Precision mixing type stacking forming method and assembly and color FDM-3D printer
[ field of the invention ]
The invention belongs to the field of machinery, and particularly relates to a transient volume type multi-channel material extruder assembly and a color FDM-3D printer manufactured by using the same.
[ technical background ]
The Fused Deposition Modeling (FDM) rapid prototyping process is a method of heating and melting various wires (such as engineering plastics ABS, polycarbonate PC, etc.) to build up and shape, abbreviated as FDM. Most FDM rapid prototyping technologies can use many types of modeling materials, such as modified paraffin, (acrylonitrile/butadiene/styrene) copolymer (ABS), nylon, rubber, and other thermoplastic materials, and multiphase hybrid materials, such as metal powder, ceramic powder, short fiber, and other blends with thermoplastic materials. PLA (polylactic acid) has lower shrinkage, and the printing model is moulding more easily to and advantages such as biodegradable, and this kind of material is all adopted to most desktop FDM type 3D printers today.
The extruder assembly is a core component of the FDM rapid forming technology, most of the aluminum blocks are indirectly heated by a heating rod, plastic wires are extruded in through an inlet end of the extruder assembly and then guided by a throat pipe to reach a heating part of the aluminum block, the aluminum block is melted and enters a nozzle area, finally the aluminum block is extruded out through an extrusion hole, and the melted plastic wires are extruded out of the nozzle under the action of the pressure of a subsequent wire feeding (piston).
The throat pipe in the extruder assembly is made of stainless steel, so that the heat conducting performance of the throat pipe is reduced, the stainless steel throat pipe is internally lined with Teflon for a certain time, the temperature inside the throat pipe is increased due to long-term heating and printing of the extruder assembly, so that materials in the throat pipe are in a molten state, the materials are bonded in the pipe after printing and cooling are stopped, the adhesion materials in the pipe cannot be melted immediately when the extruder assembly is restarted for printing next time, the throat pipe is blocked, and the Teflon is lined in the throat pipe, so that the materials in the throat pipe cannot be melted and adhered, and the problem of blocking can be greatly solved. Meanwhile, the author adds a radiating fin and a fan on the extruder assembly, mainly aims to reduce the temperature of the upper part of the throat pipe and prevent the problem of a choke plug, and also can radiate the extruder assembly. The plastic wire after heating and melting is extruded to the printing table by the nozzle, if bad phenomena such as edge warping and shrinkage and the like caused by sudden temperature reduction of the plastic are reduced, an author can make the printing table into a heating bed, a thermistor is arranged in the bed and connected with a circuit board to control the temperature of the heating bed, and the author does not use the heating bed in order to save the manufacturing cost.
The single crowded head compares, and two crowded heads adopt two extruder assemblies to arrange side by side to relative position is fixed, owing to have two shower nozzles, the printing speed of two crowded heads is faster, and printing efficiency is also higher, and two crowded heads are installed on the slider, are connected with the guide rail by the slider, because its quality is bigger, and the inertia that produces during the operation is bigger, and rigidity requirement to the guide rail is also higher, can reduce the precision of printing like this. There are four types of nozzle diameters for the lowermost nozzle head of the extruder assembly: 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.4mm is the most widely used nozzle in the market, certainly can purchase the nozzle of different diameters according to the actual need, it is worth mentioning here that, after selecting the nozzle diameter, also need set up the corresponding parameter in the software while printing, such as print layer height, printing speed, etc. in the slicing software, make the quality and precision of printing higher.
The heating nozzle carries the extrusion holes to do X-Y plane movement under the control of a computer according to the section profile information of the product part, and a layer of thin sheet profile with the thickness of about 0.127-0.50mm is formed after rapid cooling. And after the section of one layer is formed, the workbench descends by a certain height, then cladding of the next layer is carried out, the section outline is like to be 'drawn' layer by layer, and the steps are repeated, so that the three-dimensional product part is finally formed.
