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Back to Tutorials |
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Designing a casting. Part 3 Roller-nut Mounting Brackets |
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To finish off
all the mounting locations on the casting, we need three
more components, the mounting brackets for the Roller-nut and support
bearings. Because the design of the brackets relies on the position of
the casting face from the axle centres and also any pockets in the
casting, it has not been possible to design the brackets until now. |
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Hide
all the components other than the Roller-nut assembly, casting and lead
screw. It will be easier to see the available space for the bracket
without the other components.
Tab into Edit Mode for the casting and snap the cursor to the front
face. I
have selected the two vertices of the recess, so the cursor is on the
edge of the recess and aligned with the mounting face of the axle. |
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Roller-nut
Adjuster |
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Back
in Object Mode, add a Plane. Scale the left-hand side vertices to
the cursor, its height to 30mm and width to 4mm. Extrude the right hand
vertices on the X-axis 6mm then again on the X-axis 10mm, the 6mm
section will be used to form
a locating key, the 10mm section will become the bolt flange.
Extrude the three faces to give a thickness of 3mm. |
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Tab
into Edit Mode for the axle and snap the cursor to the vertices on the
flange fillet as detailed in Part 1. Tab back into the
adjuster Bracket.
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In side view add a
circle with 32 vertices and a 3mm radius.
Extrude
these vertices then press |
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Delete
some of the vertices from the outer circle and add edges back to the
mounting flange. With careful choice you can get a tangential
alignment.
Midpoint cut a row of vertices on the mounting flange and delete
the vertex that would become inside the bracket. This will remove four
faces from the mounting.
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around the hole. |
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Select the vertices indicated and
Extrude them on the X-axis 4mm then again 6mm.
In wire view delete the vertex that has been created internal to the
bracket. Select all and remove doubles.
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faces of the original face, as these will be removed by the extrusion process. |
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As
detailed in Part-1 for the V-roller adjuster brackets add two elongated
holes to the flange and also a fillet to the outer corners.
Finally the bracket needs to be constrained to a movement perpendicular
to the leadscrew. |
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To achieve this I have purposefully
created vertices that will allow the
incorporation of a key, which will be located in a slot machined into
the face of the casting.
Select the two faces indicated and extrude them 2mm.
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Support Bearing Adjusters. |
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The
support bearing adjusters are modelled in a similar way to the
Roller-nut adjuster bracket. I have slimmed down the bracket to 6mm and
moved the mounting flange above the bearing.
The right hand adjuster will be set back into the pocket provided in
the casting.
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The view from the back shows the
6mm key, which penetrates the face of the casting.
Some work will be required to provide the mating slot in the casting
and the bolt holes.
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The left-hand adjuster stands out
further from the casting to allow support forward of the leadscrew
centreline.
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Transferring
Geometry to the Casting |
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Select an adjuster and Tab into Edit Mode. In top view NumPad 7 select the vertices on the
back face of the adjuster.
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Copy the vertices Shift-D then Escape to leave the copy in place.
Separate the copy from the adjuster mesh P.
Tab
into Object Mode and select the copied adjuster face, then Shift-RMB select the casting. Join
the copied face to the casting Ctrl-J.
Repeat this for all three adjuster brackets.
Some work is now needed to modify the copied geometry to suit the
casting.
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As
with the V-roller adjuster, the lead screw adjusters will be secured
with 4mm bolts, so the casting needs 4mm-tapped holes centrally to
the
slot.
Again
these will be represented by a hole at the tapping drill size, which is
3.3mm.
Alt-RMB Select the vertices from the slot and snap
the cursor to their centre. Add a circle with 16 vertices and a radius
of 1.65mm. Repeat this for all slots. |
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Delete the unnecessary vertices,
leaving the keyway slot and tapped hole circles.
In
order for the adjuster to move in the slot the slot length needs to be
increased by at least the amount of
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elongated bolt holes. Grab
the top vertices of the slot and move them on the Z-axis 5mm. |
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I
have also cut the slot lengthways with a mid point cut. This has
enabled me to spin a radius at the top of the slot, which on the
casting will be cut
using a 6mm slot drill, giving the radius on the ends.
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horizontally across the recess to align vertices with the centre
vertices of the key slot. |
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The slot on the top right adjuster
poses a different problem, as it has to penetrate the face of the
bearing recess.
To add vertices and edges for this penetration use the Geom tool.
Select the intersecting faces and in a script |
window choose Scripts>Mesh>Geom Tool
Select Intersect: Face(s) (Cut) |
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The Geom Tool will cut a new series
of edges around the intersection. It will also triangulate all the
selected faces.
Delete all the unnecessary faces and convert the remainder to quads, Alt-J.
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Extend the top of the slot 5mm to
allow the adjuster bracket room to slide.
Cut a vertical row of vertices down the slot and bearing recess, using
the knife with a mid point cut.
Spin the top radius. |
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The left-hand adjuster slot just
needs to be extended 5mm top and bottom.
A vertical mid point cut will allow the ends to have a radius spun to
match the slot width.
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All the
mating geometry needed to complete the casting has been accurately
extracted from the component assembly.
In the next
part I will complete the casting by building faces between all the
extracted geometry elements. |
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