Grain Mill Coupler Bosch 00628702

An example 3D printing can be useful also for mechanical parts manufacturing. Maybe someone find this model useful.

My original coupler of Grain mill Bosch MUZ5GM1 has broken. It is made of some plastic material.

So I decided to design a printable spare part based on original coupler instead of ordering 5 - 8 € (w/o shipping) spare part from internet seller. 

Design of the coupler and print setup has been tested in several iterations to achieve performance similar to original coupler. Samples were tested for torque when they fail and afterwards also in real operation at grinding of some grains (actually many different grains)

Examples of several samples after torque test 

• first from left standard print setup for PLA with 100 % infill - broken at 5,0 Nm - visible gaps at breakage surface
• second - extrusion multiplier set to 1,03 and 3 perimeters - broken at 5,4 Nm
• third - extrusion multiplier set to 1,05 and 2 perimeters - broken at 5,6 Nm
• fourth - same settings as third, broken in food processor to try if it still working as protection to gearing and motor - passed

Examples of samples after real operation test. Printed coupler failed at grinding of split pea, while no issues at grinding of wheat, barley, rice, lentils, groats, rye, oats. Based on this test I designed reinforced coupler what passed grinding split pea.

Tools used for torque test - torque wrench 3 - 15 Nm and ring fork key

An example of test body after torque test at 6,0 Nm - your 3D printed part should look similar after torque test

Recommended print setup:

• layer height 0,15 mm structural
• 100 % infill
• extrusion multiplier 1,03 - 1,05 (subject of test)
• dried filament - PLA is good enough