have toolpath offset when I use Xform Roll to work on the 4th axis with '' axis substitution '' option

[jackline.rousseau]

Hello evrybody,

I have problem when I try to learn 4th axis programming, so I want to machine an open pockets using 4th axis, first I made pockets contour on the plan by means of ''Transform Roll'' , after I use it to define pocket limits with axis substitution option, the problem is the toolpath resulting are shifted compared with  regions desired , some times the toolpath is upper than the part diameter and sometimes is on the part but  with angle offset . I tried to change MD  and CD without succes .mastercam 2017 ...  See file attached.

 

Thanks for your help

[nickbe10]

Hi Jackline,

From your description of the output it seems like center of rotation problem. Or the position of the "un-rolled" geometry relative to the cylinder.

I would point out though that this is really not a good application for axis substitution. It would be better done as a 4 axis index.

I can explain further if that would be of value.

[jackline.rousseau]

Thank you nickbe10 for your help, you give me a goode idea to resolve the probleme which was the Un-rolled positioning, so I selected twice the circle center  to define the U-rolled positioning, now evry thing is ok,... The 4th axis index is better, I want just  to learn how to work with axis substitution.... thank you a lot

[Colin Gilchrist]

Axis Substitution will always have the "Centerline" of the cutter point towards the Center of Rotation. It is better suited for cutting Slots (on center), or for Drilling Holes around a diameter.

If you really want to cut those slots on a 4 Axis, you should look at the "Rolldie" C-Hook. This is designed to allow you to "offset" the centerline of the cutter, so that the edge of the cutter remains tangent to the curve you are trying to cut. This will "offset" the tool in the Y+- direction, assuming your rotary is aligned with the X axis, or will offset in X, if your rotary is aligned with the Y Axis.

[nickbe10]

Happy to help.

Notice that my suspicion was started because of your output, with profile changing in z level in the code (backplot is reading the NCI code) but not in the geometry relative to the surface....almost certainly a "center of rotation issue". Controlling your COR is the most important aspect of 4 axis programming, regardless of toolpath type or machine set up.