ACT™ Coatings can now be used as extremely efficient Direct Heating elements to provide a high degree of control over glass forming temperatures.
When ACT™ coatings are used in the Power Coatings™ configuration the coating not only provides the usual total corrosion protection but it can also be used to accurately control the cooling profile, or even add additional heat into the glass if required.
Actual and potential applications include feeder chambers, delivery tubes, heated drains, heated channels, orifice rings, or any other application where accurate temperature control of the glass is needed.
A Power Coatings™ system offers a number of fundamental improvements over alternative glass delivery systems:
· Low Precious Metal Requirements – The coating is fully adhered to, and supported by, the ceramic so it can be made much thinner than a fabricated platinum article. The typical coating thickness is in the 250 to 300 µm region compared to 1.2 to 1.5 µm for traditional fabricated direct heated systems.
· Powerful, Efficient Heating Capacity – The low coating thickness offers a much higher resistance and makes the direct heating of the platinum highly effective and efficient. The increased resistance of the system can be used to obtain more power, or the same power can be achieved using much cheaper transformers. This aspect, combined with the much lower metal requirements, offers the potential for extremely capable and cost effective direct heated glass delivery systems.
· Precise Temperature Control – The use of multiple thermocouples, strategically located immediately behind the coating, ensure that the temperature profile within the part is mapped in detail. The extremely rapid response of the Power Coatings™ system allows superb temperature control of the glass. For example, in the system pictured above the temperature is being controlled to within +/- 0.5°C in the 1200°C region.
· Accurate Gobweight Control – This temperature control, combined with the elimination of corrosion of the part, means the delivery gobweight will remain constant for the duration of the system. Gobweight variance of <0.2% is being achieved.
· Improved Product Quality – The ACT™ coating maintains a barrier between the ceramic and the glass, which eliminates the possibility of stones or cords being generated in the glass within the feeder chamber. This gives an increase in product quality and melt-to-pack ratio compared to bare ceramic delivery systems or forming parts.
· High Durability – The platinum coating is deposited via a thermal spray process so there are no welds in critical positions, the weak points of traditional platinum fabbricatons. The superb bond between the ceramic and the platinum coating means that there is no strain on the coating, it is all borne by the ceramic.