3D Printer: Sub-Assemblies

Once the frame has been assembled, the next thing was to put together some of the individual sub-assemblies. The Mendel90 design’s build process automatically generates BOMs (Bills of Materials) for each of the sub-parts. It’s also possible to render those parts alone, and in an “exploded” view, using the OpenSCAD software, and examine it from all angles. These two things together make it obvious in most cases what screws and parts go where. The build instructions add any extra tips, or hints on the order in which to do things, which may be necessary.

Let’s take an example, the X idler end. This is the assembly at the opposite end of the X carriage to the motor, which contains the pulley over which the X drive belt runs. It also has bearings so the entire X carriage can move up and down the Z axis.

The generated BOM is as follows:

 1 Ball bearing 624 4mm x 13mm x 5mm
 1 M4 cap screw x 40mm
 2 M4 hex screw x 16mm
 2 LM10UU linear bearing
 1 Nut M8
 3 Nyloc nut M4
 4 Washer M4 x 9mm x 0.9mm
 2 Washer M5 x 20mm x 1.4mm
 1 x_idler_bracket.stl

The exploded rendering of the sub-assembly from OpenSCAD looks like this (obviously, when rendered in OpenSCAD, you can rotate it to get a better view, e.g. to see the M8 nut in the trap on the bottom):

The instructions give tips on how to clear out any excess plastic, and the best way to insert the linear bearings in the channel.

Putting all that together, the result is this:

(Unfortunately, my choice of black plastic means that these photos do not come out as clearly as they might.) Some of the other assemblies are more complex than this one, but the principles are the same.

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