The near-end wire feeding is to install the extruder assembly on the printing head, directly extrude the material into the throat pipe from the extruder assembly, melt the material in the aluminum block, and spray the melted material out of the nozzle for printing. In the installation mode, the extruder assembly moves together with the printing head, the printing head has large mass and large inertia during printing, the printing is easy to be inaccurate, and the requirement on the rigidity of the guide rail by adopting the near-end wire feeding is higher. The far end wire feeding is to install the extruder assembly at a position far away from the printed object, and the driving motor is generally installed on the printer frame instead of the extruder assembly.
The circuit part includes: the 3D printer circuit part plays a role in controlling the coordinated, ordered and complete operation of the whole printing process in the printer. A typical circuit part of the FDM type 3D printer mainly comprises an Arduino mega2560 main control board, a Ramps1.4 expanding board and a stepping motor driving board. The basic parameters and functions thereof are described below. The Arduino Mega2560 main control board has the microcontroller atmega2560, the working voltage is 5V, the number of digital I/O pins is 54, the number of analog input pins is 16, the direct current of each I/O pin is 50 milliamperes, and the main control board is the brain of the 3D printer and is responsible for controlling the whole printer to complete specific actions, such as printing specific files and the like. It should be noted here that the diodes of the extended version supplying power to the main control board are not welded, that is, the diodes need to supply power to the mega2560 main control board separately, and the power is supplied directly by using the USB 5V or through a power connector. Arduino is a convenient, flexible and convenient open-source electronic prototype platform, comprises hardware (Arduino boards of various models) and software (Arduino IDE), has a circuit diagram design of open source codes, can be freely downloaded through a program development interface, can be modified according to personal needs, and meets the requirements of innovation and originality of different crowds. Before the 3D printer operation, need download Marlin firmware in Arduino IDE, part parameter satisfies the requirement of printing in modifying the firmware as required. The expansion board Ramps1.4 is inserted on the main control board and is connected with the main control board through a contact pin, and the expansion board Ramps1.4 is used for being better connected with other hardware and controlling and plays a role of a transition bridge. The expansion board needs to be connected with two 12V power supplies, wherein one power supply is 11A and is used for supplying power to the heating bed, the other power supply is 5A and is used for supplying power to elements such as an extruder, each shaft motor, a fan and the like, and the author only needs to use one 12V power supply and one 5A power supply without using the heating bed. The RAMPs1.4 extension board is also provided with LEDs for outputting fan and heating rod, the extruder assembly and each shaft motor are controlled by the main control board through the stepping motor drive board A4988, because the author adopts a single-head printer, the motor interface of the extruder assembly 2 does not need to be provided with A4988 and is positioned at the upper right corner of the extension board, and a limit switch in the direction of X, Y, Z is arranged, so that the original point of the printer during each working can be controlled. The A4988 stepping motor driving board is used for connecting a stepping motor, so that the control of the main control board on the stepping motor is realized, and the action of the XYZ-axis motor and the extruder assembly is realized. The characteristic of A4988 stepping motor drive plate is that it has only simple stepping and direction control interface, there are 5 different stepping modes: full, half, 1/4, 1/8 and 1/16, the adjustable potentiometer can adjust the maximum current output, thereby obtaining higher stepping rate, and has the functions of overheating shutdown circuit, under-voltage locking, cross current protection, and the functions of grounding short-circuit protection and loading short-circuit protection. The driving board is inserted into the corresponding interface in the expansion board through pins.
Software part examples: the authors have known that the software part of the 3D printer includes two major parts, namely upper computer software and lower computer software, each of which is subdivided, and the authors can set and control the printing parameters by the main control board only through the operation of the software. The complete running process of all software of one 3D printer is as follows: firstly, an author needs to complete part modeling in three-dimensional modeling software on a computer, such as Solidworks, UG, 3D Max and other three-dimensional software, a file is stored in an STL format after a 3D model is created, the STL file is opened in slice software Slic3r, slicing is carried out to generate codes through a series of printing settings, the codes are opened on another upper computer software Pronterface and connected with a mainboard, the lower computer software on the mainboard is Marlin firmware, parameter setting is carried out in advance before operation, after connection is successful, an LED lamp on the mainboard flickers, and printing is started after a heating pipe on a printer is heated and the temperature is raised to a set temperature. The software portion of the printer is described in detail below. The lower computer software Marlin firmware is free software and can be directly used for software development, when an author uses the Marlin firmware in a 3D printer, the author only needs to download the firmware in the Arduino IDE software to find a configuration.h file in the Marlin firmware, relevant code content can be modified according to own needs, and the printer developed by the author needs to be modified as follows.
