faq
1, horizontal stripes
(1) the causes of large spacing transverse stripes are extrusion melt pressure instability, quench roll speed or uneven temperature, air knife volume fluctuates greatly 3. the first point is more common. there are many factors that cause the unstable pressure, the main one is line speed too fast, causing the metering pump speed is improved rapidly, but on the other hand, the main extruder screw speed increase is relatively slow, resulting in die materials shortage, pressure instability.encountered such a situation, the best time to extend the line speed, speed stability, transverse stripes disappear. there is a relatively common condition, is the raw material factors. in the conditions of better control, repeated adjustments had no obvious improvement, it is necessary to consider the replacement of raw materials.
(2) small spacing of transverse stripes small spacing transverse stripes are not common in the actual production process, the reasons are 4: the nose angle is not suitable, air knife angle or wind is not suitable, near the nose airstream, quick cold roller speed instability. from these 4 aspects to solve.
2, vertical stripes
in the casting process, extrusion casting sometimes see local, continuous longitudinal stripes at a fixed position. if the casting to produce bopp films, will lead to uneven thickness of lateral film; rolling, cutting film appearance obvious protrusions (crack) or vertical stripes.
eliminate the vertical stripes usually take measures
die 1 selection of reasonable structure, good quality, ensure the lip smooth, without any mechanical damage;
2 strengthen melt filtration;
3 timely removal of debris on the lip, nose to do maintenance work;
4 to improve the uniformity of gas blowing knife;
5 reasonable control of extrusion temperature;
6 adjust the relative position of the head of roller quenching.
3, on both sides of the warp
this phenomenon is mainly caused by the effect is not good, two tablets in the casting process of large temperature difference caused by the. the casting will affect the smoothness of the warp films, pp, casting due to uneven cooling, crystallization, directly affect the film properties of films. the casting edge is usually to cooler side warp, therefore determine the temperature of the cooling water cooling roller surface and the tank height according to the warping of cast pieces in the production process, and then consider the solution.
4, bubble
if the impurities in the melt, the raw material moisture content is too high, the extrusion temperature is too high, the material heating time is too long or the extruder, the filter of air accumulation or degradation occurs, bubbles may cast film. in the normal production process if bubbles appear, to carefully observe the bubble shape, color and so on, analyze the reasons and solve. if the air screw extrusion or replacement of melt filter boot new boot again, there may be air or degradation of extruder or filter, the bubbles will generally cast film. this problem can be solved by fully discharging.
5, irregular edge
casting irregular edge may be due to damage caused by die lip seals at both ends of the edge leakage, may also be blankholding system is not normal, or extrusion melt pressure instability. after investigating the reason to use the corresponding method to solve timely, otherwise easy to cause the transverse pulling clamp.
6, other defects
there will be a casting piece containing crystal material, not melt, coke, crystallinity, gloss and not suitable for adverse sharkskin defects in the casting process. these defects in the more mature technology, high technical level of the production line generally does not appear.
two, the tensile rupture of membranes and solutions
in the production process, material from casting to rolling, the whole process are likely to rupture.usually, according to the position of the broken membrane rupture is divided into horizontal pull before rupture of membrane, membrane rupture, transverse horizontal pull after rupture of membranes.
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