Twin screw extruder is modified plastics manufacturers of equipment used, the following describes some tips can be improved twin screw extruder performance, including equipment modification, and maintenance practices three aspects.

Equipment modification

1, between the flange section and the second section of the feed plus insulation gasket

Twin screw extruder feeding zone mostly water-cooled barrel and locked together with the cylinder flange and the second section (heat), heat may be continuously transferred from the high temperature cylinder to the cold cylinder. Leading to the second paragraph of the barrel can not maintain adequate temperature. Typically, the operator set temperature 180 ℃ in the second paragraph of the cylinder, but due to the heat loss of the feed section, the actual stabilizer usually does not exceed 135 ℃.

The simplest solution is to feed zone between the cylinder and the second section flange, plus 1 to 2 insulating spacer thickness of 1 mm, and a heat insulating gasket replacement years, since the heat insulation pad tendency to aging and degradation sheet has shrunken.

2, the cooling system into the twin screw extruder high-pressure cooling system

As you know, the water pump in the turbulent than laminar flow can lead to more wall heat transfer. High voltage transmission in a high degree of turbulence in the transverse momentum transfer, which break up the boundary layer. The results of strenuous exercise causes a large amount of fluid heat exchange between the fluid and the tube wall.

Twin screw extruder cooling system generally provides a pressure of 20 ~ 60PSI. In order to achieve turbulent flow, preferably up to 120PSI of pressure. Almost all of the twin screw extruder cooling system components (valves and hoses) to be upgraded to 150PSI, to meet the safety factor of 120PSI. After the transformation is complete the cooling system may be discharged in time a lot of heat during processing.
3, using a suitable amount of increase feed conversion

The filler side feeder is typically fed into a twin screw extruder. Many processors need to do a high filler loading, and these fillers tend to have very low bulk density. The final filling amount subject to the following factors:

(1) the volume of the feed side feeder of the twin screw extruder and the ability to eat the main screw feed capability. Side feeding capacity depends on the volume and the free volume of the main feeder screw the screw, and a rotational speed of the two screws.

If a material in the test may not be the resistance of the main screw feed flows to the storage drum, the feed rate can reach this material very well. If the side next to the main screw feeder directly connected, the amount of adjuvant materials can accept the screw will be limited. Thus, the host preferably has a screw thread pitch of the long elements, 2D ~ 4D extending in the longitudinal side feeder downstream. This will allow rapid melt through a side feeder, to maximize the filler by the main screw eat. If the host-side screw design causing any accumulation of material fed into feed, the feed would severely limit the amount of filler.

(2) allow exhaust gas discharged from the capacity of the twin screw extruder . Purpose of the vent is to allow air to escape easily, but also does not significantly protect the filler from escaping exhaust port. It is preferably disposed on the upstream side of the exhaust gas feed opening facing upwardly open exhaust port. Sometimes, at the upper side of the feeder of a small open exhaust slit half.

(3) There are other factors to consider:

① blanking height of the feeder

Ideally, feed screw mounted near as possible to the top of the side feeder, to reduce the height of the blanking. If a fluffy material flowing from the air, then it may become filled with air, so that it greatly reduced bulk density after the fall.
 

② stirring type feeder

To make sure filler feeding machine without an agitator fluidized filler. Many manufacturers have designed special blender blender for filler feeding. Stocker will introduce air into the extruder together with the filler. A open top hopper chute helps to exhaust. If your chute feed hopper and a solid lid with a pipe, and a flexible connection with the feeder, then the need to design a vent.
 

③ hopper chute to be grounded, antistatic

Since some of the material powder due to static friction in the hanging wall of the hopper, resulting in a powder of the cake. A simple solution is to hopper chute is grounded.
 

④ air blaster

If the cake is persistent, often require some special way. You can use hopper vibrator, but it accounts for space, also need to install. An alternative is to install a device with the air blast nozzle, installed in the proper position on the chute, the cake before it is punctured grow.

