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          Blender Tutorials: 608 Bearing - part 1






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Video Tutorial of the details on this page




Part 1 Drawing the Cross Section

As I am going to be using a lot of these bearings in my CNC project, I thought it would be a good starting place to model the bearing. The geometry from the bearings will later be used in the design of the other components and castings. 
I will use this tutorial to introduce some of the basic modeling techniques that can be used to build accurate components. Two bearings will be covered in the tutorial, a detailed model with a large number of vertices and a low detailed one with substantially fewer vertices for use on slower computers or for use in large assemblies. The low detailed model will still be dimensionally accurate.  


First of all, I think a brief description of what we are about to model and how we will go about it is in order. Its always better to plan what you are doing before you start, rather than leaving it to chance as you work through your ideas. This model won't be used to manufacture the bearings so I am only concerned with the internal diameter, external diameter and width of the bearing being accurate, the rest is open to some artistic interpretation.

The method to create the shell of the bearing will be to draw a cross section of the inner and outer race relative to the centre of the bearing and then spin this through 360 degrees.

We will work to a scale of one blender unit equals one millimetre. Nothing has to be set in blender to achieve this, just always remember for this tutorial every dimension you input is in millimetres.


Keyboard and mouse actions will be shown in Bold type
Spinning the bearing race


Open blender, you will be presented with the default top view looking down onto the top of a cube object.
Coordinates Arrows (Top view)
In the bottom left corner the coordinates arrows show the directions of the axis

Press and hold the MMB (middle mouse button) and drag the mouse around to rotate the viewing direction, the other sides of the cube will then be seen. You can pan the view by holding down the Shift key whilst pressing the MMB and moving the mouse The top view can be reset at any time by pressing
NumPad-7 (Top View). If you loose your cube from the view you can retrieve it by pressing the Home key.
Top View


When we draw our bearing we need to orientate the model so the front face of the bearing is shown when we press the front view. The first part of the process is to draw a section through the bearing perpendicular to the front face, therefore we need to draw on the side view.

Coordinat arrows (side View) Press NumPad-3 (Side View) The the position of the cameras and light will change in the view and the coordinate arrows will change to reflect the different axes positions.

Side View
Transform Properties If you press N on the keyboard the Transform Properties window will open. This gives details of the location of the object within the 3D coordinates, the rotation around its centre point, any scale applied to the object and the size of its bounding box (box that encloses the object).


The red green and blue arrows in the centre of the cube object can get in the way when precision modeling. Press the hand icon on the Transform properties panel of the view header.

Transform Widget


The options in the Transform Properties panel will change and the hand icon will turn white. The arrows will be removed from the view.
Transform widget off
Deselect Transform properties





We need an object to build our model on but the cube isn't very useful for the bearing so we will delete it.

Press the X key to bring up the delete menu and accept the pop up menu option.
Delete The cube will be removed from the screen leaving the cursor in the centre of the global coordinates.
Cursor position x 0.0000, Y 0.0000, Z 0.0000
Cursor


In order to draw our bearing we need an object with at least one vertex. For this we will insert a Plane.

Make sure you are still in side view NumPad 3 then press the SPACE BAR to bring up the Toolbox, as we are adding a mesh object, move the mouse over "Add" a sub menu appears, move the mouse over  "Mesh", 
Toolbox
another list of options will appear, click on "Plane".

A Plane will be created, centered around the cursor and the view will have switched to Edit Mode to allow you to edit the plane.

As we need to work from one vertex centred on the cursor, press the A key to de-select all the vertices which will turn them grey and the edges black. Hold the SHIFT key to multiple select three vertices with the RMB (right mouse 
button)

Plane (Edit Mode)
Plane (Edit Mode)


Select Vertices





Delete Menue Pres the X key to bring up the delete menu. In edit mode, there are more options available than object mode.

Select "Vertices" and the three selected vertices will be removed from the view along with the face and edges of the plane. A single vertex will remain in the view and the Planes object centre will remain centred on the cursor.

In Edit Mode you can undo any changes you make by pressing Ctrl-Z
One vertice remaining





With the RMB click on the remaining vertex to select it, it will now turn yellow. We need to snap this vertex to the cursor position
 
Press SHIFT-S together to bring up the snap menu and select, Selection->Cursor.
The vertex will now snap to the cursor position, however it can't be seen as it is hidden by the object centre.
Snap Menue
Vertice behinde object centre





A 608 bearing has an inside diameter of 8mm, therefore if the object centre is on the centre axis of the bearing we need to position the inner race 4mm from the object centre.

Press E to extrude the vertex then press Z to constrain the movement of the vertex to the Z axis then press 4 the vertex will extrude 4mm along the axis. Press Enter to accept the move.

