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It is inevitable that the common problems and treatment of screw extruder are in the use of mechanical equipment. Therefore, it is very important to find out the problems and find solutions in production. In this paper, we analyze some common problems of screw extruder and discuss the best treatment method.

1、 Common problems and treatment methods of extruder

1. if the material is not eaten, there will be "missing material" and the screw heating phenomenon.

1.1 reasons and methods

1.1.1 the cutter is severely worn. If the clearance between the cutter and the inner wall of the mud cylinder is too large, or the helix angle of the blade is not correct, it should be noted to keep the clearance of 3-5mm when replacing the cutter, and make the blade according to the design angle.

1.1.2 the surface of blade of cutter is too rough and the friction between mud and blade is too large. Therefore, it is not allowed to build up the cutter in groups. After all the changes are completed at one time, it should be replaced step by step and in batches to ensure smooth brick production.

1.1.3 the liner of mud cylinder wall is severely worn. The gap between blade and wall of mud cylinder is too large, which leads to too much rotation movement of mud in the mud tank, and the mud can not be discharged or entered. At this time, a new mud cylinder liner should be replaced, or several ribs parallel or inclined to the axial should be installed on the inner wall of the liner to replace the grinding back and forth grooves, to prevent the invalid rotation of the mud and increase its effective extrusion.

1..1.4 the gap between the mud cutter plate and the cutter is too large to press the mud. At this time, the cutter plate shall be adjusted or welded or renewed to make the clearance between the cutter blade and the blade less than 10 mm.

2. movement and bending of mud bar

2.1 reasons and methods

2.1.1 the mud bar bends to one side. This is due to the machine mouth, core, mud cylinder and spiral cutter center line is not aligned or the roller bed installation tilt, adjustment of the position can be solved.

2.1.2 the mud bar has S-shaped bending. This is due to the insufficient neck compression length, the uneven top of the main and secondary blades of the first helix cutter or the serious wear of the secondary blades of the first winch, which results in the mud material only being pushed out when the main blade is in the round. At this time, the first blade should be removed and replaced, and the auxiliary blade should be welded.

3. overload

3.1 reasons and methods

3.1.1 the mud is too dry. At this time, too dry mud should be pulled out first. It is better to remove the machine mouth and head, start the machine to discharge the dry materials in the mud cylinder, and then install and run, and properly increase the forming water within the specified range.

3.1.2 if the machine stops for a long time, the surplus material in the mud tank becomes dry and hard, which will not only seriously overload, but also fail to start sometimes. In order to prevent this situation, when the machine is shut down for more than 8 hours, do not shut down the water at the machine mouth. For the double stage vacuum extruder, the mud in the upper mud tank shall be properly supplied to keep it wet. If the machine is shut down for more than 2 days, it shall be stopped after the empty mud is opened as much as possible.

3.2 precautions: when overload, the load of motor is high and clutch slips. At this time, it is forbidden to start force to avoid damaging relevant parts, even causing serious accidents such as mud cylinder and head.

4. machine "head swing"

4.1 reasons and methods

4.1.1 "swing head" is a common problem of screw extruder, because the cutter shaft is a long cantilever shaft, and its stability is poor. This situation will be aggravated when the bearing is loose, the main shaft is bent and the auxiliary blade of the first winch is too small. If the mud cylinder is not installed correctly, the clearance between the blade of the spiral cutter and the wall of the mud cylinder is not the same, and the outer edge of the blade of the spiral cutter is seriously out of circle, which causes the spindle to be uneven and the head is swinging, it should be corrected in time, and the anchor bolts and connecting bolts shall be tightened frequently to prevent the end of the swing head.

5. spiral pattern appears after the extrusion of mud strip

5.1 reasons and methods

5.1.1 due to the screw action of cutter, the mud material in the section of mud cylinder is not in the same speed, the mud near the axis moves faster, the mud at the edge moves slowly, and the interface is formed between the mud flow with different speed. Water and air are concentrated in the gap of the surface, and the phenomenon of stratification is produced. The main reasons are high plasticity of mud, too much water in forming, too high spindle speed, mud return phenomenon on the inner wall of mud cylinder. The treatment methods are as follows:

(1) The raw materials of different properties should be mixed evenly, and the water should be bubbled and aged as much as possible, so that the water can fully penetrate into the internal of the raw material particles, so as to reduce the water content on the surface of the original mud.

