Automatic online monitoring to reduce scrap rate by 35% - Database & Sql Blog Articles

In the past, the surface quality of lenses was only checked at the end of production. There is now a new way to check the finish of the lens at the previous production stage, so that the scrap rate can be reduced by up to 35%.

Traditional quality inspections in many industries are carried out in the final production process. The workpieces to be produced are found to have been mistaken if they have been processed for a long time or even finished products, if the errors in the previous steps are in the post-processing process. In the past, the benefits of the manufacturing process will be reduced. Such processing errors will lead to waste products, causing unnecessary cost increases and delays in delivery time. According to the type of manufacturing process, the increased cost mainly comes from rising energy costs. , additional material costs, unnecessary equipment time and machine wear.

Automatic quality identification between high-quality processing steps can reduce these extra costs by picking up the problematic product as early as possible or for post-processing (Figure 1), especially if the subsequent processing is time consuming or expensive. Checking the quality of semi-finished products has great advantages and can predict the success rate of subsequent processing stages.

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Publish a technical article In the past, the surface quality of lenses was only checked at the end of production. There is now a new way to check the finish of the lens at the previous production stage, so that the scrap rate can be reduced by up to 35%.

Traditional quality inspections in many industries are carried out in the final production process. The workpieces to be produced are found to have been mistaken if they have been processed for a long time or even finished products, if the errors in the previous steps are in the post-processing process. In the past, the benefits of the manufacturing process will be reduced. Such processing errors will lead to waste products, causing unnecessary cost increases and delays in delivery time. According to the type of manufacturing process, the increased cost mainly comes from rising energy costs. , additional material costs, unnecessary equipment time and machine wear.

Automatic quality identification between high-quality processing steps can reduce these extra costs by picking up the problematic product as early as possible or for post-processing (Figure 1), especially if the subsequent processing is time consuming or expensive. Checking the quality of semi-finished products has great advantages and can predict the success rate of subsequent processing stages.

The same is true for the production of lenses. The use of plastic lenses has far surpassed that of mineral lenses. At present, the market share of plastic lenses is about 85%. Their production cost is low, and the optical properties are almost the same as those of mineral lenses. In addition, the organic lenses are It is lighter and less prone to breakage, which is another big advantage for customers.

In the production of plastic lenses, the quality of the workpiece is checked after the workpiece has been of high value. After the grinding and shaping of the blank, it is a complicated polishing process, which determines the optical properties of the surface of the lens. The surface quality must pass the standard. The polishing process is realized, but only when the current grinding process makes the initial quality of the lens surface reach the standard. After polishing, the polished surface should be visually inspected. If the polishing does not achieve the required optical properties, the corresponding workpiece After the quality inspection, it will be removed from the production process, and the task must be restarted, because the separate post-processing of the lens with insufficient surface quality is technically troublesome and therefore not cost-effective.

If the quality is degraded due to the wear of the grinding tool, continuous surface finish inspection of the lens surface can be replaced before the tool quality meets the requirements. This can minimize the lack of surface quality. Waste.

Tool loss

The problem is that after a period of time, the diamond tools used will wear out gradually, so the quality of the tool will decrease, and the surface of the lens will produce more processing marks and reduce the surface quality. Figure 2 shows the surface of the lens processed by different quality grinding tools. Compared. Since the life of the grinding tool cannot be clearly predicted, it has not been possible to react immediately or predictably to the quality of the tool that has fallen in advance, and the subsequent polishing process is carried out without being affected by the previous quality, as it was previously at the end of the polishing process. After the first quality check.

With the opportunity of research projects, Deggendorf University of Technology developed an optical measurement system, and Figure 1 shows the experimental model. After grinding, the surface finish of the plastic lens is directly inspected during the production process. Since the surface finish can reflect the quality of the diamond tool, the newly developed measuring system can be used to monitor the tool quality during the production of the lens, so that when the surface finish is below the limit value It is possible to determine that the quality of the tool is not good enough to be replaced. The measuring system consists of two mutually perpendicular positioning axes and a dispersion confocal distance produced by Micro-Epsilon on a horizontal positioning table.

sensor

The IFD2451 consists of.

Figure 3 is a sketch of the system structure. The vertically mounted shaft receives the task transport box from the conveyor belt, positioning the lens under the sensor. At the same time, the barcode on the transport box is scanned, and the information of the plastic lens in the box is adjusted from the database. Take, if the item to be inspected is in place, the probe will pass the surface of the transparent lens and record the distance between the probe and the surface along the measuring section.

Measuring section close to the middle

The measuring section is close to the center of the lens because the machining marks are concentrated there and are expressed in the form of increased surface roughness due to the wear of the tool and the relative speed to the machining center during the grinding process.

The required finish value can be calculated based on the recorded distance value. The reliability can be checked by comparing the finish identification value. The arithmetic and square value of the roughness is particularly important in order to judge the tool quality based on the surface finish of the lens.

Achieving a specific threshold value indicates the quality of the tool. Sometimes the signal of the replacement tool is issued, and other information such as the finish value and the overrun limit value are transmitted to the database. Figure 4 shows the process curve of the measurement cycle.

After further testing between the lens grinding and polishing process, this automatic measuring system should be integrated directly into the production process. In order to avoid the intermediate step of this process hindering the processing of the production line, the measuring cycle time should be processed with the grinding equipment. The rhythm is matched, so in just a few seconds, the area where the error occurred is automatically recognized before the polishing process, preventing the polishing equipment from performing unnecessary processing on the lens with the initial quality defect.

Detection is performed after one hour

In the lens production process, which does not check the quality of the tool, after the blank is shaped, several subsequent processing steps are performed. The grinding process is about one hour apart from the inspection work. When people notice that the tool quality is not good, each one The grinding machine can scrape up to 60 lenses, and the precise locking of the grinding tool can reduce the waste by up to 35%.

With the measuring system, the tool can be replaced in time when the subsequent machining results cannot be guaranteed. In addition, the parts with occasional increase in surface errors can be removed before entering the next processing step. With the above-mentioned measuring system integrated on the production line, the series error can be greatly reduced. Cost, this method can also be used for similar production processes. Beijing Furui Hengchuang Technology Co., Ltd.