{"id":3926,"date":"2015-11-27T13:17:21","date_gmt":"2015-11-27T11:17:21","guid":{"rendered":"http:\/\/glastory.net\/?p=3926"},"modified":"2024-12-02T15:56:05","modified_gmt":"2024-12-02T13:56:05","slug":"6-rookie-mistakes-of-tempering","status":"publish","type":"post","link":"https:\/\/www.glastory.net\/es\/6-rookie-mistakes-of-tempering\/","title":{"rendered":"6 rookie mistakes of tempering"},"content":{"rendered":"
Glass tempering is a bit like cooking. You can have the latest and greatest equipment in your kitchen, but the food can still turn out bad. To be a great cook takes much more than just having the best equipment \u2013 it\u2019s about understanding the processes. You have to know the ingredients and techniques as well as the equipment.<\/p>\n
Automation does make things a bit easier. And let me tell you, the latest kitchen ovens do have some nifty features. To be honest, this is exactly what we\u2019re trying to do with our tempering furnaces \u2013 to automate some of the processes in order to guarantee more consistent quality. Nowadays, tempering furnaces come equipped with more sensors, allowing the operator to pull more data and measurements. They also include more automation, which in turn minimizes operational mistakes.<\/p>\n
In the long run, automation will make\u00a0operating a furnace a bit easier. But still glass processors need to do many things correctly to reach high-quality tempered glass.<\/p>\n
I have toured the world and have seen hundreds of glass processing factories. I have helped processors take the next step in their production.<\/p>\n
Below, I have collected a list of common mistakes that happen in the tempering process.<\/p>\n
1. Not learning the process basics<\/h2>\n
When a person starts a new project, he\/she has to learn something new. Let me tell you, I\u2019ve seen processors who have skipped the basics and ended up with quality problems before they even started to get the proper results. Not an ideal scenario, I would say.<\/p>\n
To me, the tempering line is not a magic black box. To be honest, the behavior of glass is relatively simple to understand. If you don\u2019t heat or cool the glass uniformly, it will bend. If you heat it too much, it will have waves.<\/p>\n
These are the basics that should be clear to anyone operating a processing machine. Manufacturers often offer their clients the basic documentation and training packages that also clearly state the fundamental facts. But make sure you select a partner who can also train and instruct you beyond the basic documentation.<\/p>\n
Take time to learn the process basics! This might take a while, but you\u2019ll benefit from it later. For example, when you introduce new coatings, it is easy to look into the heating section and see how the glass behaves in the process. If you know the basics of heat transfer, you\u2019ll find it easier to adjust the process yourself.<\/p><\/blockquote>\n
Don\u2019t get me wrong, I\u2019m happy to come around and also train you!<\/p>\n
2. Neglecting the quality of pre-processing<\/h2>\n
The tempering line is usually among the biggest investments in the glass processing factory. This means that the primary attention is directed largely towards the tempering line. However, if we look at the end product\u2019s quality, as well as the production yield, we can conclude that the pre-processing \u2013 including the cutting, grinding, washing and more \u2013 is just as important as the tempering.<\/p>\n
The pre-processing quality has a direct connection to the tempering line\u2019s yield when it comes to breakage and production quality. Sometimes, I see processing plants that have acquired a top-rank tempering line but have left the pre-processing systems untouched and out of date.<\/p><\/blockquote>\n
Poor cutting or edge work results in more breakage in the tempering line. Conversely, if the edge work is good, the glass can run at a lower temperature in the heating section, which leads to better optical quality and less breakage.<\/p>\n
For example, diamond-polished thick glass can be processed with about 20 degrees lower temperature than normal seamed glass. This already has a major impact on quality and, of course, glass breakage.<\/p>\n
3. Maximizing loading efficiency<\/h2>\n
When someone makes a new tempering line investment, very rarely does the tempering line becomes the bottleneck of the factory. Still, many obsess over the highest possible loading efficiency by putting both small and large glass sheets into the same load \u2013 long side leading and short side leading in the same pattern but with a different orientation.<\/p>\n
Mixing up the loading patterns with different glass orientation \u2013 short versus long edge leading \u2013 will result in different optical quality. If these glasses are installed in the same building, you\u2019ll see\u00a0a different optical reflection and, most likely as a result, end up with a reclamation. This is a common rookie mistake. So make sure to avoid it.<\/p><\/blockquote>\n
Don\u2019t get me wrong, maximizing loading efficiency is a good thing, and it will increase your energy efficiency as well. The point is not to compromise the quality.<\/p>\n
4. Having a heating time that is too long<\/h2>\n
The percentage of glass breakage has been a tempering line operator\u2019s most important KPI for a long time. For this reason, operators naturally do everything they can to decrease the waste.<\/p>\n
One way to prevent breakage is to increase the heating time. This will, unfortunately, have a negative impact on the glass quality. The higher the glass temperature is, the worse the quality.<\/p><\/blockquote>\n
Note that quite often operators think that poor cutting or grinding quality comes from having a temperature that is too low in the tempering process. In this case, the operator is correcting the wrong problem and, as a result, has poor quality glass with poor edge work.<\/p>\n
5. Running thick and thin glass in a similar way<\/h2>\n
Avoid putting a thick piece of glass into a very hot furnace. Trust me, you don\u2019t want to hear the \u201cBoom!\u201d That is the noise of a thick glass breaking in the furnace.\u00a0In this case, the breakage is caused by heat shock. As a result, the furnace needs to be cooled, and the broken glass removed. As a kind reminder, this process takes about two shifts to complete.<\/p>\n
Also, when running a thick glass of around 10\u201319 mm, the quenching pressure the operators are applying is often too low. A common rule is that low pressure prevents the glass from breaking in the chiller. Most often, the case is almost the opposite. So don\u2019t use pressure that is too low in the production of thick glass.<\/p>\n
6. Removing the ghost the wrong way<\/h2>\n
Many operators try to fix the white haze issue by operating the line to run the glass \u201csad\u201d in the furnace. In other words, the corners of the glass touch the rollers but the center does not.<\/p>\n
Yes, this does eliminate the white haze, also known as \u201cghosting.\u201d But running thick glass \u201csad\u201d will harm the rollers. The ghosting can chip off some glass from the sides or cause markings to the rollers. As a result, the following loads will have problems and the thin glasses will not stay stable.<\/p>\n
Here\u2019s my rule of thumb: don\u2019t exaggerate the sadness of the glass.<\/p><\/blockquote>\n
Conclusion<\/h2>\n
It seems that as we become more comfortable with our work, the more mistakes we make. And the more you think you know something, the more likely it is that your choices lead you down the wrong path. That\u2019s why even us experts should always keep the basics in mind.<\/p>\n
If you have some unanswered\u00a0questions about tempering, I recommend downloading our free eBook. It will give you more basics \u2013 and then some.<\/p>\n
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