Units issue when opening IGES file

[malcolm_smith]

When recently opening and IGES file in Inventor 2016, the units were incorrectly interpreted as inches. In several attempts, I tried setting the options to either 'units from file' and setting the units to meters. Using units from file I got a model in inches and if I chose meters, I got the same size model, with the inches converted to the equivalent metric length! I checked the IGES file and the units were correctly set as metric units. Is this a bug?

[jingyi.liu]

Hi Malcolm

Have you installed SP1? Could you upload a sample here?

I tried to direct open/import IGES file into Inventor, but couldn't reproduce the issue you described. Btw, there was document unit issue in Inventor 2016 RTM, it happened when you place imported CAD files with different units, the local document unit will be impacted. The issue has been fixed in Inventor 2016 SP1.

Regards,

[malcolm_smith]

I'm using 2016 SP! Update 1. Attached is an iges file (zipped) and the resulting .ipt:

This attached example is just a single surface. The length on the long side should be about 391 mm, but the resulting ipt file has a length of 391 inches. Changing the units in the import dialog box to milimetres results in a length of 9953 mm (which = 391 inches).

[mcgyvr]

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@malcolm_smith wrote:

I'm using 2016 SP! Update 1. Attached is an iges file (zipped) and the resulting .ipt:

This attached example is just a single surface. The length on the long side should be about 391 mm, but the resulting ipt file has a length of 391 inches. Changing the units in the import dialog box to milimetres results in a length of 9953 mm (which = 391 inches).

---

@malcolm_smith

The zip file contained an ipt not a iges..

[malcolm_smith]

Oops!  Correct file attached.

[WHolzwarth]

Hmm. I made 3 attempts:

-  Inventor 2016 imported source units as inch

-  Rhino 5 found errors in IGS file

-  ACADM 2014 imported as mm

Walter 

[malcolm_smith]

More info, the source of the IGES file was the application Resurf - Point Cloud to Nurbs. Resurf aparrently creates add-ons for Rhino. I'm just trying to determine if the source of the units error is the source application or Inventor. Has anyone had a similar error with Inventor 2016?. If the error is in the IGES file, can anyone suggest how to edit the IGES file to fix the problem?

[jingyi.liu]

Hi Malcolm

I tested by your dataset, it's just behaved as designed. For 3rd imported dataset, Inventor will keep its original size, that's why Inventor will convert it into equivalent length when you change document unit setting.

Regards,

[malcolm_smith]

OK, But what about the units themselves? As far as I can tell, the units in the IGES file are defined as millimetres, but they are showing as inches in the inventor file, not equivilent lengths, i.e. 25.4 mm in the iges file is 25.4 inches in the inventor file, not 1 inch.

[jingyi.liu]

I can't reproduce it on my workstation, please refer to below snapshot, I imported twice with differnt unit setting. 

[malcolm_smith]

You did reproduce it. The issue is that the length dimension should be 391 mm, not 391 inches.

[VinodBalasubramanian]

Hi Malcolm,

I understand your concerns here. I couldn't able to reproduce it as well. Can you please check whether your units under documents and settings are set correctly. 

If it still not working, can you do a reset to defaults using the tool and see whether it helps.

[SBix26 · Accepted solution]

I looked up the IGES standard, and found that the units in this IGES file are set to meters.  Here are the relevant sections (Start and Global):

Resurf IGES Translator                                                  S      1
1H,,1H;,,58HD:\Projects\Geelong\GEE001\Survey\30041231s.00 surface.igs,5G      1
7HIGES TRANSLATOR,                                  RESURF.,6HVER2.0,32,G      2
38,6,308,15,3HAny,1.0,6,1HM,1,1.0,15H20160301.084913,0.01,1000000.0,,,6G      3
,0,15H20160301.084913;                                                  G      4

The 6 is the Units Flag, and the M is the Units Name (1H is the number of characters in the string).  6 is the flag for meters, and the name is just a convenience unless the flag is set to 3 (which means "see Units Name").  

Since every line in an IGES file is to be 80 characters long, with the counter right justified to the 80th column, it appears that there is a character missing in this line, but I have no idea how to diagnose that issue, or whether it is an issue.

Sam B

Inventor Professional 2016 R3 SP1 Update 1
Vault Basic 2016 SP1
Windows 7 Enterprise 64-bit, SP1

[malcolm_smith]

Thanks for that. Today I went back into the Resurf program and created a new iges file from the original data. This time Inventor interpreted it correctly in mm. So it appears that the problem was in the original IGES file. Thanks again for your help everyone.