Preparation Work Before Testing

Before conducting tests on plastic products, a series of meticulous preparation work serves as the cornerstone for ensuring accurate and reliable test results.

The selection of equipment is of crucial importance, just as high-quality building materials are essential for constructing tall buildings. The visual inspection equipment we use is equipped with high-resolution lenses, capable of capturing extremely tiny traces on plastic products—even defects as thin as a strand of hair can hardly escape detection. Its advanced image sensor, like the sharp eyes of an eagle, can quickly and accurately perceive the shape and characteristics of objects, providing clear and detailed image data for subsequent testing and analysis. During the equipment debugging phase, technicians carefully calibrate the equipment parameters as if handling a delicate work of art. By adjusting the focal length, the lens can capture clear images of plastic products at different distances; optimizing the exposure time ensures that images with appropriate contrast are obtained under various light conditions, preventing the omission of important details due to excessive or insufficient light.

The control of the testing environment is equally indispensable. The impact of temperature and humidity on plastic products is as significant as the impact of climate on human health. In a high-temperature environment, plastic products may soften and deform, changing their original size and shape; in a high-humidity environment, the surface of plastic products may absorb moisture, affecting their electrical properties and appearance quality. Therefore, we strictly control the temperature of the testing environment at around 25°C and maintain the humidity within the range of 40% - 60%, creating a stable "microclimate" for the testing work. Meanwhile, the cleanliness of the testing site is crucial—tiny dust particles, once attached to the surface of plastic products, may be mistakenly identified as defects and interfere with test results. Hence, the testing site undergoes regular in-depth cleaning using professional vacuum equipment and cleaning tools to ensure it remains spotless.

Detailed Testing Process

(I) Feeding and Image Acquisition

The feeding process is the starting point of the testing workflow, and there are various feeding methods, just like different paths leading to the same destination. For small-sized plastic products, a vibratory bowl feeder is often used. The vibratory bowl, like a dynamic dancer, uses continuous and regular vibration to make plastic products move forward in an orderly manner along a specific track, being accurately transported to the testing area one by one—similar to soldiers marching neatly into a review ground. For larger-sized plastic products, a robotic arm plays a vital role. The robotic arm, like a flexible and powerful giant's hand, can accurately grasp plastic products under precise program control and place them stably on the testing platform. The entire process is completed in one smooth motion, demonstrating high precision and stability.

Once the plastic product is in place, the industrial camera begins to show its capabilities. Equipped with high-resolution lenses, these industrial cameras are like having "piercing eyes" that can capture extremely fine details. They take photos of the plastic product from multiple angles, just as a photographer takes comprehensive shots around a model. Shooting from the front allows for a clear observation of the main surface features of the plastic product; shooting from the side helps detect potential side defects; shooting from the top provides a more comprehensive understanding of the overall shape and structure. Moreover, the cameras have an extremely high shooting resolution, reaching the micrometer level. This means that even extremely tiny defects—such as small holes with a diameter of only a few micrometers or scratches as thin as a strand of hair—can hardly escape their "vision". These multi-angle, high-resolution images provide rich and accurate information for subsequent testing and analysis, just like providing doctors with comprehensive medical records to facilitate accurate diagnosis.

(2) Image Processing and Analysis

The collected images are like uncarved raw jade, requiring a series of fine processing to reveal the key information they contain. The first step is noise reduction, which aims to eliminate noise interference in the image—similar to filtering out background noise in a noisy environment to highlight clear sounds. By using algorithms such as mean filtering and Gaussian filtering, noise points caused by factors like light fluctuations and electronic interference can be effectively smoothed out, making the image clearer and cleaner. Next is image enhancement, a process similar to post-processing color adjustment for photos to make the image more vivid and distinct. Using techniques such as histogram equalization and contrast stretching, the contrast between different regions in the image can be enhanced, making defect areas more prominent and easier to identify and analyze.

After preprocessing, the image enters the critical stage of feature extraction and analysis comparison. Using algorithms such as edge detection and contour extraction, key feature information of the plastic product—such as shape, size, and edges—can be accurately extracted, just like precisely extracting the core elements from a complex object. Then, the extracted feature information is carefully compared with a pre-set standard template. The standard template is like an accurate ruler, representing the ideal state of the plastic product. Through comparison, the testing system can quickly determine whether the plastic product has defects, as well as the type, location, and severity of the defects. If the extracted edges are irregular and deviate from the edges of the standard template, it may indicate that the plastic product has edge damage or deformation; if the measured size does not match the standard size and exceeds the allowable tolerance range, the plastic product may be deemed to have size non-conformity.

Detection and Identification of Common Defects

(1) Appearance Defects

During the production of plastic products, various appearance defects often occur. Each type of defect has unique image characteristics, and visual inspection equipment has corresponding detection and identification methods.

