JP3322480B2 - Screen printing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen printing machine for applying a coating agent on a screen plate to a printed board by moving a squeegee through the screen plate.

[0002]

2. Description of the Related Art A screen printing machine of this type is disclosed in Japanese Patent Application Laid-Open No. 4-257292 filed by the present applicant. This is because when the operator opens the safety door and cleans the screen plate manually, the power supply to the motor that is the driving source of the movable part stops even if the safety door is opened. A cleaning switch is provided so that the power supply is not interrupted while the cleaning switch is operating. For example, even if an operator touches a movable part, the position is maintained. This eliminates the trouble of starting the printing operation after returning each motor to the origin position after the cleaning of the screen plate is completed, thereby preventing a reduction in the operation rate of the screen printing machine.

However, in recent years, electronic components have been reduced in size, and electronic components with leads have tended to be finer between electrodes. Accordingly, openings as printed pattern holes on a screen plate have been reduced in size and precision, and various types have been developed. Therefore, it is necessary to variously change the printing conditions such as the squeegee angle and the squeegee replacement and the screen frame replacement according to each type.

When such a changeover is performed manually by an operator, the safety door must be opened, and each time the power to the motor of each movable section is shut off, the work is performed as described above. When the user comes into contact with the stopped movable portion, the user easily moves without trying to maintain the position, and the rotation position of the motor changes from the position stored by the CPU. Even in the case of a servomotor, the position cannot be determined because the encoder circuit does not operate when the power is turned off.

Therefore, when the operation is restarted, the printing operation must be started after returning each motor to the home position, which is troublesome, resulting in a disadvantage that the operation rate of the screen printing machine is lowered.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to increase the operation rate of a screen printing machine by preventing the power supply to a drive source from being stopped even when a safety door is opened during a setup change operation of the screen printing machine. With the goal.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a screen printing machine for applying a coating material on a screen board to a printed circuit board by moving a squeegee through the screen board. A safety door that can be shielded more, a door switch that operates when the safety door is closed to enable power to be supplied to a drive source of the movable unit, and performs various setup operations by opening the safety door. Work before
A display device that displays the operation of the operation button to the
A power supply that can supply power to a drive source of the movable unit when a setup change start switch that is operated by the operation of the operation button by a trader and either the door switch or the change setup start switch is in an operating state. And a supply circuit.

When performing setup change work , open the safety door.
The display device displays the operation of the operation button on the screen before
The operator presses the operation button to activate the setup change start switch. Then, the power supply circuit continues to supply power to the driving source of the movable unit even if the worker opens the safety door and the door switch is not operated by the operation of the setup change start switch.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. A screen printing machine 1 shown in FIG. 3 is provided with an operation unit 3 including a CRT 2 screen as a display device and a CRT 62 for displaying an image picked up by a recognition camera 49 described later. Reference numeral 4 denotes an indicator light for notifying an operator by lighting, blinking, or extinguishing the operating state during production operation or abnormal stop. 65 is the printing press 1
Is a safety door capable of shielding a movable part from an operator, and is closed during operation. Reference numeral 66 denotes a door opening / closing switch for detecting opening / closing of the safety door 65.

FIG. 2 is a diagram showing the inside of the printing press 1, and 7 is a printed circuit board 8 conveyed from an upstream device (not shown).
(See FIGS. 5 and 6) to a mounting table 9 on which the substrate 8 is sucked by a suction mechanism (not shown). 10 is the mounting table 9 described above.
Is an XY-θ table that holds X, as shown in FIG.
It comprises a table 11, a Y table 12, and a θ table 13.

The X table 11 is driven by an X motor 17 along a pair of X guide rails 16 provided on a base 15 (see FIG. 2). Move in the direction. The X guide rail 16 extends from a positioning station on which the substrate 8 is mounted by the mounting table 9 to a printing station described later in the form of XY-θ.
The table 10 is provided movably.

