Help with B-spline cutting circle and creating walls

[Elder]

Hi,

I am new to CAD by using FreeCAD and have done some minor parts to learn.

I faced some problems while trying to do an adapter which involves adding some extra features to a circle and making walls.

I started making a circle and wanted to add the features, two curves and a block to the outside of the circle. While using the B-spline, I was able to make a curve similar or what I wanted. Leaving aside the problem of how to make it consistent with its sizes and duplicating or replicating it to the other curve, the real problem I faced is that I was unable to trim the lines from the circle and therefore got a "Failed to validate broken face" error.

The second problem I faced, is that I did not found a way to make a wall around the model and ended doing it manually by duplicating twice the base, one of them was modified to have 2mm smaller sizes and then merged them to create a wall.

I have been trying different things and searching information but ended doing things manually, adding constraints everywhere and somehow able to get a part similar of what I wanted after battling with it around 8 hours. Was hesitant to ask for help since it seems to be an easy part to do if I were to know the correct way to make it.

Attached is the FCStd file with what was trying to achieve and a photo of the blower I want to fit in the hole just to try to transmit my idea. The hole in the car is about 6mm bigger than the blower I have and wanted to take advantage of the opportunity to continue learning.

Any help or guide will be appreciated.

Regards,

Elder

[chrisb]

I don't see the B-splines in your model, but it may be better anyway to avoid them, because the following proposal may fail, if you use B-splines.

To get the wall you can use the thickness dressup feature. I don't recommend it often, because it is affected by the topological naming problem but in this case it is really convenient.

Besides: your sketching is close to being a mess, I will post on this later.

I have removed the image from the uploaded file, it saves bandwidth.

Snip macro screenshot-7e6e1c.png (13 KiB) Viewed 1371 times

[Shalmeneser]

...

* Open/Close Base sketch -> problem with Thickness
* change to Intersection : ok

Code: Select all

OS: Windows 7 SP 1 (6.1)
Word size of FreeCAD: 64-bit
Version: 0.20.26498 (Git)
Build type: Release
Python version: 3.8.12
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.3
Locale: French/France (fr_FR)

[Shalmeneser]

I think you photo is not exactly in front (=normal) of the part, so there are deformations.

I think there is a 120° rotation.

[Shalmeneser]

I cannot work after the Thickness operation.

[Shalmeneser]

No Thickness tool.

[chrisb]

First I would have turned the image, so that at least one of the holes lies on an axis. Then it seems that your photo shows some persepective distortion, which raises the question if the distance between the holes is equal in reality?


- Minimize the number of dimensions, prefer geometric constraints instead
- a special case of this is the occurrence of equal dimensions, have a special look at these
- center your sketch
- use symmetry

I could reduce the number of dimensions from 29 to 11 (sketch Base).
I would recommend to go even further and replace the four lines at the top by an arc , whic reduces the number of dimensions to 10 (sketch Base001).

[chrisb]

* Open/Close Base sketch -> problem with Thickness

I had done this with a slightly outdated version with older OCC.

OS: macOS High Sierra (10.13)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24276 (Git)
Build type: Release
Branch: (HEAD detached at 0.19.1)
Hash: a88db11e0a908f6e38f92bfc5187b13ebe470438
Python version: 3.8.8
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.4.0
Locale: C/Default (C)

[Shalmeneser]

[Elder]

Hi,

Thank you for all your replies. I was not expecting the great help you two have provided. I had work to do and today came back to continue this and since I did not received any notification in my e-mail inbox, I supposed that my post was not approved since I forgot to include the information of the FreeCAD version I am working on.

Anyways, I finally was able to get the measurements about right, cleared up the mess I had before and used parameters to have a little more control.
As Shalmeneser pointed out, the photo is not exactly on front and there are deformations and indeed there is a 120° rotation from each point.

I did what chrisb mentioned, adjusted the photo closer to how it should be, aligning it to the center and one hole. I will try to use the symmetry to minimize the number of dimensions.

Both of you mentioned the tool I was probably searching from the beginning which is the thickness operation or maybe how Shalmeneser end up doing it.

I am attaching the new design and will update here when I have a simpler object that works better based on your suggestions.

Regards,

Elder

Edit: Done using the thickness operation. This is almost what I wanted from the beginning, but found a problem. I still need to be able to control the thickness of the base which is different from the thickness of the wall (been calling it like that, not sure if it is its name). Is there something that can be done?
Also, I was trying the AdditivePipe Shalmeneser made to round the top of the wall but not sure what happened there. This is not important, I only wanted to know how it works.
I am attaching the new file with the thickness feature too.

Code: Select all

OS: Windows 10 Version 2009
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24291 (Git)
Build type: Release
Branch: releases/FreeCAD-0-19
Hash: 7b5e18a0759de778b74d3a5c17eba9cb815035ac
Python version: 3.8.6+
Qt version: 5.15.2
Coin version: 4.0.1
OCC version: 7.5.0
Locale: Spanish/Guatemala (es_GT)