Application Watch: Stepper motor makers plan more closed-loop releases for 3D printers

Eyeing the booming 3D printing market, mainland China companies in the stepper motor sector strive to keep up with requirements for higher precision, speed and reliability.

The technology for 3D printing, which can output metal and plastic parts, and finished products with comparable features as those churned out from industrial equipment, has been accelerating in recent years. The latest printers have better precision, faster printing and higher reliability, in addition to a reduced noise level, all of which depend largely on the performance of stepper motors used.

For this reason, mainland China motor manufacturers are focusing on boosting the production of those with a closed-loop control system, which represent a small portion of total output for the application at present. Compared with the more widely available open-loop type, the former integrates a feedback encoder, and rates higher in terms of precision, response time, speed, reliability and stability.

Beijing Times Brilliant is among the local companies that have released closed-loop kinds, which are especially designed for 3D printers. The units measuring 42x42mm exhibit additional features of low temperature rise and minimal vibration. When there is overload, these trigger an alarm.

There are more than 100 makers of stepper motors for 3D printers in the mainland, and over half are locally owned catering to the entry-level and midrange markets. The rest of manufacturers have investment from Hong Kong and Taiwan.

All companies in the line also manufacture gears and other motors such as AC and brushless DC types.

The major production hubs are in the coast, mainly in the cities of Shenzhen, Dongguan and Guangzhou in Guangdong province, Changzhou in Jiangsu and Ningbo in Zhejiang.

In the years ahead, more suppliers, including from overseas, are expected to join the mainland industry and target the 3D printing sector.

Booming application

The 3D printing market has been in an upturn and will remain so in coming years. Globally, its scale is forecast to reach $12.8 billion by this year's end, and rise to $21.2 billion in 2020 and $35 billion in 2023 at a CAGR of 28 percent, according to the Qianzhan Research Institute.

In the mainland, there is also a similar trend, according to the same source. The market value hit more than $2 billion in 2018 from $1.7 billion in the previous year. The rate of increase is projected to be sustained at 20 percent in end-2019 and 2020.

Based on estimates, the 3D printing sector accounts for between 10 and 20 percent of aggregate shipments of stepper motors. This share may exceed 20 percent by the end of 2019 and through 2020.

Open-loop systems still lead

Commonly offered stepper motors for 3D printers from mainland companies have open-loop control systems. These are NEMA 42 units in various lengths, typically 34, 40 and 48mm.

Releases have a step precision of between 3 and 5 percent. These use a single-phase power supply, and have a rated voltage of 3 to 7.2V, rated current of 0.3 to 1.5A, and rated power of 0.5 to 50W. The typical minimum insulation at 500VDC is 100Mohm, and the withstand voltage 500VAC/min. Units support an operating temperature of -20 to 50 C.

There are also stepper motors with a hybrid construction. LDO Motors Co. Ltd has introduced such types in single- and double-shaft and bi- and unipolar variants.

Most suppliers turn out products that bear CE approval, are UL-listed and comply with RoHS requirements.

The key components and materials used in the production of stepper motors include stators, rotators, bearings, gaskets, covers and shafts. These come from local or foreign providers, depending on buyer preference.

The few domestic companies making closed-loop types outsource feedback encoders.

The cost of manufacturing inputs is forecast to remain stable and will ensure no change in product prices. Some companies might continue to quote lower to attract more orders amid competition.

The products in this gallery have been handpicked by our China-based market analyst for representing current trends in stepper motors from China makers.

Stepper motor rated at 3.2V, 1.8A

Rated at 3.2V, 1.8A, this stepper motor from Guangzhou Ruibao Electrical Co. Ltd, 17HD-0040-1 model, has 1.8-degree±5 percent step angle and 580mN.m holding torque. It has 22ohm±10 percent resistance and 27mH±20 percent inductance. The unit adopting class B insulation has 100Mohm minimum insulation resistance at 500VDC and 600VAC dielectric strength at 50Hz, 1mA, 1sec.

Thenegotiable minimum order has a 7-day delivery lead time.

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Stepper motor has 2.8mH±20% inductance

From LDO Motors Co. Ltd, the model LDO-42STH47-1684L300E stepper motor with 1.8-degree step angle has 0.2kg.cm detent torque. Rated at 2.8VDC, 1.68A, the CE-approved and RoHS-compliant unit has 2.8mH±20 percent inductance.

The minimum order is negotiable. Delivery is within 25 days.

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Stepper motor with 500VDC/min dielectric strength

Ningbo Biote Electric Machine Co. Ltd markets this stepper motor, SM012 model, with accuracy of ±5 percent step angle at full speed with no load, ±10 percent resistance and ±20 percent inductance. The unit with class B insulation has 220N maximum radial and 60N maximum axial force. It has 100Mohm minimum insulation resistance at 500VDC and 500VDC/min dielectric strength. The temperature rise is 80 C.

An order of at least 100 units is for delivery within 25 days.

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Stepper motor has 55N.cm minimum holding torque

This stepper motor with 1.8-degree step angle from ZJTEX Electric Group Co. Ltd, ZJHYL23 model, has 55N.cm minimum holding and 2.5N.cm maximum detent torque. Rated at 2A, the 14mm-long unit weighing 470g has 1.2ohm and 2.5mH phase resistance and inductance.

The supplier requires an order of at least 1,000 units for delivery within 7 days.

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