[SamTaylor]

Do CNC machines and software actually recognize real curved lines? Or are they just incremental inputs of short lines to make up a curve.

Im digitizing patterns and my curves are just a bunch of little lines that and angled to make up a curve (if that makes sense)

Would that be okay or do I need to figure out a way to make sure they are smooth actually smooth like when I hand design them in Fusion.

Im about to start digitizing all of our shops patterns and I dont want to have to go back and re do them because these curves dont work.

[Jim Dawson]

The answer is: It depends When you boil it all down all in the CNC world, all arcs are a series of short line segments. This is because the controllers are digital and the points on the arc are calculated by trig in the controller. The minimum possible move increment is one encoder or stepper pulse.

Having said that, if you have line segments that are 0.001'' in length or less on the drawing, then you would normally not see any faceting on the part. Line segments that are 0.010'' might leave visible faceting on the surface depending on the tooling, machine rigidity, and material. I think Fusion has a ''curve or arc fitting'' function that will smooth out segmented arcs.

You can machine a perfectly acceptable arc using only G1 moves rather than G2 or G3 moves if the line segments are short enough but this does create huge G-code files.

[awerby]

It should work okay to do what you're doing, as long as the segment lengths are short enough (like Jim says). Smoothing them out is a separate command in G-code; G64 (continuous contouring) blends them all into one continuous motion, at a certain expense in accuracy that can be specified with a P-word (at least in some programs, like Linux CNC). G61 puts it back in Exact Stop mode, which makes it stop at the end of each segment (and makes your machine shudder like it's having convulsions). It's explained here in more detail for LinuxCNC, your controller may want it done differently: Important User Concepts

Are you using a 3D scanner to do this, or doing it by hand?

[SamTaylor]

It should work okay to do what you're doing, as long as the segment lengths are short enough (like Jim says). Smoothing them out is a separate command in G-code; G64 (continuous contouring) blends them all into one continuous motion, at a certain expense in accuracy that can be specified with a P-word (at least in some programs, like Linux CNC). G61 puts it back in Exact Stop mode, which makes it stop at the end of each segment (and makes your machine shudder like it's having convulsions). It's explained here in more detail for LinuxCNC, your controller may want it done differently: Important User Concepts

Are you using a 3D scanner to do this, or doing it by hand?

So what Im doing is digitizing patterns that will be used to manufacture wood framing for furniture, but first I will be doing the patterns that are used to eventually knife cut the fabric. So Im not sure if this is even an issue. I would assume that the more smooth all the lines are the better. but I dont know.

So our current set up, we have a camera set up and we take photos of the patterns and then they are uploaded to the computer. We have some software that auto traces the shapes but the DXF files have a lot of nodes or vertices how ever you wanna refer to them.
When I hand draw them in Fusion I can make the curves and they are real curved lines.

[awerby]

I doubt that the method you're following will yield accurate results. Cameras tend to distort things. If you aren't lined up exactly straight, or if the lens has a little spherical aberration, the result will be a DXF file that won't create the same pattern that it was based on. I'd suggest at least checking the files you're getting against some measured points on the original pattern to make sure you're not introducing errors, before wasting a lot of time doing this to your whole part library. You'd probably have better results recreating the patterns in a CAD program based on measurements rather than photographs.

Auto-tracing can introduce a lot of errors and extra points as well. I've generally had better results tracing things by hand, if the patterns aren't too complex for that.