CN113290854A

CN113290854A - Photocuring 3D printing screen-pressing-resistant locked-rotor detection method and device

Info

Publication number: CN113290854A
Application number: CN202110458381.8A
Authority: CN
Inventors: 易瑜; 方庆林; 张锐
Original assignee: Shenzhen CBD Technology Co Ltd
Current assignee: Shenzhen CBD Technology Co Ltd
Priority date: 2021-04-27
Filing date: 2021-04-27
Publication date: 2021-08-24
Also published as: WO2022228435A1

Abstract

The invention provides four photocuring 3D printing screen-pressing-resistant locked-rotor detection methods and a photocuring 3D printing screen-pressing-resistant locked-rotor detection device, wherein the device comprises: the device comprises a control unit, a door driving unit, a full-bridge chopping unit, a motor, a current detection comparison unit, a storage unit, a display and operation unit, a limit detection module, an abnormality prompting unit, a Z axis, a forming platform, a base, an LCD screen, a UVLED light source module, a liquid tank, a bottom membrane and photosensitive resin; the method mainly comprises the following steps: the control unit controls the motor to drive the forming platform to move downwards along the Z-axis; the current detection comparison unit acquires sampling current of the grounding end and/or the output end of the full-bridge chopper unit and converts the sampling current into a digital current value; the control unit compares the digital current value with a preset current threshold value; if the current is larger than the preset current threshold value, the motor is controlled to stop running and an alarm signal is sent out after the motor is judged to have a locked-rotor fault.

Description

Photocuring 3D printing screen-pressing-resistant locked-rotor detection method and device

Technical Field

The application relates to the technical field of 3D printing, in particular to a method and a device for detecting screen blockage during photocuring 3D printing.

Background

The existing LCD ascending type photocuring 3D printer generally comprises four use conditions before use, namely, the use condition of independent zero setting is used, the aim is to only zero set and lower the forming platform so as to be arranged and stored, a user gives a zero setting instruction, the 3D printer can enable the forming platform which is positioned at the highest position of the Z axis after last demoulding to return to the zero initial position of historical storage below the Z axis, and then a dark box cover is covered; secondly, only the use condition of zero calibration and no printing is achieved, at the moment, the forming platform positioned at the highest position of the Z axis after last demoulding is required to return to the historically-stored zero starting position below the Z axis, and then the platform horizontal calibration is carried out or the distance between the forming platform and the bottom film of the liquid tank is adjusted; thirdly, the use condition of automatic zero resetting during printing is realized, the zero resetting can be automatically realized during each printing use, namely, when a user introduces a printing slicing file and issues a printing instruction each time, the 3D printer can enable the forming platform which is positioned at the highest position of the Z axis after last demoulding to return to the initial zero position of historical storage below the Z axis, and then the step-by-step printing action is executed; and fourthly, preventing the screen from being pressed in the printing process, sending a printing instruction by leading in model data of a user, automatically zeroing the forming platform, continuously repeating the lifting action of the forming platform in the normal photocuring printing process, and when two or more models are simultaneously photocured and printed, if one model falls off into the liquid tank, when the forming platform normally descends, other models or the falling model is extruded to enable the falling model to downwards extrude the lower LCD screen.

In the process of zeroing the forming platform, a limit switch or a limit sensor is generally additionally arranged below a Z axis of the conventional LCD lifting type photocuring 3D printer, so that firstly, when a controller controls a motor to drive the forming platform to descend to the bottom, the position of the forming platform can be detected, and the forming platform can conveniently and accurately move to a zero initial position by taking the position as a reference; and secondly, the LCD screen for selective light transmission is prevented from being extruded to the lower part of the bottom film of the liquid bath by the forming platform directly crossing the zero starting position and being close to the bottom film of the liquid bath.

Firstly, after the last printing is finished, when a user demolds and takes off a solidified and molded model from a molding platform, the molding platform is easy to leave adhered solidified blocks, if the solidified blocks are not cleaned up, the left solidified blocks may be extruded to press a lower LCD screen in the process of descending and zeroing the molding platform, and the molding platform does not reach a limiting trigger position, so that the LCD screen is damaged by extrusion; secondly, in order to prevent photosensitive resin from being irradiated and cured by external light, the LCD photocuring 3D printer is generally positioned in a darkroom, the upper part of the LCD photocuring 3D printer generally covers a darkroom cover, the LCD photocuring process is generally slow, if a user forgets to take down the printed model after the previous printing is completed, a new user is easy to directly perform a new printing round due to unclear light, and the lower LCD screen is extruded and damaged by the previous model when the forming platform does not reach a limiting triggering position; and thirdly, in the normal photocuring printing process, when two or more models are photocured and printed simultaneously, if one model falls off into the liquid tank, other models or the models are extruded to the falling model to extrude the lower LCD screen downwards when the forming platform normally descends.

Therefore, in order to solve the above problems, it is necessary to provide a corresponding method and device for detecting the locked rotation of the pressure-resistant screen in the photocuring 3D printing process.

Disclosure of Invention

In order to solve the problems in the background art, the invention provides four photocuring 3D printing screen-pressing-prevention locked-rotation detection methods and a photocuring 3D printing screen-pressing-prevention locked-rotation detection device. The technical scheme adopted by the invention is as follows:

method 1, a method for detecting screen-pressing-resistant locked rotor during photocuring 3D printing, aiming at the use condition of independent zero return, comprises the following steps:

SA01, the user sends an instruction to the control unit 1 to zero the forming table 32 through the display and operation unit 6;

SA02 and the control unit 1 send control instructions to the door driving unit 2 to control the door driving unit and drive the motor 3 to drive the forming platform 32 to move downwards along the Z axis 31 through the full-bridge chopper unit 20;

SA03, the current detection comparison unit 4 obtains the sampling current of the grounding end and/or the output end of the full-bridge chopper unit 20;

SA04, current detection comparing unit 20 converts the analog signal of the sampled current into a digital signal, and sends the digital signal to control unit 1 after obtaining the digital current value;

SA05, the control unit 1 compares the digital current value with a preset current threshold and determines whether the digital current value is greater than the preset current threshold; if the digital current value is judged to be larger than the preset current threshold value, the step SA08 is carried out; if the digital current value is not larger than the preset current threshold value, performing step SA 06;

SA06 and a motor 3 drive the forming platform 32 to move downwards along the Z axis 31 until the limit detection module 7 is triggered and sends a limit trigger signal to the control unit 1;

SA07, the control unit 1 controls the forming platform 32 to shift to the initial position of zero by X millimeters by taking the corresponding position of the forming platform 32 on the Z axis 31 as a marking point when the limit detection module 7 is triggered, and the next step is SA 09;

SA08, after judging that the motor 3 has a locked-rotor fault, the control unit 1 controls the motor 3 to stop running and sends out a warning signal through an abnormality prompting unit 8;

SA09, the flow ends.

