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how to non-uniform scale with specific dimensions and not ratios

12 REPLIES 12
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Message 1 of 13
greenheron
2055 Views, 12 Replies

how to non-uniform scale with specific dimensions and not ratios

I'm moving from Sketchup to Inventor Fusion, and most things I find easier in Fusion (like drilling holes, building advanced shapes, and easier component manipulation). But I'm struggling with one thing, and that involves modifiying shapes in non-linear dimensions. I understand that I can scale non-linearly, but I need to specify specific dimensions for a project.  

 

I created the object below in Sketchup. It's a stack of 1/2" component slices (to be cut on a CNC router) that transition from a large elliptical/oval shape at the bottom to a round shape at the top. To create this shape, I started with the large elliptical bottom piece at one end and pulled the shape up 1/8" and then specified the dimentions (i.e 25.253in, 18.532in) for each of the two axis based on a set of values I calculated in a spreadsheet.  The shape gradually tapers to the circle at the top. 

 

In Fusion, I can only find a way to scale based on a ratio (like 1.5 being 150%) or tweak faces which also references the current size of the face. The problem with either of these methods is that an error would compound steadily through the hundreds of operations. Is there a way to scale from a center point and specify specific dimensions? Or is there a different way to model this?

 

Thanks in advance for your help!

 

elliptical tower.png

 

12 REPLIES 12
Message 2 of 13
Phil.E
in reply to: greenheron

Greenheron,

 

The thing you are trying looks like it would be better done with many separate extrusions.

 

The workflow is shown in the image below. Let me know if this helps, or mark this with 'accept as solution'.

 

platter_stack.png

 

Thanks!





Phil Eichmiller
Software Engineer
Quality Assurance
Autodesk, Inc.


Message 3 of 13
greenheron
in reply to: greenheron

Thanks--that workflow makes sense, but I can't seem to get the Sketch Dimension tool to work consistently with ellipses. It seems to work all right with other shapes (archs, circles, rectangles), but I can't seem to add dimensions to ellipses. Also, in the PDF guide, it appears that dimension boxes should be available when creating the ellipse. They don't seem to be available like they are for all other shapes. I'm using Inventor Fusion and Fusion 360 on a Mac and there doesn't seem to be any difference between the two in how ellipses function. 

 

Any tips?

Message 4 of 13
Phil.E
in reply to: greenheron

Thanks for the heads up about the help guide. I'll look into that. And it's pretty cool you are using Inventor Fusion and Fusion 360!

 

In both Inventor Fusion and Fusion 360 ellipses are dimensionable objects.

 

Inventor Fusion:

  1. Create the ellipse
  2. Use sketch dimension tool
  3. Select the ellipse
  4. Dimensions will appear
  5. Right click and OK to dismiss the dimension tool
  6. Single left click on each dimension, an edit box will appear

Fusion 360

(Do steps 1-3)

4.1 One sketch dimension appears. Axis is determined by direction of drag.Click to place.

5.1 Dimension tool is still active now. Select the ellipse again, drag to get second axis dimension

6.1 Single left click each dimension to edit the value (while dimension tool is active)

 

I hope that helps! Feel free to ask more, or just mark Accept as Solution so other users can benefit.





Phil Eichmiller
Software Engineer
Quality Assurance
Autodesk, Inc.


Message 5 of 13
greenheron
in reply to: Phil.E

Thanks for the prompt reply, Phil. Dimensions work as you describe with other objects like squares and circles, but I haven't been able to get dimensions to work with ellipses with the steps you describe. Does this have to do with a problem using the software on a Mac? I tried to attache a video of the steps I'm attempting, but the mp4 file format isn't supported on this forum. I spent at least 1/2 hour yesterday experimenting without success. Out of 30+ attempts and hundreds of clicks on the object (axis, center, surface, etc.) with the dimension tool, I only got dimensions to appear twice, but I couldn't replicate exactly how I clicked. Both Fusion 360 and Inventor Fusion seem to function the same in this regard where I can't get dimensions to work consistently with ellipses. Is this a bug in the Mac version or operator error?

