CN112406099A

CN112406099A - Melt extrusion device, 3D printer control method and application

Info

Publication number: CN112406099A
Application number: CN202011206514.4A
Authority: CN
Inventors: 魏青松; 南亚琪; 孙殷昊; 李继康; 冯琨皓; 李辽毅; 曹子怡
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2020-11-03
Filing date: 2020-11-03
Publication date: 2021-02-26

Abstract

The invention discloses a melt extrusion device, a 3D printer control method and application. The melting extrusion device is used for melting and extruding the raw materials of the 3D printer, and comprises a screw component and a spray head component connected with the screw component, wherein the screw component comprises a shell and at least two screws arranged in the shell, threads of the adjacent screws are mutually meshed, the raw materials are uniformly mixed and melted through the rotation of the screws in the same direction, and the melted raw materials are extruded through the spray head component. The invention adopts at least two screws to mutually mesh and rotate in the same direction, the raw materials are gradually melted under the rotating shearing of the screws, the shearing rate and the shearing stress of a molten mass at the meshing position are higher, better back mixing is generated, and the distribution mixing capability of various raw materials is greatly improved.

Description

Melt extrusion device, 3D printer control method and application

Technical Field

The invention belongs to the technical field of 3D printing, and particularly relates to a melt extrusion device, a 3D printer control method and application.

Background

In recent years, 3D printing technology has been developed rapidly, and according to different forming modes, the method can be mainly divided into fused deposition Forming (FDM), Selective Laser Melting (SLM), laser cladding forming (LENS), Selective Laser Sintering (SLS), photocuring forming (SLA), three-dimensional spray printing forming (3DP), and the like. The FDM technique has been most widely used because of its low cost, simple principle, and small device size. At present, the FDM technology mainly uses thermoplastic polymer wires such as PLA, ABS and the like as raw materials, the raw materials are sent into a high-temperature melting cavity at the temperature of 200-240 ℃ by a wire feeding mechanism and finally sprayed out from a spray head at a specific position of a hot bed device, and a three-dimensional object is formed by stacking layer by layer. However, the following problems still exist in the technology:

the most widely used consumable material in the market is

The homogeneous wire, which has undergone a hot forming process of wire drawing before printing, has a reduced mechanical strength. When in printing, the wire is easy to oxidize and break, block a spray head and the like, and once a certain layer has the problems, the whole printing process is abandoned, so that the material and time are wasted;

secondly, once the wire material is drawn into a wire, the material components of the wire material are permanently fixed, the material of each area of the model printed and formed by the wire material is uniform, the component proportion of the material cannot be customized point by point, line by line and layer by layer according to personal requirements, namely, functional parts such as composite materials, heterogeneous gradient materials and the like cannot be formed, and the application prospect of the technology is limited.

In view of the above problems, there are some patents disclosing improvements to the conventional FDM technique. For example, patents CN201410469682.0, CN201810973383.9, CN201810407488.8, cn201910562463.x and the like design a new extrusion mechanism, which changes the traditional wire feeding into particle feeding, and utilizes the form of a single screw to melt and extrude the particle material, so as to realize the layer-by-layer accumulation and formation of high polymers, but the mixing capability of the single screw is not strong, the melt extruded by a nozzle contains more bubbles, the density is not high, the random distortion of the extrusion direction cannot be controlled, and the material proportion control of each point cannot be realized in the forming process, i.e., a composite and heterogeneous gradient functional material cannot be formed, meanwhile, the above patent does not provide a design scheme of the whole machine, if the screw moves along three axes, the screw will vibrate the whole machine due to its heavier XYZ, large inertia, and the forming process is unstable or even cannot be formed; patent CN201910178883.8 mentions that the feeding ratio of two or more kinds of granules is controlled by using a rotary vane valve, and the extrusion system also adopts the above-mentioned single screw for rotary melting, which can theoretically overcome the above-mentioned first and second problems, but the control precision of the vane valve is limited, and the above-mentioned disadvantages still exist in the single screw; patent CN201510449256.5 adopts the mode of carousel formula shower nozzle switching and screw rod feeding to realize the complex printing of multiple material, but the material that is suitable for is the thick liquids that has certain mobility, does not have the universality to macromolecular material etc. and many shower nozzles switch the process complicacy, and the shaping is inefficient.

Therefore, a melt extrusion device and a 3D printer which are adaptable to polymer multi-material are needed, and can satisfy the control of the material component ratio point by point, line by line, layer by layer.

Disclosure of Invention

The invention provides a melt extrusion device, a 3D printer control method and application, aiming at controlling the material component proportion point by point, line by line and layer by layer in the printing process in real time and realizing the integrated forming of complex structures and functions of composite materials, heterogeneous gradient materials and the like, thereby solving the technical problems that the extruded melt contains more bubbles, the density is not high, the arbitrary distortion of the extrusion direction cannot be controlled, and the control of the material component proportion point by point, line by layer and layer by layer cannot be met in the prior art.

