CN110950073A

CN110950073A - Method for preventing lighter and thinner sheet materials from being sucked in feeding process

Info

Publication number: CN110950073A
Application number: CN201911224220.1A
Authority: CN
Inventors: 麦伟东; 李金棠; 黄达许
Original assignee: Shenzhen Micronic Technology Co ltd
Current assignee: Shenzhen Micronic Technology Co ltd
Priority date: 2019-12-03
Filing date: 2019-12-03
Publication date: 2020-04-03
Anticipated expiration: 2039-12-03
Also published as: CN110950073B

Abstract

The invention relates to the technical field of PCB detection, in particular to a method for avoiding sucking lighter and thinner plates in the feeding process, which comprises the following steps: firstly, a vacuum chuck is driven by a manipulator to slowly approach a PCB (printed Circuit Board), and then a capacitive proximity switch is triggered to send a signal along with the change of the distance between the vacuum chuck and the PCB, so that the vacuum chuck is started to absorb the PCB; on the other hand, along with the change of the air pressure between the suction nozzle and the PCB, the vacuum pressure sensor is also touched to send a signal, the information of the PCB existing in the feeding storage rack is transmitted, the manipulator firstly implements light pressing action at the middle position of the PCB according to the acquired information, but does not start the vacuum sounder, so that the stack of PCBs is slightly placed compactly. According to the invention, through the design of the improved vacuum chuck, the phenomena of errors in grabbing lighter and thinner sheet materials in the PCB detection process can be effectively avoided, and the efficiency of grabbing the PCB by a manipulator is greatly improved.

Description

Method for preventing lighter and thinner sheet materials from being sucked in feeding process

Technical Field

The invention relates to the technical field of PCB detection, in particular to a method for avoiding sucking lighter and thinner sheet materials in the feeding process.

Background

In recent ten years, the printed circuit board manufacturing industry in China develops rapidly, and the total output value and the total output both belong to the first world. Due to the fact that electronic products are changing day by day, price war changes the structure of a supply chain, China has industrial distribution, cost and market advantages, and has become the most important production base of printed circuit boards all over the world, and the printed circuit boards are developed from single-layer boards to double-sided boards, multi-layer boards and flexible boards and are continuously developed towards high precision, high density and high reliability. The size is continuously reduced, the cost is reduced, and the performance is improved, so that the printed circuit board still keeps strong vitality in the development process of future electronic products.

The development trend of the production and manufacturing technology of the future printed circuit board is to develop towards high density, high precision, small aperture, thin lead, small space, high reliability, multilayering, high-speed transmission, light weight and thin type in performance, so that more and more light weight and thin type PCB boards are available in the market, and corresponding measures are needed to reduce or even avoid errors aiming at the phenomenon that the light and thin board materials are frequently subjected to grabbing errors in the full-automatic feeding process, so that the board grabbing efficiency of a manipulator is improved, and the production efficiency of the full-automatic flying probe tester is further promoted. In view of this, we propose a method to avoid picking up lighter and thinner sheet material during feeding.

Disclosure of Invention

In order to make up for the above deficiencies, the invention provides a method for avoiding sucking lighter and thinner sheet materials in the feeding process.

The technical scheme of the invention is as follows:

a method of avoiding picking up lighter and thinner sheet material during feeding, comprising the steps of:

firstly, a vacuum chuck is driven by a manipulator to slowly approach a PCB (printed Circuit Board), and then a capacitive proximity switch is triggered to send a signal along with the change of the distance between the vacuum chuck and the PCB, so that the vacuum chuck is started to absorb the PCB; on the other hand, along with the change of the air pressure between the suction nozzle and the PCB, the vacuum pressure sensor is also touched to send a signal, the information of the PCB existing in the feeding storage rack is transmitted, the manipulator firstly implements light pressing action at the middle position of the PCB according to the acquired information, but does not start the vacuum sounder, so that a stack of PCBs is slightly placed compactly;

secondly, the manipulator slightly moves the vacuum chuck upwards according to the actual overall dimension information of the PCB, the vacuum chuck and the PCB form an acute angle, the PCB is sucked by the suction nozzle on the uppermost row of the vacuum chuck, the adsorption effect of redundant positions is eliminated, the PCB is toppled around the bottom edge of the PCB under the dual actions of the suction nozzle and the gravity of the suction nozzle, and the vacuum chuck swings along the trend and is comprehensively combined with the PCB at the moment, so that the process of smoothly grabbing the PCB is realized;

