Why The Precision of A Machine Depends on A Part You Never See

What ultimately determines the precision of an industrial machine?

Many would say the motor, the controller, or the algorithm. But the truth is, the ability of a machine to operate with precision often comes down to one inconspicuous component: the encoder.

Where Does Precision Come From?

For a CNC machine tool to machine a part with micron-level accuracy, it is not about how fast the motor spins. It is about whether the motor knows its exact position at every single moment. For a robot to perform precision assembly, it is not about how strong the arm is. It is about whether every joint knows its exact angle.

This “knowing” comes from the real-time feedback of an encoder.

An encoder converts rotation into electrical signals and tells the control system: where the shaft is, how fast it is turning, and in which direction. Without this feedback, even the best control system is operating blind.

The Core of an Encoder: Light

Among various encoder types, optical encoders offer the highest precision and are the most widely used. At their core is a code disc with precision grating lines.

Light passes through the transparent and opaque areas of the disc, generating pulse signals. The control system counts these pulses to precisely calculate rotation angle and speed. The finer and more uniform the lines on the code disc, the higher the encoder’s resolution.

In other words, the upper limit of an encoder’s precision is determined the moment the code disc is manufactured.

Why In-House Code Discs Matter

A code disc is a precision optical component. Its production requires a series of precision processes, including optical cold working, lithography, and coating. Many encoder manufacturers choose to purchase code discs from third parties. This is easier, but it also means their core precision depends on external suppliers.

Shanghai Hengxiang Optical Electronics Co., Ltd. chose a more difficult path: designing and manufacturing its own code discs.

That confidence traces back to 1985. That year, Hengxiang’s predecessor, an optical instrument factory, began producing optical lenses. Seventeen years of optical cold-working experience laid the foundation for the later independent development and manufacturing of encoder code discs. From lens grinding to grating ruling, Hengxiang has mastered the complete chain, from materials to processes.

This capability is not common in China’s encoder industry.

From Optics to Encoders: A Technical Extension

In 2002, Hengxiang partnered with the Shanghai Institute of Technical Physics to overcome key challenges in infrared optics and encoder technology. In the same year, the independently developed S25 series encoder was successfully launched.

This was not a simple business expansion, but an extension of accumulated expertise in optics into the field of industrial sensing.

Over the following two decades, Hengxiang continued to invest in R&D and has accumulated 55 patents. Among them, an invention patent granted in 2025 for a “compact bearingless absolute encoder” offers a new solution to the industry pain point of encoder damage in vibrating environments.

The Logic Behind the Products

Today, Hengxiang’s encoders cover more than 10 series and over 100 specifications. The logic behind the product line has always centered on one core question: how to meet the precision requirements of different applications with the most suitable solution?

For robot joints, what is needed is an ultra-thin, bearingless absolute encoder with power-off position memory — the ZM35 series, only 11.8mm thick, with ±80″ accuracy and multi-turn data retention.

For elevator traction machines, what is needed is a highly protected, wide-temperature, reliable absolute encoder — the KM60 series, IP65 rated, operating from -40°C to +95°C.

For textile machinery, what is needed is a contamination-resistant, maintenance-free magnetic encoder — the WSN49 series, IP67 rated, bearingless, with maximum error of ±0.3°.

For CNC machine tools, what is needed is a high-resolution, rugged incremental encoder — the K60 series, IP65 rated, with resolution up to 65,536 PPR.

Making Machines Know Where They Are

The value of an encoder lies not in itself, but in what it enables a machine to “know.”

A CNC machine tool needs to know the angle of its spindle. A robot needs to know the position of its joints. An elevator needs to know which floor it is on. All of this “knowing” depends on real-time feedback from an encoder.

Hengxiang encoders are quietly at work in these applications — from industrial robots to UAVs, from medical CT scanners to wind power, from textile machinery to semiconductor equipment. Products are exported to more than 120 countries, certified to ISO9001 and CE, and recognized as a Shanghai High-Tech Enterprise and a provincial “Specialized, Refined, Distinctive, and Innovative” Enterprise.

Conclusion

The precision of a machine ultimately depends on whether it can accurately know its own position. And that “knowing” comes from a part you rarely notice.

What Hengxiang does is make that part always reliable.

Shanghai Hengxiang Optical Electronics Co., Ltd.
www.shhxgd.com
Precision Encoders Since 2001