RU2840751C1 - Filament production line - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to processing of polymers, particularly, to extrusion of threads from synthetic stock (carbon-filled polyether ether ketone) with preset characteristics. Line for production of filament is equipped with additional high-temperature drying module installed before drying bin and connected to it. Drying bin is connected to extruder included in the line. Reinforced auger pair with increased heat resistance is installed in the extruder, which is actuated by the engine for the auger rotation. Filament cooling module is two-component, with air-vacuum cooling module and two water cooling baths. Line is equipped with an ionisation module and an additional module for high-temperature air drying of the filament. Ionisation module is installed after the pulling module. Additional module of air high-temperature drying of finished filament is installed after winding module.

EFFECT: high quality of the obtained filament, fewer defects, high strength, removal of electrostatics from the filament, and ionisation of the filament.

1 cl, 1 dwg

Description

Field of technology

The invention relates to equipment for processing polymers, in particular to equipment for producing from polymers by extrusion a thread from synthetic raw material (carbon-filled polyetheretherketone) with predetermined characteristics.

Prior art

Today, there are numerous methods of 3D printing, the main ones being selective laser sintering (SLS), stereolithography (SLA), inkjet and extrusion printing or fused deposition manufacturing (FDM). The most common method of 3D printing is FDM technology. Thermoplastic polymers from a number of engineering plastics such as:

acrylic nitrobutadiene styrene (ABS),

polylactide (PLA),

polyetheretherketone (PEEK),

polysulfone (PSU),

polyethylene (PE).

Polyacetal, polybutylene terephthalate, polyamide, polycarbonate and other engineering plastics are considered to be in high demand.

A 3D printing extruder for pellets is known, which may include a pellet hopper, a pellet loading hopper, a short feed screw, a radiator, one or more heating elements, a barrel, a melt pump and a nozzle. One or more motors may be provided (see international application WO 2022146864, IPC B29C 48/37; B29C 48/395; B29C 64/209; B33Y 30/00, 2022).

However, this extruder cannot be used to produce carbon-filled polyetheretherketone (PEEK CF-5) filament.

An extruder for additive printing with binders is known. The extruder consists of a vertically positioned housing in which a screw is installed. The housing has an outlet. A matrix plate is fixed to one end of the housing on the outlet side. A rotary sleeve is installed on the other end of the housing. An annular heat-reflecting screen is installed on the housing on the outlet side, for example, by welding. A heating element is installed inside the annular heat-reflecting screen, for example, using high-temperature glue (see Russian patent 199459, IPC B29C 48/78 (2019.01), 2020).

However, this extruder cannot be used to produce carbon-filled polyetheretherketone (PEEK CF-5) filament.

Various extrusion lines are known for producing thread from synthetic raw materials.

A universal extrusion line for the production of filament for 3D printers is known. The line is equipped with a compensator with a winding capacity of up to 140 m, which allows you to replace wound spools of 0.5-5 kg without interrupting work. The 6-meter-long cooling bath consists of three sections. The first section allows you to cool or heat water to 80 ° C. The second allows you to cool or heat water to a temperature of 50 ° C. The third section is only cooled.

The line is controlled by a PLC panel with automatic operation capability and is equipped with a three-axis filament profile measurement that automatically adjusts the filament diameter within the required tolerances.

The extrusion line consists of:

1. single screw extruder bocomatic,

2. cooling baths, filament drying,

3. drainage devices,

4. triaxial measurement of the filament profile,

5. compensator,

6. Winding devices with quick-release reel mount.

Filament extrusion line (boco-ekstrudery.ru)

The compact line is known for the production of filament for 3D printing for experimental purposes or for small-scale production.

Line equipment:

- Single screw extruder LE20-30/C, 20 mm, 30 L/D,

- Filament extrusion die,

- Stainless steel cooling and calibration bath with water heater and 1.2 meters long,

- Compact winding system with filament pulling,

- Systems for measuring and controlling the filament diameter with feedback from the drawing system.

The main component of the compact line is a single-screw extruder. The screw is driven by an AC electric motor. Its rotation speed can be adjusted steplessly from 0 to 200 rpm using a programmable frequency converter.

The extruder screw is made of wear-resistant tool steel and has a configuration that ensures the highest quality mixing or grinding of the mixture components.

The extruder barrel has several heating zones. Each of them is equipped with electric belt heaters and an air cooling system. The temperature of the heated zones can be adjusted and controlled individually using digital programmable regulators with digital indicators.

The height position of the extruder cylinder can be changed using a special adjustment mechanism. It allows you to adjust the position of the cylinder outlet and align them with the die holes.

