Construction and assembly of lead screw motors

What is a lead screw motor?

In its simplest form, an igus lead screw motor consists of a lead screw and a motor. A nut is usually required to drive something. The motor is designed as a stepper motor with hollow shaft. These motors are specially developed to absorb axial forces. Our NEMA 23 lead screw motor, for example, can axially absorb 500N. This axial load would damage conventional stepper motors.

The hollow shaft contains a holder for our lead screws so that they can be screwed and glued. This connection is so powerful that it can only be released with special tools and a specially developed process.

Stepper motor with lead screw and connection cables.

Setting the correct lead screw straightness

Lead screw motor in a technical drawing with a visible threaded spindle.

The motor can also be equipped with an encoder and/or industrial M8 connectors. The lead screw has been specially machined for this motor so that the thread starts directly from the motor flange. As a result, there is no loss of stroke.

Once the lead screw has been inserted into the motor, the lead screw is straightened. Here we distinguish between two lead screw motor precision classes.

SMP 0.2, radial run-out of 0.2mm measured from 100mm of the motor flange
SMP u, undirected without definition

The SMP 0.2 is usually sufficient, but we are currently working on processes to ensure even better radial run-out. For very cost-sensitive applications, the SMP u can also be used.

Finding the right lead screw length

Lead screw motor drawing with a 100 mm dimension for the installation length.

The definition of lead screw length for motorised lead screws can be somewhat tricky, but is easy to understand:

Lead screw length = Total length incl. assembly pin and crank
Unsupported lead screw length = Lead screw length from motor flange without assembly pin and crank
Stroke = Unsupported lead screw length minus the length of the nut

In principle, all igus lead screws can be connected to the motors. Nevertheless, sensible compatibility should be ensured. As the lead screws have to be machined, we have a defined number of lead screw geometries in stock, which are cut to length as required.

When selecting the suitable lead screw nut, you can choose one from our standard product range or request a specified geometry. We are happy to offer you a special injection-moulded nut according to your requirements and ideas.