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Back to Tutorials |
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Part 2 Detailing the Cross Section
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| Video Tutorials of this pages details. | |
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| With the corner fillets in place it's now time to define the inner and
outer race. | |
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The thickness of each
race is 1.92mm, so we need to divide the cross section accordingly.
(You
should now know the keyboard commands to select, extrude and constrain
vertices to a set axis, so from now on I will only include the
commands
for these operations occasionally.)
Select
the bottom left vertex and Extrude it 1.92mm in the Z axis. Then Extrude this vertex 7mm in the Y axis.
Select
the top left vertex and extrude it -1.92mm in the Z axis. Then
extrude this 7mm in the Y axis.
The
thickness of the Inner and outer race is now defined. |
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The
next stage is to form the groove's that the ball bearings will run in.
To do
this we must spin a circle from the centre point of the two bearing
races.
Hold
Shift
and Select RMB the four vertices that
are on the ends of the two edges that we have just created to define
the thickness of
the inner and outer race.
Press
Shift-S
and snap the cursor to the selection. Because we have selected more
than one vertex the cursor will snap to the centre of all the vertices.
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ensure
nothing is selected A and
holding the Ctrl key click LMB any where near the
cursor.
A new vertex will be created.
Snap
the vertex to the cursor. Shift-S, Selection->Cursor.
The
Ball Bearings have a diameter of 3.95mm so we need to spin a
radius of 1.975mm.
Extrude
the vertex -1,975 on the Y axis.
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In
the Mesh
Tools panel set Degr: to 360 as we are going to spin a complete circle.
Set Step: to 64. This will give us a sufficiently detailed
circle.
Its
worth
noting that if possible you should always choose a number of steps that
will give a vertex on each of the circles quadrants.
With
the vertex we have just extruded still selected spin the circle. |
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Excluding
the vertices whose edges intersect the line defining the inner
and
outer race, the centre vertices are no longer required and can be
deleted.
Rather
than Shift-RMB selecting all the vertices Blender allows you to box
select a group of vertices. To do this press the B
key, the mouse pointer will change to a cross hair. Position it above
and to the left of the vertices you need to delete. Press and hold the LMB
and drag the cross hair to the lower right of the vertices to be
deleted. release the LMB.
The vertices within the selection box will now be selected.
Press
X
and Delete the vertices.
Until
now we have been working with the pivot
set to Median. This means that if you rotate or scale a group of
vertices the centre of the rotation or scale will be the centre of the
selected vertices.
To align the end vertices of the bearing grooves we need to rotate
individual vertices around the centre of the ball bearing. |
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On
the view header click on the pivot
button and choose 3D Cursor. As the cursor is already positioned on the
centre of the ball bearing we can rotate the end vertices.
Zoom in on one of the end vertices by rotating the SW (scroll wheel)
and panning by pressing Shift
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and
holding the
MMB
whilst moving
the mouse. To rotate the vertex press R and drag the
vertex until it is
over the line defining the inner portion of the bearing race. Click the
LMB
to accept the rotation. Repeat this on all four vertices |
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The
vertices we have just rotated will be close to the edge defining the
inner surfaces of the bearing race but not exactly on it. To correct
this we will position the cursor on the inner surface edge. Select a
vertex on the edge and Shift-S
Cursor->Selection.
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Then
scale the two
vertices onto the edge. Press S to scale Z to constrain the
movement to the Z axis and 0 to position the vertices
in line with the cursor.
Repeat
this on the other edge.
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| We now have enough detail
to complete the inner race. Select the 6 reference vertices shown above
and X delete them |
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We
are left with the two corner fillets and the bearing groove.
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| To reconstruct the face
of the bearings inside diameter select the inner most vertices on the
bottom fillets and press F
to insert an edge. |
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Extrude the end vertex of
the bearing groove and constrain to the Y axis
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To
align this to the outer edge of the bearing snap the cursor to the top
vertex of the fillet. Re-select the extruded vertex and scale S constrain to the Y axis and 0 to set its
position in line with the cursor.
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The
inner edge of the
inner race has a 0.05mm chamfer. to form this press G to grab the vertex
(move), Y
to constrain, 0.05
to set its position.
