# D42.3 UHV Stepper Motor

> 1.8°, two phase hybrid stepper motors (1 x 10-10 mBar)

Canonical product page: [https://arunmicro.com/products/D42-3_UHV_Compatible_Stepper_Motor/](https://arunmicro.com/products/D42-3_UHV_Compatible_Stepper_Motor/)

550 mNm, NEMA 17

## Product details

- Product code: `d42.3`
- Category: [UHV Stepper Motors](https://arunmicro.com/products/category/motors/)
- Made in the UK
- UK-based support

## Best for

High-torque ultra-high-vacuum motion applications where the highest available torque within AML's NEMA 17 D42 motor family is required.

The D42.3 is a NEMA 17 UHV stepper motor with 550 mNm holding torque.

Choose the D42.3 when the D42.1 or D42.2 does not provide sufficient torque but retaining a NEMA 17 frame size is desirable.

It is suitable for low-speed, precision in-vacuum positioning and manipulation in UHV systems operating below 1 × 10⁻¹⁰ mbar.

## Not suitable when

Do not select the D42.3 where more than 550 mNm holding torque is required without first assessing the application's torque requirement across the required operating speed.

For higher direct-drive torque, consider the NEMA 23 D57.1 at 1,000 mNm.

An AML PG42 UHV planetary gearhead may also be considered where increased output torque or positioning resolution is required.

Where less torque is required and reduced motor length is beneficial, consider the D42.1 or D42.2.

The standard D42.3 is not suitable for operation below -65 °C; select the D42.3-C for operation down to -196 °C.

## Selection guidance

Select the D42.3 when the highest torque available within AML's NEMA 17 D42 family is required.

D42 family comparison:
- D42.1: 250 mNm
- D42.2: 450 mNm
- D42.3: 550 mNm

All three use a NEMA 17 frame size but differ in motor length and available torque.

Choose the lowest-torque model that provides sufficient performance with an appropriate engineering margin. Use the D57.1 when substantially greater torque is required.

Motor selection should also consider torque at operating speed, duty cycle, temperature and shaft loading.

## Compatibility and prerequisites

The D42.3 is a two-phase bipolar hybrid stepper motor designed for installation inside an ultra-high-vacuum system.

A compatible bipolar stepper motor drive is required. AML SMD3 and SMD4 drives are designed for use with AML D-series vacuum stepper motors.

The embedded motor temperature sensor should be used for motor protection.

The D42.3 can be combined with AML PG42 UHV planetary gearheads where increased torque, positioning resolution or inertia matching is required.

Confirm mounting, available motor length, shaft coupling, axial and radial loads, cabling and feedthrough requirements before ordering.

## Ordering guidance

Standard order code: D42.3 — 550 mNm UHV stepper motor.

Available configurations include:
- D42.3-C — cryogenic version, -196 °C to +190 °C
- D42.3-H — dry-lubricated hybrid ceramic bearings
- D42.3-P — PT100 temperature sensor instead of the standard thermocouple
- D42.3-R — gamma-radiation-hardened version, rated to 1 × 10⁶ Gy
- D42.3-X — custom shaft modification

Before requesting a quotation, provide the required quantity and identify any cryogenic, bearing, radiation, temperature-sensor, shaft, connector, cabling or gearhead requirements.

If motor suitability is uncertain, provide operating pressure, temperature range, required torque, speed, duty cycle and mechanical interface.