Method 2, a light-cured 3D printing screen-pressing-resistant locked-rotor detection method, aiming at the use condition that only return-to-zero calibration is performed and printing is not performed, comprises the following steps:

SB01, the user gives an instruction to the control unit 1 to zero the forming table 32 through the display and operation unit 6;

SB02, the control unit 1 sends a control instruction to the gate driving unit 2 to control the gate driving unit and drives the motor 3 to drive the forming platform 32 to move downwards along the Z axis 31 through the full-bridge chopper unit 20;

SB03, the current detection comparing unit 4 obtains the sampling current at the output end and/or the grounding end of the full-bridge chopper unit 20;

SB04, the current detection comparing unit 4 converts the analog signal of the sampling current into a digital signal, and sends the digital signal to the control unit 1 after obtaining the digital current value;

SB05, the control unit 1 compares the digital current value with the preset current threshold value and judges whether the digital current value is larger than the preset current threshold value; if the digital current value is judged to be larger than the preset current threshold value, the step SB10 is carried out; if the digital current value is not larger than the preset current threshold value, the step SB06 is carried out;

SB06, the motor drives the forming platform 32 to move downwards along the Z axis 31 until the limit detection module 7 is triggered and sends a limit trigger signal to the control unit 1;

SB07, the control unit 1 controls the forming platform 32 to shift X mm to zero starting position by using the corresponding position of the forming platform 32 on the Z axis 31 as a mark point when triggering the limit detection module 7;

SB08, the user judges whether the current zero initial position needs to be corrected; if the current zero starting position does not need to be corrected, the step SB11 is carried out; if the current zero initial position needs to be corrected, the step SB09 is carried out;

SB09, the user operates the display and operation unit 6 to make the motor 3 drive the forming platform 32 to lift or lower Y mm to the target position and then store it as a new zero starting position, and the next step is carried out in step SB 11;

SB10, after the control unit 1 judges that the motor 3 has the locked-rotor fault, the control unit 3 stops running and sends out a warning signal through the abnormity prompting unit 8;

SB11, the flow ends.

Method 3, a method for detecting screen-pressing-prevention locked rotor during photocuring 3D printing, aiming at the use condition of automatic zero resetting during printing, comprises the following steps:

SC01, user leads the model printing slice file into the memory unit 5 of the photo-curing printing device;

SC02, the user issues a model slice file printing instruction to the control unit 1 through the display and operation unit 6;

the SC03 and the control unit 1 send control instructions to the door driving unit 2 to control the door driving unit and drive the motor 3 to drive the forming platform 32 to move downwards along the Z axis 31 through the full-bridge chopper unit 20;

the SC04 and the current detection comparing unit 4 obtain the sampling current at the ground terminal and/or the output terminal of the full-bridge chopper unit 20;

the SC05 and the current detection comparing unit 4 convert the analog signal of the sampling current into a digital signal, and send the digital signal to the control unit 1 after obtaining a digital current value;

SC06, the control unit 1 compares the digital current value with a preset current threshold and determines whether the digital current value is greater than the preset current threshold; if the digital current value is judged to be larger than the preset current threshold value, the step SC10 is carried out; if the digital current value is not greater than the preset current threshold value, performing step SC 07;

the SC07 and the motor 3 drive the forming platform 32 to move downwards along the Z axis 31 until the limit detection module 7 is triggered and sends a limit trigger signal to the control unit 1;

the SC08 and the control unit 1 control the forming platform 32 to shift X millimeters to a zero starting position by using the corresponding position of the forming platform 32 on the Z axis 31 as a mark point when the limit detection module 7 is triggered;

the SC09 and the control unit 1 read the model printing slice file in the storage unit 5 and perform photocuring printing on the model slice data layer by layer in sequence, and then perform the step SC 11;

the SC10 and the control unit 1 control the motor 3 to stop running after judging that the motor 3 has a locked-rotor fault and send out a warning signal through the abnormity prompting unit 8;

SC11, the flow ends.

Method 4, a method for detecting locked rotor of a photo-cured 3D printing screen, aiming at the service condition of the screen during printing, the method comprises the following steps:

SD01, the user leads the model printing slice file into the storage unit 5 of the photo-curing printing device and sends a printing instruction to the control unit 1 through the display and operation unit 6;

the SD02 and the control unit 1 control and drive the motor 3 to drive the forming platform 32 to complete zeroing;

the SD03 and the control unit 1 read the model printing slice file in the storage unit 5 and perform photocuring printing on the model slice data layer by layer in sequence;

the SD04 and the control unit 1 send control instructions to the door driving unit 2 to control the door driving unit and drive the motor 3 to drive the forming platform 32 to move or stop along the Z axis 31 through the full-bridge chopper unit 20;

the SD05 and the current detection comparison unit 4 acquire sampling current of the grounding end and/or the output end of the full-bridge chopper unit 20;

the SD06 and the current detection comparison unit 4 convert the analog signal of the sampling current into a digital signal, and send the digital signal to the control unit 1 after obtaining a digital current value;

SD07, control unit 1 determines whether forming table 32 is in a down state; if the forming platform 32 is not in the descending state, the process goes to step SD 09; if the forming platform 32 is judged to be in the descending state, the step SD08 is carried out;

the SD08, control unit 1 compares the digital current value with a preset current threshold and determines whether the digital current value is greater than the preset current threshold; if the digital current value is judged to be larger than the preset current threshold value, the step SD11 is carried out; if the digital current value is not larger than the preset current threshold value, performing the step SD 09;

the SD09 and the motor 3 drive the forming platform 32 to continue moving along the Z axis 31 until the target position is reached;

SD10, completing photocuring printing of all layer slice data in the model printing slice file, and performing the next step SD 12;

the SD11 and the control unit 1 control the motor 3 to stop running after judging that the motor 3 has a locked-rotor fault and send out a warning signal through the abnormity prompting unit 8;

SD12, flow ends.

Preferably, in the steps SA06, SB06, and SC07, the manner in which the motor 3 drives the forming platform 32 to trigger the limit detection module 7 includes electromagnetic induction triggering, photoelectric induction triggering, or direct touch-press triggering.