The Y table 12 rotates along with a pair of Y guide rails 24 provided on the X table 11 via a Y nut body 23 by rotation of a Y screw shaft 22 driven by a Y motor 21 (see FIG. 1). Move in the Y direction. Further, the θ table 13 rotates θ by driving the θ motor 26 via a θ rotation mechanism (not shown). Reference numeral 40 shown in FIGS. 2 and 5 is a recognition camera driving unit. Reference numeral 41 denotes an X moving body, which moves in the X direction along an X camera guide 45 via a nut 44 by rotation of an X camera screw shaft 43 driven by an X camera driving motor 42. The X moving body 41 is driven by a Y camera driving motor 46 to rotate and rotate a Y camera screw shaft 47.
A recognition camera 49 composed of a CCD camera as a recognition device attached to a Y nut body 48 fitted to the screw shaft 47 moves along a Y camera guide 50 also provided on the X moving body 41. It is moved in the Y direction by the rotation of the screw shaft 47, and the positions of the alignment marks 51 (one not shown) provided on two diagonal lines of the substrate 8 and the printing on the substrate 8 on which the solder paste W is printed. Image the pattern.

A screen 28 shown in FIG. 6 is provided with a screen plate 30 provided with an opening (not shown) as a printed pattern hole formed in accordance with a desired circuit pattern of the substrate 8, and the screen. And a screen frame 31 surrounding the same. Reference numeral 33 shown in FIG. 2 denotes a squeegee table attached to a base (not shown). Then, the rotation of the print motor 32 is transmitted to the drive pulley and rotated, and the squeegee belt 33 attached to the drive pulley and the driven pulley are moved by moving. Is moved. Note that a pulse motor is used as a print motor. Further, a servo motor may be used.

Two opposing squeegees 34 are mounted on the squeegee table 33 so as to be vertically movable by operation of a squeegee vertical cylinder (not shown). Then, the mounting table 9 is moved via the XY-θ table 10, and the squeegee 34 is lowered while the substrate 8 on the mounting table 9 is positioned at the printing station, and the screen 28 is moved.
Is moved while pressing the screen plate 30 against the substrate 8.
The solder paste W supplied on the screen plate 30 is printed on the substrate 8 through openings provided corresponding to the pattern of the substrate 8.

The angle of the squeegee can be variously changed by an operator via an angle adjusting mechanism (not shown) in accordance with the viscosity of the solder paste, the diameter of the printed pattern, the pitch of the holes, and the like. Reference numeral 60 denotes a discharge conveyor for discharging the printed substrate 8 to a downstream device. Next, the control system will be described. 53 shown in FIG. 1 is a CPU as a control device,
The operation is performed according to an operation program stored in a ROM 55 as a storage device based on various information related to a printing operation of the substrate 8 of the screen printing machine 1 stored in a RAM 54 as a storage device.

Reference numeral 56 denotes an interface, which is a CRT
2. Start button 57, operation button 58, stop button 59
, An indicator lamp 4, a touch panel switch 5, a recognition camera 49, a CRT 62, and the like, and a relay 70. 80 is X motor 1
7, Y motor 21, θ motor 26, print motor 32, X
This is a drive circuit that drives the drive sources of each motor such as the camera drive motor 42 and the Y camera drive motor 46. 71 is a relay contact of the relay 70, and when the relay 70 operates,
It is closed.

A door opening / closing switch 66 provided corresponding to the safety door 65 which opens and closes with the upper end of FIG. 3 as a support side is connected in parallel with the relay contact 71 and the relay contact 7
1 and a switch 72 are connected in series with a relay 72. The switch 66 is closed when the corresponding safety door 65 is closed, and is opened when the safety door 65 is opened.

Reference numeral 73 denotes a relay contact of the relay 72.
Reference numeral 4 denotes an electromagnetic contactor, both of which are connected in series with each other and connected between AC lines supplied from a power supply 75. The relay contact 73 is closed when the relay 72 operates. A power supply 75 is connected to the drive circuit 80. Each line connecting the drive circuit 80 and the power supply 75 is provided with a contact 76 of the electromagnetic contactor 74, and the relay contact 73 is closed. When the contactor 74 is operated, the contact 76 is closed and the drive circuit 80 is energized.

