CN111300817A - Light curing 3D printer and 3D printing method - Google Patents

Abstract

The invention relates to the technical field of 3D printing, in particular to a light-curing 3D printer and a 3D printing method. The light-curing 3D printer comprises a container filled with photosensitive resin, the bottom of the container is a light-transmitting film, the bottom of the container is provided with a light machine, and the top of the container is arranged There is a printing platform, the printing platform is connected with a lifting mechanism through the platform bracket, and the lifting mechanism is connected with a printing control module for controlling the lifting speed. The displacement detection part, the pressure sensor and the displacement detection part are all connected with the printing control module, providing a light-curing 3D printer and 3D printing that can not only avoid the reciprocating motion of the printing platform, but also control the deformation degree of the light-transmitting film and improve the printing success rate. method.

Description

Light curing 3D printer and 3D printing method

technical field

The invention relates to the technical field of 3D printing, in particular to a light-curing 3D printer and a 3D printing method.

Background technique

3D printing is a molding process in which a three-dimensional model is created layer by layer. A common light-curing 3D printing technology on the market is called DLP. Each time the light-machine irradiates the underlying resin for a period of time, the light-machine is turned off after the resin is cured, the printing platform is lifted, and then lowered to a slightly higher position than the original. Turn on the irradiation for the next layer of curing. The reason why the platform needs to move up and down is to fill the liquid viscous material to the curing surface. This action is time-consuming, resulting in a slower printing speed of traditional DLP.

For the existing high-speed DLP printer, although the reciprocating motion is exempted, the platform has been rising slowly and uniformly since the beginning, and the part printing can be completed as long as the rising process is synchronized with the playback of the printing surface. However, this method is not suitable for printing models with continuous large-area slices, and printing failures often occur. The reason for the failure of printing is that the material in the center of the large-area slicing is difficult to flow into and cure. When the printing platform is lifted, the light-transmitting film below will be pulled by the draft force and deformed, resulting in the increase of the curing surface. When the deformation of the light-transmitting film is too large, the film will bounce back instantly. At this time, the plane of the light-transmitting film is suddenly separated from the cured surface. The newly cured material on the film cannot be glued with the printing body, resulting in a printing fault and the printing failure.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, and to provide a light-curing 3D printer and a 3D printing method which can not only avoid the reciprocating motion of the printing platform, but also control the deformation degree of the light-transmitting film and improve the printing success rate.

The technical solution adopted by the present invention to solve the technical problem is as follows: the light-curing 3D printer includes a container filled with photosensitive resin, the bottom of the container is a light-transmitting film, the bottom of the container is provided with a light machine, and the top of the container is provided with a printing platform , the printing platform is connected with a lifting mechanism through a platform bracket, the lifting mechanism is electrically connected with a printing control module for controlling the lifting speed, the platform bracket is provided with a pressure sensor for detecting the pressure of the printing platform, and the lifting mechanism is connected with a lifting mechanism for detecting lifting The displacement detecting element of the movement and displacement of the mechanism, the pressure sensor and the displacement detecting element are all electrically connected with the printing control module.

In the present invention, the pressure sensor detects the total force of the printing platform during the printing process, and after the self-gravity of the printing platform is removed, it is the draft force received by the deformation of the light-transmitting film, and the printing control module adjusts the lifting and lowering mechanism of the lifting mechanism in real time according to the size of the drafting force. Speed, and then ensure that the lifting platform has been raised to avoid reciprocating motion, and the transparent film will not be deformed too much and rebound, which improves the success rate of printing.

The lifting mechanism includes a linear rail and a lead screw parallel to the track of the linear rail. The platform support moves along the linear rail and is threadedly connected with the lead screw. The lead screw is connected with a drive motor, and the drive motor is electrically connected to the printing control module.

The displacement detecting element is a code disc, the rotating shaft of the driving motor is connected to the code disc, and the code disc is electrically connected to the printing control module.

A 3D printing method comprising the following steps:

Force measurement step: set the expected force S of the light-transmitting film, calculate the actual draft force F of the light-transmitting film in real time, and enter the speed adjustment step;

Speed adjustment steps: if F≤S, the printing platform will keep the current speed and continue to lift; if F>S, then reduce the current lifting speed of the printing platform, and enter the section rendering step;

Section rendering step: Calculate the current height H of the printing platform, slice according to the current height H and perform image processing operations on the slices, and enter the printing completion step;

Printing completion steps: Set the height L of the printing platform after printing the complete model, and determine the size relationship between H and L. If H>L, the printing is over, otherwise, enter the force measurement step.

