Split/edit part in FreeCAD?

Question

I'm trying to modify some parts on this thing. I'm kind of new to dealing with the modeling aspects of this.

I am attempting to widen the part essentially 3mm. This would involve modifying the chain segments, and the anchor points.

I have already attempted this with 3D Builder and the result was less than stellar. I split the part, cloned off about 3mm of the middle of the X-Chain (including the top & bottom bits). The intent was to break the part, translate one of the halves off 3mm, add back the 3mm into the gap.

When I put all the parts back together and merged them in 3D Builder, the resultant model, while visually on screen appeared to be one piece, the slicing proved otherwise.

Is there a way that I can do the above in FreeCAD? I'm learning this so tutorial links would be more than sufficient. But if there is someone who can explain this process to me in FreeCAD that would also be appreciated.

Answer 1

When you want to change an STL file in FreeCAD then this is how I do it. I open the STL file in FreeCAD and select the option in the Part/Component sub-menu: Make a form from mesh (hope that I translated it well. I use the Dutch version). It can take quite some time but when it is finished you have an editable object. Just remove the STL object and do what you want.

When you finished then you can perform all actions like if you created it from scratch with FreeCAD.

I am a beginner in 3D design so there might be 'smarter' solutions. When I want 1 special part then I create as many cubes as needed and perform a MINUS action on the solid and a cube. After a while I end up with only the part I need.

Answer 2

I found that the answer provided by @Marco was helpful but not the correct answer I was looking for.

Here is the general approach I used (Based on this).

1. Create new document
2. Import STL file
3. Switch to Part workbench
4. Select imported mesh
5. Part -> Create Shape from Mesh (use default tolerance)
6. Delete imported mesh
7. Select shape
8. Part -> Refine Shape
9. Delete "unrefined" shape
10. Select refined shape
11. Part -> Convert to Solid
12. Follow instructions in link provided.

Below is the list of instructions from #12

1. Have shape loaded
2. Switch to a plane that you would like to cut parallel to. e.g. XZ
3. Switch to Draft workbench
4. Draw rectangle around item to cut
5. Upgrade using '^' up arrow (blue) in toobar
6. Adjust the Placement Angle/Position via the "Data" in the property editor lower left side.
7. Switch to the "Arch" workbench
8. Double click the solid to cut in the 3d view
9. Ctrl+click the plane you will cut with
10. Select "cut-plane" and choose which side to capture

You will have to play around with the pattern in 12. The idea is to use the same Face created through 12 to cut the part at the same point twice. To create two halves. Take note of the position of the Face created in 12.

In my case, I was attempting to stretch the part along the Y axis, so I was able to cut the part with an XZ plane (created in 12) and offset with a distance in the Y plane.

After performing this "split" I created a cross-section of the at the point of the cut and extruded the cross section 3mm.

Afterward, I was able to use the Edit -> Alignment tool to attach all three parts back together.

Once attached, I selected all three and performed a "union" operation to make them all whole again, then executed the Part -> Refine shape.

End result was that I could make the chain links 3mm wider than the original.

I'm still working on tweaking out the other components that constitute this feature but still this is an interesting exercise.

Answer 3

I found Dave G's answer to be helpful, however I could only use additive features (e.g. Pad) on the created object, and could not make subtractive features into the object (e.g. Pocket).

Here's what worked for me using FreeCAD 0.19 (Instructions from this site):

1. Create new document
2. Import STL (File --> Import)
3. Part workbench --> Create shape from mesh
4. Part workbench --> Shape builder...
5. Create shape, select "Solid from shell". Make sure "Refine shape" box is checked. Press "Create" button. (You may need to switch to the "Model" tab in the Combo View and select your shape object.)
6. Change to the PartDesign workbench. Select the newly-created "Solid" in the Combo/Tree View, then select PartDesign --> "Create body"
7. A new Body will be created with your Solid as a BaseFeature that can work with Pad and Pocket features.