When the motor driven by the drive circuit 80 is a servomotor, the encoder circuit for detecting the rotational position of the motor is energized by a power supply line to the drive circuit 80 as a part of the drive circuit 80. When the valve 76 is opened, the position detection is not performed. Screen printing machine 1
During normal operation, the CPU 53 does not operate the relay 70, the relay contact 71 is opened, and when the safety door 65 is opened, the door open / close switch 66 is opened and the power supply 75 is shut off. When the safety door 65 is opened to perform various manual setup changes, the safety door 6
Before opening 5, the operation button 58 is pressed to operate the relay 70 and the relay contact 71 is closed. This allows
The power supply 75 is not shut off even when the safety door 65 is opened.

The touch panel switch 5 as a data input device is mounted on a screen of the CRT 2 via a mounting tool (not shown). In the touch panel switch 5, a transparent conductive film is coated on the entire surface of a glass substrate, and electrodes are printed on four sides. Therefore, a very small current is applied to the surface of the touch panel switch 5, and when an operator touches, current changes occur on the four electrodes, and the coordinate values touched by the circuit board connected to the electrodes are stored in the RAM5.
If the coordinates in the group of coordinate values stored in advance as a switch unit for performing the work in 4 coincide with the coordinate value, the work is performed.

Hereinafter, the operation will be described. First, when the power is turned on, the CRT is
The initial screen shown in FIG. 7 is displayed on the screen 2. On this screen, the operation switch section of "production operation" is touched, and after the screen of the production operation (stopped) shown in FIG. 8 is displayed, the start button 57 of the operation section 3 is touched to start the production operation.

When the production operation is started, first, the substrate 8 conveyed from the upstream side device by the supply conveyor 7 is mounted on the mounting table 9 located on the positioning station side. Next, the recognition of the position of the substrate 8 by the recognition camera 49 is performed. That is, the recognition camera 49 waiting at the origin position moves on the first alignment mark 51 of the substrate 8 by the rotation of the X camera drive motor 42 and the Y camera drive motor 46, and recognizes the position. The rotation of the Y camera drive motor 46 and the X motor 17 of the XY-θ table 10 are also performed.
The second alignment mark 51 moves below the recognition camera 49 during the movement of the mounting table 9 (substrate 8) to the printing station side due to the rotation of, so that the position of the mark 51 is recognized. Then, after the mark recognition, the camera 49 returns to the origin position. Based on this recognition result and the recognition result of the position of the screen plate 30 already recognized, the screen plate 3
XY so that the position of the substrate 8 is
Table 10 moves along the X guide rail 16 in the X direction by the rotation of the X motor 17 and along the Y guide rail 24 in the Y direction by the rotation of the Y motor 21 and stops below the screen plate 30.

Thereafter, the .theta. Table 13 is rotated in the .theta. Direction by the rotation of the .theta.
With respect to the position to be positioned. Next, the screen plate 30 is lowered to the vicinity of the substrate 8 by driving a screen vertical motor (not shown). Then, with the right squeegee 34 shown in FIG. 6 being adjusted to the desired squeegee angle by the angle adjusting mechanism, the squeegee vertical cylinder is driven and lowered onto the screen plate 30. And
The screen plate 3 is moved leftward in FIG. 6 based on a desired squeegee speed by driving the print motor 32.
The solder paste W supplied on the substrate 0 is printed on the circuit pattern of the substrate 8 through the opening of the screen plate 30. Next, the right squeegee 34 is raised, and the left squeegee 3
Similarly, the squeegee 34 is raised by lowering the cylinder 4 by driving the cylinder to perform printing in the backward direction. If printing in one direction is sufficient, two substrates 8 can be printed by printing in the forward direction and printing in the backward direction.

After the printing is completed, the positioning of the mounting table 9 is released, and the discharge conveyor 60 discharges the substrate 8. After the substrate 8 has been ejected, the mounting table 9 is returned from the printing station to the positioning station to prepare for the supply of the next substrate 8. Hereinafter, the printing operation is continued similarly. Hereinafter, an operation during a setup change operation for performing a printing operation under another condition will be described.

First, the operator presses the stop button 59 to stop the production operation. The screen of the production operation (during stop) of FIG. 8 is displayed on the screen. On this screen, select “Initial screen”
7 to display the initial screen of FIG. Then, the operation switch section of "setup work" on this screen is touched to display the setup work screen shown in FIG. 9, and the operation switch section of "setup change" is touched on this screen, and the setup switch shown in FIG. Display the replacement screen.