The force measuring step includes the following sub-steps:

1-1): Calculate the gravity G of the printing platform;

1-2): The pressure sensor reads the current pressure N, and the actual draft force F of the light-transmitting film is the difference between the current pressure N and the gravity G of the printing platform. During the printing process, when the printing platform is raised and drafted, the pressure detected by the pressure sensor is the detection of the printing platform's own gravity G plus the tensile force that the printing platform receives and the drafting force during drafting. Mold force F=N-G;

Decreasing the lift speed of the current print platform consists of the following sub-steps:

2-1): Set the expected lifting speed A of the printing platform, and calculate the actual lifting speed V of the printing platform;

2-2) The value range of the lifting speed V of the printing platform calculated and adjusted by the printing control module is 0≤V≤A.

The printing control module adopts the PID algorithm to calculate and adjust the lifting speed V of the printing platform.

The calculation formula of the actual lifting speed V of the printing platform is:

V=D+P*ΔF+I*∫ΔF+D*dΔF;

In the formula, Δ+=S-F; D is the actual lifting speed of the last time, in the initial state, D=0; P is the deviation ratio, I is the integral, D is the differential, and the values of P, I and D are calculated based on the PID algorithm set up. The PID algorithm is a closed-loop control method, which can effectively correct the deviation of the controlled object, so that it can reach a stable state. The PID control principle and the adjustment of various PID parameters belong to the prior art, and will not be repeated here. During the printing process, due to the different area of the printing section, the draft force of the light-transmitting film is different when the mold is drafted. To keep the draft force of the light-transmitting film fluctuating within the set range, it is necessary to adjust the lifting speed of the printing platform. to accommodate different draft forces. The lifting speed of the printing platform depends on the rotation speed of the lead screw 602, and the lead screw 602 is driven to rotate by the driving motor 603. Therefore, the printing control module calculates and adjusts the pulse frequency input to the driving motor through the PID algorithm and then adjusts the driving motor speed, so that the light-transmitting film is The force remains relatively constant.

The current height H of the printing platform is equal to the geometric displacement of the rotating shaft of the drive motor measured by the code disc.

The image processing operation is image erosion processing, including the following sub-steps:

If V=A, no image erosion processing is performed;

If V=0, perform image corrosion processing where the eroded pixel is K*K, where K is a natural number;

If 0≤V≤A, perform image erosion processing where the eroded pixel is B*B, B=int(K*(A-V)/A).

Compared with the prior art, the present invention has the following beneficial effects:

The invention provides a light-curing 3D printer and a 3D printing method. The pressure sensor is used to monitor and calculate the size of the draft force in real time, and then the speed of the motor is adjusted according to the change of the draft force to adjust the lifting speed of the printing platform in time to ensure the maintenance of the draft force. In a relatively constant range, the degree of deformation of the light-transmitting film is indirectly controlled to prevent the light-transmitting film from bouncing back due to excessive force, which can not only avoid the reciprocating motion of the printing platform, improve printing efficiency, save printing time, but also improve the success of printing Rate. During the printing process, the corresponding image corrosion treatment is performed on the slices of each layer according to the speed of the printing platform, so as to avoid dimensional changes caused by different exposure and diffusion due to changes in speed, and also ensure the printing effect.

Description of drawings

FIG. 1 is a schematic diagram of the three-dimensional structure of the present invention.

Figure 2 is a front view of the present invention.

Figure 3 is a schematic diagram of the structural principle of the present invention.

Figure 4 is a circuit diagram of the present invention.

Figure 5 is a flow chart of the present invention.

In the figure: 1. Container; 2. Light-transmitting film; 3. Optical machine; 4. Printing platform; 5. Platform support; 6. Lifting mechanism; 601, Line rail; Pressure sensor; 8. Code disc.

