Printing device

Abstract

This printing device comprises: a conveyor that conveys a substrate; a mask holder that detachably holds a mask; a measurement unit that outputs a signal corresponding to the vertical height of a measurement target; and a control unit. The conveyor has a mask overlapping surface on which the mask and the upper surface of the substrate are overlapped. The control unit executes: a first measurement process for, before the mask is held by the mask holder, measuring the height of the mask overlapping surface on the basis of a signal which is output from the measurement unit and in which the mask overlapping surface is regarded as a measurement target; a second measurement process for, after the mask has been held by the mask holder, measuring the height of the upper surface of the mask on the basis of a signal which is output from the measurement unit and in which the upper surface of the mask is regarded as a measurement target; and a process for obtaining, as the thickness dimension of the mask, the difference between measurement results in the first measurement process and the second measurement process.

Description

Printing device 【0001】 The present invention relates to a printing device that prints a coating material such as cream solder on a substrate such as a printed circuit board. 【0002】 A screen printing device that performs a printing process of printing a coating material such as cream solder on a substrate such as a printed circuit board is well known. A screen printing device (hereinafter abbreviated as a printing device) prints cream solder on a substrate through a mask aperture by moving cream solder on a mask overlapped with the substrate by a squeegee. 【0003】 In the printing process, a mask corresponding to the substrate to be printed is used from among a plurality of types of masks. In this case, printing defects occur if a mask that does not correspond to the substrate is used. Therefore, it is necessary to check in advance whether the mask set in the printing device fits the substrate before the printing process. 【0004】 For example, Patent Document 1 discloses a printing device that images a predetermined portion of a mask holder in which a mask is detachably held and determines whether the mask fits the substrate based on the acquired image. In this printing device, the position of a recognition mark provided on the mask holder moves according to the size of the mask. Therefore, it is possible to determine whether the mask fits the substrate based on the presence or absence of the recognition mark in the acquired image. 【0005】 By the way, as an element of the mask that affects the printing quality, in addition to the size (area), there is also the thickness. That is, in the printing process, there may be cases where a mask having a thickness corresponding to the substrate to be printed is used from among a plurality of types of masks having different thicknesses. Therefore, it is also necessary to check in advance whether the thickness of the mask fits the substrate. 【0006】 However, Patent Document 1 does not disclose any configuration for checking the thickness of the mask set in the printing device or any configuration for determining whether the thickness of the mask fits the substrate to be printed. 【0007】 Japanese Unexamined Patent Application Publication No. 2010-131792 【0008】The present invention aims to provide a printing apparatus capable of measuring the thickness of a mask used in a printing process, and more preferably, a printing apparatus capable of determining whether or not the thickness of the mask is suitable for the substrate to be printed on. 【0009】 A printing apparatus according to one aspect of the present invention is a printing apparatus that performs a printing process for printing a coating material on a substrate via a thin plate-shaped mask superimposed on the substrate, comprising: a conveyor for transporting the substrate to a predetermined work position; a mask holder for detachably holding the mask; a measurement unit for outputting a signal corresponding to the vertical height of an object to be measured; and a control unit, wherein the conveyor has a mask-loading surface on which the mask is superimposed together with the upper surface of the substrate, and the control unit performs a first measurement process for measuring the height of the mask-loading surface based on a signal output from the measurement unit with respect to the mask-loading surface as the object to be measured, before the mask is held in the mask holder; a second measurement process for measuring the height of the upper surface of the mask based on a signal output from the measurement unit with respect to the upper surface of the mask as the object to be measured, after the mask is held in the mask holder; and a process for determining the difference between the measurement results of the first measurement process and the second measurement process as the thickness dimension of the mask. 【0010】 Figure 1 is a block diagram of a printing apparatus according to the first embodiment. Figure 2 is a side view showing the main body of the printing apparatus. Figure 3 is a front view showing the squeegee unit of the main body. Figure 4 is an explanatory diagram of the operation of the substrate clamping mechanism. Figure 5 is a flowchart of the control of the mask inspection process. Figure 6 is a flowchart of the control of the first measurement process. Figure 7 is a side view of the main part of the main body of the apparatus during the first measurement process. Figure 8 is a side view of the main part of the main body of the apparatus during the second measurement process. Figure 9 is a flowchart of the operation start control. Figure 10 is a schematic explanatory diagram summarizing the mask thickness measurement process in the printing apparatus. Figure 11 is a side view showing the squeegee unit of the printing apparatus according to the second embodiment. Figure 12 is a side view of the main part of the main body of the apparatus during the second measurement process. Figure 13 is a front view showing the squeegee unit of the printing apparatus according to the third embodiment. Figure 14 is a side view showing the squeegee unit of the main body of the apparatus. Figure 15 is a side view of the main part of the main body of a modified printing apparatus. 