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          Blender Tutorials: 608 Bearing - part 6

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Part 6 Modeling The Dust Shield

Insert Plane
The dust shield will be formed in the same way as we made the bearing inner and outer race. We will create a section through the dust shield and spin this around the bearing centre to form the 3D component.

In the Outliner set the 608-Race to visible and hide all the other parts. In Object Mode snap the cursor to the 608-Race object to set the cursor in the centre of the bearing.

We will start this object with a plane, so press the Space Bar to open the Tools menu and Add>Mesh>Plane. The plane opens in Edit Mode.
Set Position

Drag the four vertices of the plane and position them in the retaining grove of the outer race.

Select the bottom two vertices and delete them X as we will start the dust shield using only the top two vertices.

Delete Vertices Grab G the end vertex and move it along the Y axis 1.75mm so the top edge measures 0.25mm, the thickness of the dust shield.

Extrude E (Only Vertices) the two end vertices i
n the Z axis -0.75.

Grab G the inside bottom vertex and move it
in the Z axis a further -0.144mm  to form an angle between the two vertices of 60 degrees from the vertical.
Extrude and rotate edge
Set the cursor on the inside lower vertex and then extrude this -1.5mm in the Y axis.

Rotate R this edge -30 degrees from the cursor.

Repeat this for the outer edge.

Repeat edge
Reference edge

 dust shield offsets 0.85mm so extrude two reference vertices from the top corner. -0.6 then -0.25 in the Y axis

Extrude a face from these vertices constrained to the Z axis and position the new vertices between the dust shield edges. Extrude another face along the Z axis below the dust shield.

Cut 1 We will use the reference edges to accurately cut the angled dust shield edges to length.

Select all vertices A and open the knife menu K, select Knife (Exact)

Click LMB below the lower right reference vertex,  press Ctrl and move the knife towards the bottom left vertex the cut line will snap to the vertex click LMB to set the line then move to the vertex above Ctrl LMB this vertex  to snap the cut line, then press Enter to accept the cut.
Cut 2
Repeat this on the outer edge but start the cut line on the top left vertex and cut to the vertex below.

We now have two new vertices setting the offset width of the dust shield.

Reference Vertices We no longer need the reference vertices or the end vertices of the dust shield edges.

Select these vertices and delete them X

Select ends
Select the two end vertices of the dust shield ready to extrude them.

Set cursor Before we extrude them we need to set the cursor on the top of the inner bearing race. Tab into Object mode and select 608-Race. Tab back into Edit Mode for this object. Select a vertex from the top of the inner race RMB and snap the cursor to this, Shift-S Cursor->Selection.

Tab back into Object Mode, select the Plane object (dust shield) and Tab back into Edit Mode for this object.
Extrude the two selected vertices towards the inner race constrained in the Z-axis.

We will now scale them onto the inner race.

Extrude and scale to cursor With the pivot point still set to 3D cursor press S for scale Z to constrain the movement to the Z axis and 0 to scale the lines level to the cursor.

The vertices are now touching the inner race so we need to back them off a little to provide some clearance.

Set clearance

Move the vertices G (grab) Z constrain 0.02 for the clearance. The vertices will now be clear of the inner race.

To complete the basic shape of the dust shield press F to put an edge between the vertices.
Basic Shape We now have the basic cross section of the dust shield positioned accurately against the bearing race. As we no longer need to reference the bearing race press Num-/ to go into local view for the dust shield.

The last thing to do to the cross section is add some fillet radii to the offset corners.

Adding Fillets

I will show two methods of accurately positioning the fillets, one using trigonometry and one using reference geometry that has no need for a calculator. For both methods you will need to know the angle between the edges, the fillet radius and have one edge aligned to a known axis.

Fillets - Trigonometry Method

Angle A First we need to know the angle between the edges we are going to fillet. If you haven't been planning the construction of your model and placing lines arbitrarily you can find the angle by forming a face from the three vertices and using the edge angle button in the Mesh Tools 1 panel.

Another requirement is for one of the edges to align with a known axis.
Triangle for Hypotinuse
To work out the centre point of the fillet we simply construct a right angle triangle with half angle A and the radius. The hypotenuse is the distance to the centre point at an angle of half A

Therefore   Sin 1/2A = Radius/ Hypotenuse

                Hypotenuse = Radius/ (Sin (A /2))
Once you have determined the hypotenuse simply extrude E this from the intersect along the known axis and rotate R it 1/2 angle A

Fillets - Reference Geometry Method

Extrude Along Known Axis Extrude a vertex from the intersect 1.5 times the radius.

