Depending on the method of future manifold glass units heating, the vacuum lamination furnaces may be divided into 4 types:
• Convectional heating furnace – blanks heating is carried out at the account of the heat, given up by the heat transfer agent – air, circulating in the furnace. There are two options: with forced and natural circulation.
• Radiation heating furnaces (IR) – there is applied for vacuum bag with the unit of future laminate the powerful flow of infrared radiation.
• Contact heating furnaces – there is applied for blanks heating the uniformly distributed along the entire surface of vacuum bag base electrical heater or massive steel plate heated by circulating in its channels heat transfer agent.
• Combined type – combination of several heating methods. Usually, it is the combination of radiation and convectional methods.
Examples of various types of vacuum lamination furnaces:
Convectional |
IR-furnace |
Contact furnace |
Convection | IR-furnace | Contact furnace | |
Possibility of multilevel charge |
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Possibility pf simultaneous production of various thickness workpieces |
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Design and peculiarities of heating elements location give no possibility to carry out simultaneous lamination of blanks of various thickness due to problems with uniform temperature distribution | |||
Possibility of multilevel charge without additional equipment (lifting tables and pallet accumulator) |
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Due to heating elements location | There are no multilevel | ||
Immunity to electrical power drops and quality of input voltage |
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No loss of heating elements power at long-term operation |
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No loss of heating elements power at all, as heating elements are designed for higher operation temperature and are constantly blown with air flow, so they are operated in part load mode | There is drop of heating lamps power that leads to considerable increase of process and not uniform distribution of temperatures at heating | ||
Possibility of further operation in case of heating elements failure |
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Possibility of equipment operation in case of 75% of heating elements failure | There is no possibility of further operation as in such a case there emerges the area without heating that leads to 100% rejection of the finished products | Usually, there is one heating element | |
Saving at heating elements replacement |
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In case of failure, there is replaced only failed heating element that is considerable cheaper than heating lamp for IR furnace and heating coil for contact furnace | In case of failure of one of the heating elements it is recommended to replace all of them. Otherwise there will be constant problem with uniformity of temperatures distribution | There shall be replaced the entire heating system | |
Ease of operation and maintenance |
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Special requirements for heating elements maintenance | |||
Possibility of production of the shaped glass |
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Problems with production of laminated glass from shaped (bended) blanks that is explained by the necessity to locate infrared heater strictly parallel to the blank unit surface to ensure uniformity of infrared radiation flow | Conceptual impossibility of production of laminated glass from shaped (bended) blanks that is explained by the necessity of close contact between blank, vacuum bag and heater | ||
Cooling process |
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In case of forced cooling usage there emerges the problem with heating elements life duration | |||
Electrical power consumption economy |
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Very energy-consuming heating system | |||
Silicone covers value |
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Possibility of any silicone usage | There is required special silicone with usage of inserts for higher attraction of IR beams | Possibility of any silicone usage | |
Value of furnace and operating costs |
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Average value of the equipment is the cheapest in terms of operation and maintenance. The highest reliability and performance. Minimal number of rejected products | The most expensive at initial investment and the most expensive in terms of long-term operation. The average level of rejected products | The cheapest, but has a lot of shortfalls at operation. High % of rejected products |
Summarizing comparative analysis of the main advantages and disadvantages of the lamination glass production furnaces of various types, one may make the conclusion that the most rational choice is appropriately designed convectional furnace with forced air circulation as it is the most reliable, versatile and has the best quality-to-price ratio.