During the injection molding process, when the molten plastic meets in the form of multiple strands in the cavity due to the holes in the insert, the areas where the flow rate is discontinuous, and the area where the filling material flow is interrupted, a linear weld seam is produced because it cannot be completely fused. In addition, when the gate injection molding occurs, a weld seam will also be formed, and the strength and other properties of the weld seam are poor. The main reasons are as follows: Pvc Injection,Precision Plastic Injection Mould,Oem Plastic Injection Crate Mould,Plastic Injection Mould Suzhou Dongye Precision Molding Co.,Ltd. , https://www.sjinjectionmolding.com
Processing:
The injection pressure and speed are too low, and the barrel temperature and mold temperature are too low, resulting in premature cooling of the molten material entering the mold and the appearance of weld seams.
When the injection pressure and speed are too high, injection will occur and weld seams will appear. The speed should be increased, and the back pressure should be increased to reduce the viscosity of the plastic and increase the density. Plastics should be dry well, recycled materials should be used sparingly, and weld seams may occur if the amount of release agent is too much or the quality is not good. Reduce clamping force and facilitate exhaust.
2. Mould:
If there are too many gates in the same cavity, reduce the gate or set it symmetrically, or set it as close as possible to the weld seam. The exhaust at the weld seam is poor, and an exhaust system should be set up. The sprue is too large, the size of the gating system is improper, and the gate is opened to prevent the melt from flowing around the insert hole, or use as few inserts as possible. If the wall thickness changes too much, or the wall thickness is too thin, the wall thickness of the workpiece should be uniform. If necessary, a fusion well should be opened at the fusion seam to separate the fusion seam from the workpiece.
3. Plastic aspects:
Lubricants and stabilizers should be appropriately added to plastics with poor fluidity or heat sensitivity. Plastic contains a lot of impurities, if necessary, replace the plastic with good quality.
Spiral classifier structure
The structure of the sorghum double helix classifier is shown in the "Spiral classifier classification and working principle". The semicircular water tank 2 is welded by steel plate and section steel. The middle side wall of the tank body has a feed port and the lower part of the upper end of the tank body. There is a returning sand. The bottom of the lower end of the tank has a drain valve that closes during normal operation and opens and releases the slurry in special cases such as failure. The slot is provided with a longitudinal hollow shaft, and the shaft is equipped with a bracket frame adapted to the spiral lead angle, and the left and right spiral blades are fixed on the upper side, and the screw mechanism adopts a double-head pitch spiral and is equipped with resistance at the edge of the blade. grinding plate (neutral manganese typically made of ductile iron). The spiral rotates, on the one hand, the slurry is stirred to float the light and fine particles, and the coarse and heavy particles sinking at the bottom of the groove are discharged to the upper end. Hollow shafts are usually made of seamless steel tubes or welded with long steel coils. The upper and lower ends of the hollow shaft are welded with a journal, the upper end is supported in the rotatable cross-shaped shaft head, and the lower end is supported in the lower support. The cross-shaped shaft head support is shown in Fig. 1. The shaft heads on both sides of the support are supported on the transmission frame, and the spiral shaft can be rotated and lifted.
The bearing support at the lower end requires a good seal because it is immersed in the slurry for a long time. In the past, three types of sealing devices were used: mechanical seal rolling bearing bearings, pressure water sealing resin tile sliding bearing bearings and pressure water seal rubber bushings. The sealing performance of these structural types was not satisfactory. Later, the mechanical seal rolling bearing support was improved, and the packing labyrinth and high-pressure dry oil combined sealing type (Fig. 2) was adopted, thereby improving the sealing performance and the bearing life. Extend to a year or so.
Figure 1, 2
The screw shaft is driven by a motor, a speed reducer, a spur gear and a bevel gear pair, and the transmission is mounted on the upper end of the device. Since the sand sinking after parking will cause the starting of the spiral blade, the screw shaft lifting mechanism is provided, that is, a motor drives the screw through the speed reducer and a pair of bevel gears to raise and lower the shaft. In addition, if the coarse sand sedimentation layer is too thick during rotation to make the screw shaft difficult to rotate, it can be slightly raised to prevent damage to the blade and other parts.