Tape Measure is a commonly used tool in daily life. What you often see is the Steel Tape Measure, which is a commonly used tool in construction and decoration, and it is also one of the necessary tools for the family. Divided into fiber tape measure, tape measure, waist circumference and so on. Luban ruler, Feng Shui ruler and Wen Gong ruler are also Steel Tape measures.
Henan liangjin tools co.,Ltd founded
1999, is a modern chemical measuring tool manufacturer integrating
scientific research, development, production and export sales. Abs Plastic Tape Measure,Plastic Coated Tape Measure,Plastic Tape Measure,Tape Measure Scale Henan Liangjin Tools Co.,Ltd , https://www.liangjintools.com
Common quality defects and treatment methods in extrusion process
Common quality defects and treatment methods in the extrusion process are as follows:
1. Plastic scorch
Plastic scorch is a common quality defect in the extrusion process of plastics. Its main performance is: the temperature is super high; the die has a large amount of smoke, strong irritating smell, and there is a cracking sound when it is severe; the extruded plastic layer has coke particles; There are continuous bubbles at the seams; the main reasons are:
1) The temperature control is too high to reach the thermal degradation temperature of the plastic;
2) The screw has not been cleaned for a long time, and the accumulated burnt material is extruded with the molten plastic;
3) Heating or downtime is too long, so that the plastic in the barrel is decomposed by heat for a long time;
4) The temperature control instrument is out of control or misaligned, causing pyrolysis;
5) The extruder cooling system is not opened, causing the material to shear friction and overheat.
Therefore, during the extrusion process, it should be strengthened to check whether the heating and cooling system work normally; the setting of the extrusion temperature should be determined according to the process requirements and the rotation speed of the screw; reasonable control of the temperature plus time, regular cleaning of the extrusion system.
2, poor plasticization of the extrudate
The main plastic deformation is mainly as follows: the extrusion layer has a suede-like shape; the plastic surface is black, dull, and has small cracks; the extrusion layer has obvious seams at the glue joint. The main reasons for this are:
1) The temperature control is too low, especially the nose part;
2) Other plastic particles of different properties are mixed in the insulating or sheathing material;
3) The screw is too fast to plastic, and the plastic is not completely plasticized;
4) There are quality problems in the plastic itself.
For the above reasons, attention should be paid to the rationality of extrusion temperature control; the quality of the materials to be used should be confirmed; the extrusion speed should not be pursued blindly; the storage of raw materials should be strengthened, especially in the plastic drying process; To enhance extrusion pressure and screw backflow.
3. There are pores or bubbles in the section of the extrusion layer.
The main reasons are:
1) The temperature control is too high (especially the feed section);
2) The plastic is damp and has moisture;
3) Parking for a long time, the plastic is not excluded;
4) The natural environment has high humidity;
5) The water or vapor content in the core is too high.
For the above reasons, the temperature of each section of the screw should be reasonably controlled; the materials used should be pre-dried in advance; the requirements of strict process operation should be improved, and the ability to judge the plasticization degree of plastics should be improved; attention should be paid to the production environment and storage conditions of materials.
4, the size of the package is unqualified
The main performance is eccentricity, the thickness of the sheath or the outer diameter is out of tolerance; the main reasons for its formation are:
1) Extrusion and traction speed are unstable;
2) The outer diameter of the cable core changes too much;
3) The extrusion temperature is too high to cause a decrease in the amount of extrusion;
4) too much impurities in the plastic are blocked in the filter to reduce the plastic flow rate;
5) The tension of the retracting line is unstable;
6) The core selection is too large (extrusion type) or the length of the core carrier area is too short and the core is eccentric;
7) The mode spacing is not suitable;
8) The temperature of the extruder head is not uniform;
9) The concentricity of the extrusion die is not adjusted well;
10) The inlet temperature is too high to make feeding difficult to affect the flow.
For the above reasons, the outer diameter of the sheath should be measured frequently; the extrusion die should be properly selected and adjusted; the tension change of the retractable wire should be adjusted in time; the temperature control should be consistent with the specified requirements;
5, the longitudinal bonding tape bond strength is unqualified
The main reasons are:
1) the extrudate temperature is too low;
2) excessive filling of the grease;
3) The production line is too fast, so that the jacket is rapidly cooled;
4) The temperature of the hot water tank is too low and close to the die;
5) The stretching ratio of the mold is too small, or the mold is unreasonable, so that it forms a loose bag;
6) The longitudinal melting zone composite film has too high a melting point.
According to the above reasons, attention should be paid to the mold matching requirements, if necessary, according to the core adjustment; the jacket should not be cooled rapidly to improve the bonding ability; the jacket setting temperature should not be increased to excessively reduce the head temperature; The amount, in order to use a finger to touch the core can scrape a thin layer as well.
6, the appearance of the package is unqualified
The unqualified appearance of the extrusion package is mainly caused by scratches on the surface of the extrusion layer; there are trachoma or microcracks on the rough; any defects caused by plasticization. The main reasons are:
1) The selection of the extrusion die set is unreasonable. Too small to cause a hemp pattern; too large to cause disjointed or squeezed loose;
2) Impurities in the extrusion die sleeve get stuck on the surface of the scratched jacket.
3) The heating temperature of the extruder head is too high to cause roughness, or the temperature is too low to cause microcracks;
4) There is damage to the sizing area of ​​the mold sleeve;
5) The sheath is scratched in the sink;
Defects can be excluded or prevented in production for the above reasons.