【0011】 Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. 【0012】 [Overall Configuration of Printing Apparatus] Figure 1 is a block diagram showing an example of a printing apparatus 1. Printing apparatus 1 is an apparatus that performs a printing process in the production process of component mounting substrates, printing paste solder (an example of a coating material) onto the lands of the substrate prior to mounting the components. 【0013】 The printing apparatus 1 includes a main body 2, a control unit 3, a storage unit 4, a display unit 5, and an input unit 6. The main body 2 performs a printing process to print solder paste (hereinafter abbreviated as solder) onto a substrate P. The control unit 3 controls the printing process of the main body 2 and operations related to the printing process. 【0014】 Figure 2 is a schematic side view of the main body of the apparatus 2. To clarify the directional relationships, Figure 2 shows the XYZ rectangular coordinate system, where the horizontal directions are X and Y, and the vertical direction is Z, with mutually orthogonal directions. The X direction is the transport direction of the substrate P. 【0015】 The main body of the device 2 performs printing on the substrate P using so-called screen printing. Specifically, the main body of the device 2 is configured to print solder onto the substrate P through the pattern holes, with a mask (screen plate) having pattern holes (openings) corresponding to the lands on the substrate P superimposed on the substrate P. 【0016】 The main body of the apparatus 2 includes a conveyor unit 10, a mask holding unit 13, a substrate support unit 16, a table drive mechanism 19, and a squeegee unit 20. 【0017】 The conveyor unit 10 (corresponding to the "conveyor" of the present invention) has the function of transporting the substrate P in the main body of the device 2. The conveyor unit 10 comprises a conveyor body 11 consisting of a pair of belt-type conveyors and a substrate clamping mechanism 12. 【0018】 The conveyor body 11 transports the substrate P before printing into the machine and places it in the work position, and transports the substrate P after printing from the work position to the outside of the machine. 【0019】The substrate clamping mechanism 12 comprises a pair of clamping plates 121 (corresponding to the "clamping member" of the present invention). The pair of clamping plates 121 are positioned above the conveyor body 11. The pair of clamping plates 121 move between a retracted position, which is relatively far apart, and an operating position, which is relatively close together, by the driving force of an actuator such as an air cylinder. As the pair of clamping plates 121 move to the operating position, the substrate P, which is lifted by the backup pin 172 at the work position, is clamped by the pair of clamping plates 121, as will be described later. That is, the substrate P is clamped from both sides in the Y direction by the pair of clamping plates 121. 【0020】 The mask holding unit 13 is positioned above the conveyor unit 10. The mask holding unit 13 comprises a mask 14 and a mask holder 15 that detachably holds the mask 14. 【0021】 The mask 14 consists of a thin, plate-shaped mask body 141 with the pattern holes formed therein, and a frame-shaped frame 142 fixed to its periphery. The frame 142 is held by the mask holder 15, so that the mask body 141 is positioned parallel to the XY plane at a predetermined height. In the following description, unless otherwise specified, "mask 14" refers to the mask body 141. 【0022】 The mask holder 15 is configured to be switchable between a state in which it clamps the frame 142 and a state in which it releases the clamp. This switching is performed manually by the operator or by the operation of an actuator such as an air cylinder. When the frame 142 is clamped, the mask 14 is held in the mask holder 15, and when the clamp on the frame 142 is released, the mask 14 can be attached to and detached from the mask holder 15. 【0023】 The substrate support unit 16 is located below the mask holding unit 13. The substrate support unit 16 is a unit member that positions the substrate P relative to the mask 14, and includes a substrate support portion 17 and a movable table 18. 【0024】The substrate support section 17 is assembled to the movable table 18 together with the conveyor unit 10. The substrate support section 17 comprises a lifting table 171 on which a plurality of backup pins 172 are detachably erected, and a sliding support column 173 that supports the lifting table 171 so that it can move up and down relative to the movable table 18. 【0025】 The lifting table 171 moves up and down relative to the movable table 18 by the driving force of an actuator such as a motor. The board P is transferred between the conveyor unit 10 and the backup pin 172 by the raising and lowering of the lifting table 171. For example, when the lifting table 171 rises from the home position, the board P is lifted from the conveyor body 11 by the backup pin 172. This transfers the board P from the conveyor body 11 to the backup pin 172. The board clamping mechanism 12 clamps the board P, which has been transferred to the backup pin 172 in this manner, with the clamping plate 121. 【0026】 The table drive mechanism 19 includes a Y-axis table 191 installed on the base of the main body of the device 2, an X-axis table 192 installed on the upper surface of the Y-axis table 191, an R-axis table 193 installed on the upper surface of the X-axis table 192, and a sliding support column 194 that supports the movable table 18 so that it can be raised and lowered relative to the R-axis table 193. 