jonturka wrote:Louis, thank you very much for your valuable answers. But I can't understand some points make me confused. It is said that using blowtorch damages the screw because of high heat. The method pyrolysis also says the temperature should be about 400-500C degrees. Does not it damage the screw as well ? How many degrees does the screw reach to with the blowtorch ?
Heat can damage a screw when applied unevenly as it will cause the screw to bend. In fact, bent screws can be straightened by applying heat to the "high side" and then allowing the screw to cool. The heat forces the screw to bend more in the direction that it is bent, but the cooling afterwards allows the screw to bend in the opposite direction,. That process takes skill, but I've witnessed it on many occasions.
The uniform heating and cooling of a screw in Pyrolysis does not have that same affect due to the uniform application of heat and cooling. I cannot comment on how that heat affects the surface hardening of the screw, but suspect that it does no harm, as the equipment manufacturer would soon be out of business.
email: louis AT plastics DOT com.
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