CN116494345A - Photocuring multi-material forming device and method for ceramic additive manufacturing - Google Patents

Abstract

The invention discloses a photocuring multi-material forming device and a photocuring multi-material forming method for ceramic additive manufacturing, which can overcome the defect that materials are mutually polluted or photocuring printing of multiple materials can be realized only in the longitudinal direction in the photocuring ceramic multi-material printing process. The novel synergistic composite forming strategy is adopted, and the gradient temperature control device is matched to maintain the fluidity of the material in the printing process, so that the high-precision and high-efficiency multi-material forming of the liquid photosensitive ceramic material can be realized. The invention adopts a mechanical structure of triaxial movement, in single-layer ceramic slurry printing, based on a slicing algorithm and supporting treatment of upper computer software, a digital light processing light source is used for realizing the printing of main ceramic material slices and the next layer of support of a target piece, and simultaneously, other materials are extruded at fixed points and quantitatively by matching with a direct-writing printing spray head on an X-axis, and the light source is combined with secondary curing, so that the single-layer multi-material printing of a photo-curing process is realized, and finally, the target piece is piled layer by layer, thereby completing the high-quality and integrated forming of the target piece.

Description

Photocuring multi-material forming device and method for ceramic additive manufacturing

Technical Field

The invention belongs to the field of 3D printing, and particularly relates to a photocuring multi-material forming device and method for ceramic additive manufacturing.

Background

Aeroengines and heavy duty gas turbines are moving towards high thrust to weight ratios and high power, requiring increased engine pre-turbine temperatures. In order to improve the temperature before vortex, the prior art is developed from the original polycrystalline blade to the existing single crystal blade and from the solid blade to the complex hollow cavity blade, and the aim is to continuously improve the temperature resistance of the engine blade, so that the temperature before vortex of the engine is improved. Because of the limitation of the melting point of metal, the improvement of the temperature resistance of the alloy material encounters a bottleneck, and the complex air cooling inner cavity structure of the blade becomes an important way for improving the temperature resistance of the blade. Ceramic cores are key to forming the complex air-cooled internal cavity structure of the blade, and therefore, the performance and quality of the ceramic cores directly affect the qualification rate of the blade. Several of the more critical indicators for ceramic cores include flexural strength, open porosity, firing shrinkage, and high temperature creep resistance. With the increasing complexity of ceramic cores, it has been difficult to prepare ceramic cores of more complex structures using conventional hot injection molding processes.

Ceramics are widely used in the fields of chemical industry, machinery, electronics, aerospace, biomedicine and the like due to the characteristics of high mechanical strength and hardness, good chemical stability, excellent acousto-optic electromagnetic heat and the like. However, most of these conventional manufacturing processes require a mold to be manufactured in advance, so that the overall production cycle is long, and ceramic parts having highly complex structures cannot be formed. In addition, ceramics are extremely difficult to process due to their extremely high hardness and brittleness. On the one hand, the cutting tool is easy to wear, and on the other hand, defects such as cracking of a sample piece and the like can be generated in the processing process. The light-cured 3D printing ceramic technology is adopted, so that a mold is not needed, and a reliable preparation mode is provided for preparing a more complex ceramic core. For the photo-curing 3D printing ceramic core, since the ceramic core requires a high open porosity, the bonding portion (sintering neck) between the ceramic particles is limited during degreasing and sintering, so that the strength of the ceramic core is low. Therefore, a process is needed to strengthen the firing neck of a photo-cured 3D printing ceramic core and improve the strength of the additive ceramic core.

The photocuring 3D printing technology is a novel 3D printing technology based on photosensitive materials, has the characteristics of high precision, quick forming and the like, and mainly comprises two main types: stereolithography (SL) and Digital Light Processing (DLP) are 3D printing based on the photopolymerization principle, with typical stereolithography processes providing a beam of ultraviolet light by a laser located above a shaping platen, while digital light processing techniques provide ultraviolet energy by LEDs located below the shaping platen. In the precision casting process, in order to meet the actual functional requirements, a multi-material additive manufacturing precision casting mode is adopted to strengthen the mechanical properties of part of the structure and replace special ceramic materials for part of the structure, but multi-material printing of the existing photo-curing process is still blank. At present, various implementations of longitudinal photo-curing multi-material printing exist, but single-layer multi-material photo-curing printing is still difficult to solve. Although the mode of switching printing is carried out by a plurality of material tanks at present, the photo-curing multi-material printing in the same layer is realized to a certain extent, the condition that the material tanks are mutually polluted in the printing process is still difficult to avoid. Therefore, multi-material modeling is difficult to achieve in cases where only a single material can be used for the photo-curing process.

