Patent Description:
Known in the art are 3D printing equipment using composite fibers. The analogues are described in the MarkForged applications (USA):
Known in the art are 3D printing methods and equipment using composite fibers. The closest analogues are described in the MarkForged applications (USA):.

The applications describe the method and an appropriate 3D-printer of special design for printing with the use of composite fibers. The composite fiber includes continuous or semi-continuous reinforcing fibers as a filler. The matrix is a thermoplastic material in a solid state. The composite fiber is fed into the extruder by the feeding device heated to a temperature exceeding the melting temperature of the matrix material of a composite fiber and laid out through the nozzle onto the table and fused to it, which allows for forming a part. The printer may have a composite fiber cutting system located in the area between the feeding mechanism and the nozzle.

The described device can be used only if a composite fiber is impregnated with a thermoplastic matrix. However, this approach has a number of disadvantages; in particular, it is difficult to provide high-quality impregnation of the fiber bundle with thermoplastics, which is due to the extremely high viscosity of their melts. The resulting material may have high porosity and the fibers will not work together. In order to implement high-quality impregnation, it is necessary to expose the material to high pressures (dozens of atmospheres), but in this case, the damage of fibers is possible and the internal structure of the material can be uneven. In order to avoid the difficulties associated with the impregnation of a bundle of fibers with thermoplastics, the printing can be performed using a composite fiber impregnated with a thermosetting binder and pre-cured. In this case, the extruder shall be fed with both a composite fiber and thermoplastics, which will bind the fibers together during printing.

Also, the design described in the previous applications has only one channel for feeding the composite fiber with a given volume ratio of reinforcing fibers and plastic, which does not allow for varying the volume fraction of fibers in the printing process.

The objective of the invention is the manufacture of functional parts by three-dimensional printing from composite materials with a complex shape and internal structure, which have high physical and mechanical characteristics, which implies:.

The technical result is an improvement in the physical and mechanical characteristics of parts, a reduction in the mass of parts, and a reduction in the cost of the manufacture of complex shape products from composite materials.

The task is solved and the technical result is achieved owing to the printhead disclosed in appended claims.

The technical result is also achieved due to the fact that the plastic filament feeding mechanism contains an electric drive and driven rollers, between which a plastic filament passes.

The technical result is also achieved due to the fact that the reinforcing fiber feeding mechanism contains an electric drive and driven rollers, between which a fiber passes.

The technical result is also achieved due to the fact that the reinforcing fiber cutting mechanism located between the reinforcing fiber feeding mechanism and the heating unit contains a stationary knife and a servo drive which drives a movable knife.

The technical result is also achieved due to the fact that the reinforcing fiber cutting mechanism located between the reinforcing fiber feeding mechanism and the heating unit contains a servo drive, the axle of which is fitted with a movable knife in the form of a circular cylinder with a groove made to a depth exceeding half the diameter of the cylinder.

The technical result is also achieved due to the fact that the stationary knife is a tube with two holes - namely, the inlet, and the outlet.

The technical result is also achieved due to the fact that the outer diameter of the movable knife is equal to the internal diameter of the stationary knife and the movable knife is mounted inside the stationary knife by sliding fit.

The technical result is also achieved due to the fact that the plastic filament feeding tube connects the output of the plastic filament feeding mechanism and the input channel of the heating unit intended for a plastic filament.

The technical result is also achieved due to the fact that the reinforcing fiber feeding tubes connect the output of the reinforcing fiber feeding mechanism to the input of the reinforcing fiber cutting mechanism and the output of the reinforcing fiber cutting mechanism to the input channel of the heating block intended for a reinforced fiber.

The task in view is also solved and the technical result is to be achieved by the printhead comprising a mechanism for feeding a first plastic filament, a mechanism for feeding a second plastic filament, a mechanism for feeding a reinforcing fiber, a mechanism for cutting the reinforcing fiber, a feeding tube for the first plastic filament, a feeding tube for the second plastic filament, feeding tubes for the reinforcing fiber and a heating unit, wherein the heating unit comprises a heater, a thermocouple or a thermistor, three input channels - a reinforcing fiber feeding channel, a first plastic filament feeding channel and a second plastic filament feeding channel, and two nozzles with output channels for reinforced plastic polymer and pure plastic polymer, and wherein the first plastic filament feeding channel is connected to the reinforcing fiber feeding channel inside the heating unit, and the input reinforcing fiber feeding channel is arranged coaxially with the output reinforced plastic polymer channel.

