Too fast for the naked eye – Maximized throughput thanks to automated flat glass inspection

Manual quality inspection can be a time consuming, error-prone and rather costly effort. Even though it is still quite popular among glass manufacturers, this type of quality control remains restricted in performance and in its ability to analyze faulty processes. Lacking in speed and accuracy, it becomes a bottleneck for the highest throughputs. One of the world’s most successful producers of specialized glass products, Wuhan Changli New Material Science and Technology Ltd. in China, decided to switch from manual to automated inspection. The targeted result was to increase the efficiency of its lines while ensuring a consistently high quality of its LOW-E glass – all with the help of ISRA products.

Wuhan Changli Ltd. produces over 12 Million square meters of low emissive glass per year. Their production lines reach speeds of more than 50 meters per minute. At the end of such a line at Wuhan Changli Ltd., quality inspection is conducted by experienced workers. Nearing the end of a shift, the attention of the quality control personnel, and any decisions they make, naturally suffer from poor judgement and deficient quality inspection due to the physical and visual fatigue. That alone makes automated quality inspection desirable, but additionally, a few defect types were consistently reoccurring. In order to search for the root causes of errors and to support the quality assurance team, Wuhan Changli decided to install two of ISRAs PowerPlate-Systems for LOW-E glass inspection – the P2-Color and P2-Coating.

Full area, automatic coating inspection and inline color monitoring.

Moreover edge inspection, shape inspection and homogeneity inspection is possible.The two systems are designed to detect all types of coatings defects on LOW-E glass products, offering a fast return on investment, as beside detection of small defects they can monitor the color homogeneity of the full surface. That is the big complementary over spectrometer based systems which measures the coating color.

Applying the system at Wuhan Changli Ltd.

The solution was delivered by automated inspection: it enables manufacturers to maintain a quality history of each product and offers the chance to adjust and improve production processes based on quality data. Convinced by ISRAs long expertise in coated glass inspection, the high quality of well-engineered technology and proven reputation of after sales services, Wuhan Changli Ltd. Chose the global inspection leader as its partner. And their expectations were met: “ISRA supported us all the time during the project and afterwards. The ISRA engineer contacted us by phone when he was alarmed and gave us remote support immediately to fix the problem ASAP,” states Ms Wang Gui Rong, responsible for the project with ISRA at Wuhan Changli. With P2-Coating and P2-Color, the manufacturer searches its products for pinholes, debris, scratches, arces, coating inhomogenities and many more important defects that occur after the low emissivity coatings are applied.

Benefitting from automated inspection technology

Through the ISRA P2-systems, quality engineers and inspectors on duty receive the accurate type and size of a defect and can easily reject non-optimal products or categorically stack them separately. Misdetection resulting from faulty manual quality surveillance, such as overly restrictive or subjective judgement, is successfully reduced. Scratches, arcing, water marks, glue and debris were among the first defects reliably detected and classified. Classification with the ISRA systems is based on the simple and time saving tool QuickTeach. Beyond rule based classification, QuickTeach can be trained to automatically detect the relevant features of a defect, successfully recognizing even the most complex ones. The real time defect classification can be directly refined online by the operator, while the system gathers the experience needed to deliver the highest performance in short term. Every classifying decision is documented and thus traceable, as mentioned above, one of the most important issues for Wuhan Changli.

Before installing the systems, reoccurring defects resulted in material losses for Wuhan Changli. Although the company still managed to deliver the targeted quality, glue stains and debris kept popping up repeatedly and were the first defects to be addressed. After the ISRA solutions were implemented, tracking the history of poor quality products, filtering them out and resolving a defect’s root cause became easily manageable for the quality department. “With the ISRA-systems, the quality of our entire production chain improved very quickly. They mean an important advantage in monitoring the results and corresponding processes as well as increased convenience in quality control” adds Ms Wang GuiRong. The P2-systems include a dedicated server PC with high capacity data storage to document and monitor defects and respective trends over the long-term. Operation is very simple, working with a Microsoft Windows type server structure and interface. All display windows can be organized individually, making use highly intuitive.

Mission accomplished – All targets successfully achieved

By installing automated inspection, Wuhan Changli wanted to overcome the deficits of manual inspection in a cost efficient way. This pursuit was successful: The P2-systems are enhancing the quality staff’s judgement, reducing mis-detections and are linking the quality and production departments more closely, enabling fast reaction to events on the line. Through better production monitoring, processes are continuously optimized and throughput has improved, leading to an overall yield improvement. Additionally, the impervious and intelligent design of the P2-systems allows for minimum maintenance efforts and reduces the need for spare parts, optimizing the costs of ownership and therefore a fast return on investment. By visualising quality data in trend reSeite ports, the systems deliver a very valuable precondition for production control and analysis and enable quick actions for process improvement.

Comprehensive portfolio – Optional extensions are pushing effectiveness of systems

Space saving and robust design: P²-Color integrated into P²-Coating, with advanced air cooling for easy maintenance

The ISRA inspection portfolio for glass covers many different applications and production steps. Next to the P2-Color and P2-Coating, it offers many more highly reliable system configurations allowing users to meet every specification. In addition to the inspection of architectural glass, ISRA offers unmatched inspection capability on high-end coated glass, as needed in the automotive industry or for photovoltaic pattern glass. Through various optional extensions like additional lighting or camera angles, the ISRA products form a portfolio of versatile solutions to control production lines, increase yield, and to bring the best out of any production process.

10.08.2017, Isra Vision AG

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