There are several important things to keep in mind when designing screw-driven, vertical, linear slides. First, place the motor at the top of the slide. This will keep the screw in tension preventing it from being under a compressive load which can cause buckling. Second, be sure to refer to the screw or slide manufacturer’s maximum column loading chart. Column strength (vertical or horizontal orientation) is the ability of the screw to hold compressive loads without buckling. Column strength may be substantially lower than its nominal capacity when using longer screw lengths. Third, be sure to consider the driven thrust load acting on the screw and remember to take into account the actual mass or load due to gravity. Fourth, to aid in controlling vertical loads, consider using a counter weight or balance. This can be accomplished by weights, springs, and hydraulics or air cylinders. Finally, consider utilizing a brake to ensure that the load will not suddenly drop in a crash situation. Vertical loads can also be controlled when designing resistance into the drive system by using screw drives which have built-in reduction and inefficiency, such as with Anti-back driving screw leads (acme or lead screw) with inefficiency ≥ 50%.
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