Non-contact angle measurement is a method of measuring angles without directly touching the object. Since no abrasion occurs, repeated measurement is possible, and it is superior in terms of accuracy and durability.

This article provides a comprehensive explanation of the background of the need for non-contact angle measurement, specific measurement methods, key points for improving accuracy, product examples, and case studies.

Background of the need for non-contact angle measurement

In recent years, as machines and equipment have become more precise and faster, the demand for accuracy and stability in angle measurement has increased.

With conventional contact-type sensors, there is an undeniable risk of wear and deterioration as they are used more and more frequently, resulting in a loss of accuracy. In contrast, non-contact sensors do not touch rotating parts or workpieces, so not only can wear be avoided, but stable accuracy can be maintained over the long term. Especially in high-precision machining and quality control, the slightest error in angle can lead to major defects and losses, so stable measurement is required.

Typical non-contact angle measurement methods

Although there are various principles for non-contact angle measurement, typical methods are introduced here.

In recent years, as angle sensors have become smaller and more environmentally resistant, there are more options that can be introduced to any equipment or workpiece shape. Since each sensor principle has different measurement range and installation conditions that it is good at, it is important to select the most suitable method according to the requirements of the production line and the measurement environment.

High-precision measurement with laser autocollimator

This method uses a laser beam to detect minute angle changes with high precision. A laser beam emitted from a light source is irradiated onto the target surface, and the direction of the directly reflected light is analyzed by a sensor to determine the angle shift in real time. Although adjustment of the optical system and securing of the reflective surface are essential, the main attraction of this method is that it provides high reproducibility and stable data, which is difficult to achieve with the contact method.

Angle acquisition by encoder

This method detects angles using an encoder attached to a rotating shaft or axis. Various types of encoders are available, including pulse output and analog output, making it easy to combine with control systems. It is used in a wide range of industrial fields because of its compact design, ease of integration, high durability, and relative ease of use in harsh environments such as agricultural and construction machinery.

Application of displacometer to angle measurement

A displacometer is a device used to measure the amount of movement of an object. Another method is to combine multiple displacometer to computationally determine the angle. In this case, proper layout planning is important, as it depends greatly on conditions such as the location of the sensors and the surrounding space. If an optical displacometer that does not require contact is selected, damage to the object can be prevented while ensuring accuracy, making it suitable for advanced quality control processes.

Points to improve measurement accuracy

To improve the accuracy of non-contact methods, consideration of the surrounding environment and the condition of the object is indispensable.

In pursuit of accuracy, not only the basic performance of the sensor itself, but also the installation method and the condition of the object to be measured have a significant impact. Environmental conditions should be carefully organized and measures taken to ensure stable measurement even in complex work environments.

Addressing the material and surface condition of the object to be measured

Different reflectance and surface roughness of the object to be measured can easily affect the detection accuracy and stability of the sensor. For example, in the case of an optical type, surface treatment to increase the positive reflectance or placement of auxiliary mirrors should be considered. Minimize sources of measurement error by selecting appropriate sensors and auxiliary devices and configuring them to match the surface characteristics.

Consideration of environmental factors (temperature, vibration, installation conditions)

Changes in ambient temperature and mechanical vibration can also cause fluctuations in measured values in non-contact angle measurement. For example, in the case of laser systems, changes in alignment caused by misalignment of the optical axis and mechanical vibration due to temperature changes directly affect accuracy. It is important to optimize the selection and layout of the jig so that the positional relationship between the measurement target and sensor is fixed.

Angle measurement of non-mirrored work

For non-specular workpieces, it is essential to ensure positive reflection.

In general, in optical non-contact measurement, the closer the reflective surface is to a mirror surface, the more accurate and stable the measurement can be. However, actual workpieces are often difficult to mirror-finish, so measures must be taken according to the measurement conditions.

Mirror polishing and mirror installation to ensure reflective surfaces

While mirror polishing of the workpiece itself can greatly increase measurement accuracy, it can also increase costs and the burden of the machining process. As an alternative, reflective sheets or special mirrors that can be attached to the workpiece surface are effective. This suppresses scattering and stabilizes the detection of optical sensors such as laser autocollimators, enabling highly accurate measurement even of nonmirrored workpieces.

Application to large workpieces: Aim and measurement method

Large workpieces tend to be difficult to measure with high accuracy, but non-contact angle measurement enables stable measurement.

Because of the large dimensions and weight of large workpieces, measurement with contact-type sensors requires a great deal of labor for mounting and holding. The introduction of a non-contact system streamlines integration into the production line, reducing man-hours and improving quality at the same time. It is also useful for detecting machining errors and providing feedback control to equipment, enabling stable angle control even in the manufacture of large, precise parts.

Summary: It is important to select the best non-contact angle measurement for the measurement environment.

It is important to select a measuring instrument according to the surface condition of the workpiece, the work environment, and the required accuracy, and to construct an optimal angle measurement system.

Non-contact angle measurement is attracting attention in many fields as a means of achieving high accuracy with low risk of wear and long life. Each method, such as laser autocollimators, encoders, and displacement transducers, has its advantages and disadvantages, so it is essential to comprehensively consider the application, installation cost, and ease of maintenance. By selecting and optimally combining the right sensor for the type of workpiece and production line conditions, it is expected that both quality improvement and increased productivity can be achieved.