Hamster cage part 1, FreeCAD model

11 Mar 2022

Recently I have been learning FreeCAD and at the same time my daughter wanted a new bigger cage for her hamster. So I used this opportunity to use FreeCAD to create drawings for her new cage.

I have decided to use plywood sheet with the size of 2500mm x 900mm x 12mm and I already have lots of smaller joist material, 36mm x 23mm, to use for framing where support is needed etc.

I will not do a full cover of every part I created in FreeCAD, just a short description to get you going.

Create new drawing in FreeCAD

Start by opening FreeCAD and create a new drawing

FreeCAD create new
Just because I really like the Part Design workbench I will use it. So lets select the Part Design workbench in the drop down.
FreeCAD Part Design workbench

I like the part design workbench beacause it will contain the modifications/history of the part inside a Body object, this reduces the clutter in the treeview. Yes I do know there is a Part object as well. But from my limited experience with this, is that most other workbenches will fail to contain the modifications/history inside the part object. So I have to drag it back into the part object. The clutter when not using the Part Design workbench is crazy annoying and I don’t even have OCD..

Create first part of the cage

When we are in the Part design workbench we can finally create a body for our first part which will be the bottom

FreeCAD create body
To actually start creating something in our Body object we need to create a sketch
FreeCAD body create sketch
The sketch needs to be attached to something, it can be attached to lots of things, even faces of other objects. But this is currently not recommended due to topological naming issues in FreeCAD. But this is our first part so there is no faces to select, so just select the XY_Plane for a top-down sketch view.
FreeCAD select plane
Now we are inside the sketch and looking from the top. We are going to draw the bottom of the cage, so create a rectangle
FreeCAD create rectangle
Draw it around the sketch origin point
FreeCAD place rect
Select bottom left and top right and then the sketch origin point, the order is important.
FreeCAD select points
Hit s for symetry constraint, this will create a symetrical distance between the bottom left corner, Top right corner and the origin. FreeCAD will try to maintain the symetrical distance between those two points and the origin.
FreeCAD add symetry constrain
Now select the top line of the sketch
FreeCAD select top side
Click the Horizontal constraint button
FreeCAD add horizontal constraint
Enter a value. I choose 2000mm length, 500mm shorter than my plywwod sheet
FreeCAD horizontal constraint value
Select the left side
FreeCAD select left side
and click vertical constraint button
FreeCAD add vertical constraint
Enter a value, and my plywood sheet is 900mm width
FreeCAD vertical constraint value
Now the sketch is fully constrained, which is when no line or vertex in the sketch can move, and this is the goal when creating a sketch.
FreeCAD fully constrained
Now we can close the sketch
FreeCAD close sketch
Now we are back outside of the Sketcher workbench which is used to create a sketch in FreeCAD.
FreeCAD sketch closed
But the sketch will just give us some outlines, to create a 3D object with thickness we need to select the sketch and hit Pad
FreeCAD pad selected sketch
My plywood sheet is 12mm thick, so enter 12mm value and hit OK
FreeCAD pad values
Now our first part, the bottom of the cage is finished
FreeCAD bottom done

Rename body

To keep stuff organized you can change the name of the body object. Select the body object in the treeview and hit F2 just like in Windows Explorer and now you can change the name of the object.

FreeCAD rename body bottom

Create left side

Now move on to the next part, create a new body

FreeCAD create new body
Select it and rename it so it will be easier to know what part you are working on.
FreeCAD rename left side
Create a sketch and this time select the YZ_Plane for a side view sketch.
FreeCAD create sketch yz plane
Draw a sketch of the side. I want the top corners cutoff because the back of the cage will have a net mounted there and the front will have a lid with net for airflow. The width of the side is the same as the plywwod sheet to match the side of my bottom. Then the height of the side will be 500mm which is what’s left of one plywood sheet after the bottom has been cut.
FreeCAD draw sketch
And just like the bottom part, we pad it 12mm thick
FreeCAD pad sketch
But this time we have to move the object, right click the object in the treeview and click Transform
FreeCAD move body
Now you can move the object by dragging the arrows. It is not needed for this object, but you can rotate an object by dragging the balls.
FreeCAD move body 2

The right side will be the same as the left side. And in FreeCAD you can create a link to another object, so select the LeftSide object in the treeview and click the Create link button

FreeCAD select body click link
Now you have a new object that is linked to LeftSide object, click it and hit F2 and rename it to RightSide.
FreeCAD rename link
Right click hit Transform and move it to the right side.
FreeCAD move link right side
Now the right side is a link to the left side, so any changes made to the LeftSide object will also be made to the RightSide object. This way you don’t have to make the same change on both sides.

Create more objects

This is where I cut the guide short, because those objects is pretty much the same as previous objects. Create a body, rename it and create a sketch, pad the sketch and move the body into place.

The back side is created with the same length as the bottom, but with the width to cover the bottom sheet and up to where the side cut off. The angular gap between the back and the top will be covered with a small sized net to get air into the cage.

Created back side
The top side is created with the same length as the bottom, but it will cover half the top of the sides to make room for a open able lid in the front of the cage
Created top
Two support beams are added under the top, because I think 12mm plywood stretch out over 2000mm will flex to much on it’s own. One support beam was created and the second is a link to the first, because they are the same length.
Added top support beams
Added a support frame for the bottom plywood sheet, to reduce flex in the bottom as well. And I added the triangles from the sides cut off to the bottom corners, to get a bit thicker plywood part where I can mount legs.
Bottom support
I found a cheep 1000mm x 500mm x 2mm acrylic glass sheet, so if I cut it in half it will be 2000mm long and 250mm height for the front. Two support beams was added to support the front and to screw the acrylic glass to, they are actually links to the top support beams because they are the same length.
Front support with plexiglas
Finally I created two frames for the lid, they will be attached with hinges both to each other and to the top of the cage. And the frame will be covered with some small sized net to let air in.
Lid frames
The lid frame will need some support, two bars on each side will keep the lid frame from falling down into the cage.
Lid support