Preferably, in the steps SA03, SB03, SC04 and SD05, the manner of obtaining the sampling current from the ground terminal and/or the output terminal of the full-bridge chopper unit 20 by the current detection comparing unit 4 includes directly inputting the sampling current, or collecting the sampling current by current sensing detection.

Preferably, in the steps SA05, SB05, SC06 and SD08, the preset current threshold is a fixed current value, or a dynamic following ratio value of the minimum driving current, or a dynamic following ratio value of the maximum driving current.

The utility model provides a photocuring 3D prints and prevents pressing stifled detection device that changes of screen, includes: the device comprises a control unit 1, a door driving unit 2, a full-bridge chopping unit 20, a motor 3, a current detection and comparison unit 4, a storage unit 5, a display and operation unit 6, a limit detection module 7, an abnormality prompting unit 8, a Z axis 31, a forming platform 32, a base 10, an LCD screen 11, a UVLED light source module 12, a liquid tank 9, a bottom film 90 and photosensitive resin 91;

the door driving unit 2, the current detection and comparison unit 4, the storage unit 5, the display and operation unit 6, the limit detection module 7, the abnormity prompting unit 8, the LCD screen 11 and the UVLED light source module 12 are electrically connected with the control unit 1; a user sends an instruction for enabling the forming platform to return to zero or a model slice file printing instruction to the control unit 1 through the display and operation unit 6; the storage unit 5 is used for importing a storage model printing slice file;

the gate driving unit 2 is electrically connected with the full-bridge chopping unit 20 and controls the on-off of each switching tube in the full-bridge chopping unit 20; the full-bridge chopper unit 20 is electrically connected with the windings in the motor 3 and drives the motor 3 to run; the control unit 1 sends a control instruction to the door driving unit 2 to control the operation and start and stop of the motor 3 so as to drive the forming platform 32 to lift or stop along the Z axis 31; the motor 3 drives the forming platform 32 to move downwards along the Z axis 31 until the limiting detection module 7 is triggered and sends a limiting trigger signal to the control unit 1 so as to record the mark points of the corresponding positions of the forming platform 32 on the Z axis 31;

the current detection comparison unit 4 is connected with and acquires sampling current of a grounding end and/or an output end in the full-bridge chopper unit 20, converts an analog signal of the sampling current into a digital signal and acquires a digital current value, and then sends the digital current value to the control unit 1; the control unit 1 compares the acquired digital current value with a preset current threshold value to judge whether the motor 3 has a locked-rotor fault; after the control unit 1 judges that a locked-rotor fault occurs, the control unit controls the motor 3 to stop running and sends out a warning signal through the abnormity prompting unit 8, so that the photocuring 3D printing device is prevented from extruding the LCD screen 11 when the forming platform 32 descends in the zeroing process;

the Z axis 31, the LCD screen 11, the UVLED light source module 12 and the liquid tank 9 are fixed on the base 10; the bottom film 90 is arranged at the bottom of the liquid tank 9 and is used for transmitting light; the liquid tank 9 is used for containing photosensitive resin 91 liquid; the motor 3 is arranged on the Z shaft 31 to realize electric driving lifting and drive the forming platform 32 to lift or descend along with the Z shaft;

a user sends a model slice file printing instruction to the control unit 1 through the display and operation unit 6, the control unit 1 controls the motor 3 to enable the forming platform 32 to return to a zero initial position, the control unit 1 reads the model print slice file in the storage unit 5 and carries out photocuring printing on the model slice data layer by layer, in the process, the LCD screen 11 loads and switches layer slice mask images in the model print slice file layer by layer, and the UVLED light source module 12 sends ultraviolet light and visible light to expose and irradiate the photosensitive resin 91 in the liquid tank 9 through the mask image in the LCD screen 11 and the bottom film 90 to be cured and formed; the molding platform 32 is used for attaching a cured and molded model molding resin layer in the curing and molding process so as to continuously promote and grow the resin layer until the 3D printing is completed.

Further, a photocuring 3D print and prevent pressing screen stifled commentaries on classics detection device, still include: a current sensor 30; the current sensor 30 is electrically connected to the current detection comparing unit 4; the current sensor 30 is further arranged on a line between the full-bridge chopper unit 20 and the motor 3, detects current of the line, and samples the detected current and sends the sampled current to the current detection comparing unit 4; the number of the current sensors 30 is one, or two, or three, or four.

Further, a photocuring 3D print and prevent pressing screen stifled commentaries on classics detection device, still include: an encoder 33; the encoder 33 is arranged on the motor 3 for detecting the angular displacement of the rotor of the motor 3, recording the rotor pulse count or the rotor starting position, and sending this information to the control unit 1 for controlling the forming table 7 to achieve accurate deflection.

Preferably, the motor 3 is a stepping motor, a servo motor or a direct current brushless motor; the full-bridge chopper unit 20 includes a three-phase six-switch-tube full-bridge chopper unit, or includes two single-phase four-switch-tube full-bridge chopper units.

Preferably, the abnormality prompt unit 8 is a diode, a buzzer, a speaker, or a liquid crystal display module.

Compared with the prior art, the invention has the beneficial effects that:

1. the method 1-4 of the invention provides four photocuring 3D printing screen-pressing-prevention locked-rotation detection methods, in the process of zeroing a forming platform, if a motor drives the forming platform to descend and is blocked, the motor is locked, then the sampling current of the output end and/or the grounding end of a full-bridge chopping unit is increased to exceed a preset current threshold value, a control unit judges that the motor has a locked-rotation fault, the motor stops running and sends out an alarm signal, and therefore the forming platform can also avoid the damage of an LCD screen below by extrusion before the limiting protection is not triggered.

2. The user can carry out the operation of returning to zero to 3D printer alone through method 1 to the needs of putting in order and receive and release the photocuring 3D printer, makes the shaping platform drop back to zero initial position to before the shaping platform does not trigger spacing protection, also can avoid the extrusion to damage below LCD screen.

3. The user can independently carry out zeroing and calibration operations on the 3D printer through the method 2 aiming at the use requirements of only zeroing calibration and not printing, so that the forming platform is lowered to the zero initial position, the LCD screen below the forming platform can be prevented from being damaged by extrusion before the forming platform does not trigger limiting protection, then the forming platform returning to the zero initial position is corrected, and finally the corrected position can be stored as a new zero initial position.

