The mechanical principle of the extruder is to add water or appropriate liquid into the raw powder and stir it continuously, and then extrude the well-mixed material from the porous head or metal mesh with high extrusion pressure. owin has been engaged in the plastic extruder industry for more than 20 years. During this period, we found that in the daily processing of raw materials, poor plasticization often occurs in the extruder. Our company summarized some common phenomena about poor plasticization of the extruder based on our own experience.
- Phenomenon: (1) The temperature is too high or the instrument controlling the temperature is out of order, causing the plastic to scorch due to ultra-high temperature. (2) The rubber outlet of the machine head has large smoke, strong pungent smell and crackling sound. (3) Granular scorch appears on the plastic surface. (4) There are continuous air holes at the glue joint.
- Reasons : (1) Plastic scorching caused by high temperature control. (2) The screw has been used for a long time without cleaning and the burnt materials are accumulated and extruded with the plastic. (3) If the heating time is too long, the plastic deposit will be heated for a long time which will cause the plastic to age, deteriorate and scorch. The parking time is too long, and the machine head and screw are not cleaned, resulting in plastic decomposition and scorching. (4) Changing the mold or color for many times, causing the plastic to decompose and burn. (5) The head gland is not pressed tightly and the plastic is aging and decomposing inside. (6) The instrument controlling the temperature is out of order resulting in scorching after ultra-high temperature.
- Methods: (1) Regularly checking whether the heating system is normal. (2) Cleaning the screw or head regularly and thoroughly. (3) Heating up according to the requirements of the process, the heating time should not be too long. If there is a problem with the heating system to find the relevant personnel in time to solve. (4) Changing the mold or color in a timely and clean manner to prevent miscellaneous colors or stored glue from scorching. (5) After adjusting the mold, press the gland of the mold sleeve tightly to prevent the glue from entering. (6) The head and screw should be cleaned up immediately when scorching is found.
Second: poor plasticization
- Phenomenon: (1) The surface of the plastic layer has a frog skin phenomenon. (2) The temperature control is low, the instrument pointer reflects low temperature and the actual measured temperature is also low. (3) The plastic surface is black with small cracks or small particles that are not plasticized well. (4) The plastic glue is not sewn well. There is an obvious mark.
- Reasons: (1) The temperature control is too low or inappropriate (2) There are resin particles in the plastic that are difficult to plasticize. (3) The operation method is improper, the screw and traction speed are too fast and the plastic is not fully plasticized. (4) The mixing of plastics is not uniform during granulation or there is quality problem of plastics itself.
- Methods: (1) According to the process regulations control the temperature. If the temperature is low, properly raise the temperature. (2) The speed of screw and traction shall be properly reduced to increase the heating and plasticizing time of plastics, so as to improve the plasticizing effect of plastics. (3) Using screw cooling water to strengthen the plasticization and tightness of plastics. (4) When selecting the mold, the mold sleeve should be smaller to strengthen the pressure at the rubber outlet.
- Phenomenon: (1) There are small crystal dots and small particles on the surface of the plastic layer, which are distributed around the surface of the plastic layer. (2) The bumps caused by scorching are scorched on the surface of the plastic layer, especially on the surface of the adhesive seam. (3) Impurity bumps, impurities on the plastic surface, and impurities in the knots of slices. (4) The plastic pimples caused by poor plasticization were found to be cooked glue in the pimples after sectioning.
- Reasons: (1) Due to the low temperature control, the plastic is squeezed out of the machine head before it is plasticized. (2) The plastic quality is poor, and there are resins that are difficult to plasticize. These resins are extruded without complete plasticization. (3) When feeding, some impurities are added into the hopper, resulting in impurities bumps. (4) The temperature control is too high, resulting in scorching, which leads to scorching bumps. (5) The molded cover is not pressed tightly, and it is aged and deteriorated after the injection of glue, and there are scorched bumps.
- Methods: (1) The temperature should be appropriately raised for the bumps caused by the plastic itself. (2) During feeding, strictly check whether there are sundries in the plastic and do not add other sundries into the hopper. If impurities are found, immediately clean the machine head and drain the glue in the screw. (3) If the temperature is found to be too high, the temperature should be reduced immediately and properly. If the effect is not good, the machine head and screw should be cleaned immediately to remove scorched substances. (4) In case of resin lumps and poor plasticization lumps, the temperature shall be appropriately adjusted or the speed of screw and traction shall be reduced.
Fourth: plastic layer positive and negative excess
Phenomenon: (1) The speed of screw and traction is unstable and the ammeter or voltmeter swings from side to side, thus affecting the outer diameter of the cable, resulting in the deviation of the plastic layer. (2) The quality of semi-finished products has problems, such as loose wrapping of steel strip or plastic strip, uneven convexity and concavity, or defects such as wrapping, edge and pit of plastic layer. (3) The temperature control is too high, resulting in the reduction of extrusion, so that the sudden thinning of the outer diameter of the cable and the thinning of the plastic layer, forming a negative difference.
Reasons: (1) The wire core or cable core is not round and snake-shaped, and the outer diameter changes too much. (2) Semi-finished products have quality problems, such as poor steel belt joint, loose steel belt sleeve, rolled steel belt edge, loose plastic belt sleeve, too large joint, scattered flowers. (3) During operation, the selection of mold core is too large which causes the plastic layer to deviate from the core due to the pouring of glue. (4) When adjusting the mold, the mold adjusting screw is not tightened which causes the plastic layer to be eccentric. (5) The screw or traction speed is unstable, resulting in out-of-tolerance. (6) The feeding port or filter screen is partially blocked, resulting in a negative difference due to the reduction of glue output.
Method: (1) Measuring the outer diameter of the cable and checking the thickness of the plastic layer frequently. If the outer diameter changes or the plastic layer is uneven, immediately adjust it. (2) The mold shall be selected properly. After the mold is adjusted, the mold adjusting screw shall be tightened and the gland shall be pressed tightly. (3) Paying attention to the screw and traction ammeter and voltmeter. If it is unstable, find electrician and fitter for maintenance in time. (4) Do not add strips or other sundries into the hopper. If found, remove them immediately.
Fifth: the outer diameter of the cable is uneven in thickness and bamboo-shaped
- Phenomenon: (1) The outer diameter of the cable is uneven due to unstable screw or traction. (2) Due to the sudden instability of traction, the plastic forming the cable is in the shape of bamboo-shaped. (3) The mold selection is small, and the outer diameter of semi-finished products changes greatly, resulting in uneven thickness of plastic layer of cable.
- Resons: (1) The speed of retracting and setting out or traction is uneven. (2) The outer diameter of semi-finished products changes greatly and the mold selection is inappropriate. (3) The screw speed is unstable, the main motor speed is uneven, and the belt is too loose or slipping.
- Methods: (1)Regularly checking the speed of the screw, traction, take-up and pay-off to make sure the speed is even (2) The mold should be properly selected to prevent the phenomenon of glue pouring. (3) Regularly checking the operation of machinery and electrical appliances, and immediately find fitters and electricians to repair.