In order to achieve the above object, according to one aspect of the present invention, there is provided a melt extrusion apparatus for melt extrusion of a raw material for a 3D printer, the melt extrusion apparatus comprising a screw assembly, a nozzle assembly connected to the screw assembly, the screw assembly comprising a housing and at least two screws disposed in the housing, wherein threads of adjacent screws are engaged with each other, the raw material is uniformly mixed and melted by co-rotating the screws, and the melted raw material is extruded through the nozzle assembly.

Preferably, the screw is a gradient screw with the same diameter, and the depth of the screw groove of the screw is gradually reduced along the direction from the raw material entering to the direction away from the shell; the length-diameter ratio of the screws is 10-16, and the depth of the screw ridge between adjacent screws entering the screw groove of the other screw is 0.6-1.7 times of the minimum screw groove depth.

Preferably, the screw assembly further comprises a heating assembly disposed on an outer wall of the housing and a cooling assembly disposed facing the heating assembly.

Preferably, the screw comprises a feeding section, a compression section and a metering section, the heating assembly comprises 3 heating rings, the 3 heating rings are arranged on the outer wall of the shell corresponding to the feeding section, the compression section and the metering section respectively, and cooling fins are arranged between the 3 heating rings; the cooling assembly includes three cooling fans disposed facing the 3 heating rings.

Preferably, the screw assembly further comprises a power assembly for driving the at least two screws to rotate in the same direction and in the same phase; the power assembly comprises an input motor, a transmission shaft connected with the input motor, a driving gear arranged on the transmission shaft and a transmission gear fixed on the screw rod, wherein the driving gear is meshed with the transmission gear.

According to another aspect of the present invention, there is provided a 3D printer comprising a feed compounding device, a melt extrusion device as described above, a hot bed device, a moving device and a frame for supporting and fixing the above devices;

wherein the feeding and mixing device is connected with the melt extrusion device and can provide at least two mixed raw materials for the melt extrusion device; the hot bed device is arranged below the spray head assembly, and the moving device is used for driving the hot bed device to move in the X-axis direction, the Y-axis direction and the Z-axis direction.

Preferably, the feed mixing apparatus comprises at least two feed assemblies and a mixing assembly in communication with the at least two feed assemblies;

the feeding assembly comprises a raw material barrel, a rotary driving plate arranged at the bottom of the raw material barrel and a stepping motor connected with the rotary driving plate; the outer ring of the rotary driving plate is of a tooth comb structure, and a feed hole is formed in the position, corresponding to the tooth comb structure, of the bottom of the raw material barrel and is communicated with the material mixing component; a semicircular inclined plane arranged above the feeding hole is arranged in the raw material barrel, and the rotation of the rotary driving plate (12) is controlled by a stepping motor so as to control the amount of raw materials in the raw material barrel entering the material mixing assembly;

the mixing component comprises a mixing hopper and a discharging screw rod connected with the mixing hopper; the discharging screw is used for mixing the raw materials entering the mixing hopper and then introducing the mixed raw materials into the melting extrusion device.

Preferably, the feeding assembly further comprises a weight sensor arranged at the bottom of the raw material barrel and a laser correlation sensor arranged at the outlet of the mixing hopper; and a transparent window is arranged on the side wall of the raw material barrel.

Preferably, the movement device comprises an X-axis movement structure, a Y-axis movement structure and a Z-axis movement structure; the hot bed device is fixedly connected with the Y-axis motion structure, the X-axis motion structure and the Y-axis motion structure are used for driving the hot bed device to move horizontally, and the Z-axis motion structure is used for driving the hot bed device to move up and down;

the printer also comprises a CCD camera and a laser leveling sensor which are arranged on the hot bed device.

According to another aspect of the present invention, there is provided a control method of the 3D printer as described above, the method including:

the rotating drive plates in the at least two feeding components are controlled by the stepping motor to rotate at different rotating speeds, so that at least two raw materials mixed in different proportions are provided for the extrusion device in real time;

an input motor in the melting extrusion device is rotated to drive at least two screws to rotate in the same direction and phase, a heating assembly is started to uniformly mix and melt raw materials, the melted raw materials are extruded to a hot bed device through a nozzle assembly, and the hot bed device is driven to move in the directions of an X axis, a Y axis and a Z axis through a movement device to finish printing;

and in the printing process, receiving the photo information acquired by the CCD camera, comparing the photo information with the CAD size of the layer of the three-dimensional model to obtain the size deviation, and sending out prompt correction information or stopping printing when the size deviation exceeds a set threshold.

According to a further aspect of the invention, there is provided a use of a 3D printer as described above for 3D printing of particulate polymer material.

In general, at least the following advantages can be obtained by the above technical solution contemplated by the present invention compared to the prior art.

(1) The melt extrusion device provided by the invention adopts at least two screws which are mutually meshed and rotate in the same direction, the raw materials (especially the high-molecular granular materials) are gradually melted under the rotating shearing of the screws, the shearing rate and the shearing stress of a molten mass at the meshing position are higher, better back mixing is generated, and the distribution mixing capacity of various raw materials is greatly improved. And at least two screws rotate and melt to convey various raw material particles, so that the complex process of preparing the traditional wire is avoided, the range of usable materials is expanded to a certain extent, and the production cost is reduced.