(2) The formation water should be reduced to increase the friction between the mud layers[ 2] 

2、 Common problems and treatment of finished brick

1. hair crack

There are shallow and thin cracks on the brick surface without nearly straight line, and sometimes the cracks extend to the strip or top surface. Most of these are hidden dangers left in forming, improper firing and improper use of gate, and crack expansion. Therefore, the plastic index of raw materials should be reduced properly, the rotation speed and the helix angle of the screw cutter of brick machine should be adjusted, and the separated spiral cutter should be adopted, and the mud rod should be added to the mud cylinder to reduce the layer of the mud; Or hot water, steam mixing, vacuum mud squeezing and other measures are adopted to reduce the water and gas in the mud to eliminate the stratification; In addition, the gate should be used correctly for baking, and the front gate should be implemented in different stages.

2. burst

When the residual water of brick entering the kiln is too high and the heating speed in the early pre tropical period is more than 25-35 ℃ /h, the steam rapidly vaporized in the billet can not be discharged. The brick is extruded and blasted. The higher the residual water is, the more serious the situation is. Even the crack sound can be heard at the top of the kiln. Especially, the temperature rising is very urgent after squatting fire, and the dead water is not too high. Water vapor often only pushes through the surface of the brick, In addition to controlling the residual water content of the kiln billet is less than 8%, the pre tropical zone should be extended appropriately to make the temperature rise slowly and dehydrate evenly. After squatting fire and the paper burning block of the kiln, the remote gate should be slowly lifted to increase slowly.

3. frost

A layer of white powder is produced on the brick surface, which is the residue of soluble inorganic salts such as magnesium sulfate and sodium sulfate, which is evaporated after water absorption. Because the billet contains a certain amount of crystalline water, it expands after dehydration, so the surface of brick will be cracked when frost is applied. Therefore, the content of magnesium twist in the mud should be controlled to be less than 3%. Strengthen grinding, improve fineness and extend roasting and heat preservation time properly, so as to produce silicate which is insoluble in water, and reduce or eliminate harm.

4. mute brick

Besides mute sound brick caused by under fire, invisible cracks caused by forming and invisible layers left by uneven mixing due to too much impurities in raw soil. The wet billet is too hot in preheating and heating. The brick and brick which have been frosted will form microcracks in pre tropical moisture absorption, which will cause mute sound brick, sudden cold forming microcracks, etc., and may also cause mute sound brick. In addition to strengthening the raw material treatment, removing impurities, mixing well, improving the relevant parameters of the brick machine, we should also pay attention not to burn high temperature billet and frost billet, and ensure good preheating and long enough insulation belt.

5. brick surface scorching and foaming

The reason is that the roasting zone is heated too fast, the surface layer is melted and sintered rapidly, which blocks the pores, and the gas produced by the physical and chemical reactions in the inner part is not accessible and bubbles are formed on the brick surface. Therefore, the heating speed of the baking Belt should be lower than 40-70 ℃ /h, especially when the billet has reached the temperature above 900 ℃, the continuous heating rate is lower than 20 ℃ -30 ℃ /h, so as to prevent the coking and foaming of brick surface.

What is the model mark on the extruder label?

According to the standard gb/t 12783-91 of rubber extruder, the model on the label is as follows:

From left to right: the first plastic machine code is s; The second extruder code is j; The third cell refers to the different structural form codes of extruder. The three cells are combined as follows: the plastic extruder is SJ; The plastic exhaust extruder is SJP; The plastic foam extruder is SJF; The plastic feeding extruder is SJW; The extruder for plastic shoes is sje; The step plastic extruder is SJJ; SJS is used as twin screw plastic extruder; The conical twin screw plastic extruder is sjsf; The multi screw plastic extruder is SJD. The fourth box represents the auxiliary machine, code is f; If it is an extruder, it is coded E. The fifth parameter refers to the diameter and length diameter ratio of screw. The sixth box refers to the design sequence of products, arranged in the order of letters a, B, C, etc., and the design number is not marked for the first time.