When producing products, it has been found that the pressing cylinder must be heated or cooled, because the pressing temperature must be within the corresponding temperature range. Next, I will introduce how to use the extruder for heating and cooling.
Heating and heating of extruder barrel:
The purpose of heating the extruder barrel is to provide heat to plasticize the material in the barrel, while cooling the barrel represents the material being kneaded or impacted during plasticization. It is to avoid temperature rise. The screw and barrel heating methods used for silicone resin extruders include resistance heating, electric induction heating and heating medium heating. At present, the most commonly used heating method is the resistance heating method, which uses thermocouples to achieve segmented temperature control and side induction.
1. Resistance heating method.
The current flows through a relatively large resistance wire (resistance wire), which generates heat and conducts it to the material through the barrel wall. The resistance heating method is a commonly used cast aluminum heater. Connect the resistance wire to the metal pipe, fill the insulating pipe with an insulating material such as magnesium oxide powder, and then cast the metal pipe into an aluminum alloy. The cast aluminum heater has a wide range of uses and has the following characteristics: the resistance wire is sealed in a metal tube filled with insulating material, which is resistant to oxidation and has a long service life. The contact area between the aluminum alloy sleeve and the barrel is large, and the heat transfer is good.
2. Electric induction heating method.
The coil is installed on the outer circumference of the barrel, and a magnetic silicon steel plate is installed around the coil. When current flows through the coil, the silicon steel plate and the barrel form a closed magnetic circuit. Due to the induction of AC magnetic flux, the barrel will generate current. The barrel generates heat with a corresponding resistance value. The induction heating method is used, and the barrel screw heats quickly, and the life of the parts is prolonged, but the structure is relatively chaotic.
3. Heating method of heating medium.
Use steam or oil as a heat transfer medium to heat the barrel. Steam must be provided by boiler equipment and pipelines, while oil is heated by resistance heaters. Because of their complexity, cost, and difficulty in temperature control, two types of heating devices are not often used today. However, the temperature of this heating method is soft and uniform, making it particularly suitable for heating heat-sensitive plastics.
Extruder barrel cooling:
1. Under normal circumstances, there is no need to configure a cooling control system on the barrel, and natural cooling can meet the process requirements. However, if the temperature of the water inlet is too high, a "bridge" phenomenon will appear at the water inlet, making water supply difficult or impossible to enter.
2. In order to ensure good supply and solid material transportation conditions, please install a cooling jacket (groove) at the barrel feed port so that the heat from the screw and barrel of the extruder is not transferred to the transmission components and meets the process requirements. Please follow. Adjust the amount of cooling water. In addition, when processing heat-sensitive plastics at higher speeds, the machine must be cooled and the temperature controlled to avoid thermal decomposition of the heat-sensitive plastics.
3. The machine is cooled by blowing air. An electric fan is used to blow air into the part of the extruder screw barrel that needs to be cooled, so that the cold air takes away the heat of the barrel and achieves the purpose of cooling the barrel. The fan cools and cools the barrel, because of its simple structure, low thermal shock, low cost, and easy maintenance and disassembly. Nowadays, this equipment is used more often. The disadvantage is that the barrel cooling and cooling rate are relatively slow.
