recalculated but nothing alters. I only recently upgrade to VC 10.5 but no problems up to now.
I don`t know if the tool paths can be read be read here but I have tried to attach them also but they don`t want to attach.

Regards, John

[Rcnewcomb]

Can you upload the CRV file?

[jcatcmc]

Here you go Randall,

Thanks, John

[Adrian]

A v-carve toolpath won't cut outside the specified vectors so if you're saying that some of the cuts are 3mm wide something is up outside of VCarve (by the way the vectors aren't all 2mm apart, it varies from 1.7 to 2). So in that case it could be that the material isn't flat, the z-zero hasn't been set correctly or the v-bit doesn't match the angle set in the toolpath.

The fact that the carving is much shallower at one end of the piece than the other which make the material not being flat or the router/spindle out of plumb as being the first things I would investigate. If you check the preview cut depths by hovering the mouse over the cut areas and seeing the Z depth at the bottom of the window you will see that the cuts are pretty consistent between the top and bottom.

The multiple moves on the flat depth toolpath is probably caused by your stepover setting which is 0.1%.

[jcatcmc]

Thanks for your comments Adrian but I am confident I have no hardware issues, alignment,material thickness , cutter ,or Z zero setting problems. The file shown is a node edited snip of a larger job that was quite successful, to add the oval and test. I can appreciate that it will cut deeper on the intersect oval / straight lines when no flat depth is set. The problem is I can see the variations in the G code when I stop the machine mid cut.
Regards your comment on the step over setting I have purposely set it fine. When it was a larger value there were fine ridges on the bottom of the v and it tended to lift the grain a bit ( furry finish ) I can`t comprehend the need for a step over anyway as the finish is very good with one pass.
I recalculated the design in an earlier version of V Carve but the problem still exists. ( Computer ?? )

[Adrian]

What do you mean by "variations in the g-code"? The way a v-carve toolpath works you won't see a single move to a depth. The depth varies between the minimum and maximum continually depending on where in the toolpath it is so you could see completely different z-values depending on where you stop it.

The real clue that it's not a software issue (assuming you're using the correct post processor for your machine) is when you say that "consequently the lines are approaching 3mm wide". The v-carve toolpath does not cut outside of the vectors so if the lines are wider than they should be that means the machine is cutting too deep which is the material higher than it should be, z-zero out or the machine is losing position.

I checked the generated code for the top and bottom sections and the cut depths are exactly as I would expect for a 60 degree bit on vectors that are 2mm apart on average with 90 degree corners.

The finish pass stepover is what controls the finish on the bottom of the cut when you use a flat depth. It's always going to be a compromise as it's a pointed bit. That's what the flat area clearance tool is for but you would need a really small one to make a difference in this case.