(2) According to the 3D printer provided by the invention, the material component proportion of the material layer by layer point by line in the printing process can be controlled in real time through the feeding and mixing device, and the purpose of forming complex structures such as composite materials, heterogeneous gradient materials and the like in a functional integrated manner is realized.

(3) According to the 3D printer provided by the invention, the melting extrusion device is fixed on the rack and does not do space motion, but the heating bed device is fixed on the slide block of the Y-axis module and can do XYZ three-dimensional space motion to bear the layer-by-layer stacking forming of the three-dimensional model. The problem of screw type melting extrusion device be heavier unstable, lead to printing quality poor is avoided.

(4) In the invention, the screw is strictly limited to be a constant-diameter gradual-change screw, the length-diameter ratio range is 10-16, and compared with a screw with a small length-diameter ratio, the material stays in the charging basket for a long time, so that the material is mixed and plasticized, the melt pressure is improved, and the backflow and leakage phenomena are eliminated.

(5) The feeding and mixing device in the 3D printer provided by the invention controls the feeding amount of various raw materials by adjusting the rotating speed of the rotary drive plate, can realize real-time regulation and control of different raw materials to accurately mix the raw materials in any proportion, and can effectively avoid the problem of raw material leakage when the rotary drive plate is not used due to the arrangement of the semicircular inclined surface. The transparent window is installed to former storage bucket lateral wall, can observe remaining material volume in the former storage bucket under the condition of not opening former storage bucket.

(6) In the invention, a weight sensor is arranged below each raw material barrel; can monitor the feeding weight of two kinds or multiple granule material, laser correlation sensor links to each other with the compounding funnel export, and whether the monitoring granule material is in time exported to the accurate control raw materials feeding.

(7) In the invention, 3 heating rings arranged on the melting extrusion device correspond to the feeding section, the compression section and the metering section, and the 3 heating rings can be set to different heating temperatures, so that the solid material can be rapidly heated to a viscous state in the feeding section, and the material can be fully discharged in the compression section; the melt fluidity is ensured in the compression section, and the good formability is ensured in the metering section after the material is extruded from the nozzle. Meanwhile, the cooling fan and the cooling fins can be arranged to cool so as to protect other adjacent components.

(8) The control method of the screw type multi-material 3D printer can realize monitoring of the printing quality of each layer by using the CCD camera and timely prompt when the printing quality is in problem.

(9) The 3D printer disclosed by the invention has wide applicability to most of high polymer materials, has no special requirements on the state of the materials, can form granular and powdery materials and the like, and overcomes the defects of uncontrollable material, few available material types and high production cost of the traditional wire material melting forming point-by-point channel-by-channel layer-by-layer material.

Drawings

FIG. 1 is a schematic structural diagram of a screw type multi-material 3D printer provided by an embodiment of the invention;

FIG. 2 is a cross-sectional view of a feeding and mixing device in a screw type multi-material 3D printer structure provided by an embodiment of the invention;

FIG. 3 is a bottom view of a feeding and mixing device in a screw type multi-material 3D printer structure provided by an embodiment of the invention;

FIG. 4 is a top view of a feeding and mixing device in a screw type multi-material 3D printer structure provided by an embodiment of the invention;

FIG. 5 is a schematic structural diagram of a melt extrusion device in a screw type multi-material 3D printer structure provided by an embodiment of the invention;

FIG. 6 is a cross-sectional view of a melt extrusion device in a screw-type multi-material 3D printer configuration provided by an embodiment of the invention;

fig. 7 is a schematic structural diagram of a moving device and a hot bed device in a screw type multi-material 3D printer structure provided by an embodiment of the invention.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:

1-a feeding and mixing device; 1A-a feeding assembly; 1B-a mixing assembly; 11-rotating dial gland; 12-rotating the dial; 13-rotating the dial retainer ring; 14-a coupling; 15-motor fixing plate; 16-a stepper motor; 17-a mixing hopper; 18-laser correlation sensor; 19-a mixing screw; 110-a compounding joint; 111-feedstock vat; 112-a mixing bottom plate; 113-a mixing stepper motor; 114-a mixing screw bearing block; 115-compounding screw barrel; 116-a weight sensor; 117-slope; 118-a transparent window;

2-a melt extrusion device; 2A-a screw assembly; 2B-a showerhead assembly; 2C-screw; 21-an input motor; 22-motor fixing bending piece; 23-motor shaft gear; 24-transmission case input gear wheel; 224-a first gearwheel in the transmission case; 227-a second gearwheel in the gearbox; 25-upper transmission case; 26-middle transmission case; 27-lower transmission case; 28-a showerhead support plate; 29-a feed cylinder; 210-a feed insulation panel; 211-screw barrel; 212, 214, 215-heating coil; 213-a heat sink; 216-insulating sponge; 217-heating the nozzle; 218-nozzle fixing bending piece; 219 — a cooling fan; 220-transmission case gland; 221-angular contact ball bearings; 222, 223, 228, 229-positioning sleeves; 225-a first pinion in the transmission case; 226-a second pinion in the transmission case; a 230-O type seal ring; 231-flange gasket; 232-right screw; 233-left screw; 234-baffle plate; 235-confluence core; 236-bearing end gland; 237-a drive shaft;

3-a hot bed device; 31-MK3 aluminum substrate hot bed; 32-hot bed insulation cotton; 33-hot bed support plate; 34-laser leveling sensor; 35-a heating coil; 36-leveling nut.