The control panel is located on a rotating bracket. It displays information about the heating temperature of each cylinder zone, the rotation speed of the auger, and the power consumption of the electric motor.

The extruder can be additionally equipped with melt pressure and temperature sensors, a feedback system for automatic adjustment of the screw rotation speed and maintaining a constant pressure of the melt supplied to the die, a filter replacement mechanism, and a computer control system for full automation of polymer processing processes.

The cooling and calibration bath is 1.2 metres long. Each section of the bath has stainless steel covers to prevent contamination. Calibration tubes are fitted at the inlet and outlet of the bath, including Venturi-type suction devices for drying at the end of the bath.

The line includes a winding station with an integrated filament pulling system. It ensures constant tension, uniform winding of strands onto reels and their cutting.

To control the geometric parameters of the strands, the lines are equipped with a high-precision laser measurement system (https://sntf.ru/catalog/pererabotka_polimerov/proizvodstvo_streng_dlya_3Dprinterov/kompaktnaya-liniya-proizvodstva-filamenta-dlya-3d-pechati-/ (see also Full description)).

The LIDER-3D plastic extrusion line for 3D printing is well-known - professional equipment for the production of plastic thread.

The equipment includes several modules that provide a complete and continuous production cycle for creating plastic filaments for 3D printers. The modular design consists of:

• Single screw extruder;

• High-precision extrusion mold;

• Stainless steel heating tank with automatic circulation;

• Cooling tank;

• Drying devices;

• Storage devices;

• Laser controller;

• Traction device;

• Automatic winding machine.

The extrusion line is suitable for the production of plastic with a diameter of 1.75 and 3 mm, as well as 2.0 and 2.85 mm. Equipped with sensors at each section of the production line, for example, a material counter and a tension controller, the equipment allows you to control the quality of the filament at all stages of production (https://lider-3d.ru/catalog/dopolnitelnoe_oborudovanie/ekstruzionnaya_liniya_proizvodstva_ plastika_dlya_3d_pechati_lider_3d/).

A high-speed line is known for the production of filament required for 3D printing.

The line consists of the following modules:

• Single-screw extruder equipped with a hopper-dryer;

• Three-chamber water heating and cooling calibration bath;

• High-speed filament pulling system;

• Two-axis laser diameter gauge;

• Horizontal filament accumulator;

• High speed filament winding system.

The main component of the line is a single-screw extruder. The screw and barrel are made of high-quality nitrided steel.

The extruder is equipped with an asynchronous AC motor for screw rotation. The extruder is equipped with a programmable frequency converter for stepless adjustment of screw rotation speed and high torque even at low screw speeds.

The extruder barrel has four barrel heating zones, all zones with forced air cooling. Each zone is equipped with highly efficient air cooling, with copper sheet radiators with fins installed under the heater bands. These fins catch the cold air and remove heat from the barrel. Sirocco type cooling fans are installed. The high power of the heater bands combined with an efficient cooling system ensures very fast heating and cooling of each zone. Standard heating up to 300°C (400°C or 450°C - options) Control of the zone heating temperature is provided by digital programmable temperature controllers for setting and reading data for all 6 zones (4 barrel zones and 2 head (die) zones), connected to semiconductor relays for precise heating control. The controllers are self-adjusting, equipped with programmable automatic compensation, providing precise temperature over the entire working range from room temperature to 300°C.

As an option, extruders can be equipped with:

• melt pressure and temperature sensors;

• a feedback system for automatic adjustment of the screw rotation speed and maintaining a constant pressure of the melt supplied to the die;

• filter replacement mechanism;

• computer control system for full automation of polymer processing processes.

The hopper dryer is designed for continuous extrusion process to avoid moisture accumulation on materials. The overheating cut-off function can automatically cut off the power supply of the hopper dryer when the drying temperature exceeds the set value. The maximum drying temperature is 160°C.

The filament extrusion line is equipped with a 3-meter-long calibration bath with three sections, heated to 85°C and cooled. Sections one and two are heated independently, section three with cold water. Gradual cooling avoids the formation of cavities and bubbles in the filament, prevents its shrinkage or the formation of bubbles. The sectional design of the bath provides a filament cooling path of 9 meters, saving space.

The filament is pulled at a speed of up to 130 m/min by a special roller pulling mechanism. To control the speed, it is equipped with a digital regulator with an indicator. The pressing force of the roller of the pulling mechanism is adjusted using a hand wheel.

For winding the manufactured filament, the lines are equipped with a high-speed single-station filament winding system. It provides a winding speed of up to 130 m/min. For automatic counting of the filament wound on the bobbins, the system is equipped with a meter counter. Uniformity of winding is ensured by a movable stacker.