The technical result is also achieved due to the fact that the first plastic filament feeding mechanism contains an electric drive and driven rollers, between which the first plastic filament passes.

The technical result is also achieved due to the fact that the feeding mechanism for an second plastic filament contains an electric drive and driven rollers, between which an second plastic filament passes.

The technical result is also achieved due to the fact that the feeding mechanism of reinforcing fibers contains an electric drive and driven rollers, between which the fiber passes.

The technical result is also achieved due to the fact that the cutting mechanism for reinforcing fibers, which locates between the feeding mechanism for reinforcing fibers and the heating unit, contains a stationary knife and a servo drive, which drives a movable knife.

The technical result is also achieved due to the fact that the cutting mechanism for reinforcing fibers, which locates between the feeding mechanism for reinforcing fibers and the heating unit, contains a servo drive, the axle of which is fitted with a movable knife in the form of a circular cylinder with a groove made to a depth exceeding half the diameter of the cylinder.

The technical result is also achieved due to the fact that the feeding tube for a first plastic filament connects the output of the first plastic filament feeding mechanism and the heating unit input channel intended for a first plastic filament.

The technical result is also achieved due to the fact that the feeding tube for second plastic filament connects the output of the feeding mechanism for second plastic filaments and the heating unit input channel intended for additional plastic filaments.

The technical result is also achieved due to the fact that the feeding tubes for reinforcing fibers connect the output of the reinforcing fiber feed mechanism to the input of the reinforcing fiber cutting mechanism and the output of the reinforcing fiber cutting mechanism to the heating unit input channel intended for reinforced fibers.

The following positions on the figures are indicated by numbers:.

The application describes the printhead and the process of the manufacture of composite materials (parts) based on carbon fibers in combination with thermosetting and/or thermoplastic matrix.

The task in view is solved and the technical result is achieved due to the fact that the printhead heating unit is fed with reinforcing fiber and plastic filament through two separate channels. Thus, it is possible to use different types of reinforcing fibers; and also, by changing the speed of a plastic filament in the printing process, the volume fraction of fibers in the plastic can be adjusted, in contrast to the previously mentioned analogues, in which the volume fraction of fibers is set at the stage of manufacture of composite fiber. This allows to solve the problem of creating parts from composite materials with a complex internal structure. Structures that can be manufactured in this way include, for example, lattice composite structures and other types of structures. Also, the technical result is achieved through the presence of the mechanisms for cutting and feeding a reinforcing fiber, as well as the feeding tubes, which allows to cut a reinforcing fiber in the process of printing, to feed the fiber into the heating unit after cutting to resume the printing, and also, by adjusting the feed rate of the fiber in the printing process, to control the tension of a reinforcing fiber by increasing the tension on the straight sections of the trajectory to improve the mechanical characteristics of the material and by reducing it on the sections with great curvature to avoid a slipping of a reinforcing fiber.

The schematic of the print head is shown in <FIG>. Heating unit <NUM> have input channels - thermoplastic polymer feeding channel <NUM> receiving thermoplastic polymer filament <NUM> and reinforcing fiber feeding channel <NUM> receiving reinforcing fiber <NUM>. Reinforcing fibers to be used can include composite fibers made of carbon, glass, organic or combined bundles impregnated with a polymer binder (thermoplastic resin binder or cured thermosetting binder, for example, in the form of polyester, phenolformaldehyde, urethane, epoxy, silicone, polyimide or bismaleimide resins), or metal wire. Thermoplastic filaments to be used can include filaments made of thermoplastic material such as ABS, polylactide, polyamide, polyethylene terephthalate glycol, polyethyrimide, polysulfone, polyesterephyrketone or other thermoplastic material. The channel to feed a thermoplastic polymer is connected with the channel for feeding a reinforcing fiber, allowing the thermoplastic to coat a reinforcing fiber passing through the reinforcing fiber feeding channel. Also, the heating unit is equipped with nozzle <NUM> with an output channel for reinforced thermoplastic polymer <NUM>. Output channel <NUM> is located coaxially with the input channel for reinforcing fiber <NUM>, which serves, first, to prevent the bending and damages to the fiber inside the heating unit, and, secondly, to ensure the possibility of recharging the fiber after cutting and resuming the laying-out of reinforced thermoplastics. The diameter of input channel is smaller than the diameter of output channel to minimize the thermoplastic melt yield, when printing, through the channel for feeding the reinforcing fiber. Usually, the input channel shall have its diameter greater than the reinforcing fiber diameter by no more than <NUM>-<NUM> times. Also, a gap is present between the tube for feeding reinforcing fiber to the heating unit <NUM> and the input channel <NUM> of the heating unit <NUM>, which prevents the excessive thermoplastic melt from going up to the reinforcing fiber feeding tube <NUM>, as this tube is not heated and the molten thermoplastic can cool and solidify in this tube, blocking the channel. The heating unit <NUM> is equipped with heater <NUM> and temperature sensor <NUM> (thermocouple and thermistor).