4-a motion device; a 41-Y axis motion slide; a 42-Y axis motion module; a 43-X axis motion slide; a 44-X axis motion module; a 45-Z axis motion slide block; a 46-Z axis motion module;

5-a CCD camera;

6-a frame; 61-a base plate; 62-nylon anchor feet; 63-a touch screen; 64-touch screen fixing plate.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The embodiment of the invention provides a melt extrusion device, which is used for melt extrusion of raw materials of a 3D printer, wherein the melt extrusion device 2 comprises a screw component 2A and a spray head component 2B connected with the screw component 2A, the screw component 2A comprises a shell and at least two screws 2C arranged in the shell, threads of the adjacent screws 2C are meshed with each other, the raw materials are uniformly mixed and melted through the rotation of the screws 2C in the same direction, and the melted raw materials are extruded through the spray head component 2B. In a feasible manner of the embodiment of the invention, the screw 2C is a constant diameter gradual change screw, and the depth of the screw groove of the screw 2C is gradually reduced according to the direction from the raw material entering to the direction away from the shell; the length-diameter ratio of the screws 2C is 10-16, and the depth of the screw ridge between two adjacent screws 2C entering the screw groove of the other screw 2C is 0.6-1.7 times of the minimum screw groove depth. The equal diameter gradual change formula screw rod that this embodiment adopted has great draw ratio, compares in little draw ratio screw rod, and the material stays for a long time in the storage bucket, is favorable to the material to mix the plastify, improves fuse-element pressure and eliminates adverse current and the hourglass flow phenomenon. The screw can rotate left and right, and the performance of the final extruded melt is not affected. Because of the adoption of the assembly mode of homodromous rotation and intermeshing, the axial rotation phase position of the screw rod needs to be kept consistent, otherwise the screw rod cannot work. The depth of the screw ridge between the screws entering the screw groove of the other screw is 0.6 to 1.7 times the minimum screw groove depth, and is exemplarily equal to about 0.5 to 1.4mm for the present embodiment.

Referring to fig. 5 and 6, the screw assembly 2A in the embodiment of the present invention is illustrated by taking two screws 2C as an example, it can be understood that the number of the screws 2C may also be, for example, 3, 4, 5, etc., for example, three screws in parallel and in the same direction, and there are two meshing areas (the twin screws have one meshing area), so that the meshing dispersion effect is improved by more than one time, the plasticizing effect is good, and the dispersion is more uniform. The larger the number of screws 2C, the better the meshing dispersion effect, but the weight of the screw assembly 2A also increases accordingly.

The screw assembly 2A further comprises a heating assembly disposed on an outer wall of the housing and a cooling assembly disposed facing the heating assembly. The screw 2C comprises a feeding section, a compression section and a metering section, the screw is sequentially provided with the feeding section, the compression section and the metering section along the feeding direction, the lengths of the sections are determined according to the types of materials, the printer is suitable for amorphous polymers, the length of the feeding section accounts for 10% -25% of the total working length of the screw, the length of the compression section accounts for 50% -65% of the total working length of the screw, the length of the metering section accounts for 20% -30% of the total working length of the screw, the total working length of the screw is (12-16) x the outer diameter of the screw, the diameter of the screw is 13mm in the embodiment, and the range of the diameter of the screw.

The heating assembly comprises 3 heating rings 212, 214 and 215, the 3 heating rings 212, 214 and 215 are arranged on the outer wall of the shell corresponding to the feeding section, the compression section and the metering section respectively, and cooling fins 213 are arranged between the 3 heating rings 212, 214 and 215; the cooling assembly comprises three cooling fans 219 arranged facing the 3 heating coils. The screw component 2A also comprises a power component for driving the at least two screws 2C to rotate in the same direction and phase; the power assembly comprises an input motor 21, a transmission shaft 237 connected with the input motor, a driving gear arranged on the transmission shaft 237 and a transmission gear fixed on the screw rod 2C, wherein the driving gear is meshed with the transmission gear.

More specifically, the melt extrusion apparatus 2 includes the following components: an input motor 21; the motor fixes the bending piece 22; a motor shaft gear 23; the transmission input gearwheel 24; a first bull gear 224 in the transmission case; a second bull gear 227 within the transmission; an upper transmission case 25; a middle transmission case 26; a lower transmission case 27; a head support plate 28; a feed cylinder 29; a feed insulation panel 210; a screw barrel 211; heating coils 212, 214, 215; a heat sink 213; a heat insulating sponge 216; heating the nozzle 217; a showerhead retention bend 218; a cooling fan 219; a transmission case gland 220; angular contact ball bearings 221; the

sleeves

222, 223, 228, 229; a first pinion 225 in the transmission case; a second pinion 226 in the transmission case; an O-ring seal 230; a flange gasket 231; a right screw 232; a left screw 233; a baffle plate 234; a merging core 235; a bearing end cap 236; a drive shaft 237.

