What Are The Commonly Used Products For The Level Measurement Of The Pre-expansion Machine?

The pre-expansion machine is the core equipment in the manufacturing process of foam plastic products, and it is used for the early pre-expansion of expandable polystyrene EPS and polypropylene EPP foam plastic products.
The particles foamed by the pre-expansion machine will be discharged to the fluidized bed after reaching a predetermined density, and will be matured under normal pressure, then transported to the silo, and supplied to the molding machine to make various shapes of foam packaging products (such as bicycle helmets) , car cushions, slippers, shockproof materials, sound insulation materials, etc.) and foam plastic sheets of different specifications.
The pre-expansion machine is mainly composed of feeding device, stirring device, heating device, conveying device, material level controller and so on. The raw material particles are sent to the pre-expanding machine through the feeding device such as a reducer and a screw feeder, and are pre-expanded by steam heating. The volume of the heated raw material particles increases. When the pre-expanded particles reach a certain density, the high-level material level The switch acts as an alarm, the conveying device is turned on, and the pre-released particles are transported to the fluidized bed. When all the plastic particles are discharged, a new production cycle is started through program control.

The material level control of the pre-expansion machine is an extremely important link in the whole pre-expansion process. If the material level control is not accurate, problems such as density deviation of foamed particles, particle agglomeration, excessive moisture, particle shrinkage, and unstable magnification will occur. Seriously inaccurate position measurement will lead to unqualified materials in this batch, and the pre-release machine will have to be shut down for cleaning, seriously affecting production efficiency. Due to the importance of the pre-expanding machine and the seriousness of the consequences of inaccurate material level measurement, the material level switch of the pre-expanding machine has been monopolized by imported products for a long time in the past. During the measurement process, the difficulties in the level measurement of the pre-expansion machine mainly include the following points:
1. The density of the medium is ultra-low, as low as 8g/L, and it is difficult to accurately detect the general material level switch;
2. The material particles themselves have a certain viscosity, which is prone to material hanging problems.
At present, what products are usually used for the material level control of the pre-expanding machine? The more commonly used instruments are as follows:
1. Photoelectric switch. It uses the occlusion or reflection of the light beam by the detected object, and the synchronous circuit is connected to the circuit to detect the presence or absence of the object. The photoelectric switch is cheap, and the actual use effect is not ideal. However, in order to save costs, many manufacturers still choose to use photoelectric switches.
2. Vibrator material level switch. It is composed of a sensor and a controller. Although the quality is good, the price is very high, so many manufacturers will not use this product.