4. A user can directly send a printing instruction after a model printing slice file is led in by the method 3 according to the use requirement of automatic zeroing of printing, the control unit can automatically control the forming platform to fall back to a zero initial position, the LCD screen below the forming platform can be prevented from being damaged by extrusion before the forming platform does not trigger limiting protection, and then the model slice data is subjected to photocuring printing layer by layer in sequence based on the zero initial position.

5. A user can judge the lifting or descending action of the forming platform each time by the method 4 according to the use requirement of the screen pressing prevention in the printing process, if the forming platform is in the descending process, the forming platform is compared and judged by the digital current value and the preset current threshold value, and before the forming platform does not trigger the limit protection, the forming platform can be stopped and warned to avoid the LCD screen below from being damaged by extrusion.

6. The method 1-4 of the invention provides four photocuring 3D printing screen-pressing-resistant locked-rotor detection methods, which are characterized in that whether a motor has a locked-rotor fault or not is judged by detecting and comparing the sampled current of the output end and/or the grounding end of a full-bridge chopping unit with a preset current threshold value, and the limit protection module triggers the limit protection to form a double-protection mechanism; even if the limiting protection module is damaged and is not triggered, the motor can be stopped due to the fact that a locked rotor fault is generated when the forming platform downwards extrudes the LCD screen through the bottom film.

7. The photocuring 3D printing screen-pressing-resistant locked-rotor detection device provided by the invention can also adopt two single-phase four-switch-tube full-bridge chopping units to drive a stepping motor or adopt one three-phase six-switch-tube full-bridge chopping unit to drive a three-phase direct-current brushless motor or a servo motor on the premise of following the four methods; in a specific current detection mode, current can be directly input for detection or a current sensor is adopted for isolation detection; the circuit design can be flexible and various.

Drawings

Fig. 1 is a flowchart of a photocuring 3D printing screen-pressing-resistant locked-rotor detection method 1;

FIG. 2 is a flowchart of a photocuring 3D printing screen-pressing-resistant locked-rotor detection method 2 according to the present invention;

FIG. 3 is a flowchart of a photocuring 3D printing screen-pressing-resistant locked-rotor detection method 3 according to the present invention;

FIG. 4 is a flowchart of a method 4 for detecting locked-rotor of a photo-curing 3D printing screen according to the present invention;

fig. 5 is an overall embodiment 1 of the light-cured 3D-printed screen-pressing-resistant locked-rotor detection device according to the present invention;

FIG. 6 is a schematic circuit diagram 1 of the photocuring 3D printing screen-pressing-resistant locked-rotor detection device according to the present invention;

FIG. 7 is a schematic circuit diagram of the device for detecting the locked-rotor of the pressure-resistant screen in the photocuring 3D printing of the present invention 2;

FIG. 8 is a schematic circuit diagram of the device for detecting the locked-rotor of the pressure-resistant screen in the photocuring 3D printing of the present invention;

FIG. 9 is a schematic structure and state diagram 1 of a photocuring 3D printing screen-pressing-resistant locked-rotor detection device according to the present invention;

FIG. 10 is a schematic structure and state diagram 2 of a photocuring 3D printing screen-pressing-prevention locked-rotor detection device according to the present invention;

fig. 11 is a three-dimensional state representation diagram of the photo-curing 3D printing screen-pressing-prevention locked-rotation detection device of the present invention in fig. 1;

fig. 12 is a three-dimensional state representation diagram of the photo-curing 3D printing screen-pressing-prevention locked-rotation detection device of the present invention in fig. 2;

description of reference numerals:

a control unit 1; a door drive unit 2; a full-bridge chopper unit 20; single-phase four-switch tube full-

bridge chopper units

21, 22; a three-phase six-switch-tube full-bridge chopper unit 23; switching

tubes

211, 221; flywheel diodes 212, 222;

detection resistors

201 and 202; a motor 3; a current detection comparing unit 4; a storage unit 5; a display and operation unit 6; a limit detection module 7; an abnormality presentation unit 8; a liquid bath 9; a base 10; an LCD screen 11; a UVLED light source module 12; a current sensor 30; a Z-axis 31; a forming table 32; an encoder 33; a base film 90; a photosensitive resin 91; a resin molding die 92; a controller 100.

Detailed Description

The embodiments of the present invention will be further described with reference to the accompanying drawings.

Fig. 1 is a flowchart of a method 1 for detecting screen-pressing-resistant locked rotor in photocuring 3D printing according to the present invention. As shown, it is for a single zeroed use case, which includes the following steps:

SA09, the flow ends.

Fig. 2 is a flowchart of a photocuring 3D printing screen-pressing-resistant locked-rotor detection method 2. As shown, it includes the following steps for a zero-only calibration unprinted use case:

SB11, the flow ends.

Fig. 3 is a flowchart of a photocuring 3D printing screen-pressing-resistant locked-rotor detection method 3. As shown, it is directed to a use case of print auto-zero, which includes the following steps:

SC11, the flow ends.

Fig. 4 is a flowchart of a photocuring 3D printing screen-pressing-resistant locked-rotor detection method 4. As shown in the figure, the method aims at the use condition of the anti-pressing screen in the printing process, and comprises the following steps:

SD12, flow ends.

In addition, based on the four method flow steps shown in fig. 1, fig. 2, fig. 3, and fig. 4, in the steps SA06, SB06, and SC07, the manner in which the motor 3 drives the forming platform 32 to trigger the limit detection module 7 includes electromagnetic induction triggering, photoelectric induction triggering, or direct touch-press triggering. In the steps SA03, SB03, SC04, and SD05, the manner in which the current detection comparing unit 4 obtains the sampling current at the ground terminal and/or the output terminal of the full-bridge chopper unit 20 includes directly inputting the sampling current, or collecting the sampling current by adopting a current sensing detection manner. In the steps SA05, SB05, SC06, and SD08, the preset current threshold is a fixed current value, or a dynamic following proportion value of the minimum driving current, or a dynamic following proportion value of the maximum driving current, and a specific feasible method is to make the full-bridge chopper unit 20 output the minimum driving current to drive the motor 3 to operate when the forming platform 32 is reduced to zero, and then set the preset current threshold to be 1.1 times or 1.2 times of the minimum driving current, so that the user only needs to determine the minimum driving current, and then by adjusting the proportion coefficient, the preset current threshold can be determined by the dynamic following proportion value of the minimum driving current; after the preset current threshold is determined, if the forming platform 32 is hindered from descending, the motor 3 is hindered from running and locked, the counter electromotive force disappears, and then the current of each phase of the motor 3 is increased, and as long as the increased current exceeds the preset current threshold, the motor 3 can be controlled to stop running and an alarm signal is sent out; when the forming platform 32 is facing upward, the full-bridge chopper unit 20 can output a normally required driving current to drive the motor 3 to operate, and meanwhile, the comparison between the sampled current and the preset current threshold value is shielded or cancelled, or the handling action of stopping and warning is not performed on the comparison result of the sampled current and the preset current threshold value.