## Order codes

| Order code | Description | Price |
| --- | --- | --- |
| D42.3 | 550 mNm UHV stepper motor | £1,011.00 |
| D42.3-C | D42.3, Cryogenic -196 °C to +190 °C | £1,104.00 |
| D42.3-H | D42.3, Dry lubricated hybrid ceramic bearings | £1,104.00 |
| D42.3-P | D42.3 with PT100 temperature sensor in lieu of thermocouple | £1,070.00 |
| D42.3-R | D42.3, Gamma radiation hardened | £1,104.00 |
| D42.3-X | D42.3 with shaft modification | Price on request. Contact AML for a quotation. |

## Overview

- Suitable for use below 1 x 10-10 mBar (7.5 x 10-11 Torr)

- Continuous running in vacuum at high torque and step rates with AML drive

- Bakeable to 200 °C

- Step angle of 1.8°

- Step angle tolerance of ±5%

- Operational temperature range -65 °C to +190 °C

- Embedded thermocouple or PT100 sensor

- Open construction with all internal spaces vented

- Cryogenic extended operating temperature option available, range -196 °C to +190 °C

- Gamma radiation hard versions available 1 x 106 Gy

- Standard motors are fitted with open stainless steel bearings, lubricated with NyeTorr® 6300 ultra low outgassing UHV grease 

- Hybrid silicone nitride ceramic bearings option available, dry lubricated with tungsten disulfide

- Custom shaft modifications available

## Documentation and downloads

- [Application of UHV Stepper Motors](https://arunmicro.com/documentation/APN_Application_Notes_for_UHV_Stepper_Motors.pdf)
- [Axial & Radial Loads](https://bookstack.vps-da8d40f3.arunmicro.com/books/axial-and-radial-loads-on-aml-stepper-motor-bearings)
- [Datasheet](https://arunmicro.com/documentation/Datasheet_AML_UHV_Compatible_Stepper_Motor.pdf)
- [Magnetic Leakage Fields](https://arunmicro.com/documentation/APN_Magnetic_Leakage_Fields.pdf)
- [Material Content](https://arunmicro.com/documentation/APN_Material_Content_of_AML_UHV_Stepper_Motors.pdf)
- [Operating Instructions](https://bookstack.vps-da8d40f3.arunmicro.com/books/d-series-uhv-stepper-motor-user-manual)
- [RoHS](https://arunmicro.com/documentation/CE_AML_UHV_Stepper_Motors.pdf)
- [Vacuum Performance](https://arunmicro.com/documentation/APN_Vacuum_Performance_of_AML_UHV_Stepper_Motors.pdf)
- [CAD Models (.STEP)](https://arunmicro.com/downloads/CAD_VCSM.zip)

## Related products

- [D42.2 UHV Stepper Motor](https://arunmicro.com/products/D42-2_UHV_Compatible_Stepper_Motor/): 450 mNm, NEMA 17
- [D57.1 UHV Stepper Motor](https://arunmicro.com/products/D57-1_UHV_Compatible_Stepper_Motor/): 1,000 mNm, NEMA 23
- [SMD4 Stepper Motor Drive](https://arunmicro.com/products/smd4-stepper-motor-drive/): Stepper motor drive optimised for use with AML UHV-compatible motors. Features advanced connectivity with USB, Ethernet and RS232/485 interfaces. Optional encoder module for incremental and absolute encoders
- [SMD3 Stepper Motor Drive](https://arunmicro.com/products/smd3-stepper-motor-drive/): Stepper motor drive optimised for use with AML UHV-compatible motors. Four operating modes including USB remote from a host PC and opto-isolated step and direction inputs. Continuous monitoring of motor temperature is provided with automatic shutdown to prevent motor damage.
- [UHV Stepper Motor Gearheads](https://arunmicro.com/products/stepper-motor-gearheads/): UHV planetary gearheads for use with AML stepper motors to increase step resolution and torque.
- [MLF18F](https://arunmicro.com/products/electrical-feedthrough/): MLF18F 18-way feedthrough on a DN40 CF flange (70 mm OD). Individual glass compression seals and bakeable to 250°C.
- [MLF18 UHV Connectors](https://arunmicro.com/products/vacuum-side-connector/): UHV, 18-way Vacuum-Side Connectors.
- [VCC7 UHV Connectors](https://arunmicro.com/products/vcc7-vacuum-side-connectors/): UHV, 7-Way Vacuum Compatible Connectors.