Does anyone use Fanuc's Nurbs Interpolation?

[Lars Christensen]

Just sitting here a Thursday night at home skimming through the Fanuc manuel and came across Nurbs interpolation (G06.2), and wondered if anyone is using this, and if you can get Mastercam to output this?

 

Lars

[kunfuzed]

I always wondered about that myself. I think the only advantage would be less code. But as with surfacing, finer XY segments may give you a better finsish with more control. I'm no expert though.

[Guest CNC Apps Guy 1]

It has some inherent advantages over Point to Point and Arcs. I'll elaborate more when I get out of the dog house with my wife. perhaps in the morning.

[kunfuzed]

Yeah, school us!

[Lars Christensen]

Thanks James, it sounds very interesting, I did not know Fanuc had that kind of options.

[pronc]

All of our new machines have this option. There are 3 advantages that I see with this option.

1. Program is a lot shorter especially with complex surface.

2. Better cycle time. About 15%.

3. In most cases better surface finish.

 

Basically it is a curve machining option.

[Guest CNC Apps Guy 1]

Ok, the wife is gone and I'm baby sitting my 2, 8, and 10 year olds!

 

In a nutshell NURBS (For Fanuc) has absolutely nothing to do with the surfaces.

Below you'll see a sample of the code - I personally ran this so I know it works. It is in Metric so be forewarned no guarantees, yadda, yadda, yadda.

 

%

O0005(NURBS SAMPLE FORMAT)

G0G80G40G49

G0G91G28Z0

G90

 

N5

T5

M6

G150Q4.(SUPER FINISH PARAMETERS ACTIVATED)

G90G0G54X4.422Y-14.902S20000M3

G43Z50.H5M51

G05P10000(TURNING ON HPCC)

G0X4.422Y-14.902Z50.(POSITIONING)

Z5.379

G1Z3.379F4000(FEEDING)

G06.2P3K.X4.422Y-14.902Z3.379R1.(TURNING NURBS)

K.X1.9295Z3.1895R1.

K.X-0.563Z3.R1.

K1.X-1.0315R1.

K1.X-1.5R1.

K2.

K2.

K2.

G1X-1.486Z5.5(NURBS IS OFF BECAUSE LINEAR MOVE CANCELS NURBS)

G0Z35.(POSITIONING FOR NEXT CONTOUR SLICE)

X5.106Y-14.702

Z5.219

G1Z3.219

G06.2P3K.X5.106Y-14.702Z3.219R1.(NURBS TURNS ON AGAIN)

K.X2.6085Z3.1095R1.

K.X0.111Z3.R1.

K1.X-0.6945R1.

K1.X-1.5R1.

K2.

K2.

K2.

G1X-1.277Z5.49(NURBS IS OFF)

G0Z35.

G05P0(HPCC IS TURNED OFF)

M59

G91G28Z0Y0M5

G90

M1

M30

%

 

Advantages - processes faster than point to point by 100% last I checked. BPT of 1ms or better. Less code to interpret the feature, sometimes by as much 70% depending on the complexity of the features being machined. Accuracy is said to be better than point to point but I cannot personally confirm this. In a test cut 158 minutes to cut the part using Point to Point, Same Part, Same Tolerances, Same Stepover, 111 Minutes. Pretty healthy improvement. This is an Apples to apples comparison EVERY parameter was the same for the test. Also, same machine.

 

You'll notice some different looking code;

G6.2 - this activates NURBS

P - This is the spline Order

K - This is the Knot Vector

and the XYZ is the Control Point Location

R - This is the Knot Weight.

 

It's all mathematical and there are equations that actualy define the locations. It's REALLY a dry subject. 90% is above my head but I understand the process and how it works and relates to Machien Tools which is the important thing I guess.

 

Disadvantages - BIG$$$$$ Option. You're going to need a Dataserver to run the large files that would make the NURBS option viable. It's a Hardware Option AND SOftware so Fanuc can;t just come and change a few bits in the parameters and you have NURBS. You really need to have your machine tuned afterwards to take advantage of the ACC/DEC. If your machine already has HPCC (G5P10000) then you're probably ready to go once the option has been installed. You'll need at least a 16MB, 18i, or 15 Series Control to run it. I don't believe the O series and 21 Series can do it- if I'm wrong, please correct me. You'll also need a 3rd Party Software called Metacut Finish/Pro to create the NURBS code from your Mastercam NCI or your G-Code File.

 

That's the skinny.

 

Any other questions???

[Lars Christensen]

I am babysitting my 5 year old, she is yelling at me to come back in the family room and watch a movie

 

So it is verily something that apply to high tec. company with $$$, and code would not be possible to get Mastercam to post out, pretty amazing code compared to standard G-code, how do you figure out what options that has been activated on your Fanuc control?, we just bought a Matsuura with a 31i control, and I have no idea what options it has.

 

quote:

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ANything else?

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Well now where you mention it

I can not see the pictures on your website.

