Scaling an STL file

[cjhilinski]

Is there a way to keep an imported STL file  anchored to the X plane while scaling it?

I disable timetrack, Import Mesh, locate the object on the X plane and then Modify Scale by expanding it by a factor of 2. When this is done, part of the new object is in the +Z and part in the -Z. If I then try to extrude anything, say a new hole, it will only go from the model top down to the X axis and won't go through to the bottom of the model. Somehow I managed to move the entire object by the -Z distance, but I can't remember how I accomplished that and can't repeat it. Is it a reasonable request for the ability to anchor an  object before scaling it? Or is the best approach to scale the STL in TinkerCad and then import it through Import Mesh?

[SaeedHamza]

Hi,

Working with a mesh in Fusion without converting it to BRep won't work

convert it then edit it

Regards

Saeed

[cjhilinski]

Sigh...I thought the converting to BREP was so obvious that I didn't need to mention it. Converting to BREP, as you asserted, does nothing to solve the problem.

[SaeedHamza]

is it converted in this picture? because it's not

[cjhilinski]

Well, bigosh, look at this picture, which is the correct color of a BREP. It shows exactly what I asked about in the first place. It doesn't matter if you BREP it or not. Once you scale it, it does exactly what I said.

[TrippyLighting]

Could you explain what you would want to scale a .stl file using a CAD application ?

If scaling is the only thing you want to do with this, then Fusion 360 is not the best app to o that.

[cjhilinski]

A vendor provides only an stl or an nc file for a part. It's a fan. The fan is too small for my application, so the options are to create if from scratch, try to use it too small, or enlarge it. Sure I can use another app. I scaled it in TinkerCad and brought that into F360 to do the CAM work on it, but that wasn't the point.  F360 seems to have all the tools to do it in one place, so what's wrong with trying to do it there? 

[dieselguy65]

i think the point was, an stl file is just not really acceptable format for a full blown cad software.

its like working backwards.

i would get the vendor to supply it in the preferrred format

what manufacturing process do you use to produce this part?

if 3d printing, all the software i have tried will scale parts very easily.

if you need to modify it prior to manufacture, stl is not really the format to use.

[cjhilinski]

Why can't someone just answer the question? Okay. It's only available as an stl or an nc. There is no other format. You can't just scale it because it makes the center hole too big, so you have to use some program to "plug" the hole and then redrill it to the proper size. Doesn't F360 import stl files? Of course it does. Doesn't F360 allow you to scale said stl file? Of course it does. Doesn't F360 then allow you to fill the oversized hole and drill it with a new size? Of course it does. Doesn't F360 allow you to make the outside ring a bit thicker? Of course it does. Doesn't F360 allow you to add a few more holes for mounting purposes? Of course it does. Doesn't F360 allow the user to then use 3D cam processes to build file(s) to mill the part? Of course it does. So explain to me how someone who found all the tools to do all the things needed to do the job would know that he/she shouldn't be doing the task in F360 because, well, because exactly why?

Actually, just nevermind. 

[TrippyLighting]

If you did find all the tools, then Id assume you would not have posted a question one the forum, which, BTW, has already been answered by @SaeedHamza.

You'll have to convert that .stl into a BRep. 

To do so you'll have to turn the timeline off. It also only works if the number of triangles in hat .stl is low enough, but tithe object looks fairly low poly so that might work.

Then you can scale it an perform normal modeling operations on it with some limitations. Highly faceted models are performance hogs and modeling operation that might otherwise very quick might be very slow.

Before or after scaling the object, it does not really matter if it is a uniform scale about the center axis my suggestion would be to alight maybe the bottom face of the fan )if it has one you can use as a reference surface).

Then you can add a cylinder to the object or whatever you ant to do. Perhaps it would make sense to share that .stl file so we can show you in a screencast how you can go about it.

[etfrench · Accepted solution]

The location of the sketch (with the hole to extrude) can be above, below, or somewhere inside the (Brep) model.  If the sketch is located outside of the model, then a single direction extrude will work.  If it is inside the sketch, then use a two direction extrude.  There is no need to move the model before doing the extrusion.

You can use the Align tool or a Joint if you want to move the Brep model in relation to other existing geometry.

p.s. The main Origin can be used as an alignment point in order to reposition the model at Z0.

[cjhilinski]

That worked perfectly. It's interesting that when you scale a part (say double its size) that half of the part is in the +Z and half in the -Z. Thank you for taking the time to understand the issue and providing a real answer to the question asked.

[TrippyLighting]

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@cjhilinski wrote:

That worked perfectly. It's interesting that when you scale a part (say double its size) that half of the part is in the +Z and half in the -Z. Thank you for taking the time to understand the issue and providing a real answer to the question asked.

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Whether that's a true statement depends on where the origin of that part is define in the imported .stl file. Thus the suggestion to align the object in reference to the origin in Fusion 360.

In your case it seems the object was already centered on the origin in all three coordinates. That is not always the case with imported geometry.

[cjhilinski]

I don't want to belabor this and I'll drop it after this last observation. Start with a new sketch, draw a circle and extrude it to 10mm. If you do Modify | Scale and use a factor of two, it expands in all directions doubling its size. If you want to put a hole all the way through the thing, you draw a circle on the front, for example, and you can extrude it completely through the part using the One Side direction. With the BREP you have to use the Two Sides direction. My original question was to ask if it was reasonable to expect that a BREP would act just like a normal solid that I scale. I was having a difficult time with the BREP solid residing in both the +Z and -Z spaces and trying to add features that were the full depth of the part.

[Anonymous]

Then what would be, in that case??

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@TrippyLighting wrote:

Could you explain what you would want to scale a .stl file using a CAD application ?

If scaling is the only thing you want to do with this, then Fusion 360 is not the best app to o that.

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I can give a case where you want to scale an STL file in a CAD application (or with whatever, whatever would do it!) ... making a pattern for a thing that will be cast, which requires that the pattern be, let's say 101.5% size, and using a vendor to produce the 3D printed pattern who shouldn't be asked to scale the files; they should be asked only to print what they are given in whatever units are specified. 

[TrippyLighting]

A better application to scale .stl files and generally for a lot of other modifications performed on triangulated mesh files whether in .obj or .stl or another format is Meshmixer.