At present, the color generation mode of the color FDM-3D printer has the following 3 types:
adding colors into the FDM-3D printer in 4 months in 2013 when consumables of Wisconsin-Madison university in America melt, so that the color printing of the FDM-3D printer is realized.
The development team describes this new device as a "virtual brush" to enable full color 3D printing by applying a dye process to a single polymer material. Therefore, the method is simple. Such color 3D printing does not require multiple nozzles and multiple different color wires. Spectrom works by accurately calculating what colors are needed when and then dyeing the same wire with different color inks. Color 3D printing can be achieved with only one nozzle.
The current disadvantages are the slow speed of color change: transitions of different colors are prone to confusion. (e.g. small patches of green may appear in the middle zone when changing from yellow to blue), but in principle there is an improved speed of the colour change of the material mixture, e.g. a reduced volume of the mixing chamber.
Another disadvantage is that the pigment carries a carrier defect, and the volatilization of the chemical solvent can generate harmful gas.
Multicolor material multi-hole independent extrusion FDM-3D printer multicolor desktop type 3D printers (such as ProDesk3D) require multiple extruder assemblies to produce color effects. The double-color 3D printer is provided with two extruder assemblies in a standard mode and belongs to a double-material extrusion machine type. The back of the machine body is used for mounting two material discs and supporting two consumables of ABS and PLA. And in the market, we can find universal consumables of various colors. Thus, the color matching can be freely carried out, and the proper color and material type can be selected according to the requirement. The disadvantages are as follows: abrupt color boundaries and a limited number of colors.
Polychrome material is downthehole to mix extrudes FDM-3D printer altogether: in 2015, something3D printing company, israel announced: they are launching a full-color desktop 3D printer, Chameleon (meaning Chameleon), which will provide users with a completely new FFF technology-based color 3D printing experience. The Chameleon 3D printer of sometaling 3D company mainly uses a plurality of 3D printing wires, and 5 color consumables in total are: the whole system only needs one extruder assembly, and any color can be formed by changing the mixing ratio combination of the above 5 colors according to the requirement, and the machine can realize color conversion under the condition of printing resolution of 0.5 mm.
The shortfall is still a color change speed deficiency: transitions of different colors are prone to confusion. (e.g., small blocks of green may appear in the middle when changing from yellow to blue), abrupt changes in the large color of the color cannot be accommodated. The material supply method also has defects, and cannot meet the requirement of accurate and stable color matching.
[ summary of the invention ]
In order to realize the requirement that the color of the material extruded filament needs to be instantly changed on the length of 0.5-1 mm, the volume of a material mixing cavity needs to be as small as possible, and because trace residues on the wall of the mixing cavity can interfere the mixing proportion, a measure of discarding partial molten materials in the transition period is necessary;
suitable for the precision mixing type accumulation forming method are the following 2 precision mixing type extruder assemblies, which are respectively a feeding precision mixing type extruder assembly and a color supply precision mixing type extruder assembly:
the feeding precise mixing type extruder assembly directly mixes multi-color materials into other colors of at least 4 colors, namely red, blue, green and black), and the structure main body consists of a precise feeding mechanism and a precise color mixing mechanism, wherein the precise feeding mechanism consists of a preheating treatment preceding stage and a volume pump stage, and the precise mixing mechanism consists of a material mixing cavity and a mixing rod. The working principle of the accurate feeding mechanism is that a displacement pump is utilized as follows: under the drive of a displacement pump driving motor 2, a plunger pump or a worm pump of a gear displacement pump 1 can supply materials in a thread shape, coarse particles or a powder shape; before the gear volumetric pump 1 is sucked, heating, melting and exhausting are carried out in advance; if the filamentary material is used, a far-end wire feeding mode can be adopted, the driving motor is generally arranged on a printer frame, the material is directly extruded into the throat pipe by the extrusion gear, and coarse particles or powdery consumables can be directly melted for use. The gear displacement pump 1 has the characteristics that the displacement is fixed and can discharge at high pressure, the displacement can be changed by changing the rotating speed, and the discharge is stopped instantly when the driving is stopped, so that the accurate quantitative discharge and the instant stop can be realized; the gear with millimeter level size and the tooth height with submillimeter level can be selected, and the low-pulsation material discharge capacity of 1 cubic millimeter level/second can be easily realized under the driving of medium and low rotating speed by matching with helical teeth; accurate feeding of each color is realized, and a precondition is created for the accurate mixing of the color tone in the next step.
