G03 - Egg shape

[briangYUAJN]

When cutting using a program from Fusion 360 our machine is cutting egg shape, angled holes instead of what is shown on the CAD/CAM software, looking at the g-code I cant seem to find and reason why this may be.  Hoping for someone to spot something I may have overlooked here. 

Thanks

[leo.castellon]

Your backplotted codes looks like it is cutting circles: 

 But I also noticed that your .625" end mill's RPM is extremly slow, 350 RPM. What kind of material are you cutting? What kind of machine are you using? Is the stock securely held down?

LeoC

[briangYUAJN]

The stock is securely held down, this is strictly a test program for this machine as we're just starting operations on it. We're cutting into wood currently, typically  low carbon steel. 

[briangYUAJN]

But the problem we're having is the hole is certainly not a nice circular hole as the program shows, makes me wonder if it is not compensating for the cutter, or if something is just not posting correctly - below is a picture of the hole it makes in reality. 

 

[leo.castellon]

If your RPM isn't high enough, the cutter load becomes severe and will cause issues with it fighting trying to get through the material which would cause issues with extreme loading on the axes of the machine which in turn could cause your holes being egg shaped, especially if you have any backlash on your ball screws. 

LeoC

[leo.castellon]

Looking at your program, try using 1/3 of your cutter diameter for your stepover and see if that helps.

LeoC

[briangYUAJN]

Will give that a shot and see what results come back, do you think this could be a cause even if its cutting wood? This is a 10' lucas boring mill, when looking at servo load while running its very low 

[leo.castellon]

That sounds like a hefty machine. My speed and feed calculator, FS Wizard pro, says that for a .625 end mill in wood for slotting, they recommend 5000 rpm with a feed rate of 75. Just for grins, try your current program and change the spindle speed to 3500 and see if it comes out any better. Also add a finishing pass, like maybe .030 just to see if that makes any difference. As I said previously, the back plotted code looks circular.

LeoC

[briangYUAJN]

max spindle rpm on this machine is 1200 RPM, but will at 1K + and see what the results are, at 700 RPM the results were the same 

[seth.madore]

I highly doubt that the rpm is the issue. It's wood, being run on a monster machine. Now, is it at all possible that the material has moved?

I assume this is your first time using Fusion to produce code? What other software have you used, and can you share what the code output looks like from that software?

What post processor are you using in Fusion?

[leo.castellon]

Starting to wonder about that myself. Surprisingly, Lucas has good tech support. Found this: !!! Read Me First !!! Test Programs for Lucas / DynaPath CNC Controls - Lucasprecision.com . Maybe it is something to do with your posted code and the way your machine is interpreting it.

LeoC

[briangYUAJN]

Thank you all for the help, I am now beginning to believe this is not a G-Code issue but something with the machine itself. When programing a basic square just using g01 x1 y-1 x-1 y1..etc it cut correctly except the last pass came up at a 45 degree angle before going to x-1 properly, it started to traverse around 3/4".

After putting a dwell after each line it cut a proper square. I am assuming something is telling the machine to move too early and giving me this problem, but I can not discover what that may be.  Inside the parameters it is set to be within 20 microns before movement.

Appreciate all the feedback!