Booth extruders are particularly adept at processing heat-sensitive and shear-sensitive materials, and are widely used in the cable and masterbatch industries. Next, we will delve into the potential issues that may arise in the Booth extruder manufacturing process, their causes, and solutions.

Possible reason one: The mixer speed is too high

Solution: Reduce the speed

Precautions:

① It must not affect the feeding performance of the kneader or exceed the drive torque limit.

It may be necessary to reduce production while lowering the speed.

Possible reason two: low yield

Solution: Increase production

Precautions:

① When the screw speed remains unchanged, increasing production helps significantly reduce the material temperature but shortens the material's residence time and decreases thermal stress.

② The driving torque limit must not be exceeded.

Possible Cause Three: Heating Temperature Too High

Solution: Lower the set temperature.

Precautions:

Except for the melting zone, the screw and mixing zone are cooled or the heating set temperature is reduced to remove excess heat energy.

The effectiveness of this measure is constrained by the upper limit of driving power consumption or high material viscosity (generating frictional heat, making it difficult to significantly reduce material viscosity).

③ It is essential to ensure proper wetting and homogeneous dispersion of the filler.

Possible reason four: The screw structure is too "rigid"

Solution: Change the screw structure to a "soft" structure.

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① Use a larger diameter current limiting ring.

② Replace the mixing block with a feeding screw block to shorten the mixing zone.

③ Replace the thread blocks with increased root diameter with thread blocks of the same root diameter.

④ Replace the mixing-mixing compound function element with a mixing/lower shear flight element.

Possible reason five: The back pressure of the mixer is too high

Solution: Increase the speed of the pressure build-up discharge unit (screw or melt pump).

Possible cause one: Incorrect ratio of production output to mixer speed

Solution: Optimize the yield/rotation speed ratio

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Possible reason two: the heating temperature is too low.

Solution: Increase the set temperature

Notes:

① In cases of uneven plasticization, more heating is required in the melting zone and at the screw core axis to compensate for the energy consumed in the melting process.

If the filler added through the downstream feeding port is not mixed evenly, the temperature in the plasticizing zone should be raised. The mixing and homogenizing zone, as well as the screw core, may also require additional heating.

Possible reason three: The feeding ratio of raw materials is inappropriate.

Solution: Adjust the feeding port and feeding ratio.

Precautions:

① At the first feeding port, feeding excessive fillers or viscous additives, lubricants, plasticizers, etc., along with the polymer, can affect uniform plasticization.

In this case, reduce the additive fed at the first port and increase the feeding amount at a downstream port. The liquid additive (plasticizer) can be injected into the Buss kneader at any suitable downstream position.

Possible reason four: The screw structure is too "soft"

Solution: Screw structure becomes "hard"

Precautions:

①Typically, a smaller pressure ring is used in the melting zone to increase back pressure.

In the mixing and homogenization zone, the feeding flights can be replaced with kneading flights. Increased root diameter flights, counter-rotating flights, or a smaller restrictor ring can help increase backpressure. Using flight sections with combined kneading-mixing functions instead of kneading/lower shear flights can help improve fill rate and increase shear effects.

Possible reason one: The speed of the mixer is too low

Solution: Increase the screw rotation speed

Notes:

The possible rotational speed is relatively too low for the given output.

Possible Cause Two: The feed rate is too high.

Solution: Reduce the feed amount.

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It is only adopted when the material still accumulates at the feed port after adjusting all process parameters.

Possible reason three: Inadequate exhaust and dust removal

Solution: Improve exhaust dust removal

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It is essential to equip the feed hopper with an effective dust extraction system for lightweight and easily airborne additives (such as carbon black). The air brought into the feed inlet must be expelled. Moisture must also be removed to prevent it from condensing in the hopper and causing blockages after a period of time, which is why a dust extraction system is needed. Relying solely on the filter bag on the hopper is not sufficient. The natural exhaust outlet also needs to be connected to the vacuum dust extraction system.

Possible reason four: Incorrect temperature control

Solution: Improve Temperature Control

Precautions:

The feeding section needs to be appropriately cooled.

② Reduce the screw heating temperature. Excessive screw temperature can cause the polymer and additives to melt and adhere to the screw, thereby weakening the feeding capacity.

③ The temperature in the melting zone is too low, causing pressure to build up in the feeding zone. ④ The related solution is to increase the temperature in the melting zone to lower the heating temperature of the screw.

Possible reason five: The screw structure is unsuitable

Solution: Incorrect temperature control

Precautions:

① Use a larger diameter flow restrictor to avoid back pressure in the feed zone.