Fig. 5 is an overall embodiment 1 of the device for detecting screen-pressing-resistant locked rotor in photocuring 3D printing according to the present invention. As shown in the figure, the door driving unit 2, the current detection comparing unit 4, the storage unit 5, the display and operation unit 6, the limit detection module 7, the abnormality prompting unit 8, the LCD screen 11 and the UVLED light source module 12 are electrically connected with the control unit 1; a user sends an instruction for enabling the forming platform to return to zero or a model slice file printing instruction to the control unit 1 through the display and operation unit 6; the storage unit 5 is used for importing a storage model printing slice file;

the gate driving unit 2 is electrically connected with the two single-phase four-switch tube full-

bridge chopping units

21 and 22 and controls the on-off of each switch tube in the two single-phase four-switch tube full-

bridge chopping units

21 and 22; the two single-phase four-switch tube full-

bridge chopping units

21 and 22 are electrically connected with windings in the motor 3 and drive the motor 3 to run; the control unit 1 sends a control instruction to the door driving unit 2 to control the operation and start and stop of the motor 3 so as to drive the forming platform 32 to lift or stop along the Z axis 31; the motor 3 drives the forming platform 32 to move downwards along the Z axis 31 until the limiting detection module 7 is triggered and sends a limiting trigger signal to the control unit 1 so as to record the mark points of the corresponding positions of the forming platform 32 on the Z axis 31;

in the figure, the grounding ends and the output ends of the two single-phase four-switch tube full-

bridge chopping units

21 and 22 are directly and electrically connected to the current detection and comparison unit 4, so that the current detection and comparison unit 4 can obtain sampling currents of the grounding ends and the output ends of the two single-phase four-switch tube full-

bridge chopping units

21 and 22, convert analog signals of the sampling currents into digital signals and obtain digital current values, and then send the digital current values to the control unit 1; the control unit 1 compares the acquired digital current value with a preset current threshold value to judge whether the motor 3 has a locked-rotor fault; after the control unit 1 judges that a locked-rotor fault occurs, the control unit controls the motor 3 to stop running and sends out a warning signal through the abnormity prompting unit 8, so that the photocuring 3D printing device is prevented from extruding the LCD screen 11 when the forming platform 32 descends in the zeroing process;

Similarly, the control unit 1, the door driving unit 2, the current detection comparing unit 4, the limit detection module 7, and the abnormality presentation unit 8 in the present drawing together constitute a controller 100, which corresponds to the controller 100 in fig. 9 and 10.

Fig. 6 is a schematic circuit diagram 1 of the photocuring 3D printing screen-pressing-resistant locked-rotor detection device of the present invention. As shown, two single-phase four-switch-tube full-

bridge chopper units

21 and 22 are used to drive the motor 3. The single-phase four-switch-tube full-bridge chopping unit 21 is of a full-bridge chopping structure formed by four switch tubes 211, and each switch tube 211 is reversely connected with a freewheeling diode 212 in parallel by a current input end and a current output end thereof and is used for freewheeling during switching chopping and protecting the switch tube 211; similarly, the single-phase four-switch-tube full-bridge chopper unit 22 has a full-bridge chopper structure formed by four switch tubes 221, and each switch tube 221 is reversely connected in parallel with a freewheeling diode 222 at a current input end and an output end thereof, and is used for freewheeling during switching chopping and protecting the switch tube 221; secondly, the grounding ends of the two single-phase four-switch-tube full-

bridge chopper units

21 and 22 are respectively connected with the

detection resistors

201 and 202 and then grounded, and the two

detection resistors

201 and 202 are used for raising the ground voltage when the grounding ends are directly electrically connected and current sampling is carried out, so that the current detection comparison unit 4 can effectively sample the current of the grounding ends. Specifically, in terms of the selection of the switching

tubes

211 and 221, controllable switching tubes such as MOSFET tubes, BJT tubes, thyristors, etc. may be selected, or the two single-phase four-switching-tube full-

bridge chopper units

21 and 22 may also directly adopt four-unit IGBT modules.

In addition, as shown in the figure, the door driving unit 2, the current detection comparing unit 4, the storage unit 5, the display and operation unit 6, the limit detection module 7 and the abnormality prompting unit 8 are electrically connected with the control unit 1; a user sends an instruction for enabling the forming platform to return to zero or a model slice file printing instruction to the control unit 1 through the display and operation unit 6; the storage unit 5 is used for importing a storage model printing slice file;

bridge chopping units

21 and 22; the two single-phase four-switch tube full-

bridge chopping units

21 and 22 are electrically connected with windings in the motor 3 and drive the motor 3 to run; the control unit 1 sends a control instruction to the door driving unit 2 to control the running and starting and stopping of the motor 3; the limit detection module 7 can send a limit trigger signal to the control unit 1 when being triggered;

in the figure, the grounding end and the output end of the single-phase four-switch-tube full-bridge chopping unit 21 are both directly and electrically connected to the current detection comparison unit 4, so that the current detection comparison unit 4 can obtain the sampling current of the grounding end and the output end of the single-phase four-switch-tube full-bridge chopping unit 21, convert the analog signal of the sampling current into a digital signal and obtain a digital current value, and send the digital current value to the control unit 1; the control unit 1 compares the acquired digital current value with a preset current threshold value to judge whether the motor 3 has a locked-rotor fault; after the control unit 1 judges that the locked-rotor fault occurs, the control unit controls the motor 3 to stop running and sends out a warning signal through the abnormity prompting unit 8, so that the photocuring 3D printing device is prevented from extruding the LCD screen 11 in the zeroing process.

In the figure, the single-phase four-switch-tube full-bridge chopper unit 22 and the current detection comparison unit 4 are connected by a dotted line, because, in actual needs, if the current of the motor 3 is increased, only one group of winding current needs to be detected, so the current detection comparison unit 4 can detect the current on the single-phase four-switch-tube full-bridge chopper unit 22, and the detection is not needed.

In the present figure, the control unit 1, the door driving unit 2, the current detection comparing unit 4, the limit detection module 7, and the abnormality presentation unit 8 together constitute a controller 100, which corresponds to the controller 100 in fig. 9 and 10.