Equipment maintenance

1, cooling water with an acid rinse

Water-cooled twin screw extruder barrel is actually a heat exchanger like all the same, fouling easily deteriorated waterways. Many operators noticed a new extrusion machine cooling performance better than using three or four years a lot of good extruder. A layer of old machines scale is deposited in the surface of the watercourse, it affects the heat transfer efficiency. Using a certain concentration of acid washing to clean out scale can barrel, the barrel to maintain a good heat transfer.

2, using the synthetic gear oil

Gearbox is the heart of a twin screw extruder. So we want to prevent gearbox problems, the use of synthetic gear oil can better protect gear.

Anxiety of synthetic gear oil:

(1) more slippery, resulting in less friction;

(2) gears, bearings and seals more durable;

(3) a lower gear operating temperature, quieter;

(4) synthetic oils are not lost because of machine shear viscosity;

(5) it maintains a high viscosity at high temperatures.

3, frequent cleaning machine

Purpose is to remove residual cleaning machine in the twin screw extruder and the die materials, which avoids the time-consuming cleaning disassemble. Cleaner material often divided into two categories: chemical cleaning agent, detergent and mechanical friction. Many chemical cleaning agents and friction functions simultaneously. The reaction will occur and the chemical cleaning agent away from the machine surface of the plastic residue.

Principle of mechanical friction from the metal surface is cleaned and washed away the residual friction material, the friction and shearing manner. Processors to find the appropriate cleaning materials and methods through several tests before. There is no cleaning material for all materials cleaning effect. Processors need cheap and effective cleaning material. For example, in the Midwestern United States corn many operators as a cleaning machine materia, because it is readily available and has a good cleaning effect on the twin screw extruder.

Described below are two more effective cleaning agent for twin screw extruder:

(1) 50% HDPE + 50% celite.

(2) HDPE + water + cleanser. The HDPE was added at a normal speed of the screw at a melt temperature. The cleanser with water in the bucket is stirred into a slurry, the slurry was added slowly to the main feed port. Because these slurries foaming impact, friction, washing screw.

Practices

1, the right switch Color and material

When use the twin screw extruder,people always want to engage in extrusion machine longer bloom time. But in reality, due to customer demand, we often need to constantly switch to produce 80kg product A, then reproduction 200kg of product B, and so on.

Batch (1) the product should correspond to the size of the twin screw extruder. This seems self-evident, but many processors scheduling unplanned, with 75 machines produce 500 pounds list, resulting in 300 pounds of waste.

(2) the production of each product to write clean machine or disassemble the program, which helps operators plan time and eliminate generated debate about how much they head material.

(3) assist the operator, the cleaning operation paraphernalia around the extruder, if frequent refueling, then engage in a round table in the extruder, things need to be ready.

(4) The raw materials and finished products into and out of the flow field of the order of operation. Arrangements to enable the operator to spend less energy on moving vehicles.

(5) under a clear product requirements for cleanliness of the machine. If you know where the next product called for a thorough manual clean machine, then do not waste time and materials to fool Cleaner.

(6) if possible, in order to reduce the cleaning twin screw extruder scheduling. This means that light from dark to do. On the contrary, many times you have to disassemble.

2, the right way to twin screw extruder power outages

Common mode of operation:

The operator morning habit to put twin screw extruder factory open, but other things get busy. The extruder was heated to a full-scale machine idle for several hours. Doing so will allow the polymer to adhere to the screw and barrel, and then these materials will continue to degrade the polymer and carbonization. Cleaner these materials can not be removed, once the machine is worse production of products, from the black point is periodically run out of the screw and the barrel, product contamination, due to customer complaints.

Right boot method:

Good plan when you really want to operate the twin screw extruder, and then begin heating, only temperature reaches a predetermined value, then cylinder filling material.

Correct shutdown method:

Prior to shutdown, an inert polymer filled maximize an twin screw extruder (e.g., HDPE) to seal the gap of the machine. HDPE off oxygen, the metal surface coating, which greatly reduces the formation of carbon oxides. After the extruder is “sealed”, quenching is preferably an extruder, rather than in the cold air for 18 hours. The so-called quenching, that is, all temperatures are set to zero, all the cooling water valve is opened. Open cooling water pumps, cooling water through all parts of the cylinder, rapid cooling. The rapid cooling to avoid polymer degradation and charring.

- —- From ‘engineering applications’