|Quality-Scanner integrated in an IG or tempering production|
|The total benefit of a Quality-Scanner integrated in an IG or tempering production|
|With the integration of an automated optical quality control (Quality Scanner), to detect glass defects as bubbles, scratches, dirt,... reliable, within the production process of IG or tempering several benefits regarding internal and external quality, optimization of the internal organization, quality handling of purchased glass, .. can be achieved. In general, investing in a Quality Scanner will always be justified by a significant reduction in external complaints, because of clear available figures and statistics for the complaint rates. Further extremely important reasons for the integration of a Quality Scanner into a glass processing line are the allocation of a reliable machine to control the actual quality of the glass, at any time, at the same standard of quality. Independent of motivation, stress, production pressure or just time of day or shift, a machine of this kind clearly exposes the real level of internal quality. Because it detects and rejects e.g. each scratch on the glass without doubt, instead of the 20-30% detected by human eyes, the internal quality rejections increase after the assignment of a Quality Scanner. By taking this “bad experience” to transfer the results of reject into an internal optimization process of different production steps, such as cutting or washing, an amazing new benefit occurs for such an investment: the entire quality standard of production is increased in several areas of fabrication. The result after such a total fabrication optimization of quality after 2-3 months is a reduction of external complaints for glass defects or dirt in the IG of up to 75%, in conjunction with an increase in productivity, process organization and an overall higher level of fabrication quality.
What can scanner technology in (ISO) production currently do and what future opportunities are available
Scanner technology has found its way across the board in all companies today.Viprotron itself already has 100 quality scanners in operation in the insulation glass industry. The use of these devices has not only created a secure basis for a quality system operating at least on the visual guidelines, but it has also helped in achieving cost goals through a significant reduction in the number of complaints and by improving procedures.
Quality according to guidelines or individual criteria?
The market is placing increasingly stringent demands on (insulation) glass quality. Directives such as Hadamar/BF or Cekal are now the minimum standard for certain buying groups. The criteria for the inspection system must be as variable as the demands of customers. Customised customer defect settings are therefore a MUST in user-friendly scanner systems. This also applies to quality standards going beyond the applicable directives. Systems must therefore be able to detect much more than the current norms call for. In order to avoid creating batches according to the quality demands of individual customers, a PPS connection is essential in the long run. In an intense exchange with the PPS system, order and customer data as well as quality classification stored in the client base data can be adopted. In normal batches, which define, for example, the packaging sequence for multiple customers with possibly differing quality demands after the insulation glass production line, a customised inspection of each insulation glass unit can be conducted online according to the stored quality classification.
Quality as a system or random individual activity?
The Quality Scanner provides safety. Not only for the company, but for the staff as well. A precise definition of quality classifications as well as clear and constantly improved process instructions create a consistent quality standard which does not depend on the level of training or personal dedication of the employee. In this, the Quality Scanner is both a standard and a tool. The guidelines from the PPS system define the filter for the display standard for the Quality Scanner operating at its highest detection capacity. The Quality Scanner assists in implementing the required quality goals in a factory-suitable method of operation. The fact that the quality inspection verifiably takes place during a production stage creates a different attitude towards quality even for employees working on the other production stages. All of a sudden it is no longer open to interpretation, but is measurable.
Quality or productivity?
Both, of course!Proven and new display systems assist increasing productivity and quality simultaneously. The standard traffic light was and still is a simple yet effective tool. If it shows “green“, the framesetter does not have to search for defects, but can apply a spacer or a label and send it on. A three-way traffic light, which signals "Good"/"Bad" for each individual pane of triple insulation glass, can also communicate information on problematic single panes to staff during inspection before they set the first frame. This makes it possible to remove all components of a unit (glass and spacer) in the event of panes that have not been reworked, and then replace them once the defective components have been recut. A PPS connection to the Quality Scanner ensures integration into the normal finishing process in this case. The Defect Pointer, presented for the first time at glasstec 2010, with an LED panel integrated both horizontally and vertically in the inspection, guides the framesetter to the current defect shown on the monitor (just like an X and Y coordinate) Figure 4. The panels shine white light in the pane area, while the coordinates of the defective points shown on the monitor are each marked by a red diode. This is an essential advantage, especially with large panes. The framesetter can position the ladder on the horizontal marking and ascend the ladder to reach the vertical marking.The defect can be found with certainty within a relatively small area and eliminated through repeated cleaning. The Defect Pointer thus gives the framesetter certainty that all defects on the glass which may be a source of complaints will be found and eliminated. The time-consuming process of having to scan the glass additionally is no longer necessary. In addition to the indication systems, the use of the information received on the defect itself is also of great importance. Recurring defects are identified and reported in the inspection, before they turn into serial defects. Each type of defect can be analyzed using evaluation tools. Once the source is identified, action can be taken. This may result in changes in the working processes of individual production steps or even changing preliminary suppliers.Each step will boost productivity because sources of defects will be eliminated progressively and the (insulated) glass panes only need to be made once.