Fig. 7 is a schematic circuit diagram 2 of the photocuring 3D printing screen-pressing-prevention locked-rotor detection device of the invention. As shown in the figure, the same as fig. 6, two single-phase four-switch-tube full-

bridge chopper units

21 and 22 are used to drive the motor 3. The single-phase four-switch-tube full-bridge chopping unit 21 is of a full-bridge chopping structure formed by four switch tubes 211, and each switch tube 211 is reversely connected with a freewheeling diode 212 in parallel by a current input end and a current output end thereof and is used for freewheeling during switching chopping and protecting the switch tube 211; similarly, the single-phase four-switch-tube full-bridge chopper unit 22 has a full-bridge chopper structure formed by four switch tubes 221, and each switch tube 221 is reversely connected in parallel with a freewheeling diode 222 at a current input end and an output end thereof, and is used for freewheeling during switching chopping and protecting the switch tube 221; secondly, the grounding ends of the two single-phase four-switch tube full-

bridge chopper units

21 and 22 are grounded after being connected with the

detection resistors

201 and 202 respectively, and the two

detection resistors

201 and 202 play a role in grounding protection in the scheme of the figure.

In addition, the present figure is different from fig. 6 in that a current sensor 30 is disposed on the phase a line of the motor 3 in the present figure, and is electrically connected to the current detection comparing unit 4; the B-phase line of the motor 3 may or may not be provided with the current sensor 30, so that it is connected to the current detection and comparison unit 4 by a dotted line, which indicates that both cases are possible. This is because, in actual needs, it is sufficient that the motor 3 only needs to detect one set of winding currents if the current increases, and the current sensor 30 can select any one or more of the four lines of the motor 3 for detection, without particular limitation.

Fig. 8 is a schematic circuit diagram 3 of the photocuring 3D printing screen-pressing-resistant locked-rotor detection device of the present invention. As shown in the figure, the difference between the present figure and fig. 6 is that the motor 3 in the present figure adopts a three-phase winding structure, the full-bridge chopper unit 20 includes a three-phase six-switching-tube full-bridge chopper unit 23, the full-bridge chopper unit also adopts six switching tubes to form a full-bridge chopper structure, and each switching tube is connected with a freewheeling diode in an inverse parallel manner. Secondly, the current sensor 30 is adopted to select any one or two or three of the lines of the motor 3 for detection, so that the current of the motor winding is fed back to the current detection comparison unit 4, and when the current of the motor 3 is increased and exceeds a preset current threshold value, the control unit 1 can stop the motor 3 from running. In addition, the motor 3 in the figure also adopts an encoder 33; the encoder 33 is arranged on the motor 3 for detecting the angular displacement of the rotor of the motor 3, recording the rotor pulse count or the rotor start position, and sending this information to the control unit 1 for controlling the precision motor 3 to achieve a precise angular offset.

Fig. 9 is a schematic structure and state diagram 1 of the photocuring 3D printing screen-pressing-prevention locked-rotor detection device of the present invention. As shown in the figure, the Z axis 31, the LCD screen 11, the UVLED light source module 12, and the liquid tank 9 are fixed to the base 10; the bottom film 90 is arranged at the bottom of the liquid tank 9 and is used for transmitting light; the liquid tank 9 is used for containing photosensitive resin 91 liquid; the motor 3 is arranged on the Z shaft 31 to realize electric driving lifting and drive the forming platform 32 to lift or descend along with the Z shaft;

generally, after the last resin molding model 92 is printed, the molding platform 32 will be stationary at the highest position, so the resin molding model 92 needs to be taken off in a manual demolding manner, and then a return-to-zero operation instruction is sent to return to the zero starting position; or when the resin molding model 92 is removed by manual demolding, a new printing instruction can be directly sent to the resin molding model 92, the resin molding model automatically returns to the zero starting position, and then layer-by-layer slice printing is started, so that the LCD screen 11 below the base film 90 can be easily extruded in the descending process if a user forgets to remove the resin molding model 92 or an adhered solidified block remains on the molding platform 32 in the descending process of the molding platform 32.

In addition, the limit detection module 7 in the figure can adopt electronic devices such as a proximity switch, an optical coupler, a microswitch or a touch button to realize a limit trigger function.

Fig. 10 is a schematic structure and state diagram 2 of the photocuring 3D printing screen-pressing-prevention locked-rotor detection device of the invention. As shown in the figure, on the basis of fig. 9, if the user forgets to remove the resin molding model 92 or the molding platform 32 has adhered curing blocks left thereon, during the descending process of the molding platform 32, the resin molding model 92 will first touch the bottom film 90 and further press the LCD 11 below the bottom film 90 to cause the cracking thereof, while the limit detection module 7 is not yet triggered, so that the detection method and apparatus of the present invention are required to determine whether the molding platform 32 is stopped by determining whether the molding platform 32 is stopped, and whether the current of the winding of the motor 3 is increased and exceeds the preset current threshold to control the operation and stop of the motor 3, so as to prevent the molding platform 32 from pressing the LCD 11 during the descending process.

Fig. 11 is a three-dimensional state demonstration diagram 1 of the photocuring 3D printing screen-pressing-prevention locked-rotation detection device of the present invention. As shown in the figure, in general, after the last resin molding model 92 is printed, the molding platform 32 will be stationary at the highest position, so the resin molding model 92 needs to be removed from the mold by hand, and then a return-to-zero operation command is sent to return to the zero starting position; or when the resin molding model 92 is removed by manual demolding, a new printing instruction can be directly sent to the resin molding model 92, the resin molding model automatically returns to the zero starting position, and then layer-by-layer slice printing is started, so that the LCD screen 11 below the base film 90 can be easily extruded in the descending process if a user forgets to remove the resin molding model 92 or an adhered solidified block remains on the molding platform 32 in the descending process of the molding platform 32. In addition, the limit detection module 7 in the figure can adopt electronic devices such as a proximity switch, an optical coupler, a microswitch or a touch button to realize a limit trigger function.

Fig. 12 is a three-dimensional state demonstration diagram of the light-cured 3D printing screen-pressing-prevention locked-rotation detection device of the present invention shown in fig. 2. As shown in the figure, if the user forgets to take off the resin molding model 92 or the molding platform 32 has adhered cured blocks left thereon, the resin molding model 92 will touch the bottom film 90 first and further press the LCD screen 11 below the bottom film 90 downwards to cause the molded platform 32 to crack during the descending process, and the limit detection module 7 is not triggered yet, so that the operation and stop of the motor 3 are controlled by judging whether the descending of the molding platform 32 is blocked or not, and causing the winding current of the motor 3 to increase and exceed the preset current threshold, so as to prevent the molding platform 32 from pressing the LCD screen 11 during the descending process.

