By: Derek Burkholder
Rolling Hearth Furnaces and Electrochromic Glass
Rolling hearth furnaces have traditionally been used in the glass industry for firing decorative and conductive inks into glass. The furnaces also typically include annealing sections to allow the glass to be annealed for further processing downstream. They can handle huge volumes and heavy loads. But these types of furnaces can also be utilized for electrochromic glass production. There are a number of companies developing new techniques and processes for producing electrochromic glass (glass that tints when an electric current is applied) and in many cases those processes require the glass to be raised to an elevated temperature (500°C+) for a set period of time, then annealed and cooled. Other steps may also be required, and the furnaces are modular to allow sections to be added as needed for each customer. Casso-Solar can work with your team to custom design an R&D or production-scale piece of equipment for your electrochromic glass application.
Structure and Design of Rolling Hearth Furnaces
Parts processed in a roller hearth furnace are moved into the firing/high temperature section of the furnace in batches typically. The conveyors in these furnaces consist of rollers that are made of fused silica. While most industrial roller hearth furnaces are batch based, they can also be made as continuous processes for higher production rate requirements. Rollers generally have a good operational life and maintenance requirements on the furnace are low.
In a roller hearth furnace, heating is done from both sides of the parts to ensure even heating. After the glass is heated to the target temperature for the specified amount of time, the batch would be moved to an annealing chamber for heat strengthening, which would then be followed by a cooling section where the rate of cooling is carefully controlled to ensure that the glass does not break.
Casso-Solar designs our rolling hearth furnaces so that the top and bottom halves of the furnace are separate and the top half can be lifted up to provide maintenance access. Custom refractory insulation is used to seal the top and bottom halves together around the silica rollers.
Benefits of Roller Hearth Furnaces for Electrochromic Glass Production
There are quite a few benefits these furnaces offer for electrochromic glass production. Some of them are:
• Because these furnaces are typically designed for batch processing, they have a minimal footprint which is ideal for the long processing/dwell times in many electrochromic glass processes
• Similarly, the minimal footprint of this equipment is well suited for R&D equipment that can be used for the development and testing of new processes.
• Purpose-built annealing sections post-firing ensures a consistent anneal and allows for post-processing as required.
• Additional sections can be added in the future if production requirements increase or change
Automation in Roller Hearth Furnaces
Most machines and processes in the manufacturing sector now have some level of automation built in for ease of operation. Rolling hearth furnaces can take advantage of automation in a number of ways.
• PLC systems can be used to automate glass tracking in these furnaces. This helps achieve precise control over the processing of parts.
• Loading and unloading of workpieces can also be automated, and this is especially useful in batch processing systems. The automated system will precisely locate the parts in each processing section as needed.
• The heated sections can have a large number of zones, all monitored and controlled via the automated system.
Are you looking to invest in a roller hearth furnace for your electrochromic glass application? Casso-Solar has an abundance of experience in designing and building this type of equipment that we have gathered over our 60 years of existence. Contact our sales team today to discuss your specific needs.