To control the filament thickness, the line is equipped with a laser control system. It continuously measures the diameter along two axes. The measurement accuracy of the system is ±0.0025 mm. In case of deviation from the specified values, the control system gives an alarm signal (https://sntf.ru/catalog/pererabotka_polimerov/proizvodstvo_streng_dlya_3Dprinterov/liniya-ekstruzii-filamenta-iz-inzhenernykh-plastikov-dlya-3d-pechati/ (see also the full description)).

This solution was chosen as a prototype.

The main disadvantages of the known extrusion lines for filament production, including the prototype, are the low quality of the produced thread from synthetic raw materials. This disadvantage occurs due to the fact that during the production of filament in existing lines there is no possibility of smoother cooling of the filament. Cooling is carried out in water baths in large stages, which does not allow the formation of the thread, resulting in defects (in the amount of 20% of the raw materials used). In addition, due to insufficient drying of the raw materials before feeding them to the extruder, air-gas locks occur in the heating cylinder, resulting in unstable formation of the thread diameter. All this also causes high losses during equipment readjustment (up to 10 kg of raw materials and more than 4 hours of time are wasted).

Disclosure of the essence of the invention

The technical problem solved by the invention is to ensure the possibility of forming a thread from synthetic raw materials, namely carbon-filled polyetheretherketone, with specified properties .

The technical result achieved by using the claimed invention consists in improving the quality of the obtained filament, reducing the proportion of defects, increasing strength, removing electrostatics from the filament and ionizing the filament.

The stated technical result is achieved due to the fact that in the known line for producing filament, comprising a hopper-dryer connected to an extruder equipped with a screw pair; a filament cooling module, a drawing module and a filament winding module, according to the invention, the line is equipped with an additional high-temperature drying module installed in front of the hopper-dryer and connected to it; the screw pair of the extruder is made reinforced with increased heat resistance; the filament cooling module is made two-component, with an air-vacuum cooling module connected to water cooling baths; the line is equipped with an ionization module installed after the drawing module and an additional module for air high-temperature drying of the finished filament, installed after the winding module.

The production of a filament production line, which is equipped with an additional high-temperature drying module installed before the drying bin and connected to it, an ionization module installed after the drawing module and an additional module for high-temperature air drying of the finished filament; with a reinforced extruder screw pair with increased heat resistance, with a two-component filament cooling module equipped with an air-vacuum cooling module connected to water cooling baths, allows to reduce the share of defective filament, increase its strength and size stability (thread diameter), ensure the removal of electrostatics from the filament and ensure the ionization of the thread, which improves the quality of the resulting filament.

The line is designed to produce filament from carbon-filled polyetheretherketone (PEEK CF), therefore, the preparation of raw materials by drying them in an additional high-temperature drying module at a temperature of up to 180 degrees allows for higher-quality preparation of raw materials for processing, which prevents the appearance of air-gas bubbles in the extruder barrel and ensures the production of filaments with a stable size (thread diameter).

The presence of a reinforced screw pair in the extruder with increased heat resistance up to 550°C ensures a constant supply of raw materials to the extruder head at a temperature of up to 350°C to obtain high-quality filament with a given size (thread diameter) and reduces the proportion of defective products.

At the outlet of the filament from the extruder, a filament cooling module is installed, made of two components, with an air-vacuum cooling module connected to a water cooling bath. This module allows the air-vacuum cooling module to reduce the temperature of the filament from 350°C, with which it exits the extruder, to 100°C and eliminate the sharp drop in temperature of the filament when it enters the water cooling baths, as a result of which air-gas locks in the filament are eliminated, and the share of its defects is reduced.

After the filament has cooled, it enters the drawing module. After this module, an ionization module is installed , which allows for "dusting", removing static and ionization of the filament. An additional module for high-temperature air drying of the filament installed after the winding module provides additional drying of the filament from moisture remaining on it after the water cooling bath, ensuring an increase in its quality.

Brief description of the drawings

The drawing shows a functional diagram of an extrusion line for producing thread from synthetic raw materials.

Implementation of the invention

The filament production line is equipped with an additional module 1 for high-temperature drying, installed in front of the hopper-dryer 2 and connected to it. The additional module 1 is made in the form of a drying cabinet for high-temperature (up to 180°C) drying of granules. The hopper-dryer 2 is connected to the extruder 3 included in the line. The extruder 3 has a reinforced screw pair 4 with increased heat resistance, which is driven by a motor for rotating the screw. The screw pair 4 of the extruder 3 is made reinforced with increased heat resistance from structural steel grade 40X, which has increased heat resistance. The barrel of the screw pair 4 of the extruder is equipped with a zonal heating system and forced water cooling. The barrel of the screw pair 4 of the extruder has four heating zones, all zones with forced water cooling. Forced water cooling is provided by a chiller, which supplies cooling liquid (water) to the extruder.

