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# how does the machining data library interpolate the data?

Genius

I tried to do some interpolate math, but the calculation does not works.

How do they get the feeds and speeds in the 3 examples on the help document.

https://docs.plm.automation.siemens.com/tdoc/nx/11.0.2/nx_help/#uid:xid1128418:index_mfggeneral:xid3...

Thanks

6 REPLIES 6

# Re: how does the machining data interpolate the data?

Genius

do they use simple interpolation math to calculate or other complex feeds and speeds equations ?

# Re: how does the machining data interpolate the data?

Valued Contributor

The Cutter Material, Cut Method and Stock Material must be an exact match.  Then it interpolates Cutter size, depth and width of cut based on the existing data in the table and operation settings.

In our case, we limited the cut and stock materials available to about 15 each,  Mill cutting to 5 classes.  Depths of cut to 3-4 settings.   Much easier to populate the data with limited selections.  Then we wrote a program with feed/speed knowledge rules to build the machining_data.dat file.   22 mb and 160,000+ entries was the result of all the possible combinations we had for various materials, cutter sizes, depth and width of cuts.   It takes about 15 seconds to respond the first time you retrieve Feed/Speed in the session.   Once loaded in the session it is fast from then on.

It works well enough that new NC Programmers can use "Set Machining Data" in operation Feeds/Speed settings and have usable values.

The more data you have in the table making it close to Cutter Size, depth and width of cut, the better it is.  Large interpolation gaps don't work well.

# Re: how does the machining data interpolate the data?

Genius

in the machining_data.tcl file

I found a variable: nearness 0.10

What is the use of this variable? What is the role of this parameter in the calculation of interpolation?

# Re: how does the machining data interpolate the data?

Gears Esteemed Contributor

This is applied to diameter and length values to have some kind of +/- tolerance.

See the following section in the same file:

```#  compute nearness band around input tool diameter and length
set high_diam [expr (1 + \$nearness) * \$dbc_tool_diameter]
set low_diam [expr (1 - \$nearness) * \$dbc_tool_diameter]
set high_length [expr (1 + \$nearness) * \$dbc_tool_length]
set low_length [expr (1 - \$nearness) * \$dbc_tool_length]
```

Search the file for "nearness" and find the usage for a better understanding.

In short if you have one single set of values for diameters from 0.36 to 0.44, you would only have to add the values for diameter 0.4 to the machining data file.

Stefan Pendl, Systemmanager CAx, HAIDLMAIR GmbH
Production: NX10.0.3, VERICUT 8.2, FBM, MRL 3.1.7 | TcUA 10.1 MP7 Patch 0 (10.1.7.0) | TcVis 11.4
Development: C (ITK), .NET, Tcl/Tk Testing: NX12.0 | AWC 3.4 Preparing: NX12.0

Employees of the customers, together we are strong
How to Get the Most from Your Signature in the Community
NX Customization - Best Practice Guide

# Re: how does the machining data interpolate the data?

Genius
So, if I don't want this tolerance. I want a precisely set of feeds and speeds. I should set nearness to 0. right?

# Re: how does the machining data interpolate the data?

Gears Esteemed Contributor

Do you really have tools overlapping in the range of +/- 10% of diameter and/or length?

The less you customize, the easier you maintain NX.

Tolerance is only used if there is no exact match found, which can be checked by reading through the Tcl code.

Stefan Pendl, Systemmanager CAx, HAIDLMAIR GmbH
Production: NX10.0.3, VERICUT 8.2, FBM, MRL 3.1.7 | TcUA 10.1 MP7 Patch 0 (10.1.7.0) | TcVis 11.4
Development: C (ITK), .NET, Tcl/Tk Testing: NX12.0 | AWC 3.4 Preparing: NX12.0

Employees of the customers, together we are strong
How to Get the Most from Your Signature in the Community
NX Customization - Best Practice Guide