Overview of AML Stepper Motor Modifications

Posted on Friday 29th September 2023 at 12:00

AML's UHV compatible D-series stepper motors are highly customisable. There are a wide range of standard options that tailor the motor for compatibility with specific environments, alongside unique application specific modifications designed by the end user. This blog post will give an overview of all the available modifications, starting with the standard options.

D-series motors group image

D-Series Stepper Motors


Option C:

Option C is the cryogenic version of the standard motor. This extends the operational temperature range from -196 °C to +190 °C. This is achieved by replacing the standard bearings lubricated with NyeTorr® 6300 UHV low outgassing grease with dry lubricated (tungsten disulfide) hybrid silicon nitride ceramic bearings. This is suitable for cryogenic and low temperature environments where the standard minimum operating temperature of -65 °C will be exceeded.


Option H:

Option H is the dry lubricated version of the standard motor. The changes made to the motor are identical to option C where the standard bearings are replaced with dry lubricated (tungsten disulfide) hybrid silicon nitride ceramic bearings. This option is suitable for low duty cycle applications where UHV grease is not permitted. Note that the life expectancy of dry lubricated bearings may be significantly shorter than bearings lubricated with the standard NyeTorr® UHV grease, depending on the application.


Option P:

Option P is for the inclusion of an embedded PT100 RTD sensor in leiu of the standard K-type thermocouple. A temperature sensor is included in all AML motors as temperature monitoring is critical to prevent the possible irreversible deterioration of the motor winding insulation when operating in UHV environments. For applications where a thermocouple feedthrough is not available and chamber wall temperatures may create significant thermocouple errors, then the PT100 sensor is a more accurate and reliable temperature sensor.


Option R:

Option R is the radiation hardened version of the standard motor. Radiation hardened motors are suitable for a total dose of 1E6 Gy of gamma radiation. This is a conservative figure based on the published radiation compatibility of the materials used. Radiation hardening is achieved with the removal of PTFE content in the motor. Firstly, the standard bearings lubricated with NyeTorr® 6300 UHV low outgassing grease are replaced with dry lubricated (tungsten disulfide) hybrid silicon nitride ceramic bearings. In addition, the standard polyimide wrapped motor phase leadout wire is replaced with our KW5 polyimide enamelled wire.


Option X:

Option X is for modification to motor shaft. This option encompasses a variety of modifications to the standard shaft dimensions. Examples include adding features to the shaft such as flats or holes, shortening the shaft, and adding a rear shaft. These are often customer designed modifications that are specific to their application, but AML can design the modification based on your specification requirements. If you require a shaft modification to an AML motor, please contact our sales team and we will assist with the feasibility of your design.

D35.1 shaft modification

D35.1-X. Through hole in shaft.

D42.2 with rear shaft

D42.2-X. Rear shaft.

D57.1 with threaded shaft

D57.1-X. Threaded shaft with extended length.

Option M (General Modifications):

AML offers a number of general modifications to the D-series UHV compatible stepper motors. The most common of these is a custom leadout wire length. As standard, all AML motor have a 1.5 metre leadout length. This can be shortened or extended as required. Typically, these are extended to be suitable for placement within a large vacuum chamber. The motor leadout termination can also be modified to be a suitable connector of your choice, for example AML's in-vacuum 9-way d-sub connector (VC9DF).

If you have a unique application that requires more significant modifications, AML can also offer endcap modifications. These are useful for when the motor requires additional features to seamlessly interface with your own components. AML's design engineers can work alongside you to assess the feasibility of your design and achieve a suitable solution.

D42.2 rear endcap modification

D42.2-M with custom rear endcap.


This is just an overview of the modifications available with AML's D-series stepper motors. When it comes to custom designs with shaft and endcap modifications, there are a large range of possibilities. To discuss your requirements for a UHV compatible stepper motor, please contact us at sales@arunmicro.com.