Wherein, the input motor 21 is fixed on the motor fixed bending piece 22, and the motor shaft gear 23 is fixed on the transmission shaft 237 of the motor 21; the feed cylinder 29 and the screw cylinder 211 form a housing. The upper transmission case 25, the middle transmission case 26 and the lower transmission case 27 are assembled into a transmission case body through screws, the transmission shaft 237 is fixedly connected with the transmission case input gearwheel 24, the first gearwheel 224 in the transmission case and the second gearwheel 227 in the transmission case, and the left screw 233 and the right screw 232 are respectively fixedly connected with the first pinion 225 in the transmission case and the second pinion 226 in the transmission case; the input gear 24 of the transmission box is meshed with the motor shaft gear 23, the first gear 224 in the transmission box is meshed with the first pinion 225 in the transmission box, and the second gear 227 in the transmission box is meshed with the second pinion 226 in the transmission box, so that the input motor 21 drives the left screw and the right screw to rotate in the same direction and in the same phase.

In a feasible manner of the embodiment of the present invention, the left screw 233 is provided with the positioning

sleeves

223 and 228 and the angular contact ball bearing 221, and the right screw 232 is provided with the positioning

sleeves

222 and 229 and the angular contact ball bearing 221, which are all in coaxial interference fit. The lower transmission case 27 is fixed on the nozzle fixing bending piece 218 and is fixedly connected with the motor fixing bending piece 22 and the nozzle supporting plate 28 through screws, a bearing end pressing cover 236 is arranged at the lower end of the case body, and a transmission case pressing cover 220 is arranged at the upper end of the case body to prevent the screw from generating axial displacement. An O-shaped sealing ring 230 is arranged in the feeding cylinder 29, a heat insulation plate 210 is arranged at the position of the feeding port, the heat insulation plate 210 is fixedly connected with the mixing joint 110, the feeding cylinder 29 is fixedly connected with the screw machine barrel 211 through screws, and a flange gasket 231 is arranged at the connecting position. The outer wall of the screw barrel 211 is provided with a radiating fin 213 and heating rings 212, 214 and 215 which are mica heating rings, the spray head fixing bending piece 218 is provided with a cooling fan 219 for cooling, and the temperature control of the double screws is realized through electronic components.

For the heating rings 212, 214 and 215, the heating temperature has different parameter values for different materials, the temperature setting of the three heating rings is also distinguished, the set temperature of the heating ring 212 arranged at the feeding section is about 20-30 ℃ higher than the viscous flow temperature of the materials, the solid materials need to be rapidly heated to the viscous flow state, and the materials can be fully discharged in the compression section; the heating ring 214 arranged at the compression section is set to have the temperature of +/-10 ℃ of the viscous flow temperature of the material, so that the fluidity of the melt is ensured; the temperature of the heating ring 215 arranged at the metering section is relatively low and is about 20-50 ℃ above the glass transition temperature, so that the material is ensured to have better formability after being extruded from the nozzle.

In addition, the screw cylinder 211 is fixedly connected with the confluence core 235 through screws, a flow baffle 234 and a flange gasket 231 are arranged at the joint, the outer wall of the confluence core 235 is coated by heat insulation sponge 216, a threaded hole is formed in the head of the confluence core 235 and matched with an external thread at the tail of the heating nozzle 217, a raw material belt is adhered at the threaded engagement position to prevent fluid leakage, a thermocouple and a thermistor are arranged on the heating nozzle 217, and a melt body converts rotary motion into linear motion through the flow baffle 234, and is finally converged and fused through the confluence core 235 and sprayed out from the heating nozzle 217.

In the melt extrusion apparatus 2, the input motor 21 outputs axial rotation, the rotational motion is transmitted to the transmission shaft 237 through the meshing kinematic pair of the motor shaft gear 23 and the transmission box input gearwheel 24, the transmission shaft 237 drives the left screw 233 through the meshing kinematic pair of the first gearwheel 224 in the transmission box and the transmission box first pinion 225, and drives the right screw 232 through the meshing kinematic pair of the second gearwheel 227 in the transmission box and the transmission box second pinion 226, because the transmission ratios of the two sets of kinematic pairs are the same, the rotating speeds of the left and right screws are the same, and the angular velocity output by the input motor 21 is the angular velocities of the left screw 233 and the right screw 232.

In the practical use process, the working speed of the input motor 21 in the embodiment of the invention is determined according to the length and the structure of the macromolecular chain of the raw material particles, and for the polymer materials with long and complex molecular chains, such as TPE, PA and the like, a small rotating speed of 5-12 r/min is needed to be used, so that a large shearing force is generated, the effective displacement of the molecular chain gravity center is promoted, the disordered movement of the chain segment is partially counteracted, the physical entanglement is favorably removed, and the material has good fluidity; for polymer materials with short and simple molecular chains, such as PC, PCL and the like, the higher rotation speed is 10-20 r/min, and the working speed of the printer is accelerated.

