# Thread: Is there an easy way to make a Z-axis simple curve without going full 3D?

1. ## Is there an easy way to make a Z-axis simple curve without going full 3D?

I have an arch I'd like to cut with a straight bit, just a single swoop with the Z axis changing as the bit travels along the Y axis. I have a few instances of this. The first is in fret slots. I want to follow the fingerboard radius. The other instance is in a truss rod slot. It'd be easy to draw the curve in 2D and somehow transpose it to the Z axis. Any cheats on how to do this?

2. Originally Posted by 777funk
I have an arch I'd like to cut with a straight bit, just a single swoop with the Z axis changing as the bit travels along the Y axis. I have a few instances of this. The first is in fret slots. I want to follow the fingerboard radius. The other instance is in a truss rod slot. It'd be easy to draw the curve in 2D and somehow transpose it to the Z axis. Any cheats on how to do this?
not sure if I follow you correctly , cant you just rotate 90 deg. around the Y axis...then use- Mill 3 axis- engrave

3. Originally Posted by 777funk
I have an arch I'd like to cut with a straight bit, just a single swoop with the Z axis changing as the bit travels along the Y axis.....
EDIT: just like Claude said ^^

Easiest way is to draw your 2d arc in the XY plane,
then Rotate it to the YZ plane, (you can try to draw it in the YZ plane, but the coords are very hard to follow)
then use 3D Engrave to follow it with a toolpath.
Play with the depth setting until you understand what's happening.

FWIW, someone else had the same app. but wanted to be able to ruf without burying the little cutter too deep. That solution required modeling the slot to slightly larger than cutter width and using Slice Planar with a Step Down distance defined.

4. Yep, Claude is right on the money there. The 3D Engrave feature would be good for that.
CNC Dude

• ## 3D Engrave

3D Engrave? Is that a program? Is it free? If so... Someone have a link? Thanks!

• Millwork, the 3D Engrave is a feature of the V24 software. There is a 2D Engrave and a 3D Engrave as well as V Carving with a combination V cutter and EndMill as needed. Do you have BobCAD-CAM software?
CNC Dude

• Oh... No I use AlphaCam. I guess I should pay a lil more attention. I didnt realize that this was a BobCad forum. Sorry! :-/

• No problem. Do you make guitars?

• No... I dont really know anything about guitars other than they make noise. I have a guy here in the shop thats in a local band that wants me to cut one for him on the CNC. If all goes well with the first one I might study up on it and make a few more for the heck of it.

• I tried this and no luck. What I'm trying to do is toolpath a 3/16" spiral bit to cut a curved bottom channel for the truss rod. I drew a arched line and rotated it as mentioned and that worked just fine. But when I verify it the bit is no where near the 3D engrave toolpath. It's completely off the piece. Maybe I'm setting up the 3D engrave wrong.

Also, how does engrave work? Shouldn't it follow the bottom of the arched line I drew with the tip of the bit?

Here is what I'm trying to do (but CNC of course) See Photo:

The sides of the jig are curved to create a cut that has a arched depth.

• Originally Posted by 777funk
...
Also, how does engrave work? Shouldn't it follow the bottom of the arched line I drew with the tip of the bit?...
First, make sure you're using the the Engrave feature under the 3-axis menu and not the 2-axis menu.

Also, make sure your geometry is at the depth you want to machine it at.
The Depth value will obviously adjust the Z-depth of toolpath from the geometry, but this can be set to zero and even given a neg. number to raise the path.

Couple more things to mention, the arc will be broken into small, straight line segments.
And the path is calculated from the tool centerline, so flat bottom tools will show a slight deviation. Certainly not an issue in your app.

Sometimes it's easier and cleaner to just hand code a feature like this, using the CAD data for the coords. (one arc is just a single line of code).

• Originally Posted by moldmker
First, make sure you're using the the Engrave feature under the 3-axis menu and not the 2-axis menu.

Also, make sure your geometry is at the depth you want to machine it at.
The Depth value will obviously adjust the Z-depth of toolpath from the geometry, but this can be set to zero and even given a neg. number to raise the path.

Couple more things to mention, the arc will be broken into small, straight line segments.
And the path is calculated from the tool centerline, so flat bottom tools will show a slight deviation. Certainly not an issue in your app.

Sometimes it's easier and cleaner to just hand code a feature like this, using the CAD data for the coords. (one arc is just a single line of code).
That would be awesome. Could you shed a little more light on where/how to do something like this. Sounds simple and effective.

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