On this screen, "Batch change", "Unit change", "Squeegee A (right side in FIG. 6) initial angle adjustment", "Squeegee B (left side in FIG. 6) initial angle",
"Squeegee angle adjustment", "Squeegee pushing temporary origin adjustment", "Screen frame replacement", "Paste kneading operation",
There are operation switches for "replace suction jig (mounting table)" and "replace squeegee".

On this screen, a desired setup change operation is selected. For example, when the user wants to replace the screen 28, he touches the operation switch section of "screen frame replacement" and
The screen for replacing the screen frame is displayed. When this screen is displayed, the operator presses the operation button 58. As a result, the CPU 53 outputs the
Since the relay 70 is actuated and the relay contact 71 is closed, the relay contact 71 is closed even if the worker opens the safety door 65 and the door open / close switch 66 is opened. And the power supply 7 to the drive circuit 80
5 is also maintained.

Although the CPU 53 does not issue a command to drive the motor and the cylinder, the rotational position of each motor and the state of each cylinder are stored in the RAM 54. At this time,
Even if each motor is stopped, the pulse motor is excited to maintain the current rotational position because it is excited.In the case of a servo motor, if a worker contacts the movable part, the motor rotates. Even if an external force is applied, the drive circuit 80 drives the motor so as to maintain the position commanded by the CPU 53, so that the current rotation position is also to be maintained.

Then, a replacement operation is performed based on the operation procedure displayed on the screen. That is, the operator presses the operation button 58 according to the operation procedure. Thus, the fixing of the screen frame 31 by the fixing mechanism (not shown) that fixes the screen frame 31 in the positioned state is released. The operator replaces the screen frame 31 from which the fixing by the fixing mechanism has been released with a desired screen frame 31 (positions the screen frame 31 at a position fixed by the fixing mechanism), and then closes the safety door 65. When the operation button 58 is pressed, the screen frame 31 is fixed by the fixing mechanism. As described above, when the safety door 65 is closed, the door opening / closing switch 66 is closed, and then, when the operation button 58 is pressed, the CPU 53 detects that the replacement of the screen frame 31 is completed, and The operation is stopped, and the relay contact 71 is opened, but the relay 72 remains energized and the contact 76 remains closed.

After the replacement of the screen frame 31, the printing operation is started as described above. If the safety door 65 is opened for any reason during the normal operation, the door open / close switch 66 is opened and the relay contact 71 is also in the open state, so that the relay 72 is demagnetized. Then, the relay contact 73
Is opened, the operation of the electromagnetic contactor 74 stops, and the contact 76
Is opened and the connection between the drive circuit 80 and the power supply 75 is cut off.

Thus, when the drive circuit 80 is de-energized, the motors and cylinders are stopped, the excitation is interrupted in the case of a pulse motor, and the excitation is interrupted in the case of a servo motor. Since the drive circuit 80 for holding the position does not work, when the operator touches a movable part, such as the XY-θ table 10 or the recognition camera 49, driven by the motor, the movable part moves, and the motor is rotated. Will change.

Not only a motor such as a pulse motor having no encoder circuit for detecting the rotational position but also a servo motor having an encoder circuit, the encoder circuit is de-energized because the drive circuit is de-energized. Therefore, the CPU 53 cannot detect the rotation position. Then, the operator takes some measure to take the safety door 6
When the shutter 5 is closed, it is necessary to perform the home return operation of each motor and cylinder.

When the setup change of the squeegee replacement is performed, the operation switch section of "squeegee replacement" is touched on the screen of FIG. 10 to display the squeegee replacement screen shown in FIG. Press to prevent power off. Then, a setup operation is performed based on the operation procedure displayed on this screen. That is, the operator presses the operation button 58 according to the operation procedure. Thereby, the fixing of the screen frame 31 by the fixing mechanism is released. Further, since the relay 70 is operated and the relay contact 71 is closed by pressing the operation button 58, the relay contact 71 is closed even when the worker opens the safety door 65 and opens the door open / close switch 66. As a result, the relay 70 keeps operating and the connection of the power supply 75 to the drive circuit 80 is maintained.

