The pressure sensor can be installed in the injection molding machine nozzle, hot runner system, cold runner system and mold cavity, it can measure the plastic injection molding machine, mold filling, packing and cooling process from the injection molding machine nozzle to the Plastic pressure somewhere between the mould cavities. This data can be recorded in the monitoring system for real-time adjustment of the moulding pressure and after moulding it is checked or the failures occurring during the production process are eliminated.
It is worth mentioning that this collected pressure data can be a common process parameter for this mold and this material, in other words, this data can be used to guide production on different injection molding machines (using the same mold). Only discuss the pressure sensor installed in the cavity.
Pressure sensor type
At present, there are two types of pressure sensors used in the mold cavity, namely plain and indirect type. The flush-type sensor is inserted into the cavity by drilling a mounting hole behind the cavity, and its top is flush with the surface of the cavity. Qi, its cable is passed through the mold and connected to the interface of the monitoring system on the outer surface of the mold. The advantage of this sensor is that it will not be disturbed by the pressure during demoulding, but it is easily damaged under high temperature conditions, causing Installation is difficult.
Indirect sensors are classified into two types, sliding and button type. They can transfer the pressure of the plastic melt on the ejector or the fixing pin to the sensor on the ejector plate or the moving plate. The sliding sensor is usually installed. On the ejector plate under the existing pusher pin.
When performing high-temperature molding, or when using a low-pressure sensor for a small ejector pin, a sliding sensor is generally mounted on a movable platen of the mold. At this time, the ejector pin operates through the ejector sleeve or uses another. Transition pin. The transition pin has two roles, one is to use the existing ejector, it can make the sliding sensor from the interference of the ejection pressure. The other is that when the production cycle is short, the ejection speed is fast. When it is, it can make the sensor not affected by the rapid acceleration and deceleration of the ejector plate.
The size of the pusher pin on the top of the sliding sensor determines the size of the required sensor. When multiple sensors need to be installed in the cavity, it is best for mold designers to use the same size pins on them to avoid the molder setting up. Error or calibration error. Because the top pin is used to transfer the pressure of the plastic melt to the sensor, different products must use different size pins.
In general, the button sensor should be fixed in a recess in the mold, so that the sensor's installation position must be the most interesting position of the processing staff. To disassemble this sensor, the template must be opened or pre-applied. The structure carries on some special designs.
Depending on the position of the button sensor in the mold, it may be necessary to install a cable hub on the stencil. Compared with the sliding sensor, the button sensor pressure reading is more reliable. This is because the button sensor is always fixed in In the dimples of the mold, unlike the sliding sensor, it is possible to move within the borehole. Therefore, button sensors should be used as much as possible.
Pressure sensor installation position
If the pressure sensor is installed in the correct location, it can provide the molder with the most useful information. With some exceptions, the sensors used for process monitoring should normally be installed in the back third of the cavity. The sensor controlling the molding pressure should be installed in the first third of the cavity. For extremely small products, the pressure sensor is sometimes installed in the flow channel system, but this will make the sensor not monitor the pressure of the gate.
It should be emphasized that when the injection is insufficient, the pressure at the bottom of the cavity is zero, so the sensor at the bottom of the cavity becomes an important means of monitoring the lack of injection material. With the use of digital sensors, each cavity is Sensors can be installed, and the connection from the mold to the injection molding machine requires only a single network cable. In this way, as long as the sensor is installed at the bottom of the mold cavity, and no other process control interface is required, the occurrence of insufficient shot can be eliminated. .
Under the above premise, the mold design and manufacturer must also decide which of the cavity inside the cavity the pressure sensor should be placed on, as well as the location of the outlet of the wire or cable. The design principle is that after the wire or cable is passed out of the mold Can not move freely. The general practice is to fix a connector on the mold base, and then use another cable to connect the mold with the injection molding machine and auxiliary equipment.
The important role of pressure sensor
Moldmakers can use pressure sensors to perform rigorous mold trials on molds to be delivered to improve mold design and processing. The molding process of products can be set up on the basis of the first mold test or the second mold test. And optimization. This optimized process can be directly used in the subsequent trials, thereby reducing the number of trials.
With the completion of the trial, not only did the mold meet the quality requirements, but it also enabled the mold manufacturer to obtain a set of validated process data. These data will be delivered to the molder as part of the mold. The mold maker provides the molder with more than just a set of molds, but a solution that combines the molds with the process parameters suitable for the mold. This scheme has inherent value compared to simply providing molds. The improvement not only greatly reduces the cost of the trial mode, but also shortens the trial time.
In the past, after the moldmakers had been told by their customers that the molds often had problems with poor filling and incorrect critical dimensions, they could not know the status of the plastics in the molds, and they could only guess the causes of the problems based on experience. Not only will it make detours, but sometimes it will not solve the problem completely. Now they can accurately determine the crux of the problem by analyzing information about the state of the plastic in the mold collected by the molder from the pressure sensor. Where
Although not every mold requires a pressure sensor, each mold can benefit from the information provided by the pressure sensor. Therefore, all molders should understand the importance of pressure sensors in optimizing injection molds. Role. Those mold makers who believe that the use of pressure sensors play a key role in making precision molds can enable their customers to produce products that meet quality requirements more quickly, while also promoting their mold design and manufacturing techniques. .