The structure characteristics and the theory of operation of accurate compounding mechanism: in order to realize rapid color change, the material mixing cavity can be in a central rotation symmetry shape such as a column shape, a lantern shape and the like, a plurality of holes on the side surface are inlet holes for molten materials of various colors, the lower holes are used as extrusion holes for the molten mixed materials, and the upper holes are through holes of the mixing rod and are waste material passing holes leading to the waste material caching cavity; the volume of the material mixing cavity is small enough, and the volume is determined by a thin-layer micro-space surrounded by the front end expansion part of the material mixing rod and the inner wall of the material mixing cavity; thus the volume of the materials contained in the material mixing cavity can be in the order of 0.1 cubic millimeter; the mixing rod (also used as a switching column) is structurally characterized in that the head part is a piston-shaped expansion part: when the mixing rod rotates, the head of the mixing rod is a piston-shaped expanded side part which sweeps all micropores of the material branch pore passage 12, so that extruded molten materials of various colors are fully mixed along a spiral intersection path under the drive of a rotating surface, the aim of instantaneous and trace multi-component mixed materials is fulfilled, and the mixed materials enter an extrusion hole to be discharged or are discharged to a waste material cache cavity under the drive of subsequent materials. The front end expansion part of the mixing rod is small enough in average diameter and thin enough in axial height, so that the extruded material filaments can change color within the length of 2-3 mm; the axial motion of the mixing rod can play a role in switching the column to select the material flow direction, when the mixing rod (also switches the column) moves upwards axially, the head of the mixing rod is a waste material passing hole 10 leading to the waste material buffer cavity above the piston-shaped expansion part in a sealing mode, and molten materials can only flow out of a material extrusion hole of the extruder assembly to print an object. When the mixing rod (also serving as a switching column) moves downwards and axially, the expanded part seals a material extrusion hole leading to the extruder assembly below the expanded part, and the molten material can only flow out from the waste material passing hole 10; and enters the discard buffer chamber.
The mixing of materials of various colors in the material mixing cavity can also adopt a cavity wall natural thread mixing method; the method is that the inner wall surface in the material mixing cavity is provided with a thread convex section, when the material flows through the surface of the thread section at a certain speed, the melted material can be rolled and stirred, and the aim of uniform mixing is also achieved.
In summary, the following steps: a plurality of motors which can be independently controlled are used for driving each micro displacement pump (a gear pump, a worm pump or a plunger pump and the like), molten materials of various colors after the previous stage of pretreatment are pumped into each material pore channel 12, then are converged in the material mixing cavity 9, are extruded from the material extrusion holes 11 after being mixed by the rotation of the mixing rod, and are stacked layer by layer to form an object. The color tone is controlled by the motor driving each micro-volume pump, and each independently controlled motor can control the extrusion amount of each color according to the color tone requirement.
However, even if the small space volume of the material mixing chamber is realized, the abrupt change of the color tone can not be completed in a smaller length (below 0.5-1 mm), and the part of the mixed molten material which does not complete the complete change of the color tone in the transition stage must be discarded or partially discarded, so 2 waste material integration methods, namely a waste material discharge method or a waste material buffer method, can be adopted.