After removing the screen frame 31 from which the fixing by the fixing mechanism has been released, the operator presses the operation button 5.
Press 8. As a result, the squeegee 34 is moved to a preset desired position where the operator can easily work by moving the squeegee table 33 by driving the print motor 32. Next, the operator removes the squeegee 34 screwed to the squeegee holder (not shown) from the holder and replaces the squeegee 34 with a desired squeegee 34, and then presses the operation button 58 to move the squeegee table 33 to the origin position. Then, after the screen frame 31 is again positioned at a position where the screen frame 31 is fixed by the fixing mechanism, the safety door 65 is closed, and when the operation button 58 is pressed, the screen frame 31 is fixed by the fixing mechanism. Thus, the setup change of the squeegee 34 is performed.

Further, when the mounting table 9 is to be replaced, FIG.
On the screen 0, the operator touches the operation switch section of "Suction jig exchange" to display the suction jig exchange screen shown in FIG.
When this screen is displayed, the operation button 58 is pressed to prevent the power from being shut off even when the safety door 65 is opened. Then, based on the operation procedure displayed on the screen, the mounting table 9
Exchange. That is, the operation button 58 is pressed and the XY-
Table 10 is moved to the printing station. After removing the screen frame 31, the mounting table 9 fixed to the table 10 is replaced with a desired mounting table 9. Then, after the screen frame 31 is attached again, by pressing the operation button 58, the screen frame 31 is fixed by the fixing mechanism and the table 10 is moved to the origin position. The XY chute performs automatic setup of the width. In the present embodiment, an example is shown in which the mounting table 9 on which the substrate 8 is suction-mounted is used. However, the present invention is not limited to this. 8 may be placed in a state where it is backed up horizontally.

When the solder paste W supplied on the screen plate 30 is kneaded with a squeegee 34 so as to have a desired viscosity, the operation switch unit of the "paste kneading operation" is set on the screen shown in FIG. Touch to display the screen of the paste kneading operation of FIG. When this screen is displayed, the operation button 58 is pressed to prevent the power from being shut off even when the safety door 65 is opened. Then, a paste kneading operation is performed based on the operation procedure displayed on the screen.

First, an operator sets a dummy substrate on the supply conveyor 7. Next, by touching the “number setting” key, the screen shown in FIG. 15 is displayed, and the number of paste kneading operations is set on this screen. In this case, the operator touches the operation switch section of “number of paste kneading operations” at the upper left of the screen in FIG. Then, the switch section blinks, a display section for data setting is displayed at the lower left of the screen, and the display section displays "number of paste kneading operations: (assuming that no data is currently set)". . Further, operation switches of “1 reciprocation”, “2 reciprocations”, “3 reciprocations”... “9 reciprocations” are displayed at the lower right of the screen. Then, by touching a desired (for example, three reciprocating) operation switch section, the display section displays "3 reciprocations", and the setting is made by touching a "SET" key. The blinking operation switch section indicates "3 reciprocations". And stored in the RAM 54.

When the setting of the number of times of the paste kneading operation is completed, the operator touches the operation switch section of "Return to screen" and
Screen. When the operation button 58 is pressed, the dummy substrate mounted on the mounting table 9 is moved to the printing station by moving the XY-θ table 10, and the paste kneading operation starts on the screen plate 30 on the substrate. Is done. After the kneading operation has been completed a predetermined number of times, each unit returns to the original position. The operator removes the dummy substrate from the mounting table 9.

When the batch setup is performed, the operation switch section of "Batch setup change" is touched on the screen of FIG. 10 to display the batch setup change screen shown in FIG. When this screen is displayed, the operation button 58 is pressed, and the safety door 65 is pressed.
The power should not be shut off even if the power is shut off even if the power is turned off. When the operation button 58 is pressed again, the batch change of the supply conveyor width, the discharge conveyor width, the chute width of the mounting table, the screen recognition, and the paste linear supply is started.

Hereinafter, other setup change work is similarly performed. The desired setup change is completed as described above,
When the safety door 65 is closed, the door open / close switch 6
6 is closed and then the operation button 58 is pressed, the CPU 53 detects that the replacement of the screen frame has been completed, stops the operation of the relay 70, and sets the relay contact 7
1 is opened, but the relay 72 remains energized and the contact 76 remains closed.