thirdly, when the edge part of the PCB is irregular, the number of empty holes is large, and the suction of the vacuum sucker is not facilitated, the vacuum sucker finely adjusts the vacuum sucker up and down along the plane of the PCB according to the measured value of the vacuum pressure sensor until the PCB can be sucked by the uppermost row of suction nozzles;

fourthly, moving the PCB to a laser detection area after the PCB is grabbed by the manipulator;

and step five, when the thickness b of the board detected by the laser detection area is a set value, the mechanical arm moves next step, when the thickness b of the board detected by the laser detection area is larger than the set value, the mechanical arm grabs the board again, the vacuum generator is closed at the moment, the two PCB boards which are close to each other are separated by using the uppermost row of suction nozzles in the vacuum chuck, the vacuum generator is started again, the separated PCB boards are sucked, and therefore the action that the vacuum chuck grabs one PCB board is smoothly achieved.

According to the preferable technical scheme, the manipulator is mounted on a rack of the flying probe testing machine through screws, a feeding storage rack is mounted on one side of the manipulator, and the PCB is placed on the feeding storage rack.

As a preferable technical proposal, the manipulator comprises a fixed installation bottom plate fixedly installed on the frame, a primary driving motor is arranged on the fixed mounting bottom plate, an output shaft of the primary driving motor is connected with a small belt wheel, one side of the small belt wheel is connected with a large belt wheel through a conveying belt, a secondary transmission upright post is arranged on the large belt wheel, a secondary driving motor is arranged on the secondary transmission upright post, an output shaft of the secondary driving motor is connected with a secondary rotating wheel, a third-stage transmission upright post is arranged on the second-stage rotating wheel, a third-stage driving motor is arranged on the third-stage transmission upright post, an output shaft of the third-stage driving motor is connected with a third-stage rotating wheel, install level four transmission stand on the tertiary swiveling wheel, install level four driving motor on the level four transmission stand, level four driving motor's output shaft has the level four swiveling wheel, install the vacuum chuck fixed plate on the level four swiveling wheel.

Preferably, the vacuum chuck is fixedly installed at the tail end of the vacuum chuck fixing plate.

As an optimal technical scheme, a laser displacement sensor support is arranged under the end, close to the mechanical arm, of the feeding storage rack, a laser displacement sensor is mounted on the laser displacement sensor support, and a laser transmitter is mounted on the laser displacement sensor.

Preferably, the laser emitter emits a laser beam obliquely upwards to form a laser detection area.

Preferably, the set value is a board thickness of a single PCB.

According to the preferable technical scheme, the back face of the vacuum chuck is provided with two symmetrical vacuum pressure sensors, a vacuum generator is arranged between the two vacuum pressure sensors, the front face of the vacuum chuck is provided with a plurality of suction nozzles, a capacitive proximity switch is arranged at the position, close to the top face, of the front face of the vacuum chuck, and a CCD camera is arranged at the position, located at the center, of the front face of the vacuum chuck.

As a preferred technical scheme, the vacuum chuck is a closed hollow body, the vacuum generator is connected to the vacuum chuck through a vacuum pipe, and the suction nozzles are fixedly arranged on the vacuum chuck and are arranged linearly.

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

according to the invention, through the design of the improved vacuum chuck, the phenomena of errors in grabbing lighter and thinner sheet materials in the PCB detection process can be effectively avoided, and the efficiency of grabbing the PCB by a manipulator is greatly improved.

Drawings

FIG. 1 is a schematic view of the overall structure of the present invention;

FIG. 2 is a schematic view of the overall structure of the robot of the present invention;

FIG. 3 is a schematic view of the vacuum chuck of the present invention;

FIG. 4 is a front view of the vacuum chuck of the present invention;

FIG. 5 is a schematic diagram of the operating circuit of the capacitive proximity switch of the present invention;

FIG. 6 is a schematic diagram of the operation of the vacuum generator of the present invention;

FIG. 7 is a schematic view of a control module of the vacuum chuck of the present invention;

FIG. 8 is a second control block diagram of the vacuum chuck of the present invention;

fig. 9 is a time distribution diagram of the laser displacement sensor during the detection process according to the present invention.