The above examples are only for describing the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A photocuring 3D printing screen-pressing-resistant locked-rotor detection method is characterized by comprising the following steps:

SA01, the user sends an instruction for enabling the forming platform (32) to return to zero to the control unit (1) through the display and operation unit (6);

SA02, the control unit (1) sends a control instruction to the door driving unit (2) to control the door driving unit and drives the motor (3) to drive the forming platform (32) to move downwards along the Z axis (31) through the full-bridge chopping unit (20);

SA03 and the current detection comparison unit (4) acquire sampling current of the grounding end and/or the output end of the full-bridge chopper unit (20);

SA04, a current detection comparison unit (20) converts an analog signal of the sampling current into a digital signal, and the digital signal is sent to a control unit (1) after a digital current value is obtained;

SA05, the control unit (1) compares the digital current value with a preset current threshold value and judges whether the digital current value is greater than the preset current threshold value; if the digital current value is judged to be larger than the preset current threshold value, the step SA08 is carried out; if the digital current value is not larger than the preset current threshold value, performing step SA 06;

SA06 and a motor (3) drive a forming platform (32) to move downwards along a Z axis (31) until a limit detection module (7) is triggered and sends a limit trigger signal to a control unit (1);

SA07, controlling the forming platform (32) to shift to a zero initial position again by taking the corresponding position of the forming platform (32) on the Z axis (31) as a marking point when the control unit (1) triggers the limit detection module (7), and performing the step SA 09;

SA08, after judging that the motor (3) has a locked-rotor fault, the control unit (1) controls the motor (3) to stop running and sends out a warning signal through an abnormality prompting unit (8);

SA09, the flow ends.

2. A photocuring 3D printing screen-pressing-resistant locked-rotor detection method is characterized by comprising the following steps:

SB01, the user sends the instruction to the control unit (1) to reset the forming platform (32) to zero through the display and operation unit (6);

SB02, the control unit (1) sends a control instruction to the gate driving unit (2) to control the gate driving unit and drives the motor (3) to drive the forming platform (32) to move downwards along the Z axis (31) through the full-bridge chopping unit (20);

SB03, the current detection comparison unit (4) acquires the sampling current of the output end and/or the grounding end of the full-bridge chopper unit (20);

SB04, the current detection comparing unit (4) converts the analog signal of the sampling current into a digital signal, and sends the digital signal to the control unit (1) after obtaining the digital current value;

SB05, the control unit (1) compares the digital current value with the preset current threshold value and judges whether the digital current value is larger than the preset current threshold value; if the digital current value is judged to be larger than the preset current threshold value, the step SB10 is carried out; if the digital current value is not larger than the preset current threshold value, the step SB06 is carried out;

SB06, the motor drives the forming platform (32) to move downwards along the Z axis (31) until the limit detection module (7) is triggered and sends a limit trigger signal to the control unit (1);

SB07, controlling the forming platform (32) to shift to a zero initial position again by X millimeter by using the corresponding position of the forming platform (32) on the Z axis (31) as a marking point when the control unit (1) triggers the limit detection module (7);

SB09, the user operates the display and operation unit (6) to make the motor (3) drive the forming platform (32) to lift or descend Y mm to the target position and then store it as a new zero initial position, and the next step is carried out in the step SB 11;

SB10, the control unit (1) controls the motor (3) to stop running after judging that the motor (3) has a locked-rotor fault and sends out a warning signal through the abnormality prompting unit (8);

SB11, the flow ends.

3. A photocuring 3D printing screen-pressing-resistant locked-rotor detection method is characterized by comprising the following steps:

SC01, user leads the model printing slice file into the memory unit (5) of the photo-curing printing device;

SC02, the user sends the printing instruction of the model slice file to the control unit (1) through the display and operation unit (6);

the SC03 and the control unit (1) send control instructions to the door driving unit (2) to control the door driving unit and drive the motor (3) to drive the forming platform (32) to move downwards along the Z axis (31) through the full-bridge chopping unit (20);

the SC04 and the current detection comparison unit (4) acquire sampling current of the grounding end and/or the output end of the full-bridge chopper unit (20);

SC05, current detection comparing unit (4) converts the analog signal of sampling current into digital signal, and sends the digital signal to control unit (1) after obtaining the digital current value;

SC06, control unit (1) compares the digital current value with the preset current threshold value and judges whether the digital current value is larger than the preset current threshold value; if the digital current value is judged to be larger than the preset current threshold value, the step SC10 is carried out; if the digital current value is not greater than the preset current threshold value, performing step SC 07;

the SC07 and the motor (3) drive the forming platform (32) to move downwards along the Z axis (31) until the limit detection module (7) is triggered and sends a limit trigger signal to the control unit (1);

the SC08 and the control unit (1) control the forming platform (32) to shift X millimeters to a zero initial position by taking the corresponding position of the forming platform (32) on the Z axis (31) as a marking point when the limit detection module (7) is triggered;

the SC09 and the control unit (1) read the model printing slice file in the storage unit (5) and perform photocuring printing on the model slice data layer by layer in sequence, and then the step SC11 is performed;

the SC10 and the control unit (1) control the motor (3) to stop running after judging that the motor (3) has a locked-rotor fault and send out a warning signal through the abnormity prompting unit (8);

SC11, the flow ends.

