Computer Aided Design

This week I worked on starting modeling for my new 2021 project.
I also started to learn Autodesk Fusion 360.
My last year CAD page can be seen here.

Design study for a single cat feeder

Early design stage

I used SketchUp to start thinking on how the feeder could look like, with laser cutting in mind to be able to easily produce a first prototype:





Food portion delivery

A Nema 17 stepper motor like this one could be used to rotate a "propeller" by 1/4 revolution (90°) and deliver a portion of food:

Study for the "Food access" door opening mechanism

One of the mechanism that I have to study well is the "Food access" door system.
I'd like it to be diaphragm like because I think it's a very elegant mechanism and that it's well adapted for my project.

Web research & inspiration

I found a few mechanisms that are interesting and worth studying:

Having a closer look at them, I realize that all these mechanisms need a big external diameter compared to the opening diameter.
The bowls for my cats are 10cm in diameter so I will need at least this size for my door.
So before going any further I compared the ratio of the overall system over the opening diameter for 3 of these mechanisms:



This shows that I will need nearly 3 time the size of my bowl (3 x 10 = 30cm) which is too big for a single cat feeder!
I probably won't be able to use such a mechanism and I have to find another solution...

Sliding door

Another solution could be a simple sliding door.
I will have to get an hand on a CD/DVD drive to see how the door system works. I could even reuse some parts to help reduce E-waste.
Until then I started designing a simple door mechanism. But I can see problems and this design needs to be perfected :

Here is another study that should theorically work:

And this is the simplest mechanism I can think of:

And finally here is an improved version that should work fine:

Learning a new CAD tool : Fusion 360

I've tried many CAD softwares, really many...
And I must say that Fusion 360 is really a very intuitive CAD modeler indeed ! For someone that uses SketchUp on a daily basis like I do, switching to Fusion was very easy. I would say that Fusion is like SketchUp under steroïds.
It took me a very short time to do a part from scratch as an exercice without reading any tutorial:

Fusion keeps track of your history construction and you may come back on any previous stage if you wish.
Modifications you make to a previous construction stage will propagate thru the history:


Note that you can import/export a lot of 3D formats including .skp (sketchup):

Trying to import a SketchUp model didn't work and the reason is that it's been removed from recent hobbyist versions as I found out here.
And this is also another great feature. The ability to create PDF documents (a bit like Layout for SketchUp):

I already love Fusion 360 after just a few hours playing with it!



Note that I encountered a bug when I changed my language preference for the UI from english to french.
After that change Fusion refused to start and even a uninstall/reinstall didn't solve the problem.
I finally solved the problem by following this procedure (found here):
Close Fusion 360.
Open Windows Explorer (File Browser) and browse to C:\Users\%username%\AppData\Roaming\Autodesk\Neutron Platform\Options.
If you don’t see the folder, see how to access hidden files and folders for help.
Right click on NMachineSpecificOptions.xml and select Delete
In Windows Explorer (File Browser) and browse to C:\Users\%username%\AppData\Local\Autodesk\Web Services.
If you don’t see the folder, see how to access hidden files and folders for help.
Right click on LoginState.xml and select Delete
Start Fusion 360.


Files for this week

feeder_V5_01.skp
Fusion_test.f3d