Analysis of low melt flow rate

- May 11, 2019-

Flexibility of movement of material rod

The material rod can keep the vertical movement in the inner hole of the material cylinder, depending on the two points of the axis positioning, one is the tolerance fit between the measuring head of the material rod and the inner hole of the material cylinder about 0.075mm, the other is the tolerance fit between the middle part of the material rod and the guide sleeve, so that the material rod can both move up and down freely in the material cylinder, and not skew, keep vertical.And in theory, the longer the life, the smaller the friction coefficient, the more flexible.When operating, the guide sleeve is well fixed, which can effectively prevent the bending deformation of the material rod, which is often neglected by users.

However, users sometimes pay little attention to the flexible movement of the material rod.When using after a period of time, is expected to stem deposits a layer of coking obviously will be thin, even if the user in each time carefully cleaning the material rod, a layer of sediment or slowly to form the (not to mention some of the work of cleaning the users themselves do poorly), and the guide sleeve of the lining is not to clean it, and in this way, use after a period of time, material between the rod and the guide sleeve cooperate will no longer be satisfied, so more and more viscous, but always can't afford to the user's attention.As for the guide sleeve is not properly placed, so as not to play a guiding role and make the piston rod skew, is also a common phenomenon.The result of these failures is a significantly smaller measurement, and users often blame other causes.


2 mouth mold and barrel

According to the operation requirements, the cylinder should be cleaned during each test, and the die should be cleaned at least once a day and before refuelling. However, users usually clean the drum carefully every time and neglect the die. On the one hand, the die is difficult to clean.The inner diameter of the commonly used die is 2.095 0.005mm. The inner diameter of the die directly affects the speed through which the melt flows, and its inner wall is more likely to deposit coking matter. Compared with the small diameter, a thin layer has taken up a considerable proportion, which greatly increases the resistance of the melt and significantly reduces the test value.The inner diameter of the die has been reduced.But we know, in addition to the mouth mold by the knock of external forces, so that the hole deformation, in the normal use of the case of the mouth mold diameter is always larger.


In both cases, which are the most common faults of the instrument, the test value is reduced by more than one time.The author once met with a prestigious unit, which accidentally dropped the mouth mold of an imported instrument and bought a domestically produced mouth mold. At the beginning, all the test data were normal, but later I suddenly found that the data was too small and more and more serious, so I suspected that the mouth mold was bad and asked the author to provide one.Through the author's inspection, the machine material rod is not flexible, the hole in the die is dirty, after cleaning, everything returns to normal.Cleaning method is very simple: hot state according to the conventional cleaning rod, cylinder and die after mouth, separate the rod and the guide sleeve, with the finest of metallographic sandpaper, with oil after the burnish of material of the rod surface sediments, at the same time, furl oil with a piece of sandpaper, plug the entry mode and the guide sleeve hole, gently pull, when can see metal color, can obtain the original flexible motion, test data will be back to normal.

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