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          Blender Tutorials: Designing a Casting - part 2

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Designing a casting. Part 2 Initial Layout

We now have all the components needed for the X-axis roughly positioned. So it's time to put a little thought into what shape the casting needs to be to accommodate the components.

Component Locations
In front view the components are fairly spread out and could possibly be moved closer to the centre to reduce the footprint of the X-axis.
Side View In side view its clear that some of the components will penetrate the front mounting face of the casting. It will be necessary to provide a recess behind the roller nut and top right hand bearing.

The size and location of the recesses will determine how close the other components can be to the centre of the casting.

The first part of the casting to model is the recess behind the Roller-nut. To make modelling easier you can hide the slide shaft and lead screw by clicking the eye icon in the outliner. Select an adjuster block and in Edit mode snap the cursor to the front face of one of the adjuster blocks. Tab into Object mode and in front view add a plane. In object mode move the plane central to the Roller nut and resize it so it is larger than the nut. One side should be aligned with the back of the axle flange.

Delete X Only Faces to remove the face from the plane. 
Model Recess

Extrude and add taper Extrude the four edges Y 8mm. This will add depth to the recess.

In side view Grab the top back vertices and move them, Z -8 mm to give a 45 degree angle. Move the bottom vertices up 8mm.
Taper sides In top view move the back side vertices in 1mm to add a withdrawal taper.

Finally add a face to form the back wall.

Add recess behinde bearing
I have repeated the process for the top Right-hand bearing. This time making a little extra room for the axle and nut which also penetrate the front plane of the casting.

With the two recesses modelled it's easy to see where the rest of the components can
be repositioned to make the casting more compact.

Theirs plenty of room to allow me to move the V-roller centres from 150mm to 110mm. It's also apparent the Adjuster blocks are larger than they need to be so I will reduce their size.

Position V-Rollers

Scale centre boss
Select one of the adjuster blocks and Tab into edit mode. It's not possible to just scale everything to a smaller size because this will also resize the centre hole, slots and flange widths. So I need to resize it in stages.

The square centre hub is 44mm and I am going to reduce it to 36m. Box select the centre hub and flange vertices directly above and below it. Scale this on the X-axis by 0.818181 (36 / 44).
Now box select the vertices of the right hand flange and move G these on the X-axis -4mm (1/2 the 8mm difference).

Move flange Repeat this with the left-hand flange. Moving it 4mm on the X-axis.

Box select the vertices of the centre boss and the flange vertices directly to the left and right of it and again scale this 1.2222 but on the Z-axis. Then grab and move the top and bottom flanges 4mm.

You should now have a square adjuster block.
Re-Scale Slot and centre hole. In scaling the adjuster on the Z-axis we have also just scaled the slotted bolt holes. These need to be returned to their original size.
We can do this by scaling the vertices of the slots by the inverse of the original scale (1 / 1.2222 = 0.81818).

Select the vertices of the first slot and Scale it Z 0.81818
Repeat this on the other three slots. Finally scale the centre hole on the X and Z-axis by the same amount to return the hole to the correct diameter.  (Scale Shift-Y 0.81818)

Adjusted positions

With the adjuster blocks reduced in size I have been able to further reduce the V-roller centres, which are now 100mm apart. I have also moved the bottom V-rollers in 6mm so the edge of the adjuster blocks are level with the outside of the top V-roller's.

Select front face To form the pockets in the casting where the adjuster blocks sit we can copy both adjuster blocks Shift-D then press Escape to leave them in position. We can then cut and adapt the copied adjuster blocks mesh to form the adjuster locations in the casting.

With the copied blocks still selected go into local view NumPad /. In side view select the front face of the adjusters. Snap the cursor to the selection so it's on the same plane as the front face, then delete the vertices.

Because of the chamfer the front loop of vertices is no longer aligned on to the front face of the casting. 
Loop select the front edge and in cursor select mode Scale the vertices on the Y axis to 0. This will bring the edge back into alignment.

delete verts Select and delete the vertices of the central hole, to leave us with a recess the same shape as the adjuster.

If it were left like this there wouldn't be any room for the adjuster to slide on the Z-axis. So we need to mover the top and bottom flange to allow the adjuster to move.
Extend top flange

Select the vertices of the top flange and Grab them moving them on the Z-axis 4.5mm. Move the bottom flange -4.5mm. This will give us the room for the adjuster block to move up and down.

Position hole for thread The adjusters will be secured with a 4mm bolt, so the casting needs a 4mm-tapped hole centrally to the slot.

It's not practical to model the thread so it will simply be represented by a hole at the tapping drill size, which is 3.3mm.

Select the four vertices from the straight edges of the slot and snap the cursor to their centre. Add a circle with 16 vertices and a radius of 1.65mm.
rebuild faces Delete the vertices of the slot then rebuild the faces around the hole.

Snap to other locations Using Blenders snap tools, copy and paste the hole and surrounding faces to the other locations.

At this stage it will also be good to delete unnecessary vertices and rebuild the faces as larger quads.

Blenders skin Face/Edge Loop feature will be useful for this.

Once one adjuster recess is complete, copy it and move it 88mm on the X-axis so it sits behind the other adjuster.


To position the fixed axle holes, RMB select a fixed axle and go into Local View NumPad /. Select Shift-Alt-RMB the loop of vertices at the back of the fillet and snap the cursor to the centre of them, Shift-S Cursor>Selection. This gives us the location point for the adjuster. Go into Object Mode and in front view Insert a mesh circle, SpaceBar Add>Mesh>Circle, in the popup menu set Vertices: 32 and Radius: 3. Repeat this for the other axle.

Fixed shaft location

Select the axle location circles, the pockets behind the roller-nut and bearing and the adjuster recesses and combine them into one mesh, Ctrl-J.

These are the first features of the casting.

In order to locate the roller-nut and bearings, three adjuster brackets are required. I will construct these in Part-3.  This will then allow me to add their mounting locations to the casting.
Casting elements

<< Casting Part 1 Component Positions Tutorials Casting Part 3 Roller Nut >>

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