In the figure: frame 1, manipulator 2, fixed mounting bottom plate 20, little band pulley 21, big band pulley 22, second grade transmission stand 23, second grade swiveling wheel 24, tertiary transmission stand 25, tertiary swiveling wheel 26, four grades of transmission stands 27, four grades of swiveling wheels 28, vacuum chuck fixed plate 29, vacuum chuck 3, vacuum generator 30, vacuum pressure sensor 31, suction nozzle 32, capacitanc proximity switch 33, CCD camera 34, material loading storage rack 4, PCB board 5, laser detection area 6, laser displacement sensor support 7, laser displacement sensor 8, laser emitter 9.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the equipment or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.

Referring to fig. 1-9, the present invention provides a technical solution:

firstly, the vacuum chuck 3 is driven by the manipulator 2 to slowly approach the PCB 5, and at the moment, along with the change of the distance between the vacuum chuck 3 and the PCB 5, the capacitive proximity switch 33 is triggered to send a signal, and the vacuum chuck 3 is started to suck the PCB 5; on the other hand, with the change of the air pressure between the suction nozzle 32 and the PCB 5, the vacuum pressure sensor 31 is also touched to send a signal, the information of the PCB 5 existing in the feeding storage rack 4 is transmitted, the manipulator 2 firstly carries out light pressure action at the middle position of the PCB 5 according to the acquired information, but does not start the vacuum sound generator 30, so that the stack of PCBs 5 is slightly placed compactly;

secondly, the manipulator 2 slightly moves the vacuum chuck 3 upwards according to the actual overall dimension information of the PCB 5, forms an acute angle with the PCB 5, utilizes the uppermost row of suction nozzles 32 of the vacuum chuck 3 to suck the PCB 5, and eliminates the adsorption effect of redundant positions, so that the PCB 5 is toppled around the bottom edge of the PCB 5 under the dual actions of the suction nozzles 32 and the gravity of the PCB, and the vacuum chuck 3 swings along the way and is comprehensively combined with the PCB 5, thereby realizing the process of smoothly grabbing the PCB 5;

thirdly, when the edge part of the PCB 5 is irregular, the number of empty holes is large, and the suction of the vacuum sucker 3 is not facilitated, the vacuum sucker 3 finely adjusts the vacuum sucker 3 up and down along the plane of the PCB 5 according to the measured value of the vacuum pressure sensor 31 until the PCB 5 can be sucked by the uppermost row of suction nozzles 32;

fourthly, moving the PCB to a laser detection area 6 after the PCB is grabbed by the manipulator;

and step five, when the laser detection area 6 detects that the plate thickness b is a set value, the mechanical arm 2 is close to the next step, when the laser detection area 6 detects that the plate thickness b is larger than the set value, the mechanical arm 2 grabs the plate again, at the moment, the vacuum generator 30 is closed, the two PCB plates 5 which are close to each other are separated by the aid of the suction nozzle 32 on the uppermost row in the vacuum suction disc 33, the vacuum generator 30 is started again, the separated PCB plates 5 are sucked, and accordingly the action that the vacuum suction disc 3 grabs one PCB plate 5 is achieved smoothly.

In this embodiment, the manipulator 2 is mounted on the frame 1 of the flying probe testing machine through a screw, the feeding storage rack 4 is mounted on one side of the manipulator 2, and the PCB 5 is placed on the feeding storage rack 4.

In this embodiment, the manipulator 2 includes fixed mounting bottom plate 20 of fixed mounting in frame 1, be equipped with one-level driving motor on the fixed mounting bottom plate 20, one-level driving motor's output shaft has little band pulley 21, one side of little band pulley 21 is connected with big band pulley 22 through the conveyer belt, install second grade transmission stand 23 on the big band pulley 22, install second grade driving motor on the second grade transmission stand 23, second grade driving motor's output shaft links there is second grade swiveling wheel 24, install tertiary transmission stand 25 on the second grade swiveling wheel 24, install tertiary driving motor on the tertiary transmission stand 25, tertiary driving motor's output shaft has tertiary swiveling wheel 26, install level four transmission stand 27 on the tertiary swiveling wheel 26, install level four driving motor on the level four transmission stand 27, level four driving motor's output shaft has level four swiveling wheel 28, install vacuum chuck fixed plate 29 on the level.

