{"id":13322,"date":"2021-04-26T16:35:55","date_gmt":"2021-04-26T13:35:55","guid":{"rendered":"https:\/\/www.glastory.net\/?p=13322"},"modified":"2024-12-02T15:50:41","modified_gmt":"2024-12-02T13:50:41","slug":"5-promises-of-convection-technology-in-windshield-bending","status":"publish","type":"post","link":"https:\/\/www.glastory.net\/fi\/5-promises-of-convection-technology-in-windshield-bending\/","title":{"rendered":"5 promises of convection technology in windshield bending"},"content":{"rendered":"

By the laws of physics, convection is the most efficient way to transfer heat. But what arguments back it up in practice? Let\u2019s dive deeper and explore beyond the laws of physics what convection heating promises to users in the glass industry. <\/em><\/p>\n

Promise 1: No glass breakage due to temperature differences<\/strong><\/h4>\n

An even temperature between the glass pair and the mold avoids glass breakage during heating. In furnaces using radiation heating, glass breakage is caused by the quick heating speeds inherent to radiation heating. The mold cannot heat as rapidly as the glass, creating too large of a temperature difference between them. As a result, the glass breaks from thermal shock before being bent. What a waste!<\/p>\n

With convection heating, hot air circulates in the heating chamber, heating the glass and the mold at the same speed. Thus, heating speeds can be much faster \u2013 and glass breakage is avoided.<\/p>\n

Promise 2: Better optical quality <\/strong><\/h4>\n

Convection heating is indifferent to glass surface materials. It doesn\u2019t matter whether the glass is clear, printed or coated.<\/p>\n

Think of those wide black printed areas at the sides, bottom and top of a windshield. And think of the large black printed areas reserved for the ADAS camera mounted near the top of the windshield. Without convection, you must spend a lot of time to find out the correct size and position for heat suction plates or radiation shields between the glass and the heaters to avoid overheating those black printed areas.<\/p>\n

Overheating the printed area is a well-known problem that causes an optical distortion known as the \u201cburn line,\u201d which is visible just above the printed surface of the windshield.<\/p><\/blockquote>\n

This problem doesn\u2019t occur with convection heating. Hardly any temperature difference develops between the black printed area and the clear glass area right next to it. You waste no time on extra precautions or experiments with heat suction plates or radiation shields. Convection heating delivers \u2013 every time.<\/p>\n

Promise 3: Higher heating rates for higher capacity<\/strong><\/h4>\n

A traditional infrared radiation heating furnace heats the glass at a rate of 40\u201350 \u00b0C per minute. The rate is only limited by the slower heating of the mold. Convection heating reaches a rate of 75 \u00b0C per minute.<\/p>\n

A higher heating rate means you can get along fine with a shorter furnace, a smaller furnace footprint, fewer molds and less energy, while still producing the same capacity.<\/p><\/blockquote>\n

Even more importantly, with fast convection heating at the beginning of the process, glass heating speeds in the bending chambers can be relatively slow. Therefore, convection heating allows a longer time for shaping the windshields.<\/p>\n

Promise 4: Measurable savings in millions<\/strong><\/h4>\n

As said before, convection is the most efficient way to transfer heat. Let\u2019s do some simple calculations to prove this.<\/p>\n

In a test with a convection Glaston Matrix furnace filled with windshield compositions in sizes of 2.1 + 2.1 mm and 3 + 3 mm, the power used was measured to be 5 kWh\/m\u00b2. That is significantly less power than the best non-convection furnaces use, typically around 10 kWh\/m\u00b2.<\/p>\n

To allow for measuring errors, let\u2019s say the glass processing furnace with convection technology produces 1 m\u00b2 of glass using 4 kWh\/m\u00b2 less energy than conventional machines with no convection.<\/p>\n

Now \u2013 the math. Say your annual production is 300,000 windshields. On average, the size of one windshield is 1.2 m\u00b2. So, 300,000 x 1.2 m\u00b2 results in an annual output of 360,000 m\u00b2 of glass.<\/p>\n

Let\u2019s assume the energy price is 0.12 EUR\/kWh.<\/p>\n

360,000 m\u00b2 x 4 kWh\/m\u00b2 x EUR 0.12\/kWh = EUR 172,800 in annual savings.<\/strong><\/p>\n

That\u2019s right \u2013 convection furnaces can save you a million euros in less than six years!<\/p>\n

Promise 5: Visible results<\/strong><\/h4>\n

From better glass quality to lower costs, the promises of convection technology are substantial. But perhaps the most important promise is that the benefits will be noticed. Your customers will see the optical quality improvement of the windshields they receive. And you might lose a zero or two off your energy bills.  <\/p>\n

You can\u2019t argue with the laws of physics. And the efficiency of convection heating is something glass processors can determine for themselves.<\/p><\/blockquote>\n

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