The processing of plastic raw materials is mainly the process of melting, flowing and cooling rubber particles into finished products after setting. It is a process of heating and then cooling. It is also a process of changing plastics from particles to different shapes. For the plastic thermoforming machine, the whole process can be customized for full-automatic operation without manual operation, and the product quality is stable! The following will explain the processing process from the perspective of different stages.
1. Melt
The heater of the device allows the raw material particles to gradually melt into fluid flow. Different raw materials are mainly suitable for temperature regulation. Increasing the temperature will accelerate the flow of raw materials, which can increase efficiency, but not necessarily ensure the yield. An appropriate balance must be achieved. In addition, the good effect and the characteristics of PP in case of high thermal cracking are that it is best to make the raw material flow smoothly to the die during production, so as to avoid insufficient filling or reflux. Reflux means that the raw material flow is faster than the output rate, and finally increase the average flow efficiency, which is equal to the improvement of MFR. It is one of the available methods for processing, However, it also causes abnormal MFR distribution, which may lead to increased instability and increased defect rate. However, due to the application, PP finished products are not products with high dimensional precision, so the impact is not great.
2.Screw stem
Most of the PP processing depends on the screw to drive the fluidity, so the design of the screw has a great impact. The diameter affects the output, and the compression ratio affects the pressure value. It also affects the output and finished product effect, including the mixing effect of a variety of materials (Color Masterbatch, additives and modifiers). The flow of raw materials mainly depends on the heater, but the friction and friction of raw materials will also produce friction heat energy to accelerate the fluidity. Therefore, the screw compression ratio is small, the flow is small, and the rotating speed must be increased, resulting in more friction heat energy than the screw with large compression ratio. Therefore, it is often said that there is no master in plastic processing, and the person who carefully understands the performance of the machine is the master. The heating of raw materials is not only a heater, but also includes friction heat and suffocation time. Therefore, this is a practical problem. Experience is helpful to solve production problems and improve efficiency. If the mixing effect of the screw is particularly good, sometimes two-stage different screws or biaxial screws are designed, and each section of different forms of screws are set separately to achieve various mixing effects.
3. Die or die head
Plastic reshaping depends on the mold or die head. The injection molding finished product is three-dimensional, and the mold is also complex. The shrinkage problem should be considered. Other products are plane, strip and needle continuous product dies. If they are special shapes, they are classified as special shapes. Attention should be paid to the problem of immediate cooling and sizing. Most plastic machines are designed like syringes. The extrusion force driven by the screw will cause great pressure at the small outlet and improve production efficiency. When the die head is designed as a plane, how to make the raw materials evenly distributed on the whole surface, the design of clothes hanger die head is very important. Pay attention to the extrusion opportunity to increase the fish gill pump and stabilize the supply of raw materials.
4. Cooling
In addition to pouring raw materials into the sprue gate, the injection mold also has the design of cooling raw materials in the cooling channel. Extrusion molding relies on the cooling water channel in the roller to achieve the cooling effect. In addition, there are also air knives, cooling water directly drenched on the blowing bag, hollow blowing and other cooling methods.
5. Extend
The finished product reprocessing and extension will enhance the effect. For example, the different speed of the packing belt driven by the front and rear rollers will cause the extension effect. The tensile force of the extension part of the finished product is strengthened, which is not easy to tear, but it is very easy to tear horizontally. Molecular weight distribution will also affect the extension effect in high-speed production. All extruded products, including fibers, have unequal extension. Vacuum and compressed air forming can also be regarded as another form of extension.
6. Shrink
Any raw material has the problem of shrinkage, which is caused by internal stress during thermal expansion, cold contraction and crystallization. Generally speaking, thermal expansion and cold shrinkage are easy to overcome, which can be done by prolonging the cooling time in processing and maintaining the pressure continuously. Crystalline raw materials often have greater shrinkage difference than non crystalline raw materials, about 16% for PP, but only about 4% for ABS, which is very different. This part needs to be overcome on the mold, or additives to reduce the shrinkage rate are often added, LDPE is often added to the extrusion plate to improve the necking problem.
Plastic thermoforming machine is applicable to almost all thermoplastics. In recent years, plastic thermoforming machine has also been successfully used to form some thermosetting plastics. The molding cycle of the plastic thermoforming machine is short (a few seconds to a few minutes), and it can form molds with complex shape, accurate size and at one time. GTMSMART thermoforming machines products include Plastic Thermoforming Machine, Cup Thermoforming Machine, Plastic Vacuum Forming Machine, Plastic Flower Pot Thermoforming Machine.
GTMSMART provide first-class machines at the most favorable price that can easily meet your bulk production requirements. Explore our range of products and you will find many high-performance options that suit your requirements.
Post time: Oct-31-2021