arc fitting output on nx7.5?

[codecodelin]

Does nx7.5 supports arc fitting output which is similar to nurbs but not same,arc fitting converts linear small steps in surface machining to arc curves which represents surfaces more accurately and fast

 

[JohnRBaker]

Do you mean, does the NC tool path generation code output circle-records? I suspect that that is pretty much standard practice as long as the machine tool controller is able to take advantage of that, but I'll let one of the Manufacturing experts fill in the details.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[codecodelin]

What i mean is describing a surface by arcs is more accurate than lines.For example in curved surface the shape can be represented several linear segments but if we use arc fitting less nodes are enough to represent the same surface this means faster machining less program size,Icam campost supports nurbs and arc fitting method fe.
when we use multi axis milling the program represents the surface with small lines especially if we are milling a sphere
there will be a lot of small lines and machine can not reach faster feed rates but machine has 60m/min cutting feed and 1G acc. so if can represent a sphere with g2 g3 circular code instead of small lines we reach faster feedrates.
Shortly What i want is how i can combines several small linear segments into circular output in the same direction (see the attched picture )

 

[JohnRBaker]

Now you're getting into the stuff that the CAM guys will have to respond to.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[ToigaT]

I do 4-axis Wire-EDM (as well as other things) and it would benefit me as well if there was a function to enable NX to output a fitted circular record to the post processor.

When I developed my post for a new AgieCharmilles Wire-EDM, I started working on a function that would transform the linear moves into a circular arc because there is a function called Heteromorphism which allows you to command a G2/G3 arc as a profile for both the lower and upper head, simultaneously in a block on the same line. You can even have a G2 on the lower profile and a G3 on the upper profile at the same time.

This is very nice, however, NX will only output linear moves for 4 axis Wire-EDM. In my post processor, I started working on an algorithm to fit arcs between 3 and 4 points, which I have been successful in testing but it has actually taken a back-seat for now and remains unfinished. It will take a lot of work to try and determine if these linear moves are actual linear moves or if they are part of an arc/spline move and that is why it remains unfinished.

The main problem is that NX is transforming the arcs to linear-moves and does not allow me any access at all to the spline/arc information so I have to backwards calculate between 3 and 4 points what the radius might be and compare it to the last 3 or 4 points etc etc.

I have thought about using a simulated machine but NX actually lacks native support for Wire-EDM in this regard. I have explored the possibility of tricking NX into using a Milling machine ISV for Wire-EDM use but this isn't ideal.

I don't mean to hijack your thread but I would like to point out that Wire-EDM in NX is a bit disappointing, especially for 4 axis work. Half the time I feel like tricking NX into believing it's doing milling work with a very small tool than to have NX believe it is Wire-EDM that I'm doing.

 

[codecodelin]

The arc fitting output is very important for me ,since if you want faster cycle times because cnc consume time (2-5ms) to read a command and a time to perform calculation and a time for servo to start time ,we we add all of this time even machine is faster(60m/min fanuc16imb) it can only reaches 5m/min because there are a lot of linear moves, but i tested machine with a single circular command machine reaches faster feeedrates.
I can also develop post proc. in my posts and some short algorthms,if you can send your project i can share my ideas with you

 

[ToigaT]

I am using Algebraic Matrices to determine the radius size between 3 and then check with the 4th point to determine if it's still on the same radius and so on and so forth. This works to an extent but an advanced algorithm is required.

 

[codecodelin]

nx7.5 supports maple worksheet,it is easy to make a curve fit with maple,but how to call maple function during post process or toolpath generation?

 

[markrief]

I am not sure exactly what the question is.

Under the Machine Control group, Motion output has several options for linear, various circular, nurbs, and spline. Be sure this is set to what you want.

In 3 axis milling, if the underlying geometry is analytic (plane/cylinder/cone) then the output path should be pure, without fitting or approximation.



Mark Rief
Product Manager
Siemens PLM

 

[codecodelin]

Motion output in variable streamline is only line,arc par,arc par/perp to tool axis.Nurbs is only available on 3x machining (fixed axis streamline etc.. not available for 4 or 5ax machining.)
In 3ax machining there is no need any fitting you are correct
the output is pure arc.
But in 5ax or 4ax machining there are a lot of small line segments.For example i am machining a hemisphere which tool is tangent to the sphere and tool is moving in 4ax which is in normal to the bottom face of the hemisphere.
According to this all the toolpaths should be circular not line , but i got some circular some linear segments,the cycle time is very important i give 5000mm/min feedrate for the toolpath, but machine can only reach 3000mm/min,I have tested machine for small single arc machine can reach 10000mm/min (fanuc16imb,risc cnc 60m/min cutting speed)
there are too many linear command so machine cant accelerate too much.
What i want is i replace these several linear segments into a arc segments.I tried to change tolerance but it does not solve the problem.
How ican replace these several linear segments into circular segments.
Mastercam,Icam,powermill has arc fitting output i think but not sure, it uses g02 g03 instead of g01 linear segments.

Can i use maple integration to arc fit linear segments, since maple has arc fit function ,how can i call maple from post builder?
Please help

 

[Bugie]

Do you mean like the Mastercam ARC filter? If yes then then NX does not do this. CIMCO has a tool that you can run after the post

 

[Bugie]

I think arc fitting is defined as

"When you filter a toolpath, The system replaces multiple small toolpath moves that lie within a specified tolerance with a single tool move. You can also optionally replace multiple linear tool moves with an arc move of a specified minimum and maximum radius"

 

[codecodelin]

Yes Bugie .You are completly right.
And why nx doesnot support arc filter,even there are some small cam softwares having arc filter support??

 

[raysapp]

As long as toolpath motion lies within XY XZ YZ planes NX supports arc output just as well as Mastercam. The problem is very few surface contouring and multi axis operations lie within those planes. You must force them by specifying a cut direction. It's unlikely a streamline op would qualify.

Ray S
NX 7.0.1.7
www.appliedprecisionproducts.com

 

[Bugie]

Raysapp,

Sorry but the functions are very different. ARC fitting is filtering the toolpath to a specific tolerance that has been set by the user. This is very different to just enabling ARC output

 

[codecodelin]

Bugie is right,
These functions are not same ,mastercam converts linear motion to arc motion nx gives arc motion if toolpath has arc toolpath.
Bugie have you tried cimco,if you have a demo version can u share with me
I requested a demo from cimco but doesnot get any reply yet.
thanx

 

[Bugie]

Codecodelin,

The CIMCO product is called CIMCOfilter. I have tried it for 3D work, the results were quiet good. If you have a file you want to test with this filter, let me know.

 

[codecodelin]

Yes,if i want to send you my file but due to security i can not send anything outside of factory,how can i obtain the program working demo version?
Thanks alot

 

[Bugie]

You will need to contact CIMCO

 

[raysapp]

No guys, they are not that different, Mastercam simply has more control over output.

Ray S
NX 7.0.1.7

http://www.appliedprecisionproducts.com