Creating Sketches from 3D Imports

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ADuncan28
Posts: 1
Joined: Tue Nov 05, 2019 1:02 am

Creating Sketches from 3D Imports

Postby ADuncan28 » Tue Nov 05, 2019 2:07 am

Hi,

I am new to the forum and new to FreeCAD and will try to explain what I am trying to do and the issues I am running into as best as I can.

I am trying to create a model of a "foot" to hold the linear actuator pictured below upright. I was lucky enough to find a 3D model of the actuator I want to use on the manufacturer's website.

Iso View_Actuator.PNG
Iso View_Actuator.PNG (45.4 KiB) Viewed 151 times

My idea is to create a front view sketch, side view sketch, and top view sketch from the model in order to have references that I can use to build the "foot". Sort of like when carving a block of wood you can glue pieces of paper with sketches of the front, side, and top views on the block and then easily cut the object to shape. Except in this case, I would use the object that the "foot" would hold in order to size it correctly instead of cutting the actuator itself out. I hope that makes sense.

I imported the .stp file into FreeCAD and was able to use the Draft workbench and the Shape2DView tool to create an outline of the model. As you can see, I am having trouble getting the 2D image to orient with the object even though I selected the correct face I wanted it to draw on.

Shape2DImage.PNG
Shape2DImage.PNG (99.5 KiB) Viewed 151 times

Then I converted the Shape2DView into a Sketch by using the Convert Bidirectionally Between Draft and Sketch Objects tool.

Then in the Sketcher workbench, I validated the sketch and then had FreeCAD fix all of the missing coincidences. I ended up with something nice like this (though it was still oriented the wrong way).

Actuator Sketch.PNG
Actuator Sketch.PNG (100.98 KiB) Viewed 151 times

Buuuuuut, when I double click the sketch something explodes and it looks like this mess...

ExplodedSketch.PNG
ExplodedSketch.PNG (555.77 KiB) Viewed 151 times

I was thinking I might be going about this in the wrong way and was wondering if anyone could help me out. Worse comes to worse, I could just use the dimensional drawings on the manufacturer's website to build it from scratch, but I thought it would be easier and more accurate (and more fun) to utilize the power of the program a little more.

Thank you so much in advance!
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Willem
Posts: 1291
Joined: Fri Aug 12, 2016 3:27 pm
Location: Lisse, The Netherlands

Re: Creating Sketches from 3D Imports

Postby Willem » Tue Nov 05, 2019 6:27 am

The last sketch looks normal to me. All circles and arcs are B-splines and that makes all the green lines you see.
chrisb
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Re: Creating Sketches from 3D Imports

Postby chrisb » Tue Nov 05, 2019 7:21 am

Although you can switch the curvature comb off (Menu->Sketcher->B-spline tools->Show/Hide curvature comb) I think the B-splines indicate a flaw in your workflow, because these B-Splines are rather useless.

If you want to model something matching the Step model, you can create a Body and a ShapeBinder. Then you can reference all the points in 3D space instead of reconstruct them from 3 projections.
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HarryGeier
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Joined: Mon Jul 10, 2017 12:36 pm
Location: Hof Germany

Re: Creating Sketches from 3D Imports

Postby HarryGeier » Wed Nov 06, 2019 9:27 am

I second that.

As chrisb states, you chosse a "not soo good" workflow for the task.

The B-Splines with the weird looking rays from the curvature should / can be taken away as the result of the protrusion is not necessary for your design. I will look into the design and try to find a simple approach. i could take it up try to find a simple approach, but it´s not uploaded
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vocx
Posts: 1848
Joined: Thu Oct 18, 2018 9:18 pm

Re: Creating Sketches from 3D Imports

Postby vocx » Wed Nov 06, 2019 2:58 pm

ADuncan28 wrote:
Tue Nov 05, 2019 2:07 am
...
I imported the .stp file into FreeCAD and was able to use the Draft workbench and the Shape2DView tool to create an outline of the model. As you can see, I am having trouble getting the 2D image to orient with the object even though I selected the correct face I wanted it to draw on.
...
In addition to what the other users have commented the Draft Shape2DView has a Projection property to control the direction of the projection. You may have to experiment with both positive [0,0,1] and negative vectors [0,0,-1], to get the projection from the intended direction.