Poor Surface Finish

[savtav]

When i machine a complex 3d surface sometimes the toolpath i machine looks lumpy.

The toolpath looks ok on MC ,I have set the torence to .003mm and filter .0015 in Mastercam, step size .15mm .

I have to Mazaks vqc20, avj18n .It looks like the buffer is working overtime. Does any one know how to improve my surface finish so it can smooth through out the job. i have to stop the polishers having a whinge on my cavities.... Help

[Allan Brown]

To start your filter tolerance should be larger/looser than your cut tolerance.

Consider the tolerances additive. Without considering spline, surface, and system tolerances, your cut tolerance and filter tolerance should add up to be less than or equal to your overall finish tolerance.

CNC Software recommends that the cut tolerance be roughly half of your filter tolerance. The dudes at MetaCut/Northwood Designs say slightly looser (by .0001") is often enough. Our test tend to confirm this.

e.g. aiming for 0.0009" to 0.001" finish (or final cut) tolerance

1/2 method

cut tolerance - 0.0003"

filter tolerance - 0.0006"

.0001" looser method

cut tolerance - 0.0004"

filter tolerance - 0.0005"

[Charles Davis]

Dave has some excellent suggestions. Another is to just turn filter off for now. The V9 filter will allow "one way" filtering, which should resolve this issue.

[beav700]

What's one way filtering?

[Mazakman]

Dave,

The 1/2 method sounds ok but having set the tolerane very hi means Mastercam needs a lot more time to process the toolpaths . And you know time is money.

Dosn't it depend on the type of cnc controller you have witch has infinity look ahead on buffer size, and nurbs maching? Please correct me if i am wrong..

[Allan Brown]

quote:

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Dosn't it depend on the type of cnc controller you have witch has infinity look ahead on buffer size, and nurbs maching?

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Those variables would determine how your machine handles unfiltered or poorly filtered code. This discussion is on how to properly apply the filter before the code is produced.