Now
extrude this vertex -0.05 in the Y axis then grab G, constrain Z, -0.05 to position.
The chamfer is now formed. |
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Finally join the chamfer
to the fillet with an edge. Select the end vertices on the chamfer and
fillet and F
to insert a new edge.
Repeat this on the other end to complete the section of the inner race.
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The
outer race is a little mode difficult as it contains a circlip groove
and location for the dust shield.
The
creation
of this form is fairly straight forward. From the top left corner
vertex simply extrude and constrain the movement to the Z and Y axis
at the dimensions opposite.
Once
completed repeat this on the other end of the bearing.
Once the edges are in place you can refine the cross
section by adding a 0.02mm chamfer on
each of the corners. This can be achieved by deleting one
edge, extruding the end vertices 0.02 in the direction of the deleted
edge, reinserting the edge and then moving the corner vertices 0.02 in
the perpendicular axis. |
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| Delete X the six vertices
used as reference points |
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The basic
shape of the outer race is now constructed. Select the vertices either
end of a gap and press F
to insert an edge. Do this one edge at a time until the outer race is
complete.
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The
section through the bearing is now complete and we are ready to spin
this through 360 degrees to form the 3D model. However the spin process
rotates around the cursor and it is in the wrong position. When we
started to construct the section we worked from the Object Centre which
defined the centre axis of the bearing.
To snap the cursor to the object centre press Tab to go into
Object Mode. From here you can press
Shift-S Cursor->Selection The selection point of an
object is the object centre. |
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Tab back into Edit
Mode and press A
to select all vertices.
As
we want to spin the bearing in the front
view press NumPad 1
and the view will change with the vertices lined up above the cursor.
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In the Mesh Tools panel
check Degr: is set to 360 and Step: is set to 64. Press spin. The bearings inner and outer
race will be formed.
The
last set of vertices created will now be selected but they aren't yet
connected to the first set of vertices.
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To join these press A twice to select all the
vertices then W
to bring up the Specials menu, from this select Remove Doubles, which
will merge any vertices that are sitting on top of each other.
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That's it for modelling
the inner and outer race. Press Tab
to go into Object Mode and rotate the view with the MMB to see the 3D
view of the bearing from any angle. You can pan the view with
Shift-MMB
and moving the mouse.
If you loose your model from the view you can retrieve it by pressing
the Home
key
You will notice however that all the faces are flat with faceted edges
to correct this in the view we will smooth the surfaces we need to
appear round and retain edges we need to be sharp.
Tab
back into edit mode and select all A.
In the Link
and Materials panel click "Set Smooth".
If areas of black appear on the surface of the bearing press Ctrl-N
and accept "Recalculate Normals Outside". This will allow Blender to
know which side of the faces are pointing to the outside of the object
and which are on the inside. |
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| In
the Modifiers panel press
Add
Modifier. From the pop up menu choose Edge Split. In the Edge Split
modifier "From Marked As Sharp" and "From
Edge Angle" will already be selected. Leave Split Angle:30.
Which
will
smooth the join between any faces with an angle of 30 degrees or less.
You will notice though that there is not a sharp edge between the
bearing groove and the inner edges of the race because the angle is
less than 30 degrees. This can be corrected by marking these edges for
the Edge Split modifier to recognise as sharp. |
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Select
the edge loops on the outer edges of the bearing groove. This can be
achieved by first deselecting all vertices A and then selecting
each
loop Shift-Alt-RMB
With the four loops
selected press Ctrl-E
to bring up the Edge Specials menu.
Select "Mark Sharp". This will tell the Edge Split modifier that these
edges should be viewed as a sharp edge and it won't apply any
smoothing to them.
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Before we
create the next object we will give this one a meaningful
name.
In the Links and Materials Panel Click in the OB: Plane field
Delete
plane and re name the object 608-Race
This is a good point to save your work. Press Ctrl - W and accept
the save menu.
In
Part 3 we will be placing the Ball Bearings within the Inner and Outer
Race |
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The following
are video tutorials covering the details above. |
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