Extruder Feeding Equipment

In order to improve the feeding efficiency of the extruder, mechanical devices are usually used for auxiliary feeding. Commonly used auxiliary feeding methods include screw feeding, stirring feeding, forced pressing, and pellet feeding.

Stir Feeding

The stirring feed is suitable for crushing materials. Such as woven bag waste silk and film crushed material that have been cleaned.

PP woven bag crushed material size≤40×40mm;

film crushed material size≤40×40mm;

XPS, EPS crushed material size≤30×30×30mm;

Bulk density≤150kg/m3; moisture content≤5%; suitable output: 250 -500kg/h.

Force Feeding

Working principle:

The crushed material is sent to the storage bin through the air conveying device, and there is a stirring device in the storage bin to stir the material to prevent the material from bridging. Through the screw conveyor on the storage bin, the material is controllably transported to the forced pressing bin, and then the material is sent to the extruder screw through the forced pressing screw.

Force feeding is suitable for crushed material. Such as woven bag waste silk and film crushed material that have been cleaned.

PP woven bag waste silk crushed material (clean); length≤30mm;

PP woven bag crushed material (clean)≤20×20mm;

Film crushed material (clean)≤20×20mm;

XPS, EPS crushed material (clean)≤20×20×20mm;

Bulk density≤150kg/m3; moisture content≤5%; suitable output: 250-500kg/h

Pellet feeding

Working principle:

Effective combination of cutting compactor and extruder. After the conveyed material enters the cutting and compacting machine, the functions of crushing, mixing, drying and agglomeration are completed in the cutting and compacting bin, and the agglomerated material is thrown into the extruder screw by high-speed centrifugal force.

Pellet feeding is suitable for raw materials: PE, CPP, BOPP, OPP film; stretch film.

Side Feeding

Working principle:

In the hinged bin for preventing the film from wrapping around, the plastic sheets are kept in motion by the rotation of the rotor to prevent the sheets from being entangled with each other and hinged together to ensure fluidity. In the transition area between the sheet conveyor and the extruder input, the feed screw acts like a feeder. The flakes are continuously and smoothly transported from the large feed screw into the extruder. This arrangement can speed up the processing of sheets of different sizes. As the plastic sheet enters the extruder inlet, the pressure on it increases steadily to achieve high output rates.

Material properties that affect feeding performance:

Free flow:

Plastic pellets are generally free-flowing materials that typically do not require special design or additional flow enhancement when fed by gravity.

Adhesive:

Some materials like to stick to other materials, and among them, pigments are known to stick to almost all types of contact surfaces. To prevent these materials from accumulating on the screws and pipes, they need to be cleaned frequently. When pigment is present, try to avoid feeders with internal agitation systems.

Viscosity:

Some materials tend to snowball and require flow aids such as internal agitation, air sweeping, or through an air cushion to create movement and external vibration to break up clumps. In such cases, adding a cross line at the end of the feed tube can help the material enter the thread of the feed screw better.

Inflatable/Inflatable:

Materials with these properties behave like fluids when inflated, and if the screw is not designed correctly, these materials can easily flush out of the feed screw. Therefore, such materials often require a feed screw with a central rod. The application engineer recommends that when using such materials, multiple smaller feeds can be made instead of one larger feed.

Hygroscopicity:

Materials with this property easily retain moisture. Customers often report that material is left in the feeder and found to have solidified the next day. This is because the material absorbs moisture from the environment. Such problems can be effectively avoided by placing the material in clean, dry air or N2.

Pressure sensitive:

These materials are easy to pile up in a large-capacity extension hopper, and smaller refills will give better results. Also, if using a feeder that agitates an elastic-walled hopper with external paddles, pay close attention to the frequency level at which the paddles agitate the hopper walls, as higher frequencies of agitation or vibration often cause these materials to pile up.

Low Melt Temperature:

Such materials tend to decompose, melt or coke when subjected to excessive friction or energy. Applications engineers recommend using a larger diameter feed screw and turning at a lower RPM when processing these materials, rather than a smaller diameter feed screw running at a higher RPM.