Change scale when derived component don't work

[olof_andersson]

I got parts that are laser scanned (stl file) and opened as a Meshed Feature. They are unfortunately scanned at a wrong scale. Derived components does not work since the meshed components are not recognized. Are there any other way to change the scale?

[Cadmanto]

Who is creating the stl file?  Were the options looked at to get solid geometry?

Can you attach you model here?

Windows 10 x64 -16GB Ram
Intel i7-6700 @ 3.41ghz
nVidia GTS 250 - 1 GB
Inventor Pro 2018

[olof_andersson]

Can't post the file unfortunately. I am trying to find the program that was used when scanning the object to see if I can change the scale there. But since I don't have the scanner program I was hoping that I could change the scale in Inventor.

[Cadmanto]

Unfortunately, you have to have geometry in order to change the scale.

Windows 10 x64 -16GB Ram
Intel i7-6700 @ 3.41ghz
nVidia GTS 250 - 1 GB
Inventor Pro 2018

[johnsonshiue]

Hi Olof,

Derive does not handle mesh geometry. I think you are trying to import mesh geometry to Inventor and add other features, right? Depending on the complexity of the mesh, you will get various degrees of success. Inventor is a primary precision Brep modeler (each face is mathematically defined and each geometry is measurable). At the moment, Inventor has very limited ability to handle mesh. It is mostly used as a reference geometry for modeling.

You may consider using Mesh Mixer (free download at www.meshmixer.com).

Many thanks!

[olof_andersson]

Thanks! When I use Meshmixer to open the object it is the correct scale so it is something Inventor does. I will attach one .stl file for you to test with.

[JDMather]

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@olof_andersson wrote:

 I will attach one .stl file for you to test with.

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You did not indicate your intended Units or a relative size that you are expecting for this geometry.

Tip: Do not Open a stl file directly.

Instead start a New part file from intended Units template.

Then Manage>Import the stl file.

If your intended units are Inches and the file imports incorrect size, then try importing into a Metric file and convert it to Inches. 

Once you give the intended Units and expected size for your Attached file, I can run a test.

[olof_andersson]

The intended unit is mm and the base diameter is about 75 mm. When imported in Inventor it gets the cm unit even though mm is selected in the part file prior to import. When trying to import from within a part file the option button is greyed out and there is no way to select the unit I want.

[olof_andersson]

I finally did it! Opened the stl file in Meshmixer where I changed the unit to cm and saved it. Now when I open the file in inventor the scale is correct.

[johnsonshiue]

Hi Olof,

I thought you were trying to scale mesh using Derive, which is not supported. But, your issue is actually STL comes in too small. I suspect the STL file was exported in cm scale. As a result, when you import it as mm, it is going to be small (1 cm becomes 1mm).

To change the scale, it is pretty simple in Inventor without using Mesh Mixer. On importing the STL file, you can select "cm" as unit. Please try it and see if it works for you.

Many thanks!

[Cadmanto]

Wow, this entire time it was a units issue?  Yeah, that is a pretty simple one.  Just changing the units in the Tools>Doc settings.

I have been burned by this one except mine was the other direction.  Units in inventor cause the part in the stl file to be too large.

Talk about coming full circle!!!  

Windows 10 x64 -16GB Ram
Intel i7-6700 @ 3.41ghz
nVidia GTS 250 - 1 GB
Inventor Pro 2018

[olof_andersson]

The problem is that I am not able to select units when importing the stl file into an Inventor part. I can set the units in the Tools>Doc settings but that does not affect the size of the stl object (which in my case was a factor 10 too large). But as I mention before, if I change the unit in Meshmixer to cm then it imports to Inventor with the correct size. I may off course be doing something wrong.

[JDMather]

No need to use MeshMixer.

If the file was created as cm, then set Inventor to cm units before import.

If the file was created as mm, then set Inventor to mm units before import.

If the file was created as inches, then set Inventor to inch units before import.

You experiment mix above if not sure, then examine the results.

[olof_andersson]

Well the thing is, for me at least, that the unit I set in Inventor does not at all affect the dimension of the stl part that's imported.

[johnsonshiue]

Hi Olof,

I think there is a bit confusion here. The unit setting in document setting dictates the measure unit and newly created parameter unit. This is because Inventor is a true-scale modeler. The geometry has an absolute size. The change in unit does not change the model scale.

For mesh data imported from STL and OBJ, there is no unit associated with it in the file. User has to make sure the unit is in sync in order to get the right scale. In your case, like experts already mentioned, you need to change the import unit by clicking on Options button in Import/Open dialog. There you can set the import unit (though STL is unitless). This ensures the scale is in sync with the exporting system.

Many thanks!

[olof_andersson]

The Options button in Import/Open dialog is grayed out.

[JDMather]

This question comes up so often that I decided to create a video that should provide a definitive answer.

I have to leave for work at the moment, but once I get the video compiled - I will attach it here.

[johnsonshiue]

Hi Olof,

Do you mind taking a snapshot showing the grayed out options for Open and Import dialog? Mine seems to work fine.

Many thanks!