Further proof of an increase in productivity is the identification of defects in production systems with many stages as early as possible. For example, if a pane of IG to be applied with screen printing with laminated/tempered glass is already identified as non-salvageable in the washing machine after edge processing, this pane is not subjected to any additional, expensive process stages, only to be discovered as a defective component in an otherwise standard IG at the end of production. Goodbye to IG. All glass to be newly produced is passed through production under time pressure as a damaged end runner, sometimes past the PPS system and with devastating effects on productivity.
Does defect detection remain an inspection task?
Defect detection is not just limited to the inspection. Quality Scanners for individual glass panes are being found in use increasingly after washing machines, in the polishing, tempered glass or pre-composite areas. A testing device for complete insulation glass up to a total thickness of 100mm was presented by Viprotron for the first time at glasstec 2010:the Quality Checker (Figure 5). This device belongs after the press and before sealing. In addition to testing criteria that also apply to individual panes, the straightness of lines, skewing of spacers and perpendicularity of frames is checked and butyl threads are detected; all defects that first occur after inspection. Here, a complete check of the unit is carried out before sealing, in order to compare it with the quality standard required or the customer’s requirements. The results of the tests can be documented and archived. This makes it possible to prove at any time that the product was delivered in accordance with the quality classification agreed.
Interval times as proof of increased quality
If you integrate a new Quality Scanner into your production, it provides quality control that you can rely on 100%. This means that, while out of 10 scratches on glass the purely manual check only detects 2-3 scratches, now all 10 panes of glass with scratches will be detected after introduction of the QS. Thus, instead of 2-3 panes of glass, now 10 will be removed from running production. That interval times decrease at the same time goes without saying, and is a clear consequence of the introduction of a QS, and clear proof of its improved quality! On the one hand, this consequence is a blessing because it reduces complaints, but on the other hand, it is unacceptable since good interval times and thus productivity must be present if you want to manage business well.
Total quality chain: Eliminating the root of the problem
In order to match productivity with its previous level, there are only 2 options: either you adjust the quality standards of the Quality Scanner to be more tolerant, so that many defects on the glass are ignored, or you try to find the source of the problem and prevent such defects from being produced. Option 1 is surely not the point of the exercise, because then you could just save the expense altogether. However, if you choose option 2 consistently and locate and eliminate the cause of the defect, you will be able to raise the quality of your total quality chain to a whole new level. Experience has shown that businesses can decrease external complaints by up to 70% by taking appropriate measures, while maintaining maximum productivity!
What might such internal quality measures be
On this topic, it is important to note that there are generally 2 types of defect. One is reversible defects, which can be eliminated through cleaning, while the other is irreversible defects, in which case the glass must be removed from production and disposed of. It is important to note that not only irreversible defects lead to interval problems, but also reversible defects, because it is not the staff's job to be the washing machine in production. It is therefore absolutely necessary in both cases to introduce effective quality measures in glass processing operations, in order to locate and eliminate the cause of the defects in question. When dealing with the category of irreversible defects, these can be subdivided into two categories: is external defects, which have come from the glass supplier, and internal defects, which are caused in the company’s own glass processing. To analyze external defects, the information provided by the Quality Scanner can be used very efficiently by utilizing its statistics tools for this task. These exit statistics allow you to see exactly how many square meters of glass had to be removed from production due to bubbles, coating defects, inclusions in laminated glass, etc. With this clearly structured information, you can either approach your suppliers and demand an improvement, or decide to switch to a better quality supplier. The statistics tools can also be used to analyse internal defects, although experience has shown that measures are taken very promptly since the 10 scratches that are suddenly removed have to have a cause. Usually, the conditions on the cutting table are inspected immediately to see if the tile is clean or whether the staff have not been removing the glass carefully enough. Glass handling is another common suspect. Depending on how the glass is placed in the transport cart and how it is removed, it might be necessary to either clean the transport cart or replace the protection used. If appropriate measures are taken, they quickly result in noticeable success. In the reversible defects category, i.e. defects which can be eliminated, measures are usually taken immediately to minimize the number of these defects. The first is the washing machine, which can leave spots and smears if it is not properly cleaned or maintained. Both of these are essential measures if you really want to achieve a top washing quality. Some companies resort to cleaning the washing machine up to twice a week. Other problems may include the drive rollers or back wall being dirty and leaving marks. Regular cleaning helps in this case too. Other sources of defects may come from the cutting table, such as from old cutting wheels or an improperly adjusted cutting press. This causes small glass splinters to become attached to the glass surface, which cannot be removed even in the washing machine. A wide range of additional causes and measures are also possible for reversible defects, and these may vary greatly from one company to the next.
By introducing a QS in glass production, the quality of the glass products being produced can be effectively increased to the highest level. Up to 70% of costs attributable to complaints can be saved by using such a system in glass operations. However, in all these successes, it remains important to note that the introduction of the QS makes a qualitative optimization of the entire production process necessary. The root of defects needs to be found and removed. With these measures, the total quality chain of a cmopany is given a boost and a high, even much higher, level of productivity can be achieved.The Quality Scanner from Viprotron therefore always forms the basis for the introduction of such inter-operational quality measures thanks to its very effective analysis and detection tools, and is not only a device for quality control, but also for boosting operational quality.
AUTHOR: Kai Vogel - Viprotron GmbH
Last review: February, 2012
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