How to engrave on a sphere in gibbscam?

I want to engrave on a 2.5" sphere with its center at 0,0,0. I project my geometry onto the surface of the sphere, no problem. How do I make my tool path depth trap to the surface of the sphere? I want to keep a .03" depth.
What really bothers me is that I have done this before, but cant remember how. Getting old is a bitch.
have fun
i_r_machinist

Maybe draw a sphere that is as much smaller in radius as your depth of cut? Project the toolpath onto that.

On second thought, that may give you some sort of distortion. It would probably be better to draw a sphere with a radius equal to your part radius, plus the tool radius, and minus the depth of cut. Then project to this sphere and recognize that you are programming to tool center (assuming a ball mill). So reduce the tool length offset for that tool accordingly.

The width of the engraving is only .75", so I'm not looking at a major Z change. Tool is a scribe and I'm programming on center cutting. I'll go drink a beer in the shop and do something else. Maybe it will come back to me.
thanks
i_r_

If you have the sphere as a solid in Gibbs you can create your text above the part and project it down onto the sphere. A contour path with more than one contour automatically cuts on center. The trick is to use a negative offset for the stock that is the depth you want the engraving to be. I do this a fair bit on 2d arcs (OD of a part) but I generally use a 3/64" ballmill. You also have to make sure your pick-up is on the money, if you're off at all the engraving will be heavy on one side and light on the other. Forgive me if I've covered the obvious, I never know how much experience anyone has.

i_r_machinist said:

I want to engrave on a 2.5" sphere with its center at 0,0,0. I project my geometry onto the surface of the sphere, no problem. How do I make my tool path depth trap to the surface of the sphere? I want to keep a .03" depth.
What really bothers me is that I have done this before, but cant remember how. Getting old is a bitch.
have fun
i_r_machinist

Click to expand...

What I do is this...

Create sphere so that the tangent is my Z0.
For example, create a sphere with a radius of 8.0 inches at x0y0z-8.
Create my geometry at z0 in the xy plane in 2d.
Select the geometry to engrave, and set the z depth at something like z-.375(stay with me)
and in the solids tab, set surface stock to -.030 .
Also select the surface you want to engrave ON. If you dont do this it will try to engrave at z-.375, if you do, it will drape your toolpath onto the sphere.
Touch the tool off at the x0y0z0 tangent point.


I hope this helps.

edited to add: I just re-read your initial post...my bad. If you want your z0 to be the center of the sphere you will want your z depth to be +2.125 or so, clearance planes set accordingly etc.
and you will need to comp your tool to center after touching off, in one fashion or another.

I've never done this before in gibbs, so I can't help you there but...


... If you've done it before, can you just find the .vnc file that you did before, and just take a look to see how you did it? Sometimes I do that with speeds/feeds for volumill, see what I did in a similar situation/material.

Do it all the time in Surfcam.
Can be done in 2 ways:
Set stock to leave a negative value -.03 - this way however your letter size will grow not only in deoth but with as well.

OR

Program your original toolapath at elevation z=0. With final depth being the depth of your engraving(-.03)
Then project it to your surface. Leave stock to leave =0, but check "add to z-depth"
This way the toolpath prijects on the sphere, toolpath z0 becomes the surface elevation.

This is how its done in surfacam, and i would expect yours to do it the same way.

Bingo. Don't project onto surface and control depth with -z surface stock.
Thanks Guys!
i_r_