Advance MultiAxis Toolpath

[PoNyCaR50L]

I would like to know the difference between Maximun angle step (inside tool axis control menu) and Smooth Surface Normal (inside Ultility menu)

 

Has anyone here experimented a combinition of those two parameter in five axis toolpath?

 

Which one is better and why ?

[CJep]

I did a search in the Mastercam Help for "Maximum Angle Step" and this is the description

 

quote:

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The Maximum angle step value sets the maximum allowed angle change between two consecutive toolpath positions. The calculation engine outputs 5-axis toolpath data that contains the tool tip position and the direction vector of the tool. The direction vectors are not allowed to have an angle change larger than the value specified here.

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The search for "Smooth Surface Normals"

 

quote:

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This operation will smooth the surface normal. The value is the maximum allowed rate of angle change measured in degrees divided by distance (in millimeters or inches). If the orientation of the surface normal is changing more rapidly along the surface slice than this limit value (for example, five degrees per millimeter), then this section of the surface slice is modified. A virtual surface normal is inserted between the beginning and end of this section that is basically a linear interpolation.

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From the description it looks as though smooth normals allows you to work with problem surfaces that would cause unwanted tool movement.

[Chipmakr]

I would like to know the difference between Maximun angle step (inside tool axis control menu) and Smooth Surface Normal (inside Ultility menu)

 

Has anyone here experimented a combinition of those two parameter in five axis toolpath?

 

Which one is better and why ?

 

Can anyone shed some light on this subject. Not having much luck finding anything of substance in the help files. I am trying different settings to smooth my vector changes at the machine.

[Zoober]

If you are having problems with drastic vector changes, drop the max angle. I have gone down to .01 deg. for some real lay down vanes. Think of it as adding node points (vector changes) to a spline to smooth it.

It will drastically increase your program size tho.

I just finished a 46mb program for a little impeller.

Tiny tools equals tiny stepovers equals huge program

[Chipmakr]

I am using "Tilted through curve" for tool axis control. After some experimentation I have landed on "closest point" as my curve tilt type. I tried automatic hoping the damping distance would have some smoothing effect, but the result I got was no good no matter what I tried. Anyone have experince or suggestions with Tool axis control, curve tilt type, or any other ways to drive the tool smoothly?

[Aaron Eberhard]

This is a can of worms subject, as far as tool axis control, especially without seeing the part

 

To answer the initial question, though:

 

Think of "Max Angle Step" as "Point Generators" from the flowline/port toolpath and you'll have the right idea. AFTER a toolpath is generated (For all practical discussion purposes), Max Angle Step goes back and breaks a tilting vector into smaller tilting vectors, i.e.: Say you have a movement that needs to tilt 5*, AFTER Mcam has already calculated this move, it then divides it into smaller angle steps to feed the machine, chopping it into 1* moves instead of 5*. This generally will cause your machine to move smoother, depending on the control and their multiaxis vector handling. I know our controls like to be fed smaller angle steps, so most of the time we stick @ .5 or .25 in this field. It's great because you can use a courser surface tolerance and still get a lot of angular step vectors when needed, making the calculation time a lot less.

 

Note that this WILL NOT help you if your surface is ugly/rough. This will just make the ugly/rough surface finer, not prettier.

 

Smooth Surface Normals is an attempt to smooth out rough/ugly surface normals from interfering with your toolpath. Before you can understand why this works, let's take a really basic, three sentence background on how an advanced multiaxis toolpath is generated on a surface:

 

Based on your surface tolerance, specified step over and along, the surface is broken into a stl file (a triangulated mesh file), the finer your settings, the smaller the triangles. Each one of these is an independent surface, with its own surface normal (the vector perpendicular to the surface). The toolpath is simply chaining together a movement across these surfaces, and the surface normal is used to determine how the tool should contact that triangle, your tool control is then used to figure out the tilt.

 

Now you can see how having a bunch of little triangulated surfaces with their own surface normals can cause problems if the normals don't each point in a smooth motion, you'll have one vector wanting + motion, then - and then +, which is what causes your machine & toolpath to go rough over a seemingly smooth surface. This is an attempt to smooth that out. Much like any global smoothing setting, I've had limited success with this filter..

[Chipmakr]

Zoober & Aaron thank you guys for taking the time to respond. The explanation of how the surface is calculated really helped me get a mental picture of whats going on here on what I can try to make improvments. Through trying different settings I was able to get a smooth toolpath motion at the machine, but i still get slight witness marks at the point where the tool moves (rolls) from Y+ to Y- while maintaining the same position on the part (M128 TCPM). I may try to restrict or lock down on of the axis to more resemble a fourth axis rotarty motion to get this "roll" out. Thanks again for your input.