How to clean the extruder screw? How to deal with a sudden power outage?

How to clean the extruder screw? How to deal with a sudden power outage?

For extruders used in the manufacture of thermosetting powder coatings, when changing coating resin types or color types, the machine must be cleaned to prevent interference between powder coating types and ensure the quality of the produced products. When the extruder is not cleaned thoroughly, the most obvious effect is on the color of the powder coating, which can be directly observed. In addition, the previous production of fine art powder coating without leveling agent did not clean the extruder When reproducing high-gloss powder coatings, due to the interference of the previous materials, the coating film of the subsequent products is prone to shrinkage and other disadvantages. Therefore, it is very important to thoroughly clean the machine when changing the type of paint resin and the type of design and color. There are many cleaning methods for the extruder, usually the following can be used:

Resin cleaning method

This method is to clean the machine with resin, such as polyester resin or epoxy resin. This method is generally used in the cleaning of new equipment or after the extruder has been used for a period of time, because part of the material remains on the screw or barrel and gelled, the extrusion speed of the material slows down, and the color difference of the color-changing variety is large. , this method can be used. After cleaning the machine with resin, use the resin for powder coating to be produced, and further clean the machine without adding curing agent or curing resin. When the extrudate is considered clean, it can be formally put into production. If the color difference of changing the powder coating type is small, and the time for thoroughly cleaning the machine is not too long, it is only necessary to clean the machine with the resin that will be used to produce powder coatings. In order to increase the friction of the resin and facilitate cleaning, some fillers can be added for cleaning.

Non-resin cleaning method

This method uses materials such as rice, corn, sawdust, and toilet paper that have certain friction and are easily crushed. When the extruder is heated to the normal extrusion temperature, the friction between these materials and the screw and barrel is used to remove them. Powder coating gel attached to the surface of the screw and barrel. Experience shows that the outer shell of paddy rice has high hardness and great friction, and the effect of cleaning machine is relatively ideal in comparison. After using this method to clean the machine, it is necessary to open the screw barrel to check the cleaning situation. Under normal circumstances, it is necessary to use the powder coating resin to clean the machine according to the above method before the formal product production can be carried out.

Manual cleaning method for disassembling the screw and barrel

This method is to heat the extruder to the working temperature, and manually or automatically push the screw out to remove the easy-to-remove materials while it is hot. After cooling, put it into an organic solvent tank filled with acetone or cyclohexanone and soak it. When the molten deposit attached to the screw swells, manually remove the deposit. The soaking time of the screw depends on the amount of attachment and the thickness of the gel. In order to use less solvent and facilitate the sealing of the container, use a steel pipe or stainless steel pipe slightly thicker than the diameter of the screw rod, and weld the seal at one end to use it as a soaking tank. From the perspective of safety, the container for soaking the screw must be stored in a cool place away from fire and power sources. At the same time, it should be sealed to prevent the solvent from evaporating, and a safety mark should be affixed.

If it is necessary to clean the machine thoroughly, the screw barrel can also be opened while it is hot, and the glue attached to the inner wall of the screw barrel can be removed manually or by solvent wiping.

In order not to damage the surface finish of the screw and barrel, do not beat with hard objects, but use a steel saw blade or steel brush that is softer than the steel of the screw and barrel to remove attachments, so as not to damage the screw and barrel.

Because the thermosetting powder coating in the extruder stays in the extruder for a long time, it is prone to curing reaction and gelation, and becomes the particle on the coating film when the powder coating is applied. If curing occurs, the extruder cannot even be started. . Therefore, before the extruder stops, it is necessary to use pure resin without curing properties, that is, without curing agent or curing resin, to push out the powder coating materials in the extruder to prevent these materials from remaining in the extruder and curing reaction. The standard for the amount of resin added is to ensure that the powder coating material retained inside the screw barrel can be pushed out of the screw barrel to prevent the material from solidifying in the extruder. In terms of the degree of removal of extruded materials, the standard is basically that the color of the original powder coating cannot be seen.

When starting the production with the extruder, use the pre-mixed material to push out the pure resin remaining in the extruder according to strict procedures. After confirming that the pure resin is pushed out clean, the extruded material can be used as a formal product. In order to prevent the pure resin from being brought into the product to cause disadvantages to the coated film product, the pure resin and part of the mixture pushed out during the machine cleaning can be used during pre-mixing; but it cannot be brought into the next step of fine crushing process.

When the extruder suddenly loses power during normal operation, if the material inside the extruder barrel is not discharged in time, some powder coatings will undergo curing reactions and gels, which will even be severely cured after a long time, resulting in failure to start the machine. , It is necessary to heat the material in the extruder barrel with tools such as electric heating or gas welding torch, which is easy to damage the equipment. Therefore, after the power failure, the main switch of the extruder should be turned off immediately, and the extruder motor should be manually rotated with a hand belt or a rocker, and the internal materials of the extruder should be discharged as much as possible to minimize the residue in the screw barrel. The pure resin pushes out part of the remaining powder coating materials. Since only the waste heat of the extruder can be used at this time, the amount of pure resin added should not be too much.

If the main motor of some extruders is directly connected to the gear box, and there is no device to rotate the motor with a rocker, the cooling water in the cooling system can also be increased to cool down the temperature of the barrel and screw of the extruder quickly to prevent extruding The material in the machine reacts chemically.