The most popular new laser line technology to stre

2022-08-17
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New laser line technology to strengthen the monitoring link

with the increasingly stringent requirements for testing every year, rubber and tire manufacturers urgently need to obtain more accurate and detailed information from the tire detection system. For example, the new requirements in the side wall detection link, for the needs of safety and quality, require higher accuracy in the reliability detection of smaller defects, no matter where these defects appear. In the final detection environment, the measurement of bulges and depressions on the side wall requires higher dense data, so that the bulges and depressions can be properly detected, because the analysis software must first eliminate or filter all detection points related to inscriptions, bar codes and other acceptable deviations on the surface. The height of the convex part is between 0.3mm and 3.0mm, and the width is between 5mm and 7.0mm. Now, the customer requires that the specific energy of the system should strive to reach 260 watt hours/kg, and the cost should be reduced to less than 1 yuan/watt hour. The height of the convex part should be limited to 0.2mm, because many convex parts have nothing to do with the outer tire cord fabric, but are related to bubbles

in response, suppliers are developing faster, more complex and more accurate measurement and detection equipment that can be used for both applications and offline applications. The basic requirement is that the reliability equipment used to detect rubber products has higher production capacity, higher sampling rate and higher accuracy, and can be easily installed on the detection instrument and applied in the renovation process. Higher density of data can also improve the efficiency of decision-making and minimize the cost of expensive and time-consuming manual waste re inspection

laser sensors for tire manufacturing

historically, tire detection applications rely on single point laser triangulation sensors. This measurement method can only measure one point on the tire rubber surface. Usually, when the product is driven or rotated at high speed, it can only generate a single path or route of data flow. Now, LMI technology company (LMI Tec electronic tensile testing machine meets the national standards of gb/t1447 fiber reinforced plastic tensile property method and fiber reinforced plastic tortuosity technologies, Inc.) has installed more than 3000 sensors in the tire manufacturing application, which can be used for monitoring in the process and final tire detection. Compared with the early capacitive and contact equipment based on sensors, LMI products have proven to be more reliable and accurate

for decades, high-performance non-contact triangulation sensors have been very successful in meeting the measurement challenges of tire manufacturers. The non-contact operation can measure the rubber without deformation error. The laser sensor has a large support distance (typically hundreds of millimeters or longer, depending on the type of special sensor), a wide measurement range, and can obtain reliable data even when it is not perpendicular to the surface. The large support distance can make a sensor farther away from other sensors. If the tire size is too large or the positioning on the detection station is incorrect, it can also reduce the expensive maintenance cost caused by collision. The wide measurement range allows the detection of a wide size tire mold without reconfiguring the sensor or tire positioning mechanism, and also improves and simplifies the design of the mechanical system. The capacitive sensor must be close to and perpendicular to the surface of the measured object when positioning, and it must also have a complex multi axis positioning mechanism. Due to the change of material properties, its sensitivity also changes, so it also needs to be calibrated frequently

unlike capacitive sensors, modern laser sensors do not need calibration, and changes in material properties have no impact on their sensitivity. When the surface state changes, the designed laser sensor can also compensate by itself, such as color, surface finish or the presence of spherical lubricant on the surface

the development of laser line sensors in sidewall detection

today, for the application of sidewall detection, the increase in tire quality and safety requires manufacturers to be able to detect smaller defects in a very small area of the tire surface during the process of high-speed rotation of the tire. If a single point sensor is used to track and measure one or two points on the tire surface, the minimum size defects may not be detected, Whether defects can be detected depends on the location of the sensor. In order to solve this problem, a new generation of laser line sensor has been developed and applied to detection

the basic principle of the laser line sensor (Figure 1) is very similar to the point triangulation. The main difference between it and triangulation is that the laser beam can be optically extended in one dimension, and a laser line is generated on the surface of the measured object. The camera can output the full section of the surface of the measured object every time it scans, and there are many data points intersecting with the laser line on the section. When the tire rotates, a complete 3D profile of the sidewall can also be obtained, so that small defects at any position can be detected

