A problem is met by many customers who use mould cartridge heater, the surface of heating tube will be blackening for a period of time and then burn out.
The factors affecting the life time of heating tube:
一、Power Design
The power of ordinal heating tube cannot be too large, the surface load cannot exceed 8w/cm2.. The imported tube is 11-12w/cm2. The larger the surface load of mould heating tube, the shorter the life.
二、Material Selection
Different working environment and temperature determine the material selection.
If the working temperature is 100-300℃, the material should be SUS304.
If the working temperature is 400-500℃, the heating tube can be SUS321.
If the working temperature is 600-700℃, using the SUS301S.
Therefore, if the material is not suitable, which is also shorten its service life. Also, if the mould has vibratility, it need to use nickel-chromium wire with better flexibility.
三、The clearance of die hole
The air has a hindering effect on heat conduction, if the heat is not emitted, it will rise the surface temperature of the heating tube, which causing the internal temperature of heating tube to rise as well. When the internal temperature of mold heating tube is high in some degree, the resistance wire will burn out and shorten the life time of the tube. More and worse, the tube explosion will occur. So, the gap between them should not be too large. However, the gap between then should not be too small. Due to the principle of thermal expansion and contraction, the mould heating tube will expand after electrifying, many molds cannot be taken out when the heating tube is broken. For such situations, we suggest that the gap between the pore diameter of die hole and the pipe diameter of heating tube is 0.1-0.2mm, so that the above problems can be solved perfectly.