Missing Material is one of the more common appearance defects, usually occurring at positions farthest from the gate and on thin, long ribs. Its image characteristics include smooth but irregular edges of the product, giving a sense of irregularity—like a beautiful work of art with a 残缺 (incomplete) edge. When detecting missing material defects, visual inspection equipment accurately extracts the edge contour information of the plastic product through an image contour analysis algorithm. When discontinuous, missing, or abnormal parts are found in the edge contour, it can be determined that the area may have a missing material defect. By carefully comparing with the edge contour of the standard template, the position and range of the missing material can be accurately identified.

Sink Marks are concave marks and unevenness on the surface of the material caused by product shrinkage. When observed against light, wavy patterns can be seen. Such defects often occur in areas with uneven product thickness, thick material sections, as well as pillars and ribs. In visual inspection, a grayscale analysis algorithm is used to sensitively capture changes in the grayscale value of the product surface. Due to the changed surface morphology of the sink mark area, its light reflection and absorption properties differ from those of the normal area, resulting in differences in grayscale values. The inspection equipment can identify sink mark defects by analyzing these grayscale differences and preliminarily determine the severity of the sink marks based on the degree of grayscale variation.

Flash appears as a thin layer of excess material on the edge of the product, often occurring at the parting line, moving mold cores, ejector pins, pillars, holes, and buckles. When detecting flash, visual inspection equipment uses a combination of edge detection and morphological analysis algorithms. First, edge information of the product is extracted through the edge detection algorithm, and then the morphology of the edges is further analyzed using the morphological analysis algorithm. If abnormal protrusions or burr-like structures are found at the edges, which do not match the normal edge morphology of the product, they can be determined as flash defects. By measuring the size and analyzing the shape of these abnormal structures, the size of the flash and its impact on product quality can also be evaluated.

Bubbles appear as spots on the product surface with different colors from the surrounding area. They are generally classified into bubbles formed by incompletely discharged gas, air, or moisture, and vacuum bubbles caused by thermal expansion and contraction. For transparent plastic products, the detection of bubbles is particularly important, as they can seriously affect the transparency and optical properties of the product. When detecting bubbles, visual inspection equipment mainly relies on the color and shape characteristics of the image. Bubbles have obvious color differences from the surrounding normal areas, so potential bubble areas can be quickly screened out through the color recognition algorithm. Combined with the shape analysis algorithm, the shape of these areas is judged—if they match the circular or approximately circular characteristics of bubbles, they can be identified as bubble defects. At the same time, the quality grade of the product can be evaluated based on the size and quantity of the bubbles.

(2) Dimensional Deviation

Dimensional deviation is one of the important indicators for measuring the quality of plastic products, and visual inspection equipment plays a key role in accurately measuring the dimensions of plastic products, determining whether they meet standards, and identifying dimensional deviations.

When measuring dimensions, visual inspection equipment uses advanced image processing and measurement algorithms. First, high-definition images of the plastic product are collected from multiple angles using an industrial camera to ensure that the complete outline and key dimensional features of the product are captured. Then, edge information of the product is accurately extracted using an edge detection algorithm to determine the boundaries of the product. For features with regular shapes (such as circles and squares), corresponding geometric fitting algorithms can be used to fit accurate geometric models, thereby accurately measuring dimensional parameters such as diameter and side length. For the dimensional measurement of complex shapes, a mathematical model is established to convert the image information of the product into a digital model, and then accurate dimensional calculations are performed in the model.

To determine whether the dimensions meet the standards, the measured dimensional data is strictly compared with the pre-set standard dimensions. The standard dimensions are usually determined based on the product's design requirements and quality standards, with clear tolerance ranges. The inspection equipment automatically calculates the difference between the measured dimensions and the standard dimensions, and judges whether the difference is within the allowable tolerance range. If the difference exceeds the tolerance range, the plastic product can be determined to have a dimensional deviation. For example, for a plastic cylinder requiring a diameter of 10mm ± 0.1mm, if the diameter measured by the inspection equipment is 10.15mm, it indicates that the diameter of the product exceeds the allowable tolerance range and has a dimensional deviation.

After identifying dimensional deviations, visual inspection equipment can also conduct a detailed analysis of the type and degree of deviation. If the dimension is smaller than the lower limit of the standard dimension, it may be caused by insufficient material filling during injection molding or mold wear; if the dimension is larger than the upper limit of the standard dimension, it may be due to factors such as poor mold closure or excessive injection pressure. Through the analysis of dimensional deviations, strong support can be provided for quality control and problem troubleshooting in the production process, helping enterprises adjust production process parameters in a timely manner and improve mold design, thereby enhancing the dimensional accuracy and overall quality of plastic products.

Testing Accuracy and Quality Control

(I) Accuracy Assurance Measures

The high-precision detection capability of our visual inspection equipment relies on a series of advanced hardware configurations and powerful software algorithms.

In terms of hardware, high-precision lenses are one of the key components ensuring detection accuracy. These lenses use advanced optical materials and precision manufacturing processes, featuring extremely low distortion rates and excellent resolution. They can clearly image the tiny details of plastic products on the camera's image sensor—just like a professional macro lens can capture the fine textures on a flower. Taking a lens commonly used for testing small precision plastic parts as an example, its resolution can reach more than 10 million pixels, enabling it to distinguish micron-level lines and features, and providing extremely clear and accurate original image data for subsequent image processing and analysis.