Detailed ways

Embodiments of the present invention are further described below in conjunction with the accompanying drawings:

Example 1

As shown in FIG. 1 to FIG. 5 , the light-curing 3D printer includes a container 1 containing a photosensitive resin, the bottom of the container 1 is a light-transmitting film 2, a light machine 3 is provided at the bottom of the container 1, and a printing platform 4 is provided above the container 1. The platform 4 is connected with a lifting mechanism 6 through a platform bracket 5, and the lifting mechanism 6 is electrically connected with a printing control module for controlling the lifting speed. The platform bracket 5 is provided with a pressure sensor 7 for detecting the pressure of the printing platform 4, and the lifting mechanism 6 is connected with a The displacement detecting element for detecting the movement and displacement of the lifting mechanism, the displacement detecting element is the code disc 8, the pressure sensor 7 and the displacement detecting element are all electrically connected with the printing control module.

The lifting mechanism includes a linear rail 601 and a lead screw 602 parallel to the track of the linear rail 601. The platform support 5 moves along the linear rail 601 and is threadedly connected with the lead screw 602. The lead screw 602 is connected with a drive motor 603, and the drive motor 603 is electrically connected to print control module. The rotating shaft of the driving motor 603 is connected to the code disc 8, and the code disc 8 is electrically connected to the printing control module.

Example 2

As shown in Figures 1 to 5, based on the 3D printer in Example 1, the 3D printing method includes the following steps:

Force measurement step: Set the expected force S of the light-transmitting film, the expected force S is the maximum draft force that the light-transmitting film 2 can withstand and will not fall off and rebound from the cured surface, and calculate the actual draft of the light-transmitting film in real time. Force F, enter the speed adjustment step; the force measurement step includes the following sub-steps:

1-1: Calculate the gravity G of the printing platform 4;

1-2: The pressure sensor 7 reads the current pressure N, and the actual draft force F of the light-transmitting film 2 is the difference between the current pressure N and the gravity G of the printing platform 4 . During the printing process, when the printing platform 4 rises and drafts, the pressure detected by the pressure sensor 7 is the force G detected by the printing platform 4 itself plus the pulling force that the printing platform 4 receives and the drafting force during the drafting. The draft force of the optical film 2 is F=N-G.

Speed adjustment steps: if F≤S, the printing platform will keep the current speed and continue to rise;

If F>S, reduce the lifting speed of the current printing platform, and reducing the lifting speed of the current printing platform includes the following sub-steps:

2-1): Set the expected lifting speed A of the printing platform, and the expected lifting speed A is the maximum lifting speed of the printing platform 4 to ensure that the light-transmitting film 2 will not fall off the curing surface, and calculate the actual lifting speed V of the printing platform; printing control The module adopts PID algorithm to calculate and adjust the lifting speed V of the printing platform. The calculation formula of the actual lifting speed V of the printing platform is:

V=D+P*ΔF+I*∫ΔF+D*dΔF;

In the formula, ΔF=S-F; D is the actual lifting speed of the last time, in the initial state, D=0; P is the deviation ratio, I is the integral, D is the differential, and the values of P, I and D are calculated and set based on the PID algorithm . The PID algorithm is a closed-loop control method, which can effectively correct the deviation of the controlled object, so that it can reach a stable state. The PID control principle and the adjustment of various PID parameters belong to the prior art, and this application does not improve it. , so it is not repeated here.

During the printing process, the draft force of the transparent film 2 is different due to the different area of the printing section. To keep the draft force of the transparent film 2 fluctuating within the set range, it is necessary to adjust the printing platform 4. The lifting speed can be adapted to different draft forces. The drafting force F of the light-transmitting film is detected and calculated in real time by the pressure sensor 7 , so as to calculate and adjust the lifting speed V of the printing platform 4 . The lifting speed of the printing platform 4 depends on the rotation speed of the lead screw 602, and the lead screw 602 is driven to rotate by the drive motor 603. Therefore, the printing control module calculates and adjusts the pulse frequency input to the drive motor 603 through the PID algorithm, and then adjusts the speed of the drive motor 603, so that the transparent The force of the light film 2 is kept in a relatively constant range.

2-2) The value range of the lifting speed V of the printing platform calculated and adjusted by the printing control module is 0≤V≤A.

Enter the section rendering step.

Section rendering step: Calculate the current height H of the printing platform, slice according to the current height H and perform image processing operations on the slices. The current height of the printing platform 4 is measured by the code wheel 8, so that the model to be printed can be sliced, and the synchronization of the platform and the optical-mechanical projection can be strictly maintained under the condition that the speed of the printing platform 4 changes. The image processing operation is image corrosion processing. Since the photosensitive resin has a certain light transmittance, if the lifting speed of the printing platform 4 is too slow, part of the light will diffuse, making the cured area slightly larger than the actual printed model. The etching operation is performed to avoid the above problems, including the following sub-steps:

If V=A, no image erosion processing is performed;

If V=0, perform image corrosion processing where the eroded pixel is K*K, where K is a natural number;

If 0≤V≤A, perform image erosion processing where the eroded pixel is B*B, B=int(K*A-V/A).