 

Message 6 of 13
Phil.E
in reply to: greenheron

Okay, now I realize you are using Inventor Fusion for Mac. There is currently a limitation that prevents dimensioning elipses.

 

Fusion 360 has no problem with this. It works the same on Mac or Win.

 

Let's break down the steps for Fusion 360 for extra clarity.

 

Using Fusion 360

  1. New sketch
  2. Create the ellipse using sketch > elipse tool  [do not create an ellipse by using Offset tool]
  3. Start the sketch dimension tool
  4. Select the ellipse (pick only the curve edge of the ellipse)
  5. Drag some distance
  6. One sketch dimension appears. [Please let me know if you don't see a dimension at this point]
  7. Axis is determined by direction of drag.
  8. Click to place.
  9. Dimension tool is still active now. Select the ellipse again, drag to get second axis dimension
  10. Single left click each dimension to edit the value (while dimension tool is active)

 

 

 

 





Phil Eichmiller
Software Engineer
Quality Assurance
Autodesk, Inc.


Message 7 of 13
greenheron
in reply to: Phil.E

> One sketch dimension appears. [Please let me know if you don't see a dimension at this point]

 

I don't see a dimension at that point on either Fusion 360 or Inventor Fusion.

 

Message 8 of 13
Phil.E
in reply to: greenheron

This is not expected behavior for Fusion 360. I'm going to need more information, sorry for any trouble.

 

Can you send your machine specs? Mac model and year, OS version, video card info?

 

Also, can you send me your data and a video of your sketching workflow inside Fusion 360? phil dot eichmiller at autodesk dot com

(If you go to the Fusion menu, pick Export Archive that will make a local copy of your data.)

 

Thanks,

 

 





Phil Eichmiller
Software Engineer
Quality Assurance
Autodesk, Inc.


Message 9 of 13
greenheron
in reply to: Phil.E

Video, archive, and specs sent...

Message 10 of 13
Phil.E
in reply to: greenheron

Inventor Fusion for Mac has currently has a limitation that prevents dimensioning ellipses.

 

Can you try again in Fusion 360?

 

HP EliteBook 8560w Win 7
13" MacBook Pro, mid 2009 OS X 10.8.4
Portland, Oregon

 





Phil Eichmiller
Software Engineer
Quality Assurance
Autodesk, Inc.


Message 11 of 13
greenheron
in reply to: Phil.E

You're right, that was Inventor Fusion. In 360, I'm not getting dimensions to show up when creating an ellipse, but I am able to add dimensions after creating an ellipse. Going back to your workflow, it looks like those instructions will create a stepped object rather than a smooth object. After extruding the ellipse, it doesn't look like I can add dimensions to the extruded surface (dimension tool isn't availabel for this purpose—it's grayed out) to taper the shape. I can only create a new shape on the surface, add dimensions and extrude it. Any suggestions?

Message 12 of 13
Phil.E
in reply to: greenheron

Sorry, I didn't realize you needed to include the transitions.

 

Have you tried to loft the shape and then slice it up?

 

After you loft all the sketched profiles use these offset planes that you created for the loft profiles as tools for Modify > Split body.

 

slice_the_loft_A.png

 

slice_the_loft_B.png

 

Thanks,

 





Phil Eichmiller
Software Engineer
Quality Assurance
Autodesk, Inc.


Message 13 of 13
Phil.E
in reply to: greenheron

I thought of one more option:

 

Sketch the profiles on the stack of offset planes

Make one loft per body between each successive stack part and the next sketch in line.

Use Continuity > Free to keep the sides as a straight bevel shape, instead of curving.

 

I realized that my previous pictures show curved edges on the sections which may not work well in a CNC router setup.





Phil Eichmiller
Software Engineer
Quality Assurance
Autodesk, Inc.


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