The thermoplastic filament is fed to the heating unit by means of thermoplastic filament feeding mechanism <NUM> consisting of an electric drive (for example, a stepping motor or a servo drive) and rollers. At least one roller is driving and operated by the rotating shaft of the electric drive. The driving roller has incisions allowing the feed of thermoplastic polymer filaments without slipping. The driven roller can both have notches or do not have them. The rollers are mechanically pressed against a thermoplastic filament to prevent it from slipping, for example, by means of a spring. An embodiment is possible using two driving rollers connected by a mechanical transmission.

A reinforcing fiber is fed into the heating unit by means of reinforcing fiber feeding mechanism <NUM> consisting of an electric drive (for example, a stepping motor or a servo drive) and rollers. At least one roller is driving and operated by the rotating shaft of the electric drive. At least, one of the rollers, preferably driven one, has a rubber coating in order to prevent an excessive compression and damage to the reinforcing fiber. The rollers are mechanically pressed against a reinforcing fiber to prevent it from slipping, for example, by a spring. An embodiment is possible using two driving rollers connected by a mechanical transmission.

A mechanism for cutting a reinforcing fiber is located between the feeding mechanism for a reinforcing fiber and the heating unit; the cutting mechanism consists of drive <NUM>, for example, a servo drive with a reducer connected by a mechanical transmission with movable knife <NUM> and stationary knife <NUM>. The servo drive shall provide sufficient force to cut the fiber. The amount of force depends on the type (carbon, glass, organic) and the linear density of a fiber. For example, the cutting of a carbon fiber with a linear density of <NUM> tex, a force of not less than <NUM> N is required, in the case of a density of <NUM> tex - not less than <NUM> N. Knives are made of materials with high hardness, such as hardened steel or ceramics. The reinforcing fiber cutting mechanism should be located in close proximity to the heating unit at a distance of up to <NUM>, because the minimum length of the continuous portion of a reinforced thermoplastic laid on the work surface increases with increasing this distance.

It is possible to implement a cutting mechanism in which the servo axle is fitted with movable knife <NUM> in the form of a circular cylinder with a groove made to a depth exceeding the radius of the cylinder. Stationary knife is a tube with two holes - namely, the inlet port, and the outlet port of a larger diameter. The outer diameter of the movable knife is equal to the internal diameter of the stationary knife and the movable knife is mounted inside the stationary knife by sliding fit. In the process of printing, the fiber passes through the inlet port of the stationary knife, the groove of the movable knife and the outlet port of the stationary knife. When cutting, the servo drive turns the movable knife and the fiber is cut between the edge of the movable knife groove and the edge of the inlet of the stationary knife. On cutting, the servo drive returns the movable knife to its neutral position.

Thermoplastic filament feeding mechanism of <NUM> and reinforcing fiber feeding mechanism <NUM> can be located both near the reinforcing fiber cutting mechanism and the heating block and at a distance of up to <NUM>. A thermoplastic filament from the feeding mechanism outlet to the heating unit inlet channel is fed through feed tube <NUM> and thermal barrier <NUM> interconnected by fitting <NUM>. The feeding tube is made of a material with a low coefficient of friction, for example, PTFE. The thermal barrier is made of a material with a relatively small thermal conductivity, for example, steel or titan and serves to prevent heat removal from the heating unit to the fitting and the tube. To increase its efficiency, the thermal barrier can be further cooled fan <NUM> and/or a radiator. A reinforcing fiber from the output of the feed mechanism to the input of the reinforcing fiber cutting mechanism is fed inside tube <NUM>, and from the output of the cutting mechanism to the input channel of the heating unit - with the help tube <NUM>.

