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Multi Axis Finishing with NX CAM

Siemens Legend Siemens Legend
Siemens Legend

For finishing in 5 axis, NX CAM software development is focused on the “Guiding Curves” operation. Our NX CAM customers report guiding curves to be very flexible with the geometries and patterns it handles, yet providing good machine behavior and finish quality. In the future Tech Tips I’ll write more about it, but to give a better perspective about Guiding Curves, let’s start with some explanations about Variable Contour operation using Surface Area and Streamline. Knowing how the system works, helps you guide it to do what you want it to do.

 

There are many aspects we can cover, but I will concentrate on three important ones:

  • Coverage and Pattern
  • Position, Projection and Collision Avoidance
  • Tool axis policy

The Coverage and Pattern is covered in this NX CAM Tech Tip. The other two as well as detailed description of the Guiding Curves operation will be detailed in separate Tech Tips.

 

Note: this article is describing the behavior of NX CAM software, but many pieces are common to surface base (NURBS) path generation in other software.

 

Coverage and Pattern

 

Surface Area

Generating the pattern on an arbitrary set of faces with variable slopes is pretty challenging. Some of the faces you see on the screen have a parametric representation called U and V. To visualize it you can use the modeling ‘Isoparametric Curve’ tool to draw those:

 

multi axis 1.png

 

 

In Surface area when you select this face as the drive, the system will use this parametric representation to draw the pattern. ‘Zig’ / ‘Zigzag’ / ‘Zigzag with lifts’ will go along U or V. ‘Follow Periphery’ will offset from the outer shape in the parametric field.

 

Multi axis 2.JPG

 

Helical will only work if the drive performs a close loop (i.e. - a cylinder).

 

In case that you want to machine more than one face at a time, three things may happen:

The next face I select has a matching parametrization so the system can merge those to a grid of well behaving U/V:             it also can be extended to the next row(s):


multi axis 3.JPG

 

The next face has a parametrization that do not match. This will pop up the “Grid Error”:

 

multi axis 4.JPG

 

In this case the curves on the right lower side of the selected face cannot find continous matching curves to the faces already selected.

In a limitted set of cases you can “force” the system to accept an irregular grid
like by increasing the chaining Tolerance:

 

multi axis 5.JPG

 

It is a bit experimantal and the results might not be smooth but it is useful to know it and try when needed.

 

multi axis 6.JPG

 

 Streamline

To handle the cases where a well behaving grid cannot be extracted from the cut area geometry we have Streamline. In Modeling there is a tool to create “Through Curves” surface:

 

multi axis 7.JPG

 

Which uses two flow curves to blend a surface in between. As you can see the surface is sometime inside and outside the part. As further the drive deviates from the part – your tool path will stick less to the intent. To get a bit closer you can use Through Curves Mesh.

 

multi axis 8.JPG

 

With proper selection the surface is way closer to the path, yet it is not perfect since we miss some cross curves. In manufacturing the same is available in streamline.

Only Flow:multi axis 9.JPG

Flow and Cross:

multi axis 10.JPG

 

In case you need cross curves but the geometry does not have those and you do not want to streach your modeling skills, NX CAM enables you to generate those on the part:

This will be detailed in another article.

 

multi axis 11.JPG

 

The parametric representation allows you to trim or extend. Because it is parametric – you cannot use a distance value (i.e. extend by 2 mm or 50% Tool), instead you can only use a % value:

 

multi axis 12.JPG

 

The pattern from the drive is later projected to the cut area / part so the real coverage cannot extend beyound the (extended) drive, nor beyond the cut area / part geometry. This topic and other Position, Projection and Collision Avoidance topics and a detailed description of Guiding curves and how it is different will be discussed in my next NX CAM software Tech Tip.

 

Was this information helpful?   Was it too complex?  Please tell us in the Comment section below.  Your feedback will help us to create the most helpful Tech Tips.  Thank you.

Eddy Finaro
NX CAM Product Manager
Siemens PLM
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