The matching high-pixel camera is like a sharp observer that does not miss any tiny details. High pixels mean more image details and higher resolution, allowing for more accurate capture of the outline, size information, and surface micro-defects of plastic products. For example, some industrial-grade CCD cameras have a pixel count of 20 million or higher, capable of quickly capturing high-quality images in a short time—even extremely tiny defects can be clearly recorded. Moreover, these cameras also have fast data transmission capabilities, enabling them to quickly transmit large amounts of collected image data to the image processing system, providing strong support for real-time detection and analysis.

In terms of software algorithms, our visual inspection equipment adopts a series of advanced algorithms to further improve detection accuracy. The edge detection algorithm is an important part of this—it can accurately identify the edge position and shape of the plastic product, just like drawing a clear boundary line for the object. Through accurate edge detection, the dimensions of the plastic product can be precisely measured, and whether it meets the standard requirements can be judged. For example, when testing the outer diameter of plastic pipes, the edge detection algorithm can accurately extract the edge contour of the pipe, and then calculate the precise outer diameter through mathematical calculations, with a measurement accuracy of up to ±0.01mm.

The feature extraction algorithm focuses on extracting key feature information of the plastic product, such as shape, texture, and color. This feature information is like the unique identifier of the product—by comparing it with the features in the standard template, it can quickly determine whether the product has defects. For example, when testing the texture on the surface of a plastic shell, the feature extraction algorithm can accurately extract the feature parameters of the texture (such as texture direction, spacing, and depth), and then compare them with the standard template. Once the difference in feature parameters exceeds the allowable range, it can be determined that the area has a defect.

(2) Key Quality Control Points

During the testing process of plastic products, strict quality control is crucial for ensuring reliable and accurate test results, and sampling inspection frequency and data recording and analysis are important points of quality control.

The reasonable setting of sampling inspection frequency is essential. For mass-produced plastic products (such as mobile phone cases and toy parts), we usually adopt a relatively high sampling ratio. In the early stage of production, to ensure the stability of the production process and the consistency of product quality, 5 - 10 pieces are sampled for comprehensive testing (covering appearance, size, performance, etc.) for every 100 products produced. As the production process continues, if the product quality remains stable, the sampling ratio can be appropriately reduced, but it will still be maintained at a level of 3 - 5 pieces sampled for every 200 products to ensure that potential quality problems can be detected in a timely manner. For plastic products with extremely high quality requirements (such as medical device parts and aerospace plastic parts), the sampling ratio will be even higher, and 100% full inspection may even be adopted to ensure that every product meets strict quality standards.

Data recording and analysis is another important link in quality control. Our visual inspection equipment has a powerful data recording function, capable of detailed recording of key information such as the time of each test, product batch, and test results. For defective products detected, detailed parameters such as the type, location, and size of the defect are recorded. This rich data is like a detailed quality file, providing a solid foundation for subsequent analysis and improvement. Through data analysis, we can identify trends in product quality. If the dimensional deviation of a certain type of plastic product is found to be gradually increasing over a period of time, in-depth data analysis may reveal that the mold is worn after long-term use, thereby prompting timely repair or replacement of the mold and avoiding the production of a large number of non-conforming products. At the same time, data analysis can also help us evaluate the stability of the production process, identify key factors affecting product quality, and provide strong support for the optimization of the production process, thereby continuously improving the quality and production efficiency of plastic products.

Post-Testing Processing Workflow

After the plastic product undergoes comprehensive and detailed testing, the test results become an important basis for subsequent processing. The testing equipment will automatically classify and judge the product according to pre-set standards, accurately distinguishing between qualified products and defective products.

Qualified products are transported to a dedicated packaging area in an orderly manner along a smooth conveyor path. There, staff will carefully package the qualified products in a professional and meticulous manner. Based on the characteristics and uses of the plastic products, appropriate packaging materials (such as bubble bags, cartons, and plastic films) are selected to provide comprehensive protection for the products, ensuring that they remain intact during subsequent transportation and storage—just like putting on a strong armor for precious items.

Defective plastic products identified during testing are guided to a specific defective product collection area. In this area, defective products are temporarily stored pending further processing. Corresponding treatment measures are taken for different types of defective products. For defective products with minor defects (such as slight surface scratches and small-area sink marks), professional repair personnel are arranged to carry out repair work. With rich experience and exquisite skills, the repair personnel use methods such as grinding, filling, and spraying to eliminate defects as much as possible and restore the defective products to an acceptable quality standard. For defective products with serious defects (such as severe dimensional deviation, structural damage, and functional failure), considering that the repair cost is too high or the product cannot meet quality requirements even after repair, they will be scrapped in accordance with the specified procedures. The scrapped defective products are properly collected and uniformly handed over to professional recycling institutions for environmental protection treatment, so as to realize resource recycling, reduce environmental impact, and practice the concept of sustainable development. Throughout the post-testing processing workflow, each link is closely connected, strict, and orderly, ensuring the quality control of plastic products and the rational use of resources.