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Causes of problems with screw barrels and some treatment methods

Update:06-04-2021
Summary:

There are probably several reasons: 1. Too much recycle […]

There are probably several reasons:
1. Too much recycled material is added to the plastic.
2. The screw and barrel are covered with glue-plastic wraps the screw and rotates together.
3. The screw and the barrel are worn out, or the abrasion of the rubber ring causes the plastic to leak and not be transported to the front end of the barrel.
4. Inaccurate temperature control, the temperature of the rear end of the barrel is too high, adjust the temperature setting, and check whether the cooling water circuit is blocked.
5. The feeding port of the barrel is blocked, check whether there is any melted plastic block sticking here.
6. The plastic particles are too large, causing bridging, and the plastic can be crushed again.
7. Too much oil is added to the plastic, causing the screw to slip.
8. If the newly replaced screw does not feed, it may be that the design of the screw and barrel discharge port is inappropriate. For the screw, the screw groove of the feeding section of the screw barrel is too shallow, which causes the screw to not drive the plastic forward when it rotates. The conveying, or the conveying amount of material is very small; for the barrel, it is the design of the discharge port.

Solution:
Because the twin screw is a hungry extrusion, the phenomenon of unfeeding is rarely seen. The following methods are commonly used: set an eccentric feeding port, use a large pitch and deep groove threaded element (SK) in the feeding section, and ensure that the joint cylinder is often cooled. The feeding is smooth, and for some difficult feeding, a forced feeding device can be added. According to your situation, the main reason should be that the pitch is too small, and you should consider changing to larger pitch components.

The repair method of screw barrel is as follows:
1. For the barrel with increased diameter due to wear, if there is a certain nitriding layer, the inner hole of the barrel can be directly bored and ground to a new diameter size, and then a new screw can be prepared according to this diameter.
2. The inner diameter of the barrel is machined and trimmed to recast the alloy, the thickness is between 1~2mm, and then finished to size.
3. Under normal circumstances, the homogenization section of the barrel wears quickly. This section (take 5~7D long) can be trimmed by boring, and then equipped with a nitrided alloy steel bushing. The inner hole diameter refers to the screw diameter and stays Normally fit the clearance, and carry out processing and preparation.
After the screw and barrel are repaired, the plasticization parameters of the whole machine do not need to be modified, and its service life is much longer than the conventional material parts you purchase, bringing greater wealth to the rubber and plastics industry.

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