An edge has now appeared coming from the object centre to the mid point of the inner race.
Extrude 4mm





The width of a 608 bearing is 7mm so from the centre point we need to extrude an edge 3.5mm along the Y axis.

Press E to extrude, Y to constrain it to the axis, -3.5 to set the position 3.5mm along the negative Y axis and Enter to accept.

The second edge will now have appeared.
Extrude





Repeat the extrude process for the other sides of the bearing.
The dimension between the inner and outer race is 7mm so:


Press E to extrude, Z to constrain 7 to position and Enter to accept.

Extrude the outer diameter 7mm along the Y axis.

Extrude the other side of the bearing -7mm along the Z axis.

You should now have the shape opposite in your view. 
Extrude





Select With the RMB Select the vertex under the cursor and then SHIFT-RMB the vertex directly above so both are selected. These are no longer needed so press X and delete Vertices




Select the two bottom vertices Shift-RMB and press F (face) to add an edge between them
Face





We have now created the reference geometry to construct the detailed cross section of the inner and outer race relative to the centre axis. Blender has the ability to show the length of any selected edge. To activate it go to the buttons window at the bottom of the screen.

Click the Editing Context button (1) to bring up the edit buttons.

In Edit mode the buttons panels opposite will become available spread horizontally along the bottom of the screen. It may be necessary to drag the button panels to the left to see all the options. This can be done by pressing the MMB and dragging.

Button Window


In the Mesh Tools 1 panel (2) select Edge Length and the view will display the length of any selected edge.




The bearing has a 0.6mm fillet on the edge of the inner and outer race. As Blender is not primarily a CAD program it doesn't yet have a dedicated fillet tool. However it is both quick and simple to add a fillet using the  Spin function (3) in the Mesh Tools Panel


First we need to add a vertex at the start point of the fillet and also at the centre of the fillet. The spin tool works in the clockwise direction so it is important to take this into account when positioning the first vertex.


Starting in the bottom left corner, select RMB the corner vertex. Press E to extrudeY to constrain to the Y axis, 0.6 for the length and Enter to accept. This has created the fillet start vertex. With the new vertex still selected, Extrude E, Constrain Z, Length 0.6 and accept Enter. The fillet centre has been created.
Edge Length





Repeat this sequence in the other corners.

Select RMB the top left vertex, E, Z, -0.6 and Enter. Then E, Y,0.6 and Enter.

Select RMB the top right vertex, E, Y, -0.6 and Enter. Then E, Z, -0.6 and Enter.

Select RMB the bottom Right vertex, E, Z, 0.6 and Enter. Then E, Y, -0.6 and Enter.

Your view should now look like the image opposite.
Fillet Centre Points





Select the Centre Select Vertices to spin
Snap Cursor to Centre Select Vertex to Spin
Starting in the bottom left corner select RMB the vertex on the centre point of the fillet

Press Shift - S to open the Snap menu and select Cursor -> Selection. The cursor will be positioned on the fillet centre.

Now select RMB the vertex that will be spun to form the fillet.





In the Mesh Tools panel make sure in the text box below the spin button Degr: 90 is displayed. Change the Steps: 9 to Steps: 7 as we don't need that many vertices to scribe the fillet. The number can be altered by clicking on the small arrow either side of the "Steps:" text box, or pressing Shift and clicking over the number with the LMB (left mouse button). You can then use the keyboard to enter the number. Spin Properties





Spun Vertices Press the Spin button and the first fillet will be created.
Repeat the process on the other corners

Select RMB centre vertex. Shift-S cursor->Selection. Select RMB
vertex to spin. Press Spin in Mesh Tools panel.

The vertices of the fillets are the first part of the bearings section that we will keep, the other edges are only there as drawing aides and will be removed later.
Filleted Corners





We now have the Inner diameter, outer diameter and width of the bearing cross section positioned accurately above the centre axis, together with the corner fillets. The four corner vertices and edges we have created are only reference points, which we will use to position the detail needed for the inner and outer race.




This is a good time to save your work. Blender handles this slightly different to other programs, a good description of the process can be found on the Blender Wiki. (A link to it is detailed on my Links page).  For now though press File -  Save As. The 3D view will change to the File window. Choose the folder where you want to save your file and name it as 608-Bearing.blend Click Save File and the screen will change back to the 3D Window. Save As Window





When you first use blender it may seem this is a slow and cumbersome way of drawing, but as you get used to the concept and the the keyboard shortcuts become instinctive it is extremely fast. I have timed myself and from clicking the Blender icon on my desk top to load blender, to reaching this stage takes less than two minute. This is about the same amount of time it takes just to load the CAD package on my works CAD machine.



The following is a video tutorial covering the details above
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608 Part 2 Detailing the Bearing Race










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