In order for the printhead to be able to lay not only thermoplastics reinforced with continuous fibers, but also pure thermoplastics (or thermoplastics reinforced with discrete fibers), second thermoplastic filament <NUM> can be fed into the printhead. In this case, the embodiment of a printhead has a mechanism for feeding second plastic filament <NUM>, heating unit <NUM> has port <NUM>, in which nozzle <NUM> for printing with thermoplastics is installed. The Additional thermoplastic filament feeding mechanism <NUM> and nozzle <NUM> are connected by feeding tube <NUM> and thermal barrier <NUM> in the same way as main thermoplastic filament <NUM> is fed. In order to ensure that the outlet holes of nozzles <NUM> and <NUM> are located on the same level, the embodiment provides for the possibility of shifting heating unit <NUM> and nozzle <NUM> relative to each other vertically. Fastening the parts together can be carried out, for example, using set screws <NUM>.

The printhead is mounted on a manipulator with three or more degrees of freedom (for example, a portal three-axis manipulator or a six-axis robot).

The printing process is as follows. Heating unit <NUM> using heater <NUM> is heated to a temperature exceeding the melting temperature of a thermoplastic filament and, if a reinforcing fiber impregnated with a thermosetting binder and cured is used, the glass transition temperature of the thermosetting binder of a reinforcing fiber. The temperature is kept constant by means of a feedback control system with the use of temperature sensor <NUM>.

The printhead mounted on the manipulator moves along a predetermined trajectory at a certain distance from the surface, corresponding to the layer thickness (for example, <NUM>-<NUM>). At the same time, the electric drives of the feeding mechanisms turn the rollers by commands from the control system to feed thermoplastic filaments and/or reinforcing fibers to the heating unit.

If the printing is carried out with reinforced thermoplastics, the feed is carried out by the drives of the thermoplastic filament feeding mechanism <NUM> and reinforcing fiber feeding mechanism <NUM>. By adjusting the feeding rate of reinforcing fiber during printing, its tension can be controlled. The tension can be increased when the printhead moves along a straight line relative to the printer platform to improve the mechanical properties of the material and decreased when the printhead moves along an arc to avoid a sliding of a reinforcing fiber from the laying trajectory. In addition, to prevent the reinforcing fiber from slipping, the outlet of <NUM> can be blown by cold air, for example, by means of a fan. By adjusting the feeding rate of a plastic filament during printing, you can control the volume fraction of reinforcing fibers in the resulting composite material.

If the printing is carried out with a clean thermoplastic, the feed is provided by the drive of second plastic filament feeding mechanism <NUM>.

Claim 1:
A printhead comprising:
a mechanism (<NUM>) for feeding a plastic filament,
a mechanism (<NUM>) for feeding a reinforcing fiber,
a mechanism (<NUM>, <NUM>) for cutting the reinforcing fiber,
a feeding tube (<NUM>) for the plastic filament,
a feeding tube (<NUM>) for feeding the reinforcing fiber from the feeding mechanism (<NUM>) to the cutting mechanism (<NUM>, <NUM>),
a feeding tube (<NUM>) for feeding the reinforcing fiber from the cutting mechanism (<NUM>, <NUM>) to a heating unit (<NUM>); and
the heating unit (<NUM>);
wherein the heating unit (<NUM>) comprises:
a heater (<NUM>),
a thermocouple (<NUM>) or a thermistor (<NUM>),
two input channels, namely a reinforcing fiber feeding channel (<NUM>) and a plastic filament feeding channel (<NUM>), and
a nozzle (<NUM>) having an output channel (<NUM>) for a reinforced plastic polymer;
wherein the plastic filament feeding channel (<NUM>) is connected to the reinforcing fiber feeding channel (<NUM>) inside the heating unit (<NUM>), and the input reinforcing fiber feeding channel (<NUM>) is arranged coaxially with the output reinforced plastic polymer channel (<NUM>);
characterized in that
the input reinforcing fiber feeding channel (<NUM>) of the heating unit (<NUM>) has a diameter greater than the reinforcing fiber diameter by no more than <NUM>-<NUM> times,
the diameter of the input reinforcing fiber feeding channel (<NUM>) being smaller than the diameter of the output channel (<NUM>) to minimize the thermoplastic melt yield, when printing, through the reinforcing fiber feeding channel (<NUM>),
and in that
a gap is present between the feeding tube (<NUM>) for the reinforcing fiber and the reinforcing fiber feeding channel (<NUM>) of the heating unit (<NUM>).