Another embodiment of the invention provides a 3D printer, which is a screw type multi-material 3D printer. Referring to fig. 1, the device comprises a feeding and mixing device 1, a melt extrusion device 2, a hot bed device 3, a moving device 4 and a frame 6 for supporting and fixing the devices;

wherein the feeding and mixing device 1 is connected with the melt extrusion device 2, and the feeding and mixing device 1 can provide at least two mixed raw materials for the melt extrusion device 2; the hot bed device 3 is arranged below the spray head component 2B, and the moving device 4 is used for driving the hot bed device 3 to move in the X-axis direction, the Y-axis direction and the Z-axis direction.

Referring to fig. 2-4, the feed mixing apparatus 1 includes at least two feed assemblies 1A and a mixing assembly 1B in communication with the at least two feed assemblies 1A; the feeding assembly 1A comprises a raw material barrel 111, a rotary dial 12 arranged at the bottom of the raw material barrel 111, and a stepping motor 16 connected with the rotary dial 12; the outer ring of the rotary driving plate 12 is of a tooth comb structure, the tooth width of the tooth comb structure is the same as that of the feeding hole, the feeding hole is formed in the position, corresponding to the tooth comb structure, of the bottom of the raw material barrel 111, and the feeding hole is communicated with the material mixing component 1B; the raw material barrel 111 is internally provided with a semicircular inclined surface 117 arranged above the feeding hole, and the rotation of the rotary dial 12 is controlled by the stepping motor 16, so that the amount of raw materials in the raw material barrel 111 entering the mixing component 1B is controlled.

In this embodiment, two feeding assemblies 1A are illustrated, but it is understood that the number of feeding assemblies may be adjusted according to actual situations.

Further, the rotary dial 12 is arranged in the rotary dial fixing ring 13, the gap is coaxially assembled at the bottom of the raw material barrel 111, two ends of the coupler 14 are respectively connected with the rotary dial gland 11 and the stepping motor 16, the rotary dial 12 is controlled by the stepping motor 16 to rotate, and the feeding amount of the particle raw material is controlled; the raw material barrel 111, the rotary dial gland 11, the mixing bottom plate 112, the motor fixing plate 15 and the stepping motor 16 are sequentially installed and fixed from top to bottom.

The mixing component 1B comprises a mixing hopper 17 and a discharge screw 19 connected with the mixing hopper 17; the discharge screw 19 is used for mixing the raw materials entering the mixing hopper 17 and then feeding the mixed raw materials into the melt extrusion device 2. Wherein, the mixing hopper 17 is arranged below the mixing bottom plate 112 and receives the raw materials (especially granular raw materials) conveyed by the rotary driving plate 12, and the raw materials flow into the mixing screw barrel 115 through the mixing hopper 113; the mixing stepping motor 113, the mixing screw bearing seat 114 and the mixing screw barrel 115 are sequentially connected, the raw material and the mixing screw barrel 115 are coaxially assembled, and the mixing joint 110 is installed at the discharge end of the screw.

The feeding assembly 1A further comprises a weight sensor 116 arranged at the bottom of the raw material barrel 111 and a laser correlation sensor 18 arranged at the outlet of the mixing hopper 17; a transparent window 118 is mounted on a side wall of the raw material barrel 111.

Raw material particles in the raw material barrel 111 enter tooth gaps of the driving plate (namely, a tooth comb structure) under the action of gravity, quantitative particles are contained in a single tooth gap, the driving plate rotates to drive materials in the tooth gaps to move, the weight sensor 116 monitors the materials passing through in unit time in the moving process, and the online monitoring function is realized. The granule leaks from raw materials bucket bottom aperture afterwards, gets into ejection of compact screw rod 19 through compounding funnel 17, and ejection of compact screw rod 19 rotates and accomplishes the preliminary mixing and the transport of raw materials granule. For large-particle materials (particle diameter of 1.5mm or more), the dial 12 is rotated at a low speed to prevent ineffective conveyance of particles which do not enter into gaps between teeth due to an excessively high rotation speed. For small particle materials (particle diameter is less than 1.5 mm), the driving plate 12 can adopt high rotating speed, and the working efficiency is improved.

In a possible way of the embodiment of the present invention, referring to fig. 7, the moving device 4 includes an X-axis moving structure, a Y-axis moving structure and a Z-axis moving structure; the hot bed device 3 is fixedly connected with the Y-axis motion structure, the X-axis motion structure and the Y-axis motion structure are used for driving the hot bed device 3 to move horizontally, and the Z-axis motion structure is used for driving the hot bed device 3 to move up and down; specifically, the X-axis movement structure includes an X-axis movement slider 43 and an X-axis movement module 44, the Y-axis movement structure includes a Y-axis movement slider 41 and a Y-axis movement module 42, and the Z-axis movement structure includes a Z-axis movement slider 45 and a Z-axis movement module 46.

