rapid heat temperature, is actually an old method that is often used to eliminate the weld line, the front cover products such as TV, is an example of the most frequently used method, but its use is now developed further, as demand for products with low cycle time and quality of surface nice sharp increase lately, covering progress being made is that the control system is used, so the heat on the heating rod is held constant, the only heating occurs during the process of filling, so filling process stops, and the cooling process is done, no heating rod heating process.
Advantage
Trim cycle times up to 20 %
A new unit combines rapid heating and cooling and mold-temperature control in one unit as a means to trim cycle times by up to 20% and reduce energy cost. It is the result of a collaboration between Wieder GmbH International of Germany, a supplier of pulsed mold heating/cooling systems, and Regloplas of Switzerland, a maker of fluid temperature-control units
Reduce Weld line
because during the process of filling, the mold is heated, especially at the regional meeting of the plastic, this led to the solidification of the material evenly, so that the weld line can be minimized.
injection mold is rapidly heated to a high temperature, usually higher than the glass transition temperature of the polymer material, before melt-injection and rapidly cooled down to solidify the shaped polymer melt in mold cavity for ejection. Since the elevated mold temperature can eliminate the unwanted premature melt freezing during filling stage, the melt flow resistance is greatly reduced and the filling ability of the polymer melt is also significantly improved. As a result, plastic parts with excellent surface appearance can be obtained.
Improve Appearance
rapid heat cycle method is also shown to improve the quality of the surface, this is because the process of filling with stable temperatures ranging from the gate to the end product, or it could be said to be due to differences in temperature in the cavity is not much different.
Reduce Cost
I was not sure whether this method can reduce the cost of production, when production is carried out is to a large scale, of course, 10-20% reduction in cycle time will bring a lot of meaning to the cost of production, but when the scale of SMEs, given the initial price for the application of this method expensive, I think this method will not reduce production costs.
Heating Method
various types of heating methods research has been carried out
1. use of the insulation layer, An insulation layer is coated onto the mold base then a heating layer is applied to the insulation layer as the cavity surface, for Increasing the mold surface temperature in the filling process, a coating on the cavity surfacewith TiN and Teflon has reduced the heat transfer from the melt to the mold material, the which Increased the temperature on the cavity surface.
2. the use of steam. difficulty of this method is the first installation costs are expensive, and slow increase in temperature,
3. Infrared radiation on the surface, this method has also been investigated, and are able to reduce cycle time by 20%
4. electric heating rod, this method is the method most commonly used in industry because of the installation, maintenance, repairs are relatively easy. but the price per Kw electricity is relatively expensive, because it takes a minimum of 300 watts for a heating rod.
Reference
1. S.C. Chen, H.S. Peng, J.A. Chang, W.R. Jong, Simulation and verification of induction
heating on a mold plate, International Communications in Heat and Mass Transfer
31 (7) (2004) 971–980.
2. P.C. Chang, S.J. Hwang, Simulation of infrared rapid surface heating for injection
molding, International Journal of Heat and Mass Transfer 49 (21–22) (2006)
3846–3854.
3. G.L. Wang, G.Q. Zhao, H.P. Li, Y.J. Guan, Research of thermal response simulation
and mold structure optimization for rapid heat cycle molding process,
respectively, with steam heating and electric heating, Materials and Design 31
(1) (2010) 382–395.
4. X.P. Li, G.Q. Zhao, Y.J. Guan, M.X. Ma, Optimal design of heating channels for rapid
heating cycles injection mold based on response surface and genetic algorithm,
Materials and Design 30 (10) (2009) 4317–4323.
