What is the difference between a two-board machine and a three- board machine? Which is better?

With the development of material technology, the application proportion of plastic parts on the car body is increasing, such as the car front/rear bumper, instrument panel and door guard. Plastic parts are becoming bigger and heavier, which leads to the tonnage of clamping force of injection molding machine chosen by supporting injection molding manufacturers. For the injection molding machine of more than 2 000 T, most foreign countries choose two plate injection molding machine (direct pressing mode locking), while the vast majority of domestic manufacturers choose three plate injection molding machine (crankshaft mode locking).

Two plate injection molding machine

Plastic injection molding machine referred to as injection molding machine, usually screw type and plunger type two. Screw injection molding machine of more than 2 000 T mainly includes injection device, clamping device, hydraulic transmission system and electrical control system.

The injection device is mainly composed of screw, barrel, nozzle, hopper, metering device, transmission device, injection seat and mobile hydraulic cylinder.

Clamping device is mainly composed of front/back fixed template, moving template, Lin column (commonly known as pull rod), clamping hydraulic cylinder, moving hydraulic cylinder, locking mechanism, adjusting device, product ejector device (commonly known as neutron) and so on.

Hydraulic transmission system and electrical control system. The biggest difference between two - plate injection molding machine and three - plate injection molding machine lies in the clamping device part. The mold closing device of the two-plate injection molding machine mainly includes moving template, static template, rotating nut system, hydraulic thimble system, fast mold moving system and high-pressure hydraulic cylinder mold locking system (see Figure 1). The high-pressure hydraulic cylinder provides mold locking force.

The two-plate injection molding machine mainly adopts the direct pressure mode, that is, four high-pressure locking hydraulic cylinders pull the Golin column at the same time to pressure and maintain the pressure on the mold. The main process of producing plastic parts of two-plate injection molding machine is as follows: slow mold closing - fast mold closing - low pressure slow mold closing - rotary nut locking - high pressure mold locking hydraulic cylinder mold locking - injection - pressure holding - pressure release - high pressure mold opening - nut opening - slow speed mold opening - high speed mold opening - slow speed mold opening - products ejecting - thimble back. The clamping process is relatively simple. After the clamping is in place, the nut is rotated and the high-pressure clamping hydraulic cylinder provides the clamping force. The mold opening process is opposite to the mold locking process. First, the pressure of the high-pressure mold locking hydraulic cylinder is relieved, and then the rotating nut is opened, and then the dynamic mold is returned.

advantages

Die - opening hydraulic cylinder requires less die - opening force. Generally, the opening force of the hydraulic cylinder of injection molding machine with more than 2 000 T is less than 110 T, which is half of the opening force of the three-plate injection molding machine with the same tonnage. The hydraulic cylinder with small opening force is easy to be processed, easy to maintain in the actual use of the process, long service life, not easy to be damaged.

Clamping force can be set freely. The clamping force of two-plate injection molding machine can be changed by changing the number and working force of hydraulic cylinders.

The precision of mold locking is relatively high. The error between the set clamping force and the actual clamping force of the two-plate injection molding machine is small, and the actual clamping force can be measured by measuring the oil pressure of the hydraulic cylinder through the sensor embedded in the hydraulic cylinder.

Two plate injection molding machine adopts direct pressure locking mode, the parallelism of dynamic and static templates is easy to adjust, generally it takes very short time to adjust to the parallelism required by the process (0.1mm /m).

disadvantages

The requirement of high pressure clamping hydraulic cylinder is relatively high. Two plate injection molding machine through four high pressure clamping hydraulic cylinder to achieve mold locking, working high pressure clamping hydraulic cylinder needs to provide a lot of pressure, which requires the hydraulic cylinder to have a high precision; At the same time, the use of hydraulic oil should also keep clean, no impurities; But also to avoid oil leakage in the production process of the hydraulic cylinder.

The two-plate injection molding machine realizes mold locking by pulling four Golin columns by four high-pressure hydraulic cylinders. At a certain moment, the pulling force of the four high-pressure hydraulic cylinders cannot be guaranteed to be completely consistent, which will lead to the slight imbalance of the template during operation.

Three plate injection molding machine

The mold closing device of three-plate injection molding machine mainly includes moving template, static template, crankshaft support plate, crankshaft locking system, hydraulic thimble system, rapid mold moving system and high-pressure hydraulic cylinder opening system (see Figure 3).

As can be seen from the following figure, the main component of the mold locking system of the three-plate injection molding machine is the crankshaft, which is mainly designed according to the lever principle. The mold closing process is: the hydraulic cylinder of mold opening pushes the crankshaft saving arm to drive the moving template forward, while the bending crankshaft working arm extends. When the crankshaft working arm is in parallel position, the mold is locked. The mold opening process is the opposite of the mold closing process.

advantages

Compared with the same tonnage of two plate injection molding machine, the equipment cost is low.

The hydraulic cylinder, joint, valve, servo motor, oil supply pump and other parts in the system are common commodities in the market, and it is convenient to maintain the machine.

disadvantages

It is difficult to change the clamping force on the same injection molding machine. The clamping force of the three-plate injection molding machine is provided by the crankshaft, so the length of the crankshaft and the maximum space between templates should be determined according to the clamping force in the design process of the clamping system. Once the crankshaft length and the maximum spacing between the plates are determined, the clamping force is fixed. If you want to change the clamping force of the same injection molding machine, it is difficult to change the length or structure of the crankshaft.

It is difficult to determine the actual clamping force accurately. At present, there is no good method to accurately measure the actual clamping force of crankshaft clamping mode. It is usually calculated by the pressure and lever principle of the hydraulic cylinder, which often causes a great error between the actual clamping force and the designed clamping force. If the actual clamping force is too small, the product is easy to produce "flying edge" (plastic products have unnecessary edge at the junction, influence

Appearance and quality of the product); If the actual clamping force is larger than the designed clamping force, the mold deformation is often caused. Due to the small deformation, it is difficult for human eyes to detect it, which will accelerate the damage of the mold.

When opening the die, the opening hydraulic cylinder provides a larger opening force. Taking the injection molding machine of about 3 200 t as an example, the opening force provided by the hydraulic cylinder is 200~230t. Therefore, it is required that the machining accuracy of the hydraulic cylinder is higher, and the daily maintenance cost is slightly larger than that of the ordinary hydraulic cylinder.

The development trend

In foreign countries, the injection molding machine above 1 200 t mostly uses two plate injection molding machine. In China, in the early stage, gran, Baoyuan, Haitian, Zhende and Donghua and other manufacturers have produced the two-plate injection molding machine, but because the technology is not quite mature, it is difficult to promote in the market. After more than 20 years of development, two-plate injection molding machine technology gradually mature, especially the recently developed "two-plate and a half" machine (as shown below), successfully solved the problem of template imbalance in the process of operation, gradually accepted by users. At present, the domestic market large tonnage injection molding machine mainly to three plate injection molding machine. Because three-plate injection molding machine technology has been very mature, there is little room for improvement, while two-plate injection molding machine has many superior performance and very large room for improvement, it is expected that two-plate injection molding machine in the domestic injection molding machine market will gradually become a trend.