Go to the print completion step.

Printing completion steps: Set the height L of the printing platform after printing the complete model, and determine the size relationship between H and L. If H>L, the printing is over, otherwise, enter the force measurement step.

Claims (10)

1. The utility model provides a photocuring 3D printer, is including container (1) that is equipped with photosensitive resin, container (1) bottom is printing opacity film (2), container (1) bottom is provided with light machine (3), and container (1) top is provided with print platform (4), print platform (4) are connected with elevating system (6) through platform support (5), and elevating system (6) electric connection has the printing control module who is used for controlling the elevating speed, a serial communication port, platform support (5) are provided with pressure sensor (7) that are used for detecting print platform (4) pressure, and elevating system (6) are connected with the displacement detection piece that is used for detecting elevating system removal displacement, pressure sensor (7) and displacement detection piece all with printing control module electric connection.

2. The photocuring 3D printer of claim 1, wherein the lifting mechanism comprises a linear rail (601) and a lead screw (602) parallel to the track of the linear rail (601), the platform support (5) moves along the linear rail (601) and is in threaded connection with the lead screw (602), the lead screw (602) is connected with a driving motor (603), and the driving motor (603) is electrically connected with the printing control module.

3. The photocuring 3D printer of claim 2, wherein the displacement detection piece is a code wheel (8), a rotating shaft of the driving motor (603) is connected with the code wheel (8), and the code wheel (8) is electrically connected with the printing control module.

4. A3D printing method is characterized by comprising the following steps:

force measurement: setting an expected stress S of the transparent film (2), calculating an actual drawing force F of the transparent film (2) in real time, and entering a speed adjusting step;

a speed adjusting step: if the F is less than or equal to S, the printing platform (4) maintains the current speed to continue lifting, if the F is more than S, the lifting speed of the current printing platform (4) is reduced, and the cross section rendering step is carried out;

a cross section rendering step: calculating the current height H of the printing platform (4), slicing according to the current height H, performing image processing operation on the slices, and entering a printing completion step;

a printing completion step: and setting the height L of the printing platform (4) after the complete model is printed, judging the size relationship between H and L, if H is larger than L, finishing printing, and otherwise, entering a force measuring step.

5. The 3D printing method according to claim 4, wherein the force measuring step comprises the sub-steps of:

1-1): calculating the gravity G of the printing platform (4);

1-2): the pressure sensor (7) reads the current pressure N, and the actual die drawing force F of the light-transmitting film (2) is the difference between the current pressure N and the gravity G of the printing platform (4).

6. The 3D printing method according to claim 4, wherein reducing the lifting speed of the current printing platform (4) comprises the sub-steps of:

2-1): setting an expected lifting speed A of the printing platform (4), and calculating an actual lifting speed V of the printing platform (4);

2-2) the printing control module calculates and adjusts the value range of the lifting speed V of the printing platform (4) to be more than or equal to 0 and less than or equal to A.

7. The 3D printing method according to claim 6, wherein the printing control module calculates the adjusted lifting speed V of the printing platform (4) using a PID algorithm.

8. The 3D printing method according to claim 7, characterized in that the actual lifting speed V of the printing platform (4) is calculated by the formula:

V＝D+P*ΔF+I*∫ΔF+D*dΔF；

wherein Δ F ═ S-F; d is the actual lifting speed of the last time, and in the initial state, D is 0; p is the deviation ratio, I is the integral, D is the derivative, the value of P, I, D is set computationally based on a PID algorithm.

9. The 3D printing method according to claim 4, wherein the current height H of the printing platform (4) is equal to the geometric displacement of the rotation axis of the drive motor (603) measured by the code wheel (8).

10. The 3D printing method according to claim 4, wherein the image processing operation is an image erosion process comprising the sub-steps of:

if V is equal to A, the image corrosion treatment is not carried out;

if V is 0, carrying out image corrosion processing with corrosion pixels of K x K, wherein K is a natural number;

and if V is not less than 0 and not more than A, carrying out image corrosion treatment with the corrosion pixel B, wherein B is int (K (A-V)/A).

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