The direct writing process is one of 3D printing processes, can directly print a target piece, and 3D printing based on the direct writing process has the characteristics of high precision and high speed, but has high requirements on the viscosity and the curing speed of ink, and is difficult to realize the manufacture of a large model.

In order to solve the problem that only a single material can be used in the photo-curing process, the invention provides a 3D printing system and a printing method of a composite process with the cooperation of the photo-curing process and a direct-writing nozzle.

Disclosure of Invention

In order to solve the problems, the invention discloses a composite forming device for multi-material ceramic structure additive manufacturing, which solves the problem that only a single material can be used in a photo-curing process.

The composite forming device for multi-material ceramic structure additive manufacturing comprises a digital light processing light source, a direct writing type printing spray head, an X axis, a spray head frame, a printing platform and a trough; wherein the digital light processing light source is positioned above the printing platform; the printing platform is positioned in the trough and is controlled to lift by a Z-axis motor at the bottom of the trough; the X-axis is arranged on an X-axis guide rail of the trough, a Y-axis sliding block is connected between the two X-axes, the positive movement along the X-axis is used as a machine reference, and a direct-writing printing spray head and a scraper are sequentially arranged on the Y-axis sliding block; the printing platform is parallel to the bottom surface of the trough and adopts a grid structure.

Further, the direct-writing type printing spray head is provided with a temperature control device according to the weight, the trough is used for containing liquid photosensitive ceramic materials, heating plates of the temperature control device are arranged on two sides of the trough, and a temperature control screen is arranged on the front side of the trough.

The silo bottom plate on the silo is equipped with the trompil for the lift of Z axle motor accessible screw rod structure control print platform, the hole is laminated in the contact surface of screw rod simultaneously, prevents that photosensitive ceramic material from spilling.

Further, the bottom of the direct-writing type printing spray head is provided with a nozzle, and the top of the direct-writing type printing spray head is connected with a feeding pipe; wherein the heating plate is arranged on the surface of the direct-writing type printing spray head; the back surface of the direct-writing type printing spray head is provided with a spray head frame hole and an iron sheet; the direct-write head that is not in the operating state is suspended from the head frame by a corresponding structure of the head frame Kong Zhenkong. After the electromagnet is electrified, the iron sheet is absorbed, and then the spray head can be fixed.

Further, the printing platform is provided with a grid, and the middle end of the printing platform is provided with a zeroth layer of curing surface.

The trough is composed of two parts, namely a trough and a printing platform, and the trough is fixed on the Z axis of the printing equipment and is used for bearing liquid ceramic printing materials. The printing platform is used for bearing the printing model and is in a fine grid shape, and the fluidity of the liquid photosensitive ceramic material is not affected by the grid surface during printing. The printing platform is controlled by the Z-axis motor to move up and down. Before printing, the bottom surface of the trough is required to be ensured to be parallel to the horizontal plane, so that errors generated in the photo-curing printing process are prevented, and model printing failure is avoided. In the printing process of the first layer, the printing platform rises to be flush with the horizontal plane on the groove, a certain area is solidified, and the inter-grid gaps in the area are filled with solidified ceramic materials to jointly form a plane which is used as a substrate of the printing model. In the printing process of one intermediate layer, after the printing of the previous layer is finished, the scraper trowells the surface of the layer, the printing platform moves downwards along the Z axis by a layer thickness distance, and the fine grids of the printing platform can enable liquid ceramic materials to pass through and wait for feeding to print the next layer. After printing, the printing platform is driven by the upper computer to control the Z-axis motor to rise to the highest stroke point, at the moment, the model is lifted out of the liquid ceramic material, the substrate is removed after manual mould taking, and post-treatment processes such as surface treatment and sintering are carried out, so that the final manufacturing of the ceramic model is completed.

The curing light source is a common ultraviolet light source in the digital light processing technology, can irradiate remote ultraviolet light with specific wavelength and specified pattern, irradiates each slice of the target piece in the pattern form, and cures the photosensitive ceramic printing material to finish the model manufacture of the slice of the layer. The pattern illuminated by the light source is realized by a digital micromirror device, which is a matrix of micromirrors (precision, micro-mirrors) arranged on a semiconductor chip, each micromirror controlling a pixel in the projected picture. The number of micro-mirrors is in accordance with the resolution of the projected picture, 800 x 600, 1024 x 768, 1280 x 720 and 1920 x 1080 (HDTV) are the dimensions of some common digital micro-mirror devices, enabling high precision shaping of photo-curable ceramic materials.

The printing spray head is arranged on the sliding block of the X axis, and the X axis motor is controlled by the upper computer to realize the movement of the printing spray head on the X axis. The printing nozzle adopts a nozzle process, so that higher efficiency can be realized while high-precision printing is realized. The material extrusion process of the direct-writing type spray head can be realized in various modes, and common processes include pneumatic process extrusion, screw extrusion and the like, and slice patterns are printed under the drive of a sliding block while printing materials are continuously extruded. During printing, the print head and the slider substantially form the Y-axis of a three-axis printing system. The scraper is fixed on the side face of the X axis, and after each slice is printed, the scraper scrapes the surface of the model under the drive of the X axis in the working process of the positive motion of the X axis, so that redundant printing materials are removed.

A method of photocuring multi-material forming for ceramic additive manufacturing, comprising the steps of:

step one: before printing, feeding the material to the trough manually until the liquid level of the ceramic photosensitive material is level with the upper horizontal plane of the trough, and lifting the printing platform to the highest stroke point and also level with the upper horizontal plane of the trough, wherein the printing platform is of a grid-shaped structure, so that the photosensitive ceramic material can flow through the grid, and finally, the upper surface of the printing platform is level with the liquid level and is immersed in the photosensitive ceramic material;

step two: when printing starts, firstly, printing a model substrate, printing a zeroth layer of the model according to slice picture processing of upper computer software, after the substrate is solidified, filling the solidified photosensitive ceramic material between grids, and forming a plane in a partial area of a printing platform.

Step three: printing layer by layer according to the slicing and supporting processing results of the upper computer software; the slicing and supporting process is based on the following principle: and (3) performing preliminary slicing on the model according to the set layer thickness, and processing by additionally curing a part of the area of the layer and connecting the slice pattern of the layer by using the slender structure for the situation that the next layer cannot be provided with effective support by the layer.

Step four: taking a photosensitive ceramic material in a trough as a printing material A, taking a photosensitive ceramic material in a printing nozzle as a printing material B, and taking a model of only two printing materials as an example; for any layer other than the zeroth layer, the printing flow follows the following principle: firstly, the electromagnet of the X-axis sliding block is used for absorbing the corresponding spray head and extracting, direct-writing printing is carried out on the upper layer of slice pattern and the supported solidification surface on the printing material B, after printing is finished, the X-axis is reset, and meanwhile, the direct-writing printing area is solidified by the digital light processing light source, and if the area without the printing material B in the layer is skipped; the Z axis drives the printing platform to descend by a layer thickness distance, the printing material A flows through the grid-shaped printing platform, under the work of the digital light processing light source, the slice pattern area and the support area prepared for the printing material B of the next layer are solidified, and the X axis forward motion drives the scraper to scrape redundant printing material.

Step five: based on the principle of layer printing in the fourth step, stacking layers by layers, and finally completing a printing system to realize the model manufacture of various liquid photosensitive ceramic materials.

The invention has the beneficial effects that:

1. the multi-material high-precision and high-speed molding of the photo-curing process can be realized, printing of the multi-material is carried out in a single layer, and the requirement that the ceramic core part structure adopts various materials to improve the performance is met.

2. Compared with the traditional multi-material photo-curing printing, the material pollution caused by multi-material tank printing can be avoided; near-net forming in the multi-material printing process can be realized through the cooperation of the printing spray head and the support, so that unnecessary material loss is reduced; the current situation that photo-curing printing can only finish multi-material printing in the Z axis can be changed, multi-material printing of a photo-curing single layer is realized, and then the single layer is expanded to integral multi-material printing of a model.

Drawings

FIG. 1 is a schematic diagram of a gradient temperature control composite forming device for multi-material ceramic additive manufacturing according to the present invention. The device comprises a digital light processing light source 1, a direct writing type printing spray head 2, an X-axis 3, a spray head frame 4, a printing platform 5, a trough 6, a heating plate 7 of a temperature control device and a scraper 8.

Fig. 2 is a schematic cross-sectional view of a printing platform structure according to the present invention. Among these are "print platform 5", "trough bottom plate 9", "lifting screw 10".

Fig. 3 is a front and back detail view of the print head. Among these are "feed pipe 201", "head holder hole 202", "heating plate 203", "nozzle 204", "iron plate 205".

Fig. 4 is a schematic view of the zeroth layer. Among these are "print platform 5", "grid 501", "zeroth layer cure side 502".

FIG. 5 is a schematic view of a case slice of an embodiment ((a) X layer, (b) X+1 layer, and (c) X+2 layer).

Fig. 6 is a diagram of a printing pattern of an embodiment corresponding to the slice of fig. 4 ((a) the printing of the X-th layer, (B) the printing of the x+1-th layer printing material B, (c) the printing of the x+1-th layer printing material a, (d) the printing of the x+2-th layer printing material B, and (e) the printing of the x+2-th layer printing material a.

Description of the embodiments

The present invention is further illustrated in the following drawings and detailed description, which are to be understood as being merely illustrative of the invention and not limiting the scope of the invention. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in the drawings, and the words "inner" and "outer" refer to directions toward or away from, respectively, the geometric center of a particular component.

Taking the model of two printing materials as an example: before printing starts, the material is fed into the material tank manually, the ceramic photosensitive material in the material tank is called printing material A, and the ceramic photosensitive material in the printing nozzle is called printing material B, and the description modes are cited hereinafter.

After feeding, uploading the slice model, returning the triaxial of the printing system to zero position, and preparing to start printing of the 0 th layer, namely printing of the model substrate. The Z axis is driven by a motor to rise to be level with the horizontal plane on the trough, the surface of the Z axis is immersed in the printing material A, the ceramic photosensitive material is solidified in part of grids of the printing platform to form a zero layer solidification surface 502 under the irradiation of a solidification light source, and the zero layer solidification surface and the printing platform form a plane together to serve as a substrate for subsequent printing. After the substrate is solidified, the scraper moves along with the positive direction of the X axis, redundant printing material A on the surface of the substrate is scraped, and printing of the 0 th layer is finished.

As shown in fig. 4, the X-th, x+1-th, and x+2-th layers of the model slice are shown. The printing process from the X-th layer to the x+2-th layer is described in detail below:

as shown in FIG. 4, the X-th layer is formed by printing material A only, after the printing of the X-1 th layer is finished, the Z axis is reduced by a layer thickness distance, and the ceramic photosensitive material is solidified on the surface of the X-1 th layer according to the slice pattern shape under the appointed irradiation of a solidification light source controlled by an upper computer, so that the model of the X-th layer is formed. After the X layer is solidified, the X axis is driven by the motor to move forward. At this time, the scraper is in front with the positive direction of the X axis, the printing nozzle is in front, the scraper scrapes the surface of the X layer, and when the redundant printing material A is printed, the printing nozzle firstly adsorbs and grabs the direct-writing printing nozzle 2 under the control of the upper computer, and the printing material B slice area of the X+1 layer is subjected to jet printing. When the X axis moves forward to the maximum stroke position, the slice of the printing material B of the X+1th layer is printed in an uncured form, the printing material B is irradiated by a curing light source, and the printing material B is subjected to preliminary printing by the jet of a printing nozzle, so that the jet quantity is strictly controlled by a board card, the jet quantity is almost completely cured after illumination, and the mutual pollution of the printing material caused by the sedimentation of a subsequent Z axis is avoided.

At the same time, after the ejected printing material B is solidified, the X-axis reverse motion returns to zero position, the Z-axis descends by one layer thickness distance, and printing of the printing material A area of the X+1th layer is prepared. Under the irradiation of the curing light source, the print material a slice region of the x+1th layer is cured. Because the region of the X+2 layer where the printing material B exists lacks a printing plane, the X+2 layer slice contains support printing for the X+2 layer, and the support slice is automatically generated by the upper computer software to provide support for the condition of the next layer lacking the printing plane. When the X+1 layer is completely solidified, the X axis moves forward under the drive of the motor, the scraper scrapes off the superfluous printing material A on the surface of the X+1 layer, and meanwhile, the printing material B area of the X+2 layer is subjected to jet printing. After the positive X-axis movement process is finished, the curing light source cures the printing material B area of the X+2 layer, the X-axis returns to the zero position, the Z axis descends by a layer thickness distance, and the printing material A area of the X+2 layer is cured.

In summary, the X-th layer shows the case that the layer has only printing material A and the next layer is not supported; the x+1 layer shows the case where there are two printing materials in this layer and the next layer needs to be supported; the X+2 layer shows that the layer has two printing materials, and the next layer is not required to be supported, and the support adopts an elongated structure, so that the removal of the post-mold-taking treatment process is facilitated. According to the various conditions, the single-layer printing process is continuously repeated, two printing materials are piled layer by layer to manufacture the single-layer printing material, and finally the target piece is finished.

Through the mode, on the premise of avoiding mutual pollution of various printing materials, printing of various liquid ceramic photosensitive materials in the same layer can be realized, and finally integrated printing and forming of the target piece are finished by stacking layer by layer.

In the printing process, the gradient temperature control device on the side surfaces of the direct-writing printing spray head and the trough always keeps a heating working state, so that the conditions that two lamellar structures are solidified and are difficult to connect are avoided.

