Talk about the plastic bar extruderTalk about the plastic bar extruder
Plastic rods are solid round rods. Due to their excellent physical properties, plastic extruders are widely used in the manufacturing industry, such as making plastic gears, bearings, bolts, nuts, etc. If the production volume is small, it is more economical to process it by mechanical processing; in mass production, it can be produced by extrusion.
The raw materials of plastic rods are generally engineering plastics, such as nylon, polyoxymethylene, polycarbonate, ABS, polysulfone, glass fiber reinforced plastics, etc.
Typical structure of a round bar extrusion head. The structure of the bar extruder head is simple, which is basically similar to the pipe extruder head. The difference is that there is no mandrel in the mold cavity, only the diverter. The use of a shunt can reduce the volume inside the mold cavity and increase the heating area of the plastic. If the mold cavity is streamlined without a stagnation area, the shunt may not be provided.
1-die; 2-diverter; 3-head body; 4-diverter bracket; 5-filter plate
Since the bar is solid, the cross-sectional area is much larger than that of the tube, so the head resistance is small. If the head pressure is increased, a dense bar can be obtained. The design method of the machine head structure is the same as the pipe material, and the differences are as follows:
(1) The inner surface of the mold cavity should be smooth without stagnation area. In order to increase the pressure in the machine head, the flow channel in the machine head should have the function of a choke valve.
(2) The contraction angle at the entrance of the machine head is 30o ~ 60o, and the length of the contraction part is about 50 ~ 100mm.
(3) The outlet of the machine head should be made into a trumpet shape, so that the central melting zone of the bar can be quickly refilled. The expansion angle of the trumpet can not be too large, generally less than 45o, otherwise it will produce a dead angle.
(4) The length of the sizing sleeve is 4 to 15 times the diameter of the bar, which is slightly longer than the length of the tube.
(5) The surface of the mold cavity should be smooth and the roughness Ra <0.8 μm.
8-4-2 Structure of sizing sleeve