The open mixer, also known as the double roller plastic mixer, is a basic equipment in rubber and plastic machinery. The open mill is mainly used for mixing plastics, feeding the calender and cooperating with the tablet press.

The production of refiners in major industrial countries around the world has already formed a series, with roughly similar specifications, dimensions, and appearance. Since the 1990s, China has mainly improved the degree of mechanization, increased operational measures, labor conditions, and reduced floor space of the open mill.

At present, domestic open refiners have formed a complete series with complete varieties and specifications, which can fully meet the requirements of users in all aspects. The rollers and bearings of the opening mill are equipped with double row self-aligning roller bearings, and all transmission gears are concentrated in a closed box, with a compact structure, high transmission efficiency, and good lubrication conditions. The roller distance adjustment can be monotonic or double adjusted at the same time, making the operation convenient and free.

Structural Principles

Refining is a process that utilizes the effects of high temperature, shearing, and other factors to obtain the plasticity of raw rubber, making it suitable for mixing, rolling, extrusion, and molding processes. It is a major process in rubber processing.

The opening mill generally includes a transmission device, a roller pitch adjustment device, a temperature control device, a feeding system, etc.

The transmission device mainly realizes the movement of two different speed ratios. Implement the squeezing and shearing actions of the rubber material. This is an important mechanical action of the opening mill and also the main control action;

The rolling distance adjustment device mainly realizes the distance between the two roller shafts. Different materials and process requirements have different requirements for roll spacing, requiring the opening mill to flexibly adjust the roll spacing;

The roller shaft of the mixer is hollow and can be filled with steam or water to achieve temperature regulation;

During the refining process, it is necessary to continuously add additives, softeners, etc. to the rubber material, and the injection system is responsible for this function.

The working principle of the opening mill is to use two parallel arranged hollow rollers to rotate relative to each other at different linear speeds. After adding the rubber wrapping roller, there is a certain amount of accumulated rubber above the roller pitch, which is crowded and creates many gaps. The particles of the mixing agent enter the gaps and are wrapped by the rubber, forming the mixing agent clumps. When the rubber material passes through the opening mill roller pitch together, the speed gradient is generated due to the different linear speeds of the opening mill roller, forming shear force, Under the action of shear force, rubber molecular chains are stretched, resulting in elastic deformation. At the same time, the compounding agent blocks are also broken into small blocks under the action of shear force. After the rubber material passes through the roller pitch, due to the widening of the flow channel, the stretched rubber molecular chains return to a curled state, enveloping the broken compounding agent blocks, stabilizing the compounding agent blocks in a broken state, and the compounding agent blocks become smaller, Thus, the compound with even dispersion of the mixture and Dispersity can be prepared.

control function

The opening mill control adopts the CPU module LM3109 of HOLLiAS LM PLC to collect and control various signals, LM3310 to achieve temperature and pressure collection, LM3320 to achieve frequency control of the frequency converter, touch screen for upper computer to set parameters and display data for the opening mill, and various sensors and detection devices to detect various monitoring points of the opening mill.

The control of the opening mill mainly includes the following parts:

1. Transmission and speed ratio control are important mechanical actions of the opening mill. As the speed ratio and roller speed increase, the impact on the refining effect is consistent with the law of reducing roller distance, which will accelerate the dispersion of the mixture. However, it also intensifies the shear of rubber molecular chains, making it easy to over refine, reducing the physical properties of the rubber material, accelerating the temperature rise of the rubber material, and increasing energy consumption; The speed ratio is too small, the compounding agent is not easily dispersed, and the production efficiency is low. The control of speed ratio and transmission by PLC is mainly achieved through frequency converters;

2. The automatic adjustment of roller pitch reduces the roller pitch and increases the shear deformation rate, which is conducive to the dispersion of the compounding agent. However, the chance of rubber molecular chains being sheared and broken also increases, resulting in a decrease in the physical and mechanical properties of the rubber material; The roller pitch is too large, the shear effect is too small, and the compounding agent is not easily dispersed, which brings difficulties to the mixing operation. Therefore, when starting the mixer for mixing, the roller pitch should be appropriate. The PLC calculates the required roller pitch through a pressure sensor installed on the roller shaft, and then automatically adjusts it through an adjustment device;

3. Temperature control requires different opening temperatures for different rubber materials. Set different temperature requirements according to the actual rubber material, and control the steam valve to control the temperature

4. The injection system controls the need for feeding during the opening process, including additives, softeners, antioxidants, etc. The timing, sequence, and quantity of feeding vary depending on the rubber material. The PLC controls the opening time of the injection system to control the sequence of placing different rubber materials and quantities.

After using HOLLiAS LM PLC as the control device for the opening mill, the qualification rate of the product and the operational reliability of the entire equipment have been greatly improved.