[the_canuck]

I'm using MadCam to cut out master plugs for composite molds for high end RC planes and such. I'm trying to get accurate Wing surfaces but am getting strange results both in the tool paths and in the parts. Accuracy and surface finish is key to getting good master molds.

My machine is setup in inches. I'm using the default inch mesh settings from the help file but I'm guessing they are not optimal for my application.

I have a 3-axis router running open loop servos in LinuxCNC. Servos run open loop back to LinuxCNC and closed loop to the servo controller. I drive them like steppers. My current Steps per inch is set to ~10,000 steps per inch on x and y and 25,000 steps per inch on z. I'm running a Mesa card and can still easily achieve 1,000 ipm rapids on x and y.

When I setup a planer finishing pass on a wing surface and pick contouring, I get rough tool paths especially on the leading edge of the wing which do translate to the finished part. If I pick direction as parallel to x or y I get better looking tool paths but why is contouring giving me the results it does.

My step over is 0.0223" and I'm running a 2 flute 1/4 carbide ball mill at 24K RPM at 100ipm (yes I'm burnishing my cutter). Current test was out of MDF but am about to cut a bunch of RenShape and would like to solve this before cutting this expensive stuff.

Attached is a screen capture of what I'm seeing in the tool paths. I get the same results in the finished part with the same waves showing on the LE of the wing surface. They are visible in good lighting and you can feel them when sliding your finger across the LE. At first I thought it was machine induced or servo tuning but I've spent quite some time messing with settings, check the machine mechanics etc. but now I'm thinking it's a tool path issue as I'm slowly ruling out the other possible root causes.

I need to get to a surface finish that is accurate to +/-0.001" worst case with minimal hand finish work after machining is complete.

Andrew

[JOM]

If you are working in inch, the maximum distance edge to surface should be set to about 0.001 or 0.0005 for the Rhino mesh settings. It seems like you have set it to 0.025. If you have the latest service release of madCAM, you can set this tolerance once and for all in madCAM options.
Attachment 273836

The tolerance that you set with your cutter tool is used for calculating the toolpath curves. It should be set to about 0.001-0.0005 inch.
Attachment 273838

I think if using these settings, you will get a much better result. There is one more thing that you could change and that is the surface angle limit option when you use the planar finishing. This is used for separating steep areas from planar areas. Since your model is relatively shallow, I would recommend to set the angle limit = 0. This will make a more continuous toolpath, especially for the planar finishing with contouring.
Attachment 273840

I hope this will give you some help.

/Joakim