# D42.1 UHV Stepper Motor

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

Canonical product page: [https://arunmicro.com/products/D42-1_UHV_Compatible_Stepper_Motor/](https://arunmicro.com/products/D42-1_UHV_Compatible_Stepper_Motor/)

250 mNm, NEMA 17

## Product details

- Product code: `d42.1`
- Category: [UHV Stepper Motors](https://arunmicro.com/products/category/motors/)
- Made in the UK
- UK-based support

## Best for

Ultra-high-vacuum motion applications requiring substantially more torque than AML's smaller D28.1 or D35.1 motors while retaining a standard NEMA 17 frame size.

The D42.1 is a NEMA 17 UHV stepper motor with 250 mNm holding torque. It is the lowest-torque and shortest D42-series motor.

Choose the D42.1 when 250 mNm holding torque is sufficient and there is no requirement for the additional torque provided by the longer D42.2 or D42.3 motors.

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 D42.1 where more than 250 mNm holding torque is required.

For higher torque while retaining a NEMA 17 frame size, consider:
- D42.2: 450 mNm
- D42.3: 550 mNm

For requirements above the D42.3 torque range, consider the D57.1 at 1,000 mNm.

Where 75 mNm or less is sufficient and installation space or motor size is a higher priority, consider the smaller D35.1 or D28.1.

The standard D42.1 is not suitable for operation below -65 °C; select the D42.1-C for operation down to -196 °C.

## Selection guidance

Select the D42.1 when a NEMA 17 UHV motor is appropriate and 250 mNm holding torque is sufficient.

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

All three use the NEMA 17 frame size, allowing selection primarily according to required torque, motor length and available installation space.

Choose the lowest-torque D42 model that provides sufficient torque with an appropriate engineering margin.

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

## Compatibility and prerequisites

The D42.1 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 temperature sensor should be used for motor protection.

The D42 motor family can also be used with AML PG42 UHV planetary gearheads where increased torque, increased positioning resolution or inertia matching is required.

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

## Ordering guidance

Standard order code: D42.1 — 250 mNm UHV stepper motor.

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

For custom shaft configurations, provide a dimensional drawing or sketch.

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

## Order codes

| Order code | Description | Price |
| --- | --- | --- |
| D42.1 | 250 mNm UHV stepper motor | £756.00 |
| D42.1-C | D42.1, Cryogenic -196 °C to +190 °C | £849.00 |
| D42.1-H | D42.1, Dry lubricated hybrid ceramic bearings | £849.00 |
| D42.1-P | D42.1 with PT100 temperature sensor in lieu of thermocouple | £815.00 |
| D42.1-R | D42.1, Gamma radiation hardened | £849.00 |
| D42.1-X | D42.1 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](https://arunmicro.com/downloads/CAD_VCSM.zip)

## Related products

- [D35.1 UHV Stepper Motor](https://arunmicro.com/products/D35-1_UHV_Compatible_Stepper_Motor/): 75 mNm, NEMA 14
- [D42.2 UHV Stepper Motor](https://arunmicro.com/products/D42-2_UHV_Compatible_Stepper_Motor/): 450 mNm, NEMA 17
- [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.