In this embodiment, the vacuum chuck 3 is fixedly installed at the end of the vacuum chuck fixing plate 29.

In this embodiment, the laser displacement sensor support 7 is arranged under the end of the loading storage rack 4 close to the manipulator 2, the laser displacement sensor 8 is arranged on the laser displacement sensor support 7, and the laser emitter 9 is arranged on the laser displacement sensor 8.

In this embodiment, the laser transmitter 9 emits a laser beam obliquely upward to form the laser detection region 6.

In this embodiment, the set value is the plate thickness of the single PCB 5.

In this embodiment, the back of the vacuum chuck 3 is provided with two vacuum pressure sensors 31 which are symmetrical to each other, a vacuum generator 30 is arranged between the two vacuum pressure sensors 31, the front of the vacuum chuck 3 is provided with a plurality of suction nozzles 32, a capacitive proximity switch 33 is arranged at a position, close to the top surface, of the front of the vacuum chuck 3, and a CCD camera 34 is arranged at a position, at the center, of the front of the vacuum chuck 3.

In this embodiment, the vacuum chuck 3 is a closed hollow body, the vacuum generator 30 is connected to the vacuum chuck 3 through a vacuum tube, the suction nozzle 32 is installed and fixed on the vacuum chuck 3 and is arranged linearly, the vacuum generator 30 provides vacuum for the vacuum chuck 3 and sucks and fixes the PCB board 5 through the suction nozzle 32, the vacuum pressure sensor 31 is used for measuring the vacuum degree in the vacuum chuck 3, the vacuum pressure sensor 31 has an analog output and provides a signal proportional to a required vacuum value, and the signal is connected to the analog-digital converter and is further connected to the control computer for data analysis and processing.

It should be noted that the operation principle of the vacuum generator 30 is based on the theory of fluid mechanics, and the continuity equation for the non-compressible air (the air is moving at a low speed and can be considered as non-compressible air) is as follows:

A1v1＝A2v2，

wherein A1 and A2 are the cross-sectional areas of the pipelines, the unit is m2, v1 and v2 are the flow velocity of the air flow, the unit is m/s, and the cross section is increased and the flow velocity is reduced; the cross-section decreases and the flow velocity increases.

For horizontal lines, the Bernoulli ideal energy equation for incompressible air is

P1+1/2ρv1²＝P2+1/2ρv2²，

Wherein P1, P2 is section A1, the corresponding pressure at A2 is in Pa, v1, v2 is section A1, the corresponding flow velocity at A2 is in m/s, ρ is the density of air in kg/m 2;

from the above formula, the flow velocity is increased and the pressure is decreased, when v2 is greater than v1, P1 is greater than P2, and when v2 is increased to a certain value, P2 is smaller than one atmospheric pressure, i.e. negative pressure is generated, so that the negative pressure can be obtained by increasing the flow velocity to generate suction.

It should be noted that the operating principle of the vacuum pressure sensor 31 is that the pressure of the medium directly acts on the diaphragm of the vacuum pressure sensor 31, so that the diaphragm generates a micro-displacement proportional to the pressure of the medium, the resistance of the vacuum pressure sensor 31 changes, the electronic circuit detects the change, and the electronic circuit converts the change to output a standard signal corresponding to the pressure.

It should be added that, after the vacuum generator 30 is started, the first situation is that if all the suction nozzles 32 on the vacuum chuck 3 are in contact with the PCB 5 at this time, that is, when the vacuum chuck 3 is in the closed state, the vacuum chuck 3 will generate 50% vacuum, and at this time, the measurement can be performed by the vacuum pressure sensor 31; the second situation is that if all suction nozzles 32 on the vacuum cup 3 are not in contact with the PCB 5 at this time, i.e. corresponding to the vacuum cup 3 being in an open state, the vacuum level in the vacuum cup 3 drops to a level of 10%, which can be measured by the vacuum pressure sensor 31 at this time as well.

