Ridges in a vcarving

[garylyb]

I ran a simple v carving and noticed that there were some ridges at the corners of a a letter.

I've attached the .crv file and a photo.

This is very consistent when there is a flat depth on the letter.

I originally thought that it must be a vectric issue and sent them a email, but the say the if the preview is good, then it's not a vcarve issue, it's probbaly the bit. This is very consistent with 4 different 90 degree vbits, so I don't think it's a bit issue.

That leaves the hhc or my machine. I've got the A11 controller. Slowing down the feed rate doesn't make any difference. 

It happens when there is that curved path at the corners.

If there is no flat depth, the carving is fine, but it carves a straight line there, not the curved line.

I'm out of ideas at this point, any suggestions would be appreciated.








Thanks,

Gary

Attachments:

S1503 test2 round monogram.crv (61.5 KB)

[Mezalick]

Gary,
A few questions.
First, I don't understand your comment of "
If there is no flat depth, the carving is fine, but it carves a straight line there, not the curved line.
"
Can you explain.

Second, is the ridge your are commenting about the same as in my attached picture ?

Third, are you sure the bit is 90 degrees as advertised ?

And lastly,,,,can you create the same curved vector with out the center node, as indicated in my attached photo.
If so can you re-cut the file and let us know if that made a difference.

Thanks,
Michael

[garylyb]

Yes, the ridges are right there.

I've used 4 v bits, and tested them against an engineers square. 1 was perfect, the others have slight gaps. All produce the ridges.

I even change the bit angle in vcarve to between 87 and 92 degrees and still get the ridges.

Forget the straight line comment.

Here is what I mean about no flat depth:




The toolpath is the same shape. There is a slight bump on the top of the carving. It's where the horizontal line turns to curves.

That toolpath is critical as the bit has to traverse it twice, once going in to the corner and again coming out.

I'm starting to think that this is at the limits of tolerance for the hardware. The positional accuracy is rated +/- .00393 inches, so it could be off twice that in that area.

[Mezalick]

Gary,
How about changing from Climb to Conventional cutting ?
I know it's for the Flat area but it also changes the direction of the V-Bit toolpath.
~M

[Axiom Tool Group]

Any chance that the collet is not locked in the nut? May resulting in bit movement or deflection?

[garylyb]

I think Mezalick got it. I changed to conventional, and it feels very flat and straight.

It's hard to see in this pic because the ridge is right where the grain is, but they feel vastly different.

The climb cut has the ridge, the conventional cut is straight.





The right one is climb cut.

I wasn't paying attention to that setting but it looks like the climb cut can pull the bit into the work.


Thanks,

Gary

[Mezalick]

So, to review the issue and the fix, 
1. Was it the software that caused the issue ?

    A comparison of the G-Code ( climb vs conventional ) may shed some light on that.

2. Is it a machine issue?

    Backlash or lack of tight tolerances.

3. Is it a material issue ?
    
    The material moved under the strain of the cutter.

But the real question would be to see if you ran the file again, after the first toolpath, while the materiel was still secured to the machine, would the new toolpath remove the ridge.
Or is that cutting another beautiful piece of firewood ?

Glad it worked for you.
Michael