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Variable Lead Angle

I am milling an airfoil helically, and I am getting some odd undulations on the edges of the airfoil where the tool is wrapping the edge(as shown in picture).  Watching the program running at the machine it appears that the machine is hesitating while some of the axis' are "catching" up to the programmed lead angle of 7.5 degrees.  A tooling application engineer said he had seen this before at another company and said that company was able to eliminate the problem by giving the lead angle a tolerance so the tool wouldn't have to wait for everything to catch up before moving on.  He said he believed that they were doing that in their cam software.  My question, is there a way to do this in NX?  I am using a Variable Contour toolpath with the tool axis set to relative to drive with a 7.5 degree lead angle.  Is there a way to give that lead angle a +/- tolerance so it will be smoother?  


I am using NX







Re: Variable Lead Angle

Siemens Legend Siemens Legend
Siemens Legend

you probably are looking to 'Optimize to Drive':

Optimize to Drive.jpg

it may require a special license, so if you do not see it - please contact you NX provider.

the reasom you see those "hesitations" is that our relative to drive processor tries to be "mathematically accurate" and with the blade geometry often comming from a CAE / flow analysys curves the normal to the surface at the leading / trailing edge do not develop smoothly. the Optimize to drive tries to dump the changes. To resolve it we are also working on a spcial Interpolate Angle to Drive / Part that will allow you to auto initiate as many vectors around the blade as you like (with the requested lead / tilt angle), modify those locally as needed and generation will do an absolute interpolation between the user points. this is expected to reduce the 'noise' you mentioned without losing the lead angle intent and ability to locally modify one or more vectors. 

if you are interested - once the development is stabilized you can try it through our Early Validation Program (EVP).

Hope it answers your questionsSmiley Happy,



Eddy Finaro
NX CAM Product Manager
Siemens PLM

Re: Variable Lead Angle



Thank you for the response, we do have a license for the optimize to drive and I have been toying with that recently.  Looking at the help file on it, it suggests to not specify the max and nominal angle and let NX determine those automatically.  So when I set the options to "None" and generate the toolpath when I go back into the dialog box it reverts back to what I originally tried as my Max and Nominal lead angles.  Not sure if this is intentional or if I am missing something.  When using the same tool shown in my picture I also got one area on the blade that had a retract and engage in the middle of the toolpath, I am not sure what caused that either.  I have recently tried the optimize to drive method using a larger tool and it seems to have generated with no issues and I will be trying that today to see how it runs. 

I am interested in learning more about the EVP program, is there something we(as a Company) need to do to join that program?

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