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How do I make a Turner's Cube?

A Turner's Cube is one of the first workshop exercises when a machinist learns to mill with a CNC machine.

Image- derived from 'https://www.cnccookbook.com/how-to-make-cnc-turners-cube'

Image result for turners cube]

Let's go through the steps on creating the 3D object in DesignSpark Mechanical:

1. First, design a cube with a side of 24mm. You can change the dimension to your needs.

2. Draw 3 concentric circles on each face. In this example, the radii are 5mm, 8mm and 11mm (going outwards).

Redo this step for the other 5 faces.

3. Depth of the circular pockets: Depending on whether you'd like the nested inner cubes to free-float or remain fixed, the depth will vary but there is a mathematical relation to help you out.

Enter the highlighted dimensions (x - side of cube, r - radius of the circular pocket) to get the depth value (d) at which the nested cube will free-float but can also be taken out of the assembly.

formulae.svg

 As you keep going inwards, x and r will change to match the side of the cube that encloses the new concentric circular pocket. So, you would to recalculate the incremental reference depth for the next pocket (this needs to be added to the first value of d that you calculated). It's up to you if want certain cubes to remain fused or free to move.

To get you going with this example, we use 3mm, 5.25mm and 6.9375mm.

4. Open DesignSpark options and change the default extrude behaviour to 'Cut'. This saves you time from having to set that option for every single operation.

Next, starting from the inner most pocket use the PULL tool to cut the holes in the solid. The depth values were calculated in the last step.

5. You may note that during some of the PULL operations, there are artefacts left behind in the walls of the pockets. To avoid this, undo the last PULL operation and cut out the pocket in 2 steps.

Example: if the depth is 5.25mm, cut down to 5.24mm and then keyboard ESC to end the operation. Using PULL again, remove the last 0.01mm.

 

6. Once you finish 3 pockets all 6 sides, your final result will look similar to:

7. Also, remember that change in step 4? Make sure to switch the default extrude behaviour back to 'Automatic' in DesignSpark options menu to avoid any surprises in your next project.

Try 3D printing this or send to a CAM software to prep for CNC milling.

 

View the original article here

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A curious mind with a passion for 3D CAD & rapid prototyping.

29 Mar 2020, 13:02