4. A photocuring 3D printing screen-pressing-resistant locked-rotor detection method is characterized by comprising the following steps:

SD01, the user leads the model printing slice file into a storage unit (5) of the photocuring printing device and sends a printing instruction to the control unit (1) through a display and operation unit (6);

the SD02 and the control unit (1) control and drive the motor (3) to drive the forming platform (32) to return to zero;

the SD03 and the control unit (1) read the model printing slice file in the storage unit (5) and perform photocuring printing on the model slice data layer by layer in sequence;

the SD04 and the control unit (1) send control instructions to the door driving unit (2) to control the door driving unit and drive the motor (3) to drive the forming platform (32) to move or stop along the Z axis (31) through the full-bridge chopping unit (20);

the SD05 and the current detection comparison unit (4) acquire sampling current of the grounding end and/or the output end of the full-bridge chopper unit (20);

the SD06 and the current detection comparison unit (4) convert the analog signal of the sampling current into a digital signal, and send the digital signal to the control unit (1) after obtaining a digital current value;

the SD07 and the control unit (1) judge whether the forming platform (32) is in a descending state; if the forming platform (32) is not in the descending state, the step SD09 is carried out; if the forming platform (32) is judged to be in the descending state, the step SD08 is carried out;

the SD08 and the control unit (1) compare the digital current value with a preset current threshold and judge whether the digital current value is greater than the preset current threshold; if the digital current value is judged to be larger than the preset current threshold value, the step SD11 is carried out; if the digital current value is not larger than the preset current threshold value, performing the step SD 09;

the SD09 and the motor (3) drive the forming platform (32) to continue to move along the Z axis (31) until the forming platform reaches a target position;

the SD11 and the control unit (1) control the motor (3) to stop running after judging that the motor (3) has a locked-rotor fault and send out a warning signal through the abnormity prompting unit (8);

SD12, flow ends.

5. The method for detecting screen rotation blockage during photocuring 3D printing according to any one of claims 1 to 3, wherein in steps SA06, SB06 and SC07, the manner in which the motor (3) drives the forming platform (32) to trigger the limit detection module (7) comprises electromagnetic induction triggering, photoelectric induction triggering or direct touch and press triggering.

6. The method for detecting screen jam prevention during photocuring 3D printing according to any one of claims 1 to 4, wherein in the steps SA03, SB03, SC04 and SD05, the manner of obtaining the sampling current at the ground terminal and/or the output terminal of the full-bridge chopper unit (20) by the current detection comparison unit (4) comprises directly inputting the sampling current or collecting the sampling current by adopting a current sensing detection manner; in the steps SA05, SB05, SC06, and SD08, the preset current threshold is a fixed current value, or a dynamic following ratio value of the minimum driving current, or a dynamic following ratio value of the maximum driving current.

7. The utility model provides a photocuring 3D prints and prevents pressing stifled detection device that changes of screen, its characterized in that includes: the device comprises a control unit (1), a door driving unit (2), a full-bridge chopping unit (20), a motor (3), a current detection comparison unit (4), a storage unit (5), a display and operation unit (6), a limit detection module (7), an abnormity prompting unit (8), a Z axis (31), a forming platform (32), a base (10), an LCD screen (11), a UVLED light source module (12), a liquid tank (9), a bottom film (90) and photosensitive resin (91);

the door driving unit (2), the current detection and comparison unit (4), the storage unit (5), the display and operation unit (6), the limit detection module (7), the abnormity prompting unit (8), the LCD screen (11) and the UVLED light source module (12) are electrically connected with the control unit (1); a user sends an instruction for enabling the forming platform to return to zero or a printing instruction of the model slice file to the control unit (1) through the display and operation unit (6); the storage unit (5) is used for importing a storage model printing slice file;

the gate driving unit (2) is electrically connected with the full-bridge chopping unit (20) and controls the on-off of each switching tube in the full-bridge chopping unit (20); the full-bridge chopping unit (20) is electrically connected with a winding in the motor (3) and drives the motor (3) to run; the control unit (1) sends a control instruction to the door driving unit (2) to control the operation and start and stop of the motor (3) so as to drive the forming platform (32) to lift or stop along the Z axis (31); the motor (3) drives the forming platform (32) to move downwards along the Z axis (31) until the limiting detection module (7) is triggered and sends a limiting trigger signal to the control unit (1) so as to record corresponding position mark points of the forming platform (32) on the Z axis (31);

the current detection comparison unit (4) is connected with and acquires sampling current of a grounding end and/or an output end in the full-bridge chopping unit (20), converts an analog signal of the sampling current into a digital signal and acquires a digital current value, and then sends the digital current value to the control unit (1); the control unit (1) compares the acquired digital current value with a preset current threshold value to judge whether the motor (3) has a locked-rotor fault; after the control unit (1) judges that a locked-rotor fault occurs, the control unit controls the motor (3) to stop running and sends out a warning signal through the abnormity prompting unit (8), so that the photocuring 3D printing device is prevented from extruding the LCD screen (11) when the forming platform (32) descends in the zeroing process;

the Z axis (31), the LCD screen (11), the UVLED light source module (12) and the liquid tank (9) are fixed on the base (10); the bottom film (90) is arranged at the bottom of the liquid tank (9) and is used for transmitting light; the liquid tank (9) is used for containing photosensitive resin (91) liquid; the motor (3) is arranged on the Z shaft (31) to realize electric driving lifting and drive the forming platform (32) to lift or descend along with the Z shaft;

a user sends a model slice file printing instruction to a control unit (1) through a display and operation unit (6), after the control unit (1) controls a motor (3) to enable a forming platform (32) to return to a zero initial position, the control unit (1) reads a model printing slice file in a storage unit (5) and carries out photocuring printing on model slice data layer by layer in sequence, in the process, an LCD screen (11) loads and switches layer slice mask images in the model printing slice file layer by layer, and an UVLED light source module (12) sends ultraviolet light and visible light to expose and irradiate photosensitive resin (91) in a liquid tank (9) through the mask images in the LCD screen (11) and a bottom film (90) to be cured and formed; the forming platform (32) is used for attaching the cured and formed model forming resin layer in the curing and forming process to enable the cured and formed model forming resin layer to be continuously lifted and grown until the 3D printing is completed.

8. The photo-curing 3D printing screen-pressing-prevention locked-rotation detection device according to claim 7, further comprising: a current sensor (30); the current sensor (30) is electrically connected with the current detection comparison unit (4); the current sensor (30) is also arranged on a line between the full-bridge chopper unit (20) and the motor (3), detects the current of the line, and samples the detected current and sends the sampled current to the current detection comparison unit (4); the number of the current sensors (30) is one, or two, or three, or four.

9. The photo-curing 3D printing screen-pressing-prevention locked-rotation detection device according to claim 7, further comprising: an encoder (33); the encoder (33) is arranged on the motor (3) and used for detecting the angular displacement of the rotor of the motor (3), recording the pulse count of the rotor or the initial position of the rotor, and sending the information to the control unit (1) for controlling the forming platform (7) to realize accurate offset.

10. The device for detecting the blockage of the pressure-proof screen in the photocuring 3D printing process according to claim 7, wherein the motor (3) is a stepping motor, a servo motor or a DC brushless motor; the full-bridge chopping unit (20) comprises a three-phase six-switch-tube full-bridge chopping unit or two single-phase four-switch-tube full-bridge chopping units.