How to generate 2D cam contour toolpath with high accuracy with MasterCAM/How to fab precision CAM with MasterCAM?

[Toolpathgeneration]

How to generate 2D cam contour toolpath with high accuracy with MasterCAM/How to fab precision CAM with MasterCAM?

 

Accuracy requirement: tool path profile error within 1um, or chord error within 0.5um.

 

My machining vendor convert 2D cam cotour to arc with chord error setting to 0.5um but actual maximum chord error is 3.7um.

CAM contour is comprise of convex and concave profiles.

The converted arc is comprise convex arcs and linear lines only. There are no concave arc. The maximum chord error is near center of concave profile.

The chord error of most converted arcs are less than 0.25um. This generate unnecessary high number of arcs. The total number of arcs/lines is about 350 per cam profile.

 

Thanks

[Allan]

Welcome to the forum.

 

The tolerance settings are bi-lateral so you would want to set less than half of your tolerance.

Do you have a geometry file to share?

 

 

Allan

[Toolpathgeneration]

The requirement is profile error 1um (an GT&T tolerance). It is the same as MasterCAM chord error 0.5um.

[Colin Gilchrist]

The tolerances in Mastercam can be changed, depending on the accuracy you need. Who is your Reseller? I'm sure they can help you get the tolerances for Mastercam and for the Toolpath/Post set properly.

[Toolpathgeneration]

Machining contractor use break many to convert spline to arc. The result is no so good. A correct direction/method is needed for machining vendor.

I have asked contractor to contact his MasterCAM reseller for help but no feedback.

[Colin Gilchrist]

I would recommend not converting the Spline, but driving the Spline itself as the geometry. Then you can adjust the System Tolerance and the Toolpath Tolerance to give you the precision you need.

 

Again, your Mastercam Reseller should be contacted to help you with this.

 

You mentioned a "Contractor", but provided no details about them or who their Mastercam Reseller is.

 

I'm not trying to accuse you, but the vagueness of your answers leads me to believe that you don't have a legal seat of Mastercam. If you do indeed have a legal seat, PM me and I can help you get in touch with your Reseller.

[John Summers]

One micron is about .00004, so 3.7 microns is about .00015. You could set the tolerance to either .00015 or .0001. To break up an arc you can use this formula: chord = sqrt(8*err*r), where err is the chord height tolerance. You could analyze the linear results of breaking the spline into linear segments by analyzing the spline dynamically, and comparing the chord length with the radius at a given point by using the above formula.

[Todd Tracey from Fastech]

Question, can you say what kind of machine you are programming for that will hold that tolerance?

[generaldisarray]

http://www.fanuc.co.jp/en/product/robonano/index.htm

[Toolpathgeneration]

Hi Colin,

 

The contractor told me they have large quantity of legal MasterCAM liscences (about 15 seats). They told me they will ask their reseller for help. The responses are slowly. I have to accept "break many" for prototype even if it may not the best method. Thanks.