It is worth to be noted that the working principle of the capacitive proximity switch 33 is: when no object to be measured is close to the capacitive proximity switch 33, C1 and C2 are small, the LC oscillator stops vibrating, when the object to be measured is close to two concentric circular electrodes of the capacitive proximity switch 33, the two electrodes and the object to be measured form a series equivalent capacitor C, when C is increased to a set value, the LC oscillator starts vibrating (working current is increased along with the C), high-frequency output voltage U0 of the oscillator is detected by a diode VD and filtered by an RC low-pass filter to obtain an average value of positive half-cycle signals, the output voltage U01 amplified by a direct-current voltage amplifying circuit is compared with a reference voltage UR, if U01 exceeds the reference voltage, the comparator is turned over to generate an action signal, and when the object to be measured is a conductive metal object, even if the distance between the two is long, the equivalent capacitor C is still large, the LC loop is easy to start vibrating, and the sensitivity is high; if the area of the object to be measured is less than 2 times the diameter of the capacitive proximity switch 33, the sensitivity is significantly reduced, and therefore, the vacuum chuck 3 on the manipulator 2 can accurately determine whether the PCB 5 is in front or not by means of the capacitive proximity switch 33.

It should be noted that the specific detection process of the laser displacement sensor 8 is as follows:

1) when the movement starts (t ═ 0), the PCB board 5 is located outside the laser beam, the laser displacement sensor 8 does not detect any object, the distance value is the maximum limit because there is no object within the effective distance area;

2) when the PCB panel 5 enters the laser beam (t ═ t1), the laser displacement sensor 8 detects the lower edge of the PCB panel 5, and the distance value in the active area is at a reasonable value;

3) when the PCB panel 5 continues to move away from the laser beam, t2, the laser beam is also not detecting any objects and the value returns to the maximum limit;

4) the t1 and t2 values can be determined by a processor of the laser displacement sensor 8, the whole operation process is uniform motion, the velocity v value can be determined, and finally the thickness s value of the PCB 5 can be determined by calculation as follows:

S＝v*t2-t1，

where v is the known constant speed of movement of the PCB board 5 during acquisition; in the above process, the determination of the value of t1 is ensured, and as shown in the above figure, when an object enters the range of the laser beam, the distance value will change from max value to a reasonable value, and the starting time is t 1; in the above process, the determination of the value of t2 is ensured, when an object leaves the range of the laser beam, the distance value will change from a reasonable value to a max value, and the ending time is t 2; in the process, the absolute distance value between the sensor and the PCB 5 does not need to be considered, and only the measured object is required to be ensured to be within the measuring range of the sensor, so that the distance between the manipulator 2 and the laser displacement sensor 8 in the vertical direction is not a fixed value but a range value in the whole detection movement process when the manipulator grabs different PCBs 5, and the flexibility of the whole detection process is highlighted; we need only find the incremental value: Δ ═ t2-t1, while the absolute position of t1 or t2 is not important. This allows a certain high tolerance to the start and end points of the movement during the whole detection movement;

5) and the digital signal processor outputs the comparison result to the control computer, and the control computer sends a control instruction to the vacuum chuck 3 on the manipulator 2.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and the preferred embodiments of the present invention are described in the above embodiments and the description, and are not intended to limit the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A method for avoiding sucking lighter and thinner sheet materials in the feeding process is characterized in that: the method comprises the following steps:

firstly, a vacuum chuck (3) is driven by a manipulator (2) to slowly approach a PCB (5), and at the moment, along with the change of the distance between the vacuum chuck (3) and the PCB (5), a capacitive proximity switch (33) is triggered to send a signal, so that the vacuum chuck (3) is started to suck the PCB (5); on the other hand, with the change of the air pressure between the suction nozzle (32) and the PCB (5), the vacuum pressure sensor (31) is also touched to send a signal, the information of the PCB (5) existing in the feeding storage rack (4) is transmitted, and the manipulator (2) firstly implements light pressing action at the middle position of the PCB (5) according to the acquired information but does not start the vacuum sounder (30), so that the stack of PCBs (5) is slightly placed compactly;

secondly, the manipulator (2) slightly moves the vacuum chuck (3) upwards according to the actual overall dimension information of the PCB (5) and forms an acute angle with the PCB (5), the PCB (5) is sucked by using the uppermost row of suction nozzles (32) of the vacuum chuck (3) to remove the adsorption effect of redundant positions, so that the PCB (5) is toppled around the bottom edge of the PCB (5) under the dual actions of the suction nozzles (32) and the gravity of the suction nozzles, and the vacuum chuck (3) swings along the trend and is comprehensively combined with the PCB (5) at the moment, thereby realizing the process of smoothly grabbing the PCB (5);