The X-axis movement module 44, the Y-axis movement module 42 and the Z-axis movement module 46 comprise a stepping motor, a synchronous belt, a belt wheel, a linear guide rail and the like, and the movement sliding blocks are in clearance fit with the linear guide rail and can move linearly along the guide rail; wherein, the X-axis motion sliding block 43 is assembled on the X-axis motion module 44, and the bottom of the X-axis motion module 44 is fixed on the Z-axis motion sliding block 45; the Y-axis motion sliding block 41 is assembled on the Y-axis motion module 42, and the Y-axis motion module 42 is installed on the X-axis motion sliding block 43; the Z-axis movement module 46 is fixed on the bottom plate 61 and the rack 6 through screws, the Z-axis movement sliding block 45 is assembled on the Z-axis movement module 46, and the XYZ three-dimensional space movement of the heat bed device is realized through the sliding of the sliding block on the movement module; the hot bed supporting plate 33 is fixed on the Y-axis moving slide block 41 and can do X, Y, Z axial movement in three directions, so that the molten raw material extruded by the molten extrusion device 2 falls on the hot bed device 3, and the three-dimensional model is formed by stacking layer by layer.

X, Y, Z

axle motion modules

44 and 42 and 46 adopt ball screw slider structure, and the inside is equipped with accurate ball screw and accurate linear guide, and the slider motion straightness accuracy is high, the position precision is high, and X, Y,

Z axle slider

43 and 41 and 45 adopt wholly closed carriage, prevent that external impurity from getting into in the module, influence the ball screw precision.

The hot bed device 3 comprises an MK3 aluminum substrate hot bed device 31, hot bed heat preservation cotton 32, a hot bed supporting plate 33, a laser leveling sensor 34, a heating coil 35 and a leveling nut 36. The overall structure is similar to that of a traditional FDM printer hot bed, and the MK3 aluminum substrate hot bed device 31, the hot bed heat preservation cotton 32 and the hot bed supporting plate 33 are fixedly connected with one another sequentially from top to bottom through screws. The heating coil 35 is positioned below the MK3 aluminum substrate 31 and can heat up to 100 ℃; the laser leveling sensors 34 are located above the hot bed device 3, the number of the leveling nuts 36 is four, the leveling nuts 36 are located at four corners below the hot bed supporting plate 33 respectively, the heights of four points of the hot bed device are measured in a non-contact mode through the leveling sensors 34, the heights of the four points are made to be consistent with the maximum height through manual adjustment of the leveling nuts 36, and therefore leveling of the hot bed device can be achieved.

The printer further comprises a CCD camera 5 arranged on the hot bed device 3. The CCD cameras 5 are respectively arranged on the left side and the right side of the upper part of the hot bed device, the printing surface of each layer is photographed in real time, a boundary contour curve is extracted based on a binocular vision theory and a related image processing algorithm and is compared with the CAD size of the layer of the three-dimensional model, if the size deviation exceeds a set threshold value, an operator is prompted to correct or stop printing, and therefore the printing quality of each layer is monitored.

The frame 6 is formed by assembling 40 × 40 sectional materials through T-shaped nuts, screws and corner pieces, and further comprises a bottom plate 61, nylon feet 62, a touch screen 63 and a touch screen fixing plate 64. As a feasible manner, the above-mentioned feeding speed of each feeding component in the feeding and mixing device, the rotation speed of a screw in the melt extrusion device, the heating temperature of the heating component, the movement of the movement device, the online monitoring of the raw material condition by the weight sensor and the laser correlation sensor, the online monitoring of the printing quality process of each layer, and the like can all be completed by a control system electrically connected with the corresponding components, and the control system can be, for example, a single chip, a chip, and other components with a control function that can be integrated into a whole on a touch screen, or a terminal, and the like.

The invention further provides a control method of the screw type multi-material 3D printer, and specifically, the method comprises the following steps: the rotating drive plates in the at least two feeding components are controlled by the stepping motor to rotate at different rotating speeds, so that at least two mixed raw materials are provided for the extrusion device; an input motor in the melting extrusion device is rotated to drive at least two screws to rotate in the same direction and phase, a heating assembly is started to uniformly mix and melt raw materials, the melted raw materials are extruded to a hot bed device through a nozzle assembly, and the hot bed device is driven to move in the directions of an X axis, a Y axis and a Z axis through a movement device to finish printing; and in the printing process, receiving the photo information acquired by the CCD camera, comparing the photo information with the CAD size of the layer of the three-dimensional model to obtain the size deviation, and sending out prompt correction information or stopping printing when the size deviation exceeds a set threshold.

More specifically, the entire forming process of 3D printing includes the steps of: s1, building a three-dimensional model by UG, Pro/E and other modeling software, defining the material component proportion of each region, and then slicing the model in layers by using slicing software to obtain data information such as each layer of outline of the model and material components of different regions; s2, importing the data information into control software/system, and generating driving programs including drive plate rotation, discharging screw rotation, double-screw extrusion rotation, three-axis movement of a hot bed, temperature control and the like according to the materials sliced layer by layer and path planning data; s3, the driving program is led into the 3D printer, the point-by-point and channel-by-channel layer-by-layer accumulation forming is started, in the forming process, the rotating speed of a rotating dial and the rotating speed of a double screw are controlled to control the material composition of each layer of each point, each layer is formed, the height of a set layer thickness is reduced, then a spray head deposits the next layer on the formed layer, and the layers are circularly stacked layer by layer until the forming of the whole model is completed; s4, carrying out post-treatment such as support removal, surface polishing and the like on the formed primary blank to obtain the required composite material and heterogeneous gradient material parts.

