Hi Martin, are you sure the file you attached has units set to mm?

I tried importing it into a couple of other CAD programs like Rhino and ViaCAD and they both also seemed to think the units in the file were actually inches and not mm.

I seemed to get the same result in both of those other CAD programs as opening the file in MoI.

Is there possibly some setting for overriding units that you need to clear in the program that you're using to export this or something like that?

- Michael

Hi Michael.

Here's a video of the export from ViaCAD 7 Pro and the import into MoI.
The file does come back into ViaCAD OK, so I thought I'd let you know about it.

Although not shown in the video, if I do the same export as a SAT file it works fine.

http://screencast.com/t/cPncpmTZH


Martin.

Hi Martin, when you do a File > Import into MoI, it merges the file you pick into the current model and various settings like the current unit system will stay the same as they were before.

There is a setting for whether you want to have an import of a different unit system to be scaled into the current system or not - have you possibly disabled that option? If so then that's probably the problem.

Please take a look under Option > General > Unit options:



Push that button to bring up this dialog:



Make sure both "Scale on unit system change" and "Scale when importing different units" are both checked. They should be on by default, but if you unchecked the option to scale on import then that would cause the kind of problem that you are describing.


Also another way you could do it is to use File > Open to bring the file into MoI, which compared to File > Import replaces all content with the file you pick and also the unit setting of the file will become the current units.

If you do that you'll see that the units in the file happen to actually be set to Inches for whatever reason by Viacad (with objects scaled accordingly to preserve them to the same size as you had in mm) and then if you change the unit system to mm you'll end up with the result you want, as long as you have "Scale on unit system change" also turned on in the above dialog.

Does that help? Please let me know if you are still seeing a problem.

- Michael

> Although not shown in the video, if I do the same
> export as a SAT file it works fine.

Probably what happens with that is that it actually writes the SAT file with millimeter units in the file, so there is no mismatch between the file units and the current unit system and in that case it doesn't matter if scaling on import is turned off or not.

- Michael

Michael.

I *think* I've done as you said in your last post, but I'm still getting similar results.
Does this video highlight anything to you?

http://screencast.com/t/VXmY9d32xw6



Martin.

Hi Martin - in your new screencast above you seem to be importing a different file named "Untitled 2.stp" - note the "2" - which is a different file than the one you attached in your original message here which was "Untitled 1".

If I repeat the same steps you are doing with the "Untitled 1" file I get the proper result that you were expecting. Can you verify that?

How did you generate the "Untitled 2" file, did you possibly save it out from MoI after having done an import with that "scale on import different units" option turned off? If so then that would explain it because that "Untitled 2" file is now a file that has its units set to mm but did not have the objects in it scaled from inches to mm.

Please let me know if that does not seem to be right.

- Michael

Hi Michael.

Yes, I did make a new file (untitled2), just to be sure I knew I was working afresh.
I can't export from MoI because I am running the 'no save' demo.

I work in metric - could that be part of the problem?

To try and avoid further confusion I've done another video that shows the whole creation and transfer into MoI.
I'll also attach the relevant file.

I shall delete the other two videos in a day or so, to recover some space.

http://screencast.com/t/hqNWje6Npt4t


Martin.

Hi Martin, somehow that's a bug that's in the "no save" trial version that is not present in the regular release version of MoI.

Maybe I forgot to include one of the last set of bug fixes in that particular trial version or something like that.

I was getting confused because on my regular v2 version over here it behaves like you want, but I can repeat that using the "no save" trial version behaves differently.

Let me take a look and see if I can figure out why there is a difference in behavior between the full v2 version and the no-save trial version.

- Michael

Hi Martin and Michael,

I opened the file in NX and it come in as an Imperial file, I also noticed these statements in the STEP file

#36=UNCERTAINTY_MEASURE_WITH_UNIT(LENGTH_MEASURE(1.0E-006),#38,'','');
#38= (CONVERSION_BASED_UNIT('INCH',#70)LENGTH_UNIT()NAMED_UNIT(#73));

but further down it has this;

#119= (NAMED_UNIT(#73)LENGTH_UNIT()SI_UNIT(.MILLI.,.METRE.));

-

A difference in MoI is that it's import and export work a bit differently... With PunchCad, you cant "save" a STEP file.. You just export one. In MoI, if you are set to mm and "Import your file" it will have correct scale. If you "Open" it, it will default at inches...

Delcam Powershape handles this file the same way... I dont think that "MM" is defined in the file correctly. It seems to be just "Units" with a scale factor.

Hi Danny, I think it's one of these files that has units set to something like MM but with an additional scale factor applied to it which actually makes the real units as inches if you take mm times the scale factor.

Martin - there was a bug in the regular MoI v2 release that did not deal with that kind of unit setup properly, it misses the scale factor that's additionally applied to the unit system.

There is a patch available that can be applied to the full v2 release which fixes a couple of bugs and adds a new lwo export feature, it can be found attached to this forum message here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3926.4

If you apply that patch to the full release version of v2 then your STEP import will work properly after that. It's also fixed in the v3 beta releases as well.

I do not currently have any version of that patch for updating the v2 trial version though.

So the bug in the trial version that you're currently using is that MoI thinks that the units in the file are MM when actually they are stored in inches in the file itself (when you take the MM unit setting and also applied scale factor together into consideration).

So in order to get the units correct in your trial version of MoI, you will need to get the units converted from mm to inches without applying any scale factor to the objects. Then after that you can switch to mm with a scale factor applied which will then end up with the proper result.

The easiest way to do that is to leave those 2 checkboxes turned on, and then do the following:

Do a File > Open of any of your files.

You'll now see that the units are set as mm - this is actually incorrect, the objects at their current size are actually in inches units.

So now go to Options > General and switch the unit system from mm to "No unit system" - switching from any unit system to "no unit system" does not change the scale of the objects. Now switch the units again to Inches. Again there will be no scaling applied since you're coming from "No unit system" into inches. At this point the objects are correct. Now you can switch from inches to mm and the objects will scale and you'll have the proper final result.

Sorry for all my confusion over this, I had that patch applied to my regular v2 version and so I did not run into the same bug that you ran into with the no-save trial version. That caused me to get really confused as to why I was seeing a different result from you.

Hope this does now explain things properly!

- Michael

Sat and IGES files from Punchcad com in as MM when the file is set to that value.

I don't think that either SAT or IGES has quite the same kind of unit setup where it can be a unit system flag then with a separate additional scale factor.

I don't know why you would want to store a file that is actually in inches with the "units are millimeters" flag and then with a scale factor that converts from mm to inches but that's apparently what ViaCAD or maybe ACIS decides to do. I mean it seems easier if you want the units to be inches to set the units value to inches and then it's done. But anyway the stock MoI v2 doesn't get this kind of extra scale factor situation figured out correctly but that's been fixed up since then.

- Michael

Thanks for the feedback, Michael and everyone else.

It seems that this is just one of those problems that comes about when we exchange formats between applications.
See here for an explanation/discussion as to why ViaCAD STEP files are saved in imperial units.

http://forum.punchcad.com/showthread.php?t=732&highlight=internal+units


Martin.

Hi Martin, I can't seem to read that message until my forum registration there is approved or something.

But anyway, it was definitely a bug in MoI that MoI did not handle STEP files that used this style of unit system setting - that is fixed though with the above v2 patch for the v2 full release version, or with the v3 beta version.

- Michael