thirdly, when the edge part of the PCB (5) is irregular, the number of empty holes is large, and the suction of the vacuum sucker (3) is not facilitated, the vacuum sucker (3) finely adjusts the vacuum sucker (3) up and down along the plane of the PCB (5) according to the measured value of the vacuum pressure sensor (31) until the PCB (5) can be sucked by the uppermost row of suction nozzles (32);

fourthly, moving the PCB to a laser detection area (6) after the PCB is grabbed by the manipulator;

and fifthly, when the laser detection area (6) detects that the plate thickness b is a set value, the mechanical arm (2) is tightly moved next step, when the laser detection area (6) detects that the plate thickness b is larger than the set value, the mechanical arm (2) re-grabs the plate, at the moment, the vacuum generator (30) is closed, the uppermost row of suction nozzles (32) in the vacuum suction disc (33) is utilized to separate two PCB plates (5) which are tightly moved together, then the vacuum generator (30) is started again to suck the separated PCB plates (5), and therefore the action that the vacuum suction disc (3) grabs one PCB plate (5) is smoothly achieved.

2. A method of avoiding picking up lighter and thinner sheet material during feeding as claimed in claim 1, wherein: the manipulator (2) is installed on a frame (1) of the flying probe testing machine through screws, a feeding storage rack (4) is installed on one side of the manipulator (2), and the PCB (5) is placed on the feeding storage rack (4).

3. A method of avoiding picking up lighter and thinner sheet material during feeding as claimed in claim 1, wherein: the manipulator (2) comprises a fixed mounting base plate (20) fixedly mounted on a rack (1), a first-stage driving motor is arranged on the fixed mounting base plate (20), an output shaft of the first-stage driving motor is connected with a small belt wheel (21), one side of the small belt wheel (21) is connected with a large belt wheel (22) through a conveying belt, a second-stage transmission upright post (23) is mounted on the large belt wheel (22), a second-stage driving motor is mounted on the second-stage transmission upright post (23), a second-stage rotating wheel (24) is connected with an output shaft of the second-stage driving motor in a chain mode, a third-stage transmission upright post (25) is mounted on the second-stage rotating wheel (24), a third-stage driving motor is mounted on the third-stage transmission upright post (25), a third-stage rotating wheel (26) is, four-stage driving motor is installed on four-stage transmission upright post (27), four-stage driving motor's output shaft is connected with four-stage rotating wheel (28), vacuum chuck fixed plate (29) is installed on four-stage rotating wheel (28).

4. A method of avoiding picking up lighter and thinner sheet material during feeding as claimed in claim 1, wherein: the vacuum chuck (3) is fixedly arranged at the tail end of the vacuum chuck fixing plate (29).

5. A method of avoiding picking up lighter and thinner sheet material during feeding as claimed in claim 1, wherein: the feeding storage rack (4) is provided with a laser displacement sensor support (7) under the end close to the manipulator (2), the laser displacement sensor support (7) is provided with a laser displacement sensor (8), and the laser displacement sensor (8) is provided with a laser emitter (9).

6. A method of avoiding picking up lighter and thinner sheet material during feeding as claimed in claim 1, wherein: the laser emitter (9) emits laser beams obliquely upwards to form a laser detection area (6).

7. A method of avoiding picking up lighter and thinner sheet material during feeding as claimed in claim 1, wherein: the set value is the plate thickness of a single PCB (5).

8. A method of avoiding picking up lighter and thinner sheet material during feeding as claimed in claim 1, wherein: the back of vacuum chuck (3) is equipped with two vacuum pressure sensor (31) of mutual symmetry, is equipped with vacuum generator (30) between two vacuum pressure sensor (31), the front of vacuum chuck (3) is equipped with a plurality of suction nozzles (32), and the position that the front of vacuum chuck (3) is close to the top surface is equipped with capacitanc proximity switch (33), and the front of vacuum chuck (3) is located central point and puts and is equipped with CCD camera (34).

9. A method of avoiding picking up lighter and thinner sheet material during feeding as claimed in claim 1, wherein: the vacuum sucker (3) is a closed hollow body, the vacuum generator (30) is connected to the vacuum sucker (3) through a vacuum tube, and the suction nozzles (32) are fixedly arranged on the vacuum sucker (3) and are arranged linearly.