Why are hot runner nozzles made of titanium zirconium molybdenum (TZM)?
Since its introduction to the industry, hot runner has played a key role in improving the injection molding process. Although the capital cost is higher than the cold runner, its high production efficiency makes it a more economical option in the long term, and the improvement of system performance can lead to the production of cosmetionally superior parts and increased function of parts. In addition, the hot runner improves energy efficiency and saves on plastic feedstock, resulting in shorter cycle times and lower component costs.
Due to the advantages of hot runner, including the above mentioned large and small enterprises in the world are implementing hot runner and seeking various solutions for further optimization. Of course, the focus of this article is not this, but in one of the important parts of the hot runner - nozzle.
Hot runner technology is mainly to make the injection molding machine between the nozzle to the cavity of the plastic melt insulation, in order to reduce the injection pressure, so that the plastic melt smoothly filled the cavity, so as to obtain good quality plastic products. The choice of nozzle material is related to the production efficiency, cost and finished product quality of the hot runner system.
Pure molybdenum has very high melting point, good strength, low coefficient of thermal expansion and excellent thermal conductivity, making it a good comprehensive candidate for most high temperature applications. TZM, an acronym for Titanium-Zirconium-Molybdenum, is a molybdenum alloy. Like pure molybdenum, TZM can be produced by a powder metallurgy process.
Although TZM is 25% more expensive than pure molybdenum, in some applications the additional cost is offset by its increased strength at high temperatures. The recrystallization temperature of TZM is higher than that of pure molybdenum, which reduces the possibility of embrittlement at high temperature. In high temperature applications, TZM has higher strength, hardness, creep resistance and ductility to ensure that it does not become weak or soft.
Therefore, titanium zirconium molybdenum alloy is currently used in the manufacture of nozzle suitable material. The advantages of TZM hot runner nozzle are as follows: there is no residue mark of the gate on the product, and the trace at the gate is smooth; Large diameter gate can be used to speed up cavity filling, further reduce injection pressure and reduce product deformation. It can prevent the phenomenon of wire drawing and salivation when opening the mold. When the screw of the injection molding machine recedes, the material can be effectively prevented from being sucked back from the mold cavity. Can cooperate with sequence control to reduce weld mark of products.