 

Thanks James, I appreciate you taking the time expand my horizon yet again.

 

Lars

[Guest CNC Apps Guy 1]

For some reason neither can I, Adelphia cannot explain it either... Go figure... It looks good on my computer though.

 

As for finding out what options your machine has on it, your Machne Tool Dealer could tell you that information. I'd be willing to bet at the very least you have AI-NANO (G5.1Q1). Not necessarrily a high tech company, just a company with the right application and a means to justify the added expense of the options and extra software you'll need.

 

As always Lars, it's my pleasure to help in any way possible.

[pronc]

"In a nutshell NURBS (For Fanuc) has absolutely nothing to do with the surfaces."

 

This is what i found in one of the article from MMS ONLINE.com.

 

Take the following points away from this article:

 

* Nurbs interpolation offers an alternative to traditional chord interpolation for machining complex contoured forms, like dies or molds. If you are instead machining geometrically simple parts, nurbs interpolation can't help you.

* Nurbs interpolation may let you machine these complex forms at a higher average feed rate than you would achieve using chords, without compromising accuracy. CNC processing speed may provide the reason why, but there are other reasons, too.

* By itself, nurbs interpolation is not more accurate than chord interpolation. But when accuracy is required, nurbs can offer a more efficient way to achieve it.

 

Here is the link to the article

 

http://www.mmsonline.com/articles/079901.html

 

Please look at the test part they used. It seems to me nurbs interpolation is only idealy for machinging complex surfaces.

 

James kinda lost me a bit there when he said NURBS has nothing to do with surfaces. I guess he was refering to NURBS itself. i think all along we were talking about NURBS interpolation.

[Guest CNC Apps Guy 1]

quote:

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...James kinda lost me a bit there when he said NURBS has nothing to do with surfaces. I guess he was refering to NURBS itself. i think all along we were talking about NURBS interpolation...

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Often people confuse the two, they think because their CAD model has NURBS surfaces and they are programming to those surfaces that it takes that NURBS data from the surface and goes directly to the CNC Program. That was the reason for that comment. Sorry for the confusion...

 

Yes NURBS Interpolation is ideally suited for the Mold and Die Industry, but I have seen successful application in the medical industry as well. AI-NANO and HPCC are just fine for Aerospace and Automotive.

 

The test part I machined with NURBS to get the cycle times was a VERY complex shoe sole mold in ALuminum.

[Lars Christensen]

Ok, so it verily sounds to me that if you machine a lot of mold cavities, or such 3D models, and especially if it is in the category of "long cycle times" 2+ range, you might be stupid not looking into this option even if it is $$, you could earn that back in the long run.

 

Again thank you James and pronc, I feel like I was just told the earth is round

 

I would not have any use for this application for what I do now, but hey who knows maybe down the road, and you know what they say"knowledge is key"

 

Lars

[Guest CNC Apps Guy 1]

Yes Lars, you are correct. The money spent would be WELL worth it for the right application and could very well pay for itself in VERY SHORT order. Weeks or Months if not sooner. Knowledge is key... knowledge is key. Learn whatever you can, wherever you can I always say.

[YoDoug®]

James,

 

I just want to make sure I got this. NURBS interpolation is kind of a very complex version of circular interpolation. The CNC controller interpolates an arc based off G02-G03 input values rather than having to list point to point moves to generate the arc. Likewise any bezier spline that can be defined by a mathematical algorithm can be NURBS interpolated as long as it lies in one of the three planes (G17,G18,G19.

[Guest CNC Apps Guy 1]

quote:

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...The CNC controller interpolates an arc...

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No, it interpolates a spline. Splines are defined by Knot Vectors, Knot Weights, and Control Points. NURBS Splines are not necessarrily planar. Yes they are defined mathematically which is where the inherent advantage over Point To Point. The control is able to more quickly interpret a spline as opposed to interpreting a ton of small line segments.

[YoDoug®]

Thanks James, and Thanks emastercam forum. I learn something new every time I'm in here.

[Guest CNC Apps Guy 1]

You're welcome Lars. Glad I was able to help.

[Cannon]

quote:

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You'll also need a 3rd Party Software called Metacut Finish/Pro to create the NURBS code from your Mastercam NCI or your G-Code File.

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So you cannot create NURBS code straight from Mastercam. Can anyone tell if this is going to change in near future or is this just the way it works?

[Guest CNC Apps Guy 1]

As of now you need the 3rd Party Add-On. AFAIK there are no plans to change this. It's REALLY a VERY small percentage of the market that is even capable of NURBS Interpolation. I'd rather see CNC get on with Multitasking on Lathes than this.

[Greg Williams]

quote:

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I'd rather see CNC get on with Multitasking on Lathes than this.

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Absolutely, I would much rather have MMT than NURBS machining

[Guest CNC Apps Guy 1]

I have a half dozen Multitasking lathe projects going on in the next few months. I SURE with they would hurry!!!!

[Greg Williams]

quote:

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I SURE wish they would hurry!!!!

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Me Too