②In the feeding zone, appropriate feed screw blocks need to be used. Selecting more suitable screw blocks can minimize the back pressure generated in the homogenization zone.

Possible reason one: The mixing machine speed is too low.

Solution: Increase the screw rotation speed

Precautions:

This is the simplest method.

Possible reason two: back pressure is too high

Solution: Reduce back pressure

Precautions:

The low discharge unit speed of the flange connection causes back pressure on the bus mixing machine. If necessary, increase the discharge unit speed.

The number or size of the holes in the granulation template is inappropriate, or the filter screen is clogged.

③If the screw barrel is not properly cleaned when changing formulations (from high melting point polymer to low melting point polymer), the unmelted material remaining at the end of the screw can also generate back pressure.

Possible reason three: Too high production output.

Reduce production

Precautions:

If the problem persists after optimizing all other parameters, then it is necessary to reduce the yield.

Possible reason four: The vacuum level is too high

Solution: Reduce the degree of vacuum

Notes:

Excessive vacuum may cause low-viscosity melt and high-filled powder added at the second feed port to be sucked out. Reducing the vacuum can solve these two problems.

Possible reason five: The screw structure is unsuitable

Solution: Adjust the screw structure

Precautions:

An upstream back pressure and subsequent expansion are required at the exhaust port. Back pressure can be generated by using root diameter thickened thread blocks, reflux blocks, or flow restriction rings. For high viscosity and "dry" melts, appropriate types of feeding threads can be used at the exhaust port (such as PVC or highly filled elastomers). For low viscosity melts (such as PE or EVA), it is better to use low shear or standard mixing screws at the exhaust port.

Possible Reason Six: Powder Material Being Sucked Out

Solution: Decelerate and add corresponding nuts

Notes:

To prevent the powder from being sucked out during the exhaust process, reducing the screw speed of the mixer (while monitoring torque and feeding conditions) can increase the fullness upstream of the exhaust port in the mixer barrel. If this still does not solve the problem, a flow restrictor ring or a screw block with an increased root diameter should be used upstream of the exhaust port to compress the melt and prevent the powder from being sucked out through voids in the melt.

Possible cause one: The screw speed is too low.

Increase the screw speed.

Notes:

This is the simplest solution, but it is important to find the cause of the problem.

On one hand, increasing the screw speed reduces the back pressure to some extent, while on the other hand, excessive shear may cause overheating of heat-sensitive products.

Possible reason two: Incorrect temperature control at the feed inlet

Solution: Improve temperature control

Precautions:

The general method is to cool the feed section. For products prone to solidification, the cooling water flow should be moderate to ensure the material does not solidify on the barrel wall.

Possible Reason Three: The heating temperature of the screw and barrel is incorrect.

Solution: Adjust the temperature setting

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The screw temperature must generally be much lower than the theoretical melting point of the material; otherwise, the product will adhere to the screw.

Possible reason four: back pressure is too high

Solution: Check and make corresponding adjustments.

Precautions:

The reason for excessively high back pressure is usually due to incorrect molds or residual material on the filter screen.

If the undispersed filler enters the discharge screw and blocks the die hole, remove and clean the die; flush the discharge screw.

③ Due to the product being plasticized on the screw or due to an unheated die, back pressure often increases during start-up. In cases where the die is heated and the extruder screw has been thoroughly flushed after production interruptions, increasing the screw speed during start-up can resolve this issue.

Possible reason five: The structure of the discharge screw is not suitable.

Solution: Adjust the screw structure

Notes:

Possible reason one: Product solidification

Solution: Preheat the melt pump sufficiently before driving.

Notes:

The heating temperature should be approximately 40°C higher than the theoretical melting point of the product. Ensure that the melt pump is fully heated.

Possible reason two: The product is not plastified.

Solution: Unmelted pellets can block the melt pump. Start the mixer more carefully to ensure uniform melting from the beginning, or remove the melt pump when starting the mixer.

Possible reason three: filler not dispersed

Solution: Remove the body pump and clean the packing.

Precautions: Translate the above content from Chinese to English and output the translation result directly without any explanation.

During driving, undispersed filler entering the melt pump can block the melt pump. In this case, the melt pump must be removed to clean the filler. The melt pump is protected by a torque limit switch or shear pin coupling (depending on the pump size and manufacturer's safety rules) to prevent damage from blockage.

Possible reason four: Product cracking

Solution: If the heated melt pump filled with product is shut down for too long at high temperature, the polymer at the bearings and seals will crack.

Warning:

The polymer-filled melt pump must not be stopped for too long (i.e., several hours) without reducing the heating temperature.

Possible Cause Five: Unsuitable structure of the discharge screw

Solution: Adjust the screw structure

Precautions: