阅读说明：本技术 一种高速树脂涂层3d打印系统 (High-speed resin coating 3D printing system ) 是由 夏春光 于 2019-09-23 设计创作，主要内容包括：本发明公开本种高速树脂涂层3D打印系统,包括曝光光学系统、薄膜、激光位移计、滚刀、气泡刮刀、树脂槽、样品台；所述的样品台与升降装置连接,样品台位于树脂槽内,薄膜覆盖在树脂槽内的树脂上；树脂槽安装在三维的运动控制轴上；曝光光学系统位于树脂槽上方,曝光光学系统的投影镜头朝向薄膜,投影镜头外套有电磁线圈；投影镜头一侧设有激光位移计；薄膜上方还设有滚刀,下方设有气泡刮刀。本发明不仅提供了高速,大幅面的加工能力,还引入了磁场在打印过程中控制磁性树脂的磁化方向,提高了目前基于树脂的3D打印速度,还允许使用高粘度或者高含量的固液混合树脂。(The invention discloses a high-speed resin coating 3D printing system, which comprises an exposure optical system, a film, a laser displacement meter, a hob, a bubble scraper, a resin groove and a sample platform, wherein the exposure optical system is used for carrying out exposure; the sample table is connected with the lifting device, the sample table is positioned in the resin groove, and the film covers the resin in the resin groove; the resin tank is arranged on the three-dimensional motion control shaft; the exposure optical system is positioned above the resin tank, a projection lens of the exposure optical system faces the film, and an electromagnetic coil is sleeved outside the projection lens; a laser displacement meter is arranged on one side of the projection lens; a hob cutter is arranged above the film, and a bubble scraper is arranged below the film. The invention not only provides high-speed and large-breadth processing capability, but also introduces a magnetic field to control the magnetization direction of the magnetic resin in the printing process, improves the 3D printing speed based on the resin at present, and also allows the use of high-viscosity or high-content solid-liquid mixed resin.)

1. A high-speed resin coating 3D printing system is characterized by comprising an exposure optical system, a film, a laser displacement meter, a hob, a bubble scraper, a resin groove and a sample platform;

The sample table is connected with the lifting device, the sample table is positioned in the resin groove, and the film covers the resin in the resin groove; the resin tank is arranged on the three-dimensional motion control shaft; the exposure optical system is positioned above the resin tank, a projection lens of the exposure optical system faces the film, and an electromagnetic coil is sleeved outside the projection lens; a laser displacement meter is arranged on one side of the projection lens; a hob cutter is arranged above the film, and a bubble scraper is arranged below the film.

2. The high-speed resin-coated 3D printing system according to claim 1, wherein the roller cutter comprises a cylinder and further comprises two parallel rails, the guide rails are longitudinally arranged along the resin tank, both ends of a central shaft of the cylinder are arranged on the rails and move along the rails, and at least one of the rails is provided with a central shaft driving device for driving the roller cutter to roll back and forth on the upper surface of the film.

3. A high speed resin coated 3D printing system as in claim 1 wherein the roller cutter comprises a plurality of bearings arranged coaxially, each bearing rotating independently.

4. A high speed resin coated 3D printing system as claimed in claim 1, wherein the resin tank further comprises a film holder and a heating unit for controlling the temperature of the resin.

5. A high speed resin coated 3D printing system as claimed in any one of claims 1 to 4 wherein the bubble blade comprises a blade having a smooth cylindrical cross section with a roughness of less than 0.4 micron and a radius of 1.5 mm and a length to cover the largest printed swath; the blade is arranged on the scraper body through a spring.

Technical Field

The invention belongs to the technical field of 3D printing, and particularly relates to a high-speed resin coating 3D printing system.

Background

Stereolithography (printing) was first to appear as a rapid prototyping technique. Rapid prototyping or 3D printing refers to a series of techniques that generate full-scale prototypes directly from computer models, which are much faster than conventional machining. Since the invention of stereolithography in 1986 by Chuck Hull, it has been economically and rapidly performing its role in many fields, such as visualization of complex parts, error detection of initial design, verification of design functions of important initial parts, checking theoretical design, and the like. In the past decades, with the investment of micro-electro-mechanical systems (MEMS), micro-scale stereolithography has been promoted, which inherits the basic principle of conventional stereolithography, but can achieve micro-scale precision. Resin curing techniques based on single and two photons can even reach accuracies of 200 nm. However, these techniques are based on serial sequential scanning of laser spots at or within the resin level, which greatly affects printing speed and cost economy. This has also contributed to the emergence of projection micro-stereolithography. The core of this technology comes from the advent of microdisplay devices such as micro Liquid Crystal Displays (LCDs) and texas instruments Digital Light Processors (DLPs), 3D printers that cure by imaging and projecting a picture on the microdisplay through an optical engine onto a photosensitive resin liquid surface, and replicating a computer generated model design through the superposition of multiple layers. In these 3D printing technologies using liquid photosensitive resin as a working medium, three types of definitions are provided for each resin layer: a free liquid surface, a transparent film window, and a transparent hard window. The free liquid level defines the resin layer by relying on the surface tension and gravity of the resin, the speed is slowest, but the influence on the optical precision is minimum; the film window utilizes the stretching force of the film to drive the movement of the resin, and the force can be determined by the mechanical property and the stretching state of the film; the rigid window is actually a mechanically strong membrane, which produces a high pressure and therefore a fast printing speed. In high precision 3D printing, the thickness of each layer is less than 30 microns. For resins with a viscosity of only 10cP, defining a 10 micron thick layer of resin above a free liquid level of 10 mm X10 mm requires waiting more than half an hour, which is clearly unacceptably slow in practical applications; under the same condition, the film with the thickness of 50 microns generally needs to wait for 2-3 minutes; although the hard window does not need to wait, the moving speed of the sample is severely limited because the sample can generate solid-liquid force which can damage the sample in the movement relative to the hard window. Under the same force, the flow velocity of the liquid linearly decreases with the increase in the viscosity of the liquid, and therefore, for a resin having a self viscosity of more than several hundreds of cP or a resin having a high viscosity with the addition of high-component particles, the existing 3D printing technology is obviously not preferable in high-precision sample processing.

Disclosure of Invention

Aiming at the technical problems, the invention provides a high-speed resin coating 3D printing system, which is a novel coating technology based on a film, and not only solves the defects of long time and slow printing of the conventional free liquid level and transparent film window in the treatment of high-viscosity resin, but also solves the problem that a sample is damaged due to large solid-liquid acting force when a transparent hard window is used. Moreover, the printing speed of the prior transparent film technology to low-viscosity resin is further improved.

The specific technical scheme is as follows:

A high-speed resin coating 3D printing system comprises an exposure optical system, a film, a laser displacement meter, a hob, a bubble scraper, a resin tank and a sample table;

The sample table is connected with the lifting device, the sample table is positioned in the resin groove, and the film covers the resin in the resin groove; the resin tank is arranged on the three-dimensional motion control shaft; the exposure optical system is positioned above the resin tank, a projection lens of the exposure optical system faces the film, and an electromagnetic coil is sleeved outside the projection lens; thereby controlling the direction and magnitude of the magnetic field at each exposure; a laser displacement meter is arranged on one side of the projection lens; a hob cutter is arranged above the film, and a bubble scraper is arranged below the film.

The hob comprises a cylinder and two parallel rails, the guide rails are longitudinally arranged along the resin groove, two ends of a central shaft of the cylinder are arranged on the rails and move along the rails, and a central shaft driving device is arranged on at least one rail and drives the hob to roll back and forth on the upper surface of the film.

Or the hob comprises a plurality of bearings which are coaxial and rotate independently.

Further, the resin tank also comprises a film clamp and a heating unit, and the heating unit is used for controlling the temperature of the resin.

The scraper comprises a blade, the cross section of the blade is a smooth cylindrical surface, the roughness is less than 0.4 micron, the radius is 1.5 mm, and the length covers the largest printing breadth; the blade is arranged on the scraper body through a spring.

According to the high-speed resin coating 3D printing system provided by the invention, due to the introduction of the hob system, the high-speed and large-breadth processing capacity is provided, and the magnetization direction of magnetic resin is controlled in the printing process by introducing a magnetic field. Therefore, the invention not only greatly improves the 3D printing speed based on the resin at present, but also allows the use of high-viscosity or high-content solid-liquid mixed resin. The technology provides an advanced and accurate cut-in means in the fields of Micro Electro Mechanical Systems (MEMS), biomedicine, industrial connectors and other fields needing micro processing.

drawings

FIG. 1 is a schematic diagram of the structure of the apparatus of the present invention.

Fig. 2 is a schematic view of the linear moving hob structure of the present invention.

Fig. 3 is a schematic view of a rotary version of the hob of the present invention.

Fig. 4 is a schematic view of the structure of the bubble doctor blade of the present invention.

Fig. 5 is a cross-sectional view a-a of fig. 4 of the present invention.

FIG. 6 is a schematic diagram of the printing steps of the present invention.

Detailed Description

The specific technical scheme of the invention is described by combining the embodiment.

A high-speed resin coating 3D printing system as shown in fig. 1, comprising an exposure optical system 1, a film 5, a laser displacement meter 3, a hob cutter 4, a bubble scraper 8, a resin tank 6, a sample stage 7;

The sample table 7 is connected with the lifting device, the sample table 7 is positioned in the resin groove 6, and the film 5 covers the resin in the resin groove 6; the resin tank 6 is arranged on a three-dimensional motion control shaft; the exposure optical system 1 is positioned above the resin tank 6, a projection lens of the exposure optical system 1 faces the film 5, and an electromagnetic coil 2 is sleeved outside the projection lens; a laser displacement meter 3 is arranged on one side of the projection lens; a hob cutter 4 is arranged above the film 5, and a bubble scraper 8 is arranged below the film.

As shown in fig. 2, the hob 4 includes a cylinder and two parallel rails, the guide rails are longitudinally arranged along the resin tank 6, two ends of the central shaft of the cylinder are mounted on the rails and move along the rails, and at least one of the rails is provided with a central shaft driving device for driving the hob to roll back and forth on the upper surface of the film.

As shown in fig. 3, the hob 4 includes a plurality of bearings 41 coaxial with the axis, and each bearing 41 rotates independently.

The resin tank 6 also comprises a film clamp and a heating unit, and the heating unit is used for controlling the temperature of the resin.

as shown in fig. 4 and 5, the bubble doctor 8 includes a blade 81, the blade 81 has a smooth cylindrical cross section, a roughness of less than 0.4 μm, a radius of 1.5 mm, and a length covering the largest printing surface; the blade 81 is mounted to a scraper body 83 by a spring 82.

The device can be used for curing each layer of image by scanning laser points like SLA or DLP of a reflective liquid crystal screen LCOS or Texas instrument in a surface projection mode. For resins with particles added, 3D molding is easier due to the relatively high power of the laser. The electromagnetic coil 2 can be added above the thin film 5 to generate a magnetic field with a specific direction on the bottom surface of the processed thin film 5, and the magnetic field can be perpendicular to the thin film 5 or form a certain angle with the thin film 5 according to different designs of the electromagnetic coil 2. The generated magnetic field can be used to control the magnetization direction of the magnetic particles in each layer of resin, and even multiple exposures can be used to control the magnetization direction of the magnetic particles in different regions of the same layer.

The use of the film 5 is mainly for: (1) the deformation of the film 5 is utilized to reduce the force born by the sample when moving up and down in the resin, thereby ensuring the integrity of the fine structure; (2) the strong stretching tension of the film 5 is used for driving the resin to move along the film surface to define the thickness of each layer of resin, so that the printing time is reduced; (3) the film 5 is interposed between the roller cutter 4 and the resin, and prevents the resin from directly contacting the roller cutter 4 to cause printing failure. In use the membrane 5 is pre-stretched by 20-30%. The material of the film 5 here can be Polydimethylsiloxane (PDMS), PFA or other transparent plastics, with a thickness from 25 to 100 μm; glass/quartz films less than 100 microns thick, coated with PFA, Teflon or other non-stick coating several microns thick, may also be used in this invention. Meanwhile, the laser displacement meter 3 is to measure whether the resin stops flowing and the film 5 has been returned to the set position and leveled after the film 5 moves on the sample stage 7. The invention uses a laser displacement meter of Keyence company, and the precision of the laser displacement meter reaches 1 micron. However, other types of displacement meters are also feasible for different accuracy requirements, such as ultrasonic displacement meters. The laser displacement meter 3 is parallel to the optical axis of the projection lens, so that a plane perpendicular to the displacement meter probe is perpendicular to the optical axis. The displacement meter may also determine the perpendicularity of this plane with respect to the displacement meter by three points on the same plane but not on a line.

The roller cutter 4 is a cylinder with precision bearings and precisely controlled dimensions (dimensional error less than 10 microns), as shown in fig. 2, the material may be metal, plastic, or ceramic, but the roughness of the surface of the roller cutter 4 in contact with the film is low, e.g., RA0.4 microns or less. The central shaft of the hob 4 is connected with the rails with two parallel ends, and the two rails can be synchronous driving rails at the same time; one could also be driven and the other a passive Gantry system. The roller cutter 4 rolls back and forth on the upper surface (dry surface) of the film 5, the film 5 is flattened in the rolling process, and meanwhile, the friction force between the roller cutter 4 and the film 5 is reduced due to the rotation of the bearing, so that the service life of the film is prolonged. The movement of the roller 4 can be a linear movement on the surface of the film 5 perpendicular to the direction of the roller; the roller 4 may rotate on the surface of the film 5 at a point on the axis, and as shown in fig. 3, a differential principle is required to release the deformation of the film in order to prevent the film from being torn and damaged due to the difference between the linear speeds of the inside and outside of the roller 4 during rotation. As shown in fig. 3, the hob 4 is formed by juxtaposing a plurality of bearings 41, each bearing 41 being independently rotatable, so that the bearings 41 at different positions can be operated at different linear speeds, preventing sliding friction between the hob 4 and the film 5.

The resin tank 6 includes a film clamp and an underlying resin container, which may be provided with a heating unit to control the temperature of the resin.

the laser displacement meter 3 is used for monitoring the difference between a point of the upper surface of the membrane in the working area of the hob and the height of the membrane when the membrane is calm, when the difference is less than a set value, such as 10 microns, the membrane is considered to be flat, and the movement of the hob can be stopped.

Gases are inevitably dissolved during the preparation of the resin and during printing, and fine bubbles are generated by the interaction of the resin and the movement of the film 5 and heat generated during photocuring during printing, and are gradually combined with each other to form millimeter-sized bubbles. Since the air bubbles are wrapped by the film 5 at the interface between the resin and the film 5, which may cause defects in the final printed sample, the apparatus frame in this invention is projected from above in the direction of gravity onto the film 5 below, so that the air bubbles are converged below the film 5 by buoyancy, and a specially designed bubble scraper 8 is introduced below the film 5. The edge 81 of the bubble doctor 8 is blunt, presents a smooth cylindrical surface with a roughness of less than 0.4 micron, a radius of 1.5 mm and a length covering the maximum printed format. And the blade 81 is supported by a spring 82 on the scraper body 83 so that the blade 81 is in elastic contact with the film 5 or the hard window during scraping without causing surface damage. While the supporting shape of the film 5 is designed to be tilted by about 20 degrees at both ends, as shown in fig. 2 and 3, so that when the bubbles are pushed to the tilted position by the bubble blade 8, they stay in the tilted area due to the buoyancy and are not brought back to the printing area by the bubble blade 8.

The apparatus of the present invention has 6 motion axes in total, and as shown in FIG. 1, the two axes control the simultaneous movement of the resin tank 6 and the sample stage 7 on the XY plane, the Z1 axis controlling the height of the sample stage 7, the Z2 axis controlling the height of the resin tank 6 and the film 5, the axis controlling the bubble scraper 8, and the axis controlling the hob 4. In addition to the movement accuracy (0.1 mm) of the axes of the control bubble scraper 8 and the control hob 4, the accuracy of the other axis movement control is much higher than the optical accuracy according to the optical accuracy design of the equipment, for example, for the optical accuracy of 10 micrometers, the embodiment selects the axis control accuracy of 1 micrometer; an optical precision of 2 microns, with an axis control precision of 0.5 microns being chosen for this example.

As shown in fig. 6, the printing of the invention begins with the creation of a geometric model on a computer, which requires the addition of a small support structure, typically a thin post, if there is a suspended structure. The three-dimensional geometric model is further cut into two-dimensional pictures in one direction, generally black and white, and may have gray scales. Each picture represents a thin layer in the three-dimensional model. The slice direction of the model will be the print direction of the printer. The series of pictures produced will be read by the printer in turn and projected onto the interface of the film 5 and the resin. Where there is light for a certain period of time, a solidified layer of a certain thickness is produced, which represents a corresponding layer in the model represented by the projected picture. When the previous layer is exposed and printed, the sample stage 7 and sample will drop 1-4 mm or more away from the film 5, the distance of drop being determined by the particular film 5 size and the adhesion of the cured resin to the film 5. When the sample table 7 returns to the original position, the thickness of the next layer is reduced. However, since the sample is large or the viscosity of the resin is high, the fluidity of the resin between the sample stage and the film 5 is poor after the sample stage is returned to the original position, thereby causing the film 5 to protrude. If the tension of the film 5 itself is used, it is necessary to wait for a long time to allow the resin in the middle of the sample to flow around, thereby restoring the flatness of the film 5. The printing speed is greatly limited because of the time for waiting for the film 5 to flatten. In this invention, a hob cutter 4 is introduced, the hob cutter 4 is tangent to the upper surface of the film 5 when it is still, and when the sample table 7 is returned, the hob cutter 4 simultaneously rolls back and forth (at a speed of the order of cm/s) or rotates on the upper surface of the film 5, thereby rapidly driving the convex film 5 to flatten. Because the resin under the convex portion of the film 5 is pressed by the roller 4 and flows rapidly toward the outer circumference when the roller 4 rolls. The number of times the roller cutter 4 rolls is determined by the feedback from the displacement gauge of the membrane 5, and the roller cutter 4 will stop outside the projected area when the displacement gauge reading indicates that the membrane 5 has returned within the allowed tolerance. The size of the area scanned by the hob 4 can be adjusted correspondingly according to the size of the printed sample, the scanning area of the small sample can be reduced correspondingly, but the small sample must cover the sample, and the edge has a certain margin. After the film 5 is flattened, the gap between the sample and the film 5 is filled with the resin layer required for printing the next layer (fig. 5). At this time, the hob 4 is moved out of the exposure area, and at the same time, current is supplied to the projection lens electromagnetic coil 2 according to the design requirement of the sample so as to generate a magnetic field with certain intensity and direction, then exposure is carried out, and the exposure is repeated in sequence, and the model is copied in the resin groove 6 along with the layer-by-layer descending of the sample table 7.