The invention further provides application of the screw type multi-material 3D printer, which is applied to 3D printing of granular high polymer materials. The problems that a 3D printer is not suitable for printing of various granular high polymer materials, a molten mass extruded by a nozzle contains more bubbles, the density is not high, the extrusion direction is randomly distorted and cannot be controlled, and the material proportion of each point cannot be controlled in the forming process and the like in the prior art are solved.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. The utility model provides a melt extrusion device for the raw materials melt extrusion of 3D printer, its characterized in that, this melt extrusion device (2) include screw assembly (2A), shower nozzle subassembly (2B) of being connected with screw assembly (2A), screw assembly (2A) include the casing and set up two at least screws (2C) in the casing, and the screw thread intermeshing of adjacent screw (2C), through the syntropy rotation of screw (2C) with raw materials misce bene and melting, extrude the melting raw materials through shower nozzle subassembly (2B).

2. A melt extrusion apparatus as claimed in claim 1, wherein the screw (2C) is a constant diameter gradual change screw, and the depth of the screw (2C) groove is gradually reduced in a direction from the raw material entering to the exit of the housing; the screw assembly (2A) further comprises a heating assembly arranged on the outer wall of the shell and a cooling assembly arranged facing the heating assembly.

3. A melt extrusion apparatus as defined in claim 2, wherein the screw (2C) includes a feed section, a compression section and a metering section, the heating assembly includes 3 heating rings (212, 214, 215), the 3 heating rings (212, 214, 215) being provided on an outer wall of the housing corresponding to the feed section, the compression section and the metering section, respectively, and heat radiating fins (213) being provided between the 3 heating rings (212, 214, 215); the cooling assembly comprises three cooling fans (219) arranged facing the 3 heating coils.

4. A melt extrusion apparatus as claimed in claim 1, wherein said screw assembly (2A) further comprises a power assembly for driving the at least two screws (2C) to rotate in phase and in the same direction; the power assembly comprises an input motor (21), a transmission shaft (237) connected with the input motor, a driving gear arranged on the transmission shaft (237) and a transmission gear fixed on the screw rod (2C), and the driving gear is meshed with the transmission gear.

5. A 3D printer, characterized by comprising a feed mixing device (1), a melt extrusion device (2) according to any one of claims 1 to 4, a hot bed device (3), a moving device (4) and a frame (6) for supporting and fixing the above devices;

wherein the feeding and mixing device (1) is connected with the melt extrusion device (2), and the feeding and mixing device (1) can provide at least two mixed raw materials for the melt extrusion device (2); the hot bed device (3) is arranged below the spray head component (2B), and the moving device (4) is used for driving the hot bed device (3) to move in the X-axis direction, the Y-axis direction and the Z-axis direction.

6. The printer according to claim 5, characterized in that said feed mixing device (1) comprises at least two feed assemblies (1A) and a mixing assembly (1B) communicating with the at least two feed assemblies (1A);

the feeding assembly (1A) comprises a raw material barrel (111), a rotary dial plate (12) arranged at the bottom of the raw material barrel (111), and a stepping motor (16) connected with the rotary dial plate (12); the outer ring of the rotary driving plate (12) is of a tooth comb structure, and a feeding hole is formed in the position, corresponding to the tooth comb structure, of the bottom of the raw material barrel (111) and communicated with the mixing component (1B); a semicircular inclined surface (117) arranged above the feeding hole is arranged in the raw material barrel (111), and the rotation of the rotary driving plate (12) is controlled by the stepping motor (16), so that the amount of raw materials in the raw material barrel (111) entering the mixing component (1B) is controlled;

the mixing component (1B) comprises a mixing funnel (17) and a discharging screw (19) connected with the mixing funnel (17); the discharging screw (19) is used for mixing the raw materials entering the mixing hopper (17) and then introducing the mixed raw materials into the melt extrusion device (2).

7. The printer according to claim 6, characterized in that said feeding assembly (1A) further comprises a weight sensor (116) arranged at the bottom of said raw material vat (111) and a laser correlation sensor (18) arranged at the exit of the mixing hopper (17); a transparent window (118) is mounted on the side wall of the raw material barrel (111).

8. The printer according to claim 5, characterized in that said movement means (4) comprise an X-axis movement structure, a Y-axis movement structure and a Z-axis movement structure; the hot bed device (3) is fixedly connected with the Y-axis motion structure, the X-axis motion structure and the Y-axis motion structure are used for driving the hot bed device (3) to move horizontally, and the Z-axis motion structure is used for driving the hot bed device (3) to move up and down;

the printer further comprises a CCD camera (5) and a laser leveling sensor (34) which are arranged on the hot bed device (3).

9. A method of controlling a 3D printer according to any one of claims 5 to 8, the method comprising:

the rotating drive plates in the at least two feeding components are controlled by the stepping motor to rotate at different rotating speeds, so that at least two mixed raw materials are provided for the extrusion device;

10. Use of a 3D printer according to any of claims 5 to 8 for 3D printing of particulate polymer material.