Figure 1 principle of laser line sensor

the principle of laser line sensor has been applied to the measurement of surface profile in other industries, but so far, the operation speed is still very low in the need to provide a high-speed data density for side wall detection. The development of high-speed digital camera chip technology and compact solid-state sensor, as well as the improvement of high-speed image processing performance in the sensor head and the latest multi camera image synchronous processing technology enable the application of extremely high-speed laser line sensor in side wall detection, and its configuration is very cost-effective

the secondary eyecon-2 laser line sensor (Figure 2) with LMI technology is specially designed for the final detection of the side wall using laser line technology. Its operation speed in terms of data rate is twice that of the current sensor, and it can measure the profile 2000 times or more per second, providing a very high data density for the detection of minor defects when the tire is rotating

Figure 2 eyecon-2 sensor

the uniqueness of this kind of sensor is that it uses two cameras under the same sensor housing, respectively on both sides of the laser line (Figure 3). The sensor using a single camera may not see the laser line at the steep edge, so it is impossible to provide data information close to the edge, and it is impossible to detect defects in this area. This is a common mistake in the process of tire sidewall detection. There are usually a large number of raised inscriptions, bar codes and other geometric features on the tire sidewall. The use of dual cameras can ensure that any one of them can "see" a complete laser line. Even when it is in good condition after testing, the profile data of the side wall close to the steep edge can be provided at the steep edge of the convex or convex geometric feature. This unique design ensures that data loss or data invalidation is avoided and provides complete contour information. Figure 4 shows the legend of a sidewall section, which can even detect defects on the edge of the inscription

Fig. 3 a sensor block; B dual sensor

Figure 4 side wall surface profile

this new sensor also uses the "smart sensor" technology to process image data from the inside, linearize the data, convert the data into engineering units, and output the measured 3D side wall profile

application in the final detection of sidewall

in the application of tire sidewall detection, two eyecon-2 sensors are used, one for each sidewall. A third sensor can also be used to measure the out of roundness of the tire surface (Figure 5). The scanning bit data concentrator can collect and combine the data from multiple sensors and the tire uniformity mechanical spindle encoder into a single synchronous data stream and distribute power. This fully integrated structure simplifies the installation process, and can send real-time tire maps in a real-time range through Ethernet connection

Figure 5 typical application of side wall using three sensors

other applications of laser line sensor

there is not much difference in developing the same laser line technology for side wall detection, and it has been applied in other measurement and control applications in the rubber manufacturing industry. For example, the application of eyecon-1tm line laser sensor in cross-section stereo section scanning. Eyecon-1 is mainly used in the preparation of equipment, such as the geometric monitoring of tire tread extrusion. Laser line technology can also provide complete cross-sectional profile measurement without mechanical scanning or the use of other moving components, which reduces the complexity of operation, costs and maintenance costs. The image processing software runs inside the sensor without using external computing devices. The communication with external devices is carried out through Ethernet, which is easy to install and integrate

the same technology can also be used in other application environments, such as conveyor belt production. In this production process, the centerline sensor can continuously monitor the thickness and width of the conveyor belt, or provide signals for edge positioning and navigation (Fig. 6)

Figure 6 laser line sensor shaped extrusion and shaped belt

conclusion

now we can supply high-speed laser line sensor with unique dual video camera performance, which can provide higher data density along the whole laser line. For sidewall detection where the relative humidity will reach 100% RH, these sensors monitor small bulges or depressions in the sidewall of the tire by scanning the geometry of the tire intersecting the laser line at a frame speed of 2000 or more profiles per second. When the tire rotates, it can provide a complete three-dimensional profile of the sidewall, so that small defects at any position can be detected. In addition, the technology can also be used to monitor the profiling geometry in the extrusion and measurement links of the conveyor belt

laser line sensing greatly improves the performance of detecting side wall defects and extrusion molding, and can also be used in other application environments, such as the monitoring of conveyor belt geometry. (end)

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