The waste material discharge method is that the mixed material of the abrupt change of the unfinished color tone in the transition stage is extruded to the object to be printed outside the area of the object to be printed, and then the formed object is continuously printed; or directly printing the color on the filling area or the surface area of the molded object without coloring;
one of the abandoned material caching methods is that under the coordination of axial movement of the mixing roller, the mixing roller moves downwards to seal the extrusion hole, and part of the mixed material which does not finish sudden change of color tone in the transition stage is extruded to a abandoned material caching cavity; the waste material buffer cavity is positioned above the extrusion hole, is integrated with the extrusion head and maintains high temperature, so that the waste material stored in the waste material buffer cavity is in a molten state.
Adding a set of volumetric pump feeding mechanism which is the same as the accurate feeding mechanism, and reversely running the pump during the transitional color period to reversely guide the mixed material out of the material mixing cavity, wherein the abandoned material is also called as buffer material; when the relative rotating speed of the volumetric pumps of other colors is controlled, the variable volume rate of the volumetric pumps of other colors is smaller than the sum of the variable volume rates of the volumetric pumps of other colors, so that the total inflow and outflow amounts of the mixed materials in the material mixing cavity are not equal, and the mixed materials are extruded from the extrusion holes; the running speed of the material extrusion hole is in direct proportion to the flow difference, at the moment, the displacement speed of the extrusion hole is reduced compared with the normal speed, the color change rate of the unit displacement length is increased, the extrusion hole is in a slow displacement state, and the color change is shown on a small scale; when the method is used, the waste can be recycled and reused, the volumetric pump feeding mechanism for caching the waste can also rotate in the forward direction to pump materials to the material mixing cavity, and in the condition, the cached material waste can be printed on parts (such as filling structures, inner spaces, inner surfaces and the like) of an object, which are not required to be colored. Specific mention is made of: the volumetric pump used for reject buffer must be a bi-directional volumetric pump because the added set of volumetric pump feed mechanisms, identical to the precision feed mechanism, is reversed during the transition color.
In addition; the buffer memory material is in the suction material mixing chamber after, is gone into high temperature storage chamber by the pump, and the inner space shape can be inverted circular truncated cone shape, is favorable to taking out after solidifying.
A color-supplying fine-mixing type extruder assembly:
the color supply is that a special channel is used for directly supplying various colors of pigments to a material mixing cavity, and the color supply is greatly similar to a material supply precision mixing type extruder assembly in structure and principle, except that only 1 or 2 paths of precision feeding mechanisms 1 are used for stacking formed materials, and the other 1 path is used for constructing supporting materials) and a waste material caching structure for realizing a waste material caching method are adopted, and a set of volumetric pump feeding mechanism which is the same as the precision feeding mechanism is adopted, and during the slow transition color, the pump reversely operates to guide the mixed materials as caching materials into a waste material caching cavity 19 from the material mixing cavity; controlling the relative rotation speed and proportion of other volumetric pumps with various colors to obtain various colors; the difference between the amount of material fed to the material mixing chamber and the amount of material pumped from the material mixing chamber is also the flow rate of the extrusion orifice, which when reduced means that the match of the running speed of the extruder assembly is slowed down, the rate of change of colour per unit running distance of the extruder assembly increases and the capability of expression of tonal details increases.
In addition; the buffer material can be discarded or selectively printed on a filling area or a surface area of the molded object which is not required to be colored (the volumetric pump feeding mechanism can also rotate in the forward direction).
In addition to the above, at least 3-4 paths (generally red, blue, green and black pigments) of precise feeding mechanisms (wherein the material refers to pigment, the pigment of each color can be liquid, solid and the like) are required to be combined into rich colors, and a volumetric pump feeding mechanism is also absolutely necessary, and the mixing system is the same as above.
[ description of the drawings ]
The invention is further described in the following preferred embodiments with reference to the accompanying drawings in which:
FIG. 1 is an exploded view of a core body of a single buffer type fine mixing extruder assembly structure.
FIG. 2 is an assembly view of a core body of a single buffer type precision mixing extruder assembly structure.
FIG. 3 is an external view of a core body of a single buffer type fine mixing extruder assembly structure.
FIG. 4 is a schematic sectional view of a main body of a reversible buffer type fine-mixing extruder assembly.
FIG. 5 is a schematic view of an appearance of a main body of a reversible buffer type fine mixing extruder assembly.