The technical means disclosed by the scheme of the invention is not limited to the technical means disclosed by the embodiment, and also comprises the technical scheme formed by any combination of the technical features.

Claims (6)

1. Composite forming device is made to multi-material ceramic structure additive, its characterized in that: the device comprises a digital light processing light source (1), a direct-writing type printing spray head (2), an X-axis (3), a spray head frame (4), a printing platform (5) and a trough (6); wherein the digital light processing light source (1) is positioned above the printing platform (5); the printing platform (5) is positioned in the trough (6) and the lifting of the printing platform (5) is controlled by a Z-axis motor at the bottom of the trough (6); the X-axis (3) is arranged on an X-axis guide rail of the trough (6), a Y-axis sliding block is connected between the two X-axes (3), the forward motion along the X-axis (3) is used as a machine reference, and the Y-axis sliding block is sequentially provided with a direct-writing printing spray head (2) and a scraper (8); the printing platform (5) is parallel to the bottom surface of the trough (6) and adopts a grid structure.

2. The multi-material ceramic structure additive manufacturing composite forming device of claim 1, wherein: the direct-writing type printing spray head (2) is provided with a temperature control device, a trough (6) is used for containing liquid photosensitive ceramic materials, heating plates (7) of the temperature control device are arranged on two sides of the trough, and a temperature control screen is arranged on the front side of the trough.

3. The multi-material ceramic structure additive manufacturing composite forming device of claim 1, wherein: wherein be equipped with the trompil on silo bottom plate (9) of silo (6) for the lift of Z axle motor (10) accessible screw rod structure control print platform (5), the hole is laminated in the contact surface of screw rod simultaneously, prevents that photosensitive ceramic material from spilling.

4. The multi-material ceramic structure additive manufacturing composite forming device of claim 1, wherein: the bottom of the direct-writing type printing spray head (2) is provided with a nozzle (204) and the top of the direct-writing type printing spray head is connected with a feeding pipe (201); wherein the heating sheet (203) is arranged on the surface of the direct-writing type printing nozzle (2); the back surface of the direct-writing type printing spray head (2) is provided with a spray head frame hole (202) and an iron sheet (205); the direct-writing type spray head (2) which is not in the working state is hung on the spray head frame (4) through a structure corresponding to a needle hole of the spray head frame hole (202).

5. The multi-material ceramic structure additive manufacturing composite forming device of claim 1, wherein: and a grid (501) is arranged on the printing platform (5).

6. The photocuring multi-material forming method for ceramic additive manufacturing is characterized by comprising the following steps of:

step one: before printing, feeding the material tank (6) manually until the liquid level of the ceramic photosensitive material is level with the upper horizontal surface of the material tank (6), and lifting the printing platform (5) to the highest stroke point and also level with the upper horizontal surface of the material tank (6), wherein the photosensitive ceramic material can flow through the grid due to the fact that the printing platform (5) is of a grid-shaped structure, and finally, the upper surface of the printing platform is level with the liquid level and immersed in the photosensitive ceramic material;

step two: when printing is started, firstly printing a model substrate, printing a zeroth layer of the model according to slice picture processing of upper computer software, filling a cured photosensitive ceramic material between grids after the substrate is cured, and forming a plane in a partial area of a printing platform;

step three: printing layer by layer according to the slicing and supporting processing results of the upper computer software; the slicing and supporting process is based on the following principle: performing preliminary slicing on the model according to the set layer thickness, and processing by additionally solidifying a part of the area of the layer and connecting the slice pattern of the layer by using a slender structure under the condition that a certain layer cannot provide effective support for a next layer;

step four: taking a photosensitive ceramic material in a trough (6) as a printing material A, taking a photosensitive ceramic material in a printing nozzle as a printing material B, and taking a model of only two printing materials as an example; for any layer other than the zeroth layer, the printing flow follows the following principle: firstly, the electromagnet of the X-axis sliding block is used for absorbing the corresponding spray head and extracting, direct-writing printing is carried out on the upper layer of slice pattern and the supported solidification surface on the printing material B, after printing is finished, the X-axis is reset, and meanwhile, the direct-writing printing area is solidified by the digital light processing light source, and if the area without the printing material B in the layer is skipped; the Z axis drives the printing platform to descend by a layer thickness distance, the printing material A flows through the grid-shaped printing platform, under the work of the digital light processing light source, the slice pattern area and the support area prepared for the next layer of printing material B are solidified, and the X axis forward motion drives the scraper to scrape redundant printing material;

step five: based on the principle of layer printing in the fourth step, stacking layers by layers, and finally completing a printing system to realize the model manufacture of various liquid photosensitive ceramic materials.