Repair methods and normal parking sequence for small extruders

During the operation of a small extruder, the screw and barrel may wear out from time to time. The internal hardness of the screw and barrel of the extruder is better than that of the screw. The waste of extruder screws and barrels is due to the increase in inner diameter caused by time wear. The repair methods for small extruders are as follows:

1, Under normal circumstances, the homogenization section of the plastic extruder screw and barrel will wear out quickly. This section (5 × 17D in length) can be trimmed by boring and equipped with a nitriding alloy steel lining. The inner hole diameter refers to the diameter of the screw, which leaves a normal gap during processing and preparation.

2, The diameter of the barrel increases due to wear. If there is a corresponding nitriding layer, we can directly drill holes in the inner hole of the extruder screw barrel, grind it into a new diameter size, and then prepare new screws according to the diameter.

3, From the beginning, the inner diameter of the plastic extruder screw and barrel is processed and trimmed to cast alloy, with a thickness usually between 1 mm and 2 mm, and then precision machined into some sizes.

Exaggerated here, the two main parts of the screw and barrel are a slender threaded rod and a hole with a relatively small diameter and a long hole. Their processing and heat treatment processes are relatively complex and accurate. They are more difficult. Therefore, from an economic perspective, analyze whether two parts need to be repaired or replaced with new parts after wear and tear. If the cost of patching is still comparable to the cost of replacing new screws, then it is decided to proceed with the repair. This is an accurate choice. The comparison between repair costs and repair costs is only one aspect.

The screw and barrel of the extruder depend on the repair cost and the ratio of the application time of the repaired screw to the cost and application time of the newer screw. Adopting a small ratio plan is economical and a correct choice.

The normal parking sequence for small extruders is:

1, Adjust the screw speed of the feeder to zero and press the feeder stop button.

2, Gradually reduce the speed of the main screw, exhaust the remaining materials in the cylinder, and use washing materials to clean the main engine before stopping. After the materials are basically discharged, stop the plastic main engine, adjust the speed to zero, and press the main motor stop button.

3, Disconnect the main power switch of the electrical instrument operation screen.

4, Clean the die surface of the machine head and the entire surface of the unit.

5, Close all inlet pipe valves.

The daily maintenance of plastic extruders includes:

1, After 500 hours of use, there will be iron filings or other impurities from gear wear in the gearbox, so the gears should be cleaned and the gearbox lubricating oil should be replaced.

2, After a period of use, a comprehensive inspection of the extruder should be conducted to check the tightness of all screws.

3, If there is a sudden power outage during production, the main drive and heating will stop. When power is restored, each section of the material barrel needs to be reheated to the specified temperature and kept warm for a period of time before the extruder can be started.

4, If the full rotation of the instrument and pointer is found, check whether the contact of the thermocouple and other lines is good.

The following is a brief knowledge of small extrusion unit feeding:

The processing method involves dividing the material cylinder into several sections and then connecting each section with flanges or other forms.

Advantages: Simple processing, easy to change the aspect ratio, often used in situations where the screw aspect ratio needs to be changed.

Disadvantages: High precision is required for processing, and due to the large number of segments, it is difficult to determine the coaxiality of each segment. The flange connection destroys the uniformity of the material cylinder heating, increases heat loss, and makes it difficult to set up and maintain the heating and cooling system.

Small extruders - single screws are generally divided into three sections in length, determined by the diameter, pitch, and depth of the screw, with each section accounting for one-third. The thread behind the material mouth is called the conveying section: the material here is required not to be plasticized, but to be preheated and compressed. In the past, the old extrusion theory believed that the material here was loose, but later it was proven that the material here is actually a solid plug, which means that the material here is a solid plug like structure after being compressed. Therefore, as long as the conveying task is completed, its function is fulfilled. The second stage is called the compression stage, where the volume of the screw groove gradually decreases and the temperature reaches the degree of material plasticization. Compression occurs in this stage through the conveying stage three, where it is compressed to one, which is called the compression ratio of the screw -3:1. Some machines also have changes, and the material that has completed plasticization enters the third stage. The third section is the measuring section, where the material is kept at the plasticizing temperature, just like a metering pump that accurately and quantitatively delivers the molten material to the machine head. At this time, the temperature cannot be lower than the plasticizing temperature, usually slightly higher.