Rotate this vertex 1/2 angle A
Rotate to Centre
From the intersect extrude a vertex perpendicular to the edge on the known axis and the length of the fillet radius.

Extrude radius
Extrude another vertices from this parallel to the edge on the known axis.

Where these two lines cross is the centre point for the fillet.

Cut to Form Vertex on Center Using the knife tool K snap a cut line Ctrl-LMB between the two reference vertices parallel to the known axis line and cut a new vertex on the centre point of the fillet.
Extrude Radius From the centre point extrude a vertex perpendicular to the edge on the known axis at the length of the fillet radius.

Set Cursor and spin Set the cursor on the centre point and spin the vertex on the end of the radius edge through an angle of

180 - Angle A
Delete reference geometry Delete the reference vertices.

Replace edges Re make the edges between the fillet and surrounding vertices.

Getting back to the dust shield we will use the reference geometry method to position the fillets with a small radius of 0.1mm and a large radius of 0.35mm. The angle between the edges is 120 degrees.

Extrude From the intersect on the inside of the angle extrude E a vertex along the Z axis 0.15mm, then rotate R the vertex -60 degrees. Rotate
Again from the intersect extrude a vertex -0.1 in the Y axis (distance of radius ) and then extrude this above the 60 degree edge. Extrude cut line

Select all A and then K Knife (Exact) a vertex on the 60 degree angled line snapping the cut
Cut Ctrl-LMB to the edge set at the radius distance from the dust shield.

Select the new vertex which has been 
created on the fillet centre and snap the cursor to it.
Extrude Vertices to spin
From the fillet centre extrude a vertex 0.1 on the Y axis for the front fillet then extrude this 0.25 on the Y axis for the back fillet.

Spin Fillets
In the Mesh Tools panel set Degr:60 and Step:7 and spin the two vertices.

Delete Edges In edge select mode press B twice to bring up the selection painter reduce the size of the selection circle MW and select LMB the
Repeat on other bend
edges between the fillets. Delete X these edges.

Repeat this procedure to produce the bottom fillet.

Back in Vertex Select mode, select the reference vertices along with those on the original angle intersects and delete them. We are now left with the fillet's and top and bottom edges of the dust shield.
Delete reference vertices

Fillets and end edges Select a vertex either end of a missing edge and press F to insert a new edge.

Repeat this for all the open sections.
Make Edges
We are now left with a completed cross section through the dust shield ready to spin into the 3D object, however as before the cursor is in the wrong position.

Select all A the vertices and Tab into Object Mode.
Dust Shield Cross Section

Set cursor Snap the cursor onto the object centre. Shift-S Cursor->Selection.

Tab back into Edit Mode and go to front view NumPad-1.

In the Mesh Tools panel set Degr:360 and Step:64 press spin to form the 3D object.

Select all vertices
A and remove Doubles W.
Spin section

Dust shield The dust shield is now almost complete, but chamfers are required on the corners.

In edge select mode loop select the four edge loops indicated Shift-Alt-RMB.
Using the Bevel Centre script detailed in
Part 4, add a 0.05mm chamfer.

Finish the dust shield by adding an Edge Split modifier also detailed in Part 4.
Select Edges to Bevel
A Dust shield will also be required on the other side of the bearing. Rather than repeating the modeling process we will duplicate this dust shield and Mirror it across the bearing centre.

Tab into Object Mode and go to the side view NumPad-3. Check the cursor is still on the object centre.

Mirror Object
Press Shift-D to duplicate the object then Esc to leave the duplicate on top of the original.

Press Ctrl-M to open the Mirror sub menu and select "X Local".

Both Dust shields have now been created so it is time to give them a meaningful name. Select Plane in the outliner and then in the Links and Materials panel change its name to OB:608-ShieldA. Repeat this for Plane.001 naming it OB:608-ShieldB.

Press Ctrl-W and save your work.

The final components for the bearing assembly are the circlips that retain the dust shields in place. These are covered in the next section.

<< 608 Part 5 The Cage Clasp Tutorials 608 Part 7 Circlip >>

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