Injection Molding Machine with plastic screw conveying. […]
Injection Molding Machine with plastic screw conveying. Melting. Mixing. Compression. Metering and exhaust functions. Plasticization plays a very important role in the quality is the key factor affecting the quality of plasticization. There are several parameters of the screw affect the quality of plasticization.Generally according to the following principles.Select the injection molding machine screw:
Screw diameter (D)
A. Corresponds to the required injection volume: Injection Volume = 1/4 * π * D2 * S (Injection stroke) * 0.85,
B. In general, the screw diameter D is inversely proportional to the maximum injection pressure and is proportional to the plasticizing ability.
2. Conveying section
A. Responsible for the transport of plastic. Push and preheat. Should be guaranteed to preheat to the melting point,
B. Crystalline plastic should be long (such as: POM.PA) followed by amorphous materials (such as: PS.PU.ABS). The shortest thermal sensitivity (such as: PVC).
A. Responsible for the mixing of plastics. Compression and pressurization of the exhaust. The raw materials passed through this section are almost completely melted, but not necessarily uniformly mixed,
B. In this area, the plastic gradually melts. The volume of the screw channel must be reduced correspondingly to the decrease of the geometric volume of the plastic. Otherwise, the material pressure is not high.
c. Generally account for more than 25% of the working length of the screw, but the compression section of the nylon (crystalline material) screw accounts for about 15% of the working length of the screw. High viscosity, fire resistance, low conductivity, \ 50% of the screw length of work. PVC screw can account for 100% of the working length of the screw. In order to avoid intense shear heat.
A.General account for the working length of 20 \ 25% screw to ensure the plastic is completely melted and the temperature is uniform.Mixing,
B.Measurement of the length of the long section of the mixing effect is too long is easy to make the melt stay for too long and produce thermal decomposition is too short to easily make the temperature uneven,
C. PVC and other thermosensitive plastics should not stay too long, so as to avoid thermal decomposition. Can be used to measure the shorter section or not to measure the segment.
5. Feed groove depth. Metric groove depth
the deeper the feed screw groove, the larger the feed volume, but the screw strength should be considered. The shallower the metering screw groove depth, the plasticizing and heating will produce higher mixing performance index, but the metering screw groove depth is too shallow Increased heat. Increased self-heat. Temperature rise is too high, resulting in plastic discoloration or scorch. In particular, is not conducive to heat-sensitive plastic,
B. Measuring groove depth = KD = (0.03 \ 0.07) * D.D increases, then K choose a small value.
Screw can be said that the heart of the injection molding machine. The quality of the screw determines the quality of the product is good or bad.