Illustration of the drawings:
1-gear displacement pump
2 displacement pump driving motor
3 abandon material buffer memory chamber
4 mixing stick and switching pole (expansion part)
5-gear displacement pump
7 copper body (heater body)
8 mixing rod motor
9 Material mixing chamber
10 abandoned material passing hole
11 material extrusion hole
12 material channels
15 wire
16 heater aluminum body
17 guide hole disc
18 mixing roller
19 abandoned material buffer cavity
20 dye inlets of different colors
22 extrusion orifice disc
23 gear displacement pump cover plate
24 material inlet hole
25 gear displacement pump rotating shaft
26 material silk melts storage chamber
[ examples of embodiment ]
The invention is further illustrated by the following extruder assembly, the most important component of a 3D molding machine to which the present technology is applied:
as shown in fig. 1,2, and 3:
need to explain: the mixing rod motor 8 is fixed on a bracket, the bracket can only slightly reciprocate along the axial direction of the motor under the driving of an electric appliance, and the mixing rod and switching column 4 is driven to slightly reciprocate along the axial direction to determine whether to block the abandoned material passing hole 10 or the material extrusion hole 11; the displacement pump driving motor 2 is rigidly fixed on an extrusion head assembly; these brackets are not shown in this figure, as they are not important to the technology and are generally understood. The extrusion orifice disc 22 is threaded to be screwed into the copper body 7 and to seal off the guide orifice disc 17 inside. When the thread can be twisted into place, a gap will be created between the bore disc 17 and the copper body 7, causing leakage from the individual bores and must therefore be twisted into place.
Fig. 1 is an exploded view of a core main body of a single buffer type precision mixing type extruder assembly structure, and with reference to fig. 2-5, the connection relationship between 5 gear volumetric pumps and a branch material channel, a waste buffer chamber and a material mixing chamber can be clearly seen; the wire 15 passes through the wire inlet hole 24 and is melted in the wire melting storage cavity 26 after the contact heat transfer of the heater aluminum body 16.
Fig. 2 is an enlarged view of the structure near the extrusion hole, and the material mixing chamber 9 is a closed cylindrical space composed of the copper body 7 and 2 cylindrical spaces of the pilot hole disk 17; on the cylindrical wall of the cylindrical space in the center of the guide orifice disk 17, 5 material inlet holes are provided, which communicate with the material branch ducts 12 via the upper surface of the solid to which the guide orifice disk 17 opens, so that 5 independent material channels are established, controlled by the gear displacement pump 1, of a strand melt storage chamber 26 (fig. 1) which opens into the material mixing chamber 9.
FIG. 3 is a rear view of the extruder assembly; it can be clearly seen that: a displacement pump driving motor 2, a discarded material buffer chamber 3, a mixing rod and switching column 4 (shown in figure 1) and the like. The volumetric pump drive motor 2 drives the gear volumetric pump shaft 25) to rotate purely. The gear displacement pump cover plate 23 is used for sealing the upper end surfaces of the gears in the 5 displacement pumps. The copper body 7 is heated by the electric heating rod, and the heat is conducted to the copper body 7 through the contact surface.
The single buffer type means that the waste buffer chamber only stores the waste, but not uses the waste, and the waste is manually removed after excessive accumulation.