The filament cooling module 5 is made of two components, with an air-vacuum cooling module 6 and two water cooling baths 7. The air-vacuum cooling section 6 includes a chamber with a vacuum pump for pumping out air, which ensures rapid cooling of the filament to a temperature of 100°C. In the first water cooling bath 7, the temperature is maintained at 85°C, and in the second bath 7, the water is at room temperature. This sequence of filament cooling allows eliminating a sharp drop in filament temperature, as a result, air-gas locks are eliminated, which lead to filament defects.

The filament feed module 8 consists of two sets of paired rollers, each set consists of two strong and wear-resistant rubber rollers. The roller pressure is adjusted by a flywheel that moves the upper rubber rollers up and down. Adjustable rubber roller drive with a maximum feed speed of up to 130 m/min.

The line is equipped with an ionization module 9 and an additional module 10 for high-temperature air drying of the filament. The ionization module 9 is installed after the drawing module 8. The ionization module 9 is made in the form of an ionizing gun and allows for "dusting", removing static and ionization of the filament to facilitate its winding on the reel by the filament winding module 11. The winding module 11 is made standard. The additional module 10 for high-temperature air drying of the finished filament is installed after the winding module 11 and is a high-temperature drying cabinet (provides a temperature of up to 160-180 ° C).

The production and assembly of individual modules of the line is carried out on existing technological equipment.

Examples

The line works as follows.

The material (granules of carbon-filled polyetheretherketone PEEK CF5) is poured into an additional module 1 of high-temperature temperature drying of granules, where the raw material is dried in a drying cabinet at a temperature of 180°C. The dried granules are poured into a hopper-dryer, where a constant temperature of up to 60°C is maintained, from where the dried and heated PEEK CF5 granules are fed to the screw pair 4 of the extruder 3. In the barrel of the screw pair 4, the material is gradually heated, melted and at a temperature of 350°C is fed to the head of the extruder to obtain a filament with a given size (thread diameter). Then the filament enters a chamber with a vacuum pump for pumping out air of the air-vacuum cooling module 6, which ensures rapid cooling of the filament to a temperature of 100°C. The cooled filament enters the first water cooling bath 7, where the temperature is maintained at 85°C, then into the second bath 7 with water at room temperature. Thus, the temperature of the filament before entering the drawing module 8 is equal to room temperature. The filament drawing module 8 ensures constant movement of the filament and its tension. Subsequent treatment of the filament with the ionizing gun of the ionization module 9 ensures "dust removal", removal of static and ionization of the filament to facilitate its winding onto the reel by the filament winding module 11. After winding onto the reel, the filament ready for shipment is placed in the high-temperature drying cabinet of the additional air drying module 10, where it is additionally dried at a temperature of up to 160-180°C to remove residual moisture from drawing through the cooling water baths.

The claimed line can be used to obtain a filament not only from granules of carbon-filled polyetheretherketone PEEK CF5, but also from granules of carbon-filled polyetheretherketone PEEK CF10 and other PEEK raw materials mixed with granulated carbon in other proportions to obtain the corresponding filament from carbon-filled polyetheretherketone with specified properties.

The implementation of this technology allowed:

- significantly reduce the share of defects, prevent unstable formation of thread during production due to preliminary drying and heating of raw materials and elimination of air-gas locks in the cylinder of the screw pair 4 of the extruder 3;

- reduce losses during equipment readjustment (time - from 4 hours, raw material - from 10 kg) due to preliminary high-temperature drying of raw materials, stabilization of the temperature in the cylinder and elimination of a sharp drop in the temperature of the filament at the exit from the cylinder and its preliminary cooling in a chamber with a vacuum pump for pumping out air from section 8 of air-vacuum cooling.

The claimed invention can be used in the production of high-quality filament for 3D printing from carbon-filled polyetheretherketone by the extrusion method.

Claims (1)

A filament production line comprising a hopper-dryer connected to an extruder equipped with a screw pair; a filament cooling module, a drawing module and a filament winding module, characterized in that the line is equipped with an additional module for high-temperature drying of granules, installed in front of the hopper-dryer and connected to it; the screw pair of the extruder is made of structural steel grade 40X with heat resistance up to 550°C; the filament cooling module is made in two components, with an air-vacuum cooling module connected to water cooling baths; the line is equipped with an ionization module installed after the drawing module, and an additional module for high-temperature air drying of the finished filament, installed after the winding module.