Then, the printing operation is restarted as described above. Further, if the CPU 53 detects that the safety door 65 is closed irrespective of the pressing of the operation button 58, it is determined that some setup change work is completed and the relay 7
The operation of 0 may be stopped. Further, a button other than the operation button 58 may be used.

In this embodiment, the CPU 53 operates the relay 70 by pressing the operation button 58 during the setup change operation. However, the safety door 65 is opened during the automatic operation of the screen printing machine. If it is necessary to perform the work, the relay 70 may be operated before the work is performed, so that the supply of power to a driving source such as a motor for driving the movable portion is not interrupted.

Further, not only the screen printing machine but also a safety door is provided, and when the door is opened, supply of power to a driving source such as a motor for driving a movable portion of the apparatus is stopped. In a device such as a device for mounting electronic components on a printed circuit board or a device for applying an adhesive for temporarily fixing the electronic components to the printed circuit board, the work performed by an operator by opening a safety door during automatic operation. In some cases, especially when the operation is a regular operation, a circuit such as the relay 70 of the present embodiment may be provided so as to supply power to the drive source even when the safety door is opened. Can be.

Further, instead of the operation button 58, the relay 70 and the relay contact 71 of this embodiment, a switch for manually opening and closing is provided at the position of the relay contact 71 so that power is supplied even when the safety door is opened. You may do it. Further, in the present embodiment, the drive circuit 80 is shown as a circuit common to all motors and cylinders for convenience, but if the drive circuits for driving each motor and cylinder are independent, The connection line from the power supply may be connected to each drive circuit in parallel on the drive circuit side from the contact 76.

[0045]

As described above, according to the present invention , the display device operates the operation button before the safety door is opened during the setup change operation.
Since the power is supplied to the drive source even if the operator opens the safety door by pressing the operation button by pressing the operation button , the movable part does not move easily due to the contact of the worker, Immediately after the completion of the setup change operation, the printing operation can be started, the labor of the operator is reduced, and the operation rate of the screen printing machine is improved.

[Brief description of the drawings]

FIG. 1 is a configuration circuit diagram of a screen printing machine.

FIG. 2 is a view of the screen printing machine with a cover removed.

FIG. 3 is a front view of the screen printing machine.

FIG. 4 is a diagram showing a mounting table.

FIG. 5 is a plan view showing a recognition camera.

FIG. 6 is a front view illustrating a printing operation.

FIG. 7 is a diagram showing a screen displayed on a CRT.

FIG. 8 is a diagram showing a screen displayed on a CRT.

FIG. 9 is a diagram showing a screen displayed on a CRT.

FIG. 10 is a diagram showing a screen displayed on a CRT.

FIG. 11 is a diagram showing a screen displayed on a CRT.

FIG. 12 is a diagram showing a screen displayed on a CRT.

FIG. 13 is a diagram showing a screen displayed on a CRT.

FIG. 14 is a diagram illustrating a normal printing state displayed on a CRT.

FIG. 15 is a diagram showing a defective printing state displayed on a CRT.

FIG. 16 is a diagram showing a screen displayed on a CRT.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 screen printing machine 8 printed circuit board 9 mounting table 31 screen frame 34 squeegee 53 CPU 58 operating button (switch for starting setup change) 65 safety door 66 door open / close switch (door switch) 70 relay (switch for starting setup change) 71 relay contact (Switch for starting setup change) 72 Relay (power supply circuit) 73 Relay contact (power supply circuit) 74 Electromagnetic contactor (power supply circuit) 75 Power supply 76 Contact (power supply circuit) 80 Drive circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41F 15/12 B41F 15/08 303

Claims (1)

(57) [Claims] 1. A screen printing machine for applying a coating agent on a screen plate to a printed circuit board by moving a squeegee through the screen plate, wherein a safety door capable of shielding a movable portion of the printing machine from an operator, and A door switch that operates when the door is closed to enable power to be supplied to the drive source of the movable unit, and that the operator operates the operation button before opening the safety door and performing various setup operations. Screen display
Display device, and the operation of the operation button by an operator.
A changeover start switch that operates more, and a power supply circuit that can supply power to the drive source of the movable unit when either the door switch or the changeover start switch is in an operating state. A screen printing machine characterized by the following.