Convex Instead of Concave Radius Generated

[tspinetti]

I'm relatively new to Fusion 360 but up until now I've been able to work through my issues by reading through the forums for info and systematically making changes to either my model or CAM, and sometimes both.  This one has me stumped.  I'm at a loss as to why a convex radius tool path is generated instead of a concave radius tool path.  Look at Setup 3 - Contour 5 in my f3d file attached.  I've gone through just about every CAM setting one by one and it doesn't change.  Thinking it might be my model I deleted the .015" corner radius' but that had no effect.  I'm sure it's me and not Fusion because Contour 4 works as intended.  I've got over a hundred of these to make and I'd like to get going.

For info I'm using the Mach3 post processor.

Thanks    

[LibertyMachine]

What you are seeing as a "Convex" toolpath is the centerline of the tool itself. In the simulation, you can run it through and see:

Although, to be sure, there IS material being left on the part, but that mostly goes away when you enable "Machine Shallow Areas" on the Passes tab.

Am I not seeing what you are referring to?

[tspinetti]

I responded earlier on my cell phone but I don't think it came through.  I ran a sample part this morning and the radius is machined convex.  Sorry for the fuzzy picture but it is attached.  It shows the finish pass machines the upper corner radius then machines the convex radius.

[LibertyMachine]

From the photo, I'd almost be tempted to thing that your Z zero is off. It looks like it's cutting convex, but we are seeing the actual top of the part, whereas the island above is needing to be cut away.

hmm....

And no, if you respond by email and include a photo, I don't believe the post will go through..

[tspinetti]

Take a look at contour 4.  This is the roughing pass before contour 5.  In simulation and on the machine it cuts the radius correctly.  The simulation tool path between the two operations are significantly different with contour 4 cutting a concave path and contour 5 cutting a convex path.  Settings in both operations are the same. 

[LibertyMachine · Accepted solution]

Mmhm. And what you are seeing with Contour 4 is because it is a straight flute endmill. If it had a small corner radius, you would see similar to the ball endmill toolpath.

The "convex" you are seeing in the toolpath itself is because it's tracing out the centerline of the tool, at the tip. The convex is what it's rolling as it machines over that top .015" radius

And if we turn on Stock and run through the simulation, you get this:

You have not positioned your stock correctly on the model. Your Face toolpath is going to -.005 below STOCK top, whereas the model itself is quite a ways away from that point.

I personally prefer to have my Stock Top positioned about .01 from the top of the part, and then I use "Model Box Point" when I choose my origin

[tspinetti]

Ahhh!  I see what you are saying about Z height.  I'll check my tool length offsets in the morning.  

[tspinetti]

You were correct. My Z height was not set correctly. I ran a sample part this morning after tweaking my CAM and the part came out perfect. Another day and another lesson learned. Thanks.