The main part of the accurate mixed type extruder assembly of feed comprises accurate feed mechanism and accurate colour mixture mechanism, and accurate feed mechanism is by: the gear displacement pump 1 finishes feeding under the drive of a displacement pump drive motor 2, and the accurate mixing mechanism consists of a material mixing cavity 9 and a mixing rod and switching column 4; in order to realize rapid color change, the material mixing cavity can be in a central rotation symmetry shape such as a column shape, a lantern shape and the like, a plurality of holes on the side surface are inlet holes for molten materials of various colors, the lower holes are used as extrusion holes for the molten mixed materials, and the upper holes are through holes of the mixing rod and are waste material passing holes leading to the waste material caching cavity; the volume of the material mixing cavity is small enough, and the volume is determined by a thin-layer micro-space surrounded by the front end expansion part of the material mixing rod and the inner wall of the material mixing cavity; thus the volume of the materials contained in the material mixing cavity can be in the order of 0.1 cubic millimeter; the mixing rod (also used as a switching column) is structurally characterized in that the head part is a piston-shaped expansion part: when the mixing rod rotates, the head of the mixing rod is in a piston shape, and the expanded side surface part sweeps all micropores of the material branch pore passage 12, so that extruded molten materials of various colors are fully mixed along a spiral intersection path under the driving of a rotating surface, the aim of instantaneous and trace multi-component mixed materials is achieved, and the mixed materials enter an extrusion hole to be discharged or are discharged to a waste material buffer cavity under the driving of subsequent materials. The front end expansion part of the mixing rod is small enough in average diameter and thin enough in axial height, so that the extruded material filaments can change color within the length of 2-3 mm; the axial motion of the mixing rod can play a role in switching the column to select the material flow direction, when the mixing rod (also switches the column) moves upwards axially, the head of the mixing rod is a piston-shaped expanded part which is sealed and leads to a waste material passing hole 10 of the waste material caching cavity 3, and molten materials can only flow out of a material extrusion hole of the extruder assembly to print objects. When the mixing rod (also serving as a switching column) moves downwards and axially, the expanded part seals a material extrusion hole leading to the extruder assembly below the expanded part, and the molten material can only flow out from the waste material passing hole 10; and into the reject buffer chamber 3.
In summary, the following steps: the above mode results in an accurate FDM color 3D printing method, which is characterized in that: a plurality of motors which can be independently controlled are used for driving each micro displacement pump (a gear pump, a worm pump or a plunger pump and the like), molten materials of various colors after the previous stage of pretreatment are pumped into each material pore channel 12, then are converged in the material mixing cavity 9, are extruded from the material extrusion holes 11 after being mixed by the rotation of the mixing rod, and are stacked layer by layer to form an object.
The color tone is controlled by the motor driving each micro-volume pump, and each independently controlled motor can control the extrusion amount of each color according to the color tone requirement.
16 is a heater aluminum body, and 15 is a material wire.
As shown in fig. 4 and 5:
the basic construction is substantially the same as that of figures 1,2 and 3, except for the features and location of the reject buffer chamber 19. The structure and function of the heater aluminum body are the same as those of fig. 1,2 and 3, and are shown in the structure.
FIG. 4 is a sectional view of the main structure of the extruder assembly, and a discard buffer chamber 19 is established on the consent passage with the gear displacement pump 5 and the material mixing chamber 9; thus, the abandoned material can be transferred between the material mixing cavity 9 and the abandoned material buffer cavity 19 in a bidirectional way; conditions are established for the reuse of reject. The number of the gear displacement pumps can be set to 6 or more as required; the coloring material can better express colors only by at least more than 4 inlet holes. The mixing rod motor 8 directly drives the mixing rod 18 to rotate only singly, and the mixing rod 18 only rotates singly and does not move axially any more, so that the mixing rod motor 8 and the displacement pump driving motor 2 are rigidly kept static with the copper body.
FIG. 5 is a rear view of the extruder assembly; it can be clearly seen that: the positive displacement pump driving motor 2, abandon material buffer memory chamber 19, compounding rod 18,4 material silks 15 and hand-hole etc.. And 23 is a gear displacement pump cover plate. The reversible buffer type means that the waste buffer chamber can return to the mixing chamber for reuse under the volumetric pump instead of only storing the waste.
Similar to the configuration of fig. 1, 3 different colors can be supplied by 3 gear volumetric pumps 5, 1 gear volumetric pump being used to pump out the printed molding compound; the 1 gear volumetric pump is used for recovering waste materials and buffering the waste materials in the waste material buffering cavity 19, and the gear volumetric pump returns the waste materials to the material mixing cavity 9 in a reverse work mode.
The heater aluminum body 21 is used for heating each cavity needing to be heated; and 5 material pore canals 12 play a role in connecting the discarded material caching cavity, the pigment cavity, the molding material cavity of the material wire 15 and the traffic key relation of the material mixing cavity 9.
The length of the extrusion orifice represents the residual amount of material and should be matched to 1-2 times the diameter.