Reasons And Solutions For PVC Profile Surface Black Line
Date:2022-4-06 Author:hcscrew
On the surface of PVC profiles, there are two types of black lines.
1. Unsure about the position, continuous line, or cloud-like pattern on the surface of PVC profiles.
The main reasons behind this are as follows:
(1) The barrel, the transition body of the conical twin-screw, the porous plate, or the dead corner of the mouth mould caused by the paste materials.
(2) Screw head oil leakages or too much mouth mould oiling induced by.
(3) The PVC profile formula has too many low molecular components. Furthermore, the breakdown does not have to discharge into the vent port.
2. The intermittent line or cloud pattern is always on the lower surface of the PVC profile.
The most common causes of PVC profile black lines are:
(1) an increase in calcium powder in the PVC profile formula.
If the conical twin screw and barrel are in poor condition, the screw barrel should be cleaned. Furthermore, the gap between the screw and barrel would have been re-adjusted. It should be used to replace the new conical twin screw and barrel in extraordinary situations.
(2) a lubrication system imbalance.
You may either switch to later external lubrication (such as PE wax, etc.) or raise the quantity accordingly.
(3) Increase the amount of stabiliser as needed.
This is caused by the anisotropic external rotation of the conical twin-screw extruder. The two screws from the two material strands meet in the transition body portions and meet at the barrel bottom.
Then,
a. If the screw’s fourth and barrel’s fourth sections are both worn.
In this place, the direction of the PVC material travelling would shift. The material will suffer unimaginable heat damage due to the concave and convex parts of the screw barrel. The low molecular components in the PVC profile formula will instantly breakdown. When they meet, grey clouds pattern on the PVC profile’s bottom surface.
b. If there is too much internal slip in the formula.
The material will be shared at an inconsistent rate due to the uneven gap between the two screws. In other words, part of the material is over-plasticized and part is under-plasticized. In the second cross-linking, the material will be segregated, and white clouds will be produced when the transition body parts meet.
As far as possible, we advise avoiding using lipid slip agents. When this happens, you may increase the temperature of the barrel in the fourth section and the transition section of the screw, or you can increase the feeding volume to increase the internal pressure. In this way, black lines on PVC profiles might be reduced.
c. Influence of PVC resin batch (especially calcium carbide production).
This phenomena will be caused by its apparent density and viscosity number, as well as the molecular weight of the high and low. It can be found in both white and grey PVC profiles, although it is more noticeable in the through-body.
3. PVC profile black lines remedies must be considered completely from the formulation of the main causes.
I. The gap between two conical screws is too small.
II. The heating temperature is too low.
III. The host current is excessive.
4. Solutions for such PVC profile black lines include:
a. Replace the old screw with a new one.
b. Mill the combined flow core with crushed material.
c. Mill the screw with crushed materials.
d. Make the screw gap narrower.
e. Does the screw touch the barrel?
f. The current should not be excessively high.
HUACHEN Screw Manufacturing Co., Ltd. is based in the picturesque coastal city of Thousand Islands, Jintang Town, Zhejiang Province, China. It is also China’s largest plastic and rubber screw and barrel manufacturing base.
Our plant concentrates on making HUACHEN brand bimetallic screw barrel, SKD bushing barrels, and various conical twin screw barrel series, and has over 23 years of expertise in plastic extrusion engineering. Plastic extruder spare parts, injection moulding machine replacement parts, and other items are available.
To learn more about the PVC profile conical twin screw barrel, get a quotation or contact HUACHEN Screw Barrel.
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