News Time2016.05.24 News Sources Views
Auxiliary equipment
Auxiliary machine of plastic granulator mainly includes pay-off device, straightening device, preheating device, cooling device, traction device, the meter machine, sparks machine and take-up device. Different auxiliary equipment depends on uses of extruder unit. It includes cutter, blow dry device, printing equipment, etc.
Straightening device: eccentricity is one of the most common type in plastic extruding waste. While various types of bending line core is one important reason for the insulation eccentricity. In sheathed extrusion, scratches on the surface of the sheath results from cable bending. Therefore, it is essential to have straightening device in extruder unit. The main types of straightening device are: drum (divided into horizontal and vertical); Pulley (divided into single block and block and tackle); Ground wheel, and a variety of action such as drag, straightening and stable tension; Pressure wheel (divided into horizontal and vertical), etc.
Preheating device
Preheat for insulation extrusion and cable core sheathed extrusion is necessary. Insulation, especially the thin layer of insulation, can not allow the existence of the porosity. Wire core before extruded through high temperature preheating can completely remove water and oil on its surface. For sheathed extrusion, the main function is to dry the cable core, to prevent porosity in the sheath because of the moisture (or winding and the moisture content in the cushion layer). Preheating can also prevent quenching residual stress when extruding plastic. In the process of extruding plastic, preheating can eliminate cold line into the nose by high temperature and form wide temperature difference in gate touching the plastic. It also avoids plastic temperature fluctuations caused by extrusion pressure fluctuations, in order to ensure stable extrusion quantity and the quality of extrusion. Extruder unit adopts electric hotline core preheating device, requiring enough capacity required and the rapid temperature rise to make high efficiency of the line core preheating and core drying. Preheating temperature is restricted by the feeding speed, similar with the nose temperature.
Cooling device
Plastic extrusion cladding after leaving the nose, should immediately be cooled, otherwise it will deform under gravity. Usually adopts water cooling is divided into mild and cold according to the water temperature. Quenching is cold water cooling, good for plastic extrusion cladding to finalize the design. Because of the sudden heat cooling, crystal polymer is easy in extrusion cladding organizat, ion internal residual stress, leading to cracks in the course of using, and general PVC plastic layer adopts rapid cooling. Slow cooling is to reduce the internal stress of products, and different temperature of the water is placed in the cooling water tank, cooling the products gradually to finalize the design. The extrusion of PE, PP adopts a slow cooling including hot water, warm water and cold water.
Control system
Plastic granulator control system includes heating system, cooling system and the process parameters measurement system which is mainly composed of electrical appliances, instruments and actuators (i.e., control panel and work station). Its main role is: control and adjustment of the main auxiliary drive motor. Output should meet the technological requirements of speed and power, and it can coordinate the main auxiliary; Testing and adjusting temperature, pressure and flow of the plastic in the extruder machine; Implementation of the entire unit control or automatic control.
Extruder unit electrical control is roughly divided into drive control and temperature control, to control the extrusion process including temperature, pressure, screw revolution, screw cooling, barrel cooling, products cooling and diameter. It also controls drawing speed, neat row line and ensure the constant tension of line plate from empty plate to full one.
1.The temperature control of the extruding machine mainframe
Wire and cable insulation and sheath of plastics extrusion are based on the characteristics of thermoplastic deformation to make them viscous flow. Except for screw and barrel external heating, the plastic is melt and extruded. Temperature requirements of the host should be considered from overall. Therefore, it should not only have the heater heating on and off, but have the screw of cooling the heat. And the machine requires correct and reasonable method determination the location of the measuring element thermocouple and installation method. From the temperature control meter, we can read the actual temperature of the host's components. And require the precision of temperature control instrument and system cooperate well, the whole host fluctuations in temperature control system stability reached the requirements of all kinds of plastic extrusion temperature.
2. Extruding machine pressure control
In order to reflect the extrusion of the nose, we should detect the head pressure of extrusion, because domestic squeeze extruding machine lacks head pressure sensor. It is generally measurement of alternative head pressure after the screw extrusion force; screw load table (ammeter or a voltmeter) can correctly reflect the size of the extrusion pressure. Extrusion pressure fluctuation also is one of the important factors of instability caused by extrusion quality, extrusion pressure fluctuations and the use of the extrusion temperature. Cooling device is closely related to factors such as the length of the continuous operation time. The extruding machine pressure control can quickly ruled out abnormal phenomenon. Production should be stopped decisively , which not only can avoid the waste, but can prevent accident. By measuring the pressure gauge reading, we can know plastic extrusion stress, generally using thrust limit alarm control.
3. The screw rotation speed control
The adjustment and stability of screw speed is one of requirements in main engine rotation. The screw rotation speed directly determines the quantity of glue and the extruding speed. The normal production always requires the highest rotational speed and high yield as much as possible. The speed range is bigger than the screw rotation speed extruding machine from the beginning. And demand in stability of the speed is high, because the rotation speed fluctuation will lead to the fluctuation of extrusion quality.Then traction linear speed does not change, which can cause the change of the cable diameter. Large fluctuation in the same way as traction device wire speed, which can cause the change of the cable diameter. Screw and traction linear velocity can be reflected on the corresponding instrument. We should closely observe, when it is squeezed, to ensure good quality and high yield.
4. Diameter control
As mentioned above, to guarantee the products size of cable diameter, in addition to the required control line core (core) size tolerance, the extrusion temperature, screw speed and traction device linear velocity should be controlled. And outer diameter measuring control comprehensively reflects the control precision and level. In extruder unit equipment, high speed extrusion production line, in particular, should be equipped with online diameter detector, testing the cable outer diameter at any time. It is useful to the error signal feedback to adjust traction or screw speed and out-of-tolerance correct diameter.
⒌ Winding tension control
In order to ensure speed take-up of different wire , from empty plate to full one, this requires constant tension, receives wiring device and has storage line tension adjustment mechanism, considering constant linear velocity and constant tension on electric system of winding and so on.
6. Electrical automation control of the machine
It is requirement that the machine needs to realize the high speed extrusion line it mainly includes start temperature interlock, working pressure protection and interlock, out of the proportion of two parts, traction drive synchronous control, take-up and traction synchronous control and outside diameter on-line detection and feedback control under the requirements of the various components of the single machine and control the machine track.
