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MESYS Calculation Software

Navigation: MESYS Ball Screw Calculation > Input Parameters > Ball screw geometry

Shoulder diameter of inner and outer ring

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The shoulder diameter of inner and outer ring can be defined.

The shoulder diameter is compared to the maximum extension of the contact ellipsis. A warning is shown if the ellipsis would extend above the shoulder. The Hertzian stress is not valid in that case.

The required shoulder diameter is shown in the report together with a length ratio eLR_i, eLR_e which is showing a safety of shoulder length. The length ratio is defined as the length from lower end of contact ellipsis to shoulder (the green line the graphics) divided by the length of the contact ellipsis 2a (red line in the graphics). The value should therefore be larger than 1 or 100%.


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Instead of using an absolute value, the shoulder height can be defined using a percentage of ball diameters. A factor of 50% would be a shoulder up to the pitch diameter, so the factor should be between 10% and 40%. Using this factor allows to have default geometry on changing ball diameter or pitch diameter.