【0027】 The Y-axis table 191, X-axis table 192, R-axis table 193, and movable table 18 each move in a predetermined direction by the driving force of an actuator such as a motor. Specifically, the Y-axis table 191 moves in the Y direction relative to the base of the device body 2, and the X-axis table 192 moves in the X direction relative to the Y-axis table 191. The R-axis table 193 moves in the R direction (rotational direction around the axis extending in the Z direction) relative to the X-axis table 192, and the movable table 18 moves up and down relative to the R-axis table 193. 【0028】In other words, the table drive mechanism 19 moves the conveyor unit 10 and the substrate support section 17, which are assembled to the movable table 18, in the X, Y, Z, and R directions, thereby bringing the substrate P supported by the substrate support section 17, more specifically the substrate P supported by the backup pins 172 and clamped by a pair of clamp plates 121, into contact with the lower surface of the mask 14. As a result, the substrate P is superimposed on the mask 14. 【0029】 The squeegee unit 20 is positioned above the mask holding unit 13 and moves horizontally in the Y direction by the drive of an actuator such as a motor. 【0030】 The squeegee unit 20 (corresponding to the "movable member" of the present invention) comprises a print head 22 (corresponding to the "lifting and lowering section" of the present invention) and a squeegee 24 supported by the print head 22. 【0031】 The print head 22 moves up and down relative to the mask 14 held in the mask holder 15. The squeegee 24 is a plate-shaped spatula member extending in the X direction. The squeegee 24 is supported at its longitudinal center so as to be able to swing relative to the print head 22 about an axis extending in the X direction. The squeegee 24 is brought into contact with the upper surface of the mask 14 (mask upper surface 141a) at a predetermined angle θ (attack angle θ) and printing pressure (pressing pressure), and moves along the mask 14 in the Y direction at a predetermined speed (squeegee speed) as the squeegee unit 20 moves. This moves the solder S along the mask upper surface 141a and prints the solder S onto the substrate P through the pattern holes. The attack angle θ is the angle formed between the mask upper surface 141a and the squeegee 24 (the pressing surface for the solder S). 【0032】 The squeegee 24 can swing between a position where the pressing surface faces one side in the Y direction and a position where it faces the other side in the Y direction. As a result, this printing apparatus 1 can perform both forward printing, where the squeegee 24 is moved from one side to the other in the Y direction, and reverse printing, where the squeegee 24 is moved from the other side to the one side in the Y direction, using a single squeegee 24. 【0033】 Here, we will describe the more specific configuration of the squeegee unit 20. 【0034】 Figure 3 is a front view showing the squeegee unit 20. The squeegee unit 20 has a movable base 21 that moves horizontally in the Y direction by the driving force of the actuator. The movable base 21 is equipped with a print head 22 and a lifting mechanism 23 that raises and lowers the print head 22 relative to the movable base 21. 【0035】 The print head 22 comprises an upper frame 221 and a lower frame 222, an intermediate frame 223 positioned between these frames 221 and 222 and fixed to the upper frame 221 via a connecting shaft 224, and a load cell 225 (corresponding to the "load sensor" of the present invention) interposed between the intermediate frame 223 and the lower frame 222 and fixed to both frames 222 and 223. The upper and lower frames 221 and 222 are movably supported by a pair of guide columns 232 extending in the Z direction and fixed to a movable base 21. As a result, the print head 22 is supported so as to be able to move up and down relative to the movable base 21. 【0036】 The lifting mechanism 23 consists of a so-called screw feed mechanism. Specifically, the lifting mechanism 23 includes a pair of guide columns 232 that support the print head 22 (upper frame 221, lower frame 222), a screw shaft 233 extending in the Z direction between the two guide columns 232, a nut member 234 fixed to the print head 22 (upper frame 221), a motor 231, and a transmission mechanism 235 that transmits the driving force of the motor 231 to the screw shaft 233. The screw shaft 233 is screwed into and inserted into the nut member 234. In other words, the lifting mechanism 23 is configured to raise and lower the print head 22 along the pair of guide columns 232 by rotationally driving the screw shaft 233 with the motor 231. 【0037】 The motor 231 is an encoder-integrated motor comprising a motor body 231a that generates rotational force and an encoder 231b (corresponding to the "measurement unit" of the present invention) attached to the motor body 231a. The encoder 231b outputs an electrical signal corresponding to the rotation generated by the motor body 231a to the control unit 3. Either an incremental or absolute type encoder 231b is used. 【0038】The squeegee 24 is pivotably supported at the lower end of the print head 22, which is configured as described above. The squeegee 24 is supported by the lower frame 222 of the print head 22 via a gearbox (not shown) and is driven by a motor 25 connected to the gearbox. The motor 25, like the motor 231 of the lifting mechanism 23, is an encoder-integrated motor comprising a motor body and an encoder, and outputs an electrical signal corresponding to the rotation generated by the motor body to the control unit 3. 【0039】 A load cell 225, provided on the print head 22, measures the printing pressure of the squeegee 24. That is, when the squeegee 24 is brought into contact with the mask 14, the gap between the intermediate frame 223 and the lower frame 222 decreases, and a load equivalent to the pressing force of the squeegee 24 acts on the load cell 225. The load cell 225 outputs an electrical signal corresponding to this load to the control unit 3. 【0040】 The basic operation of the printing process in the device body 2 configured as described above is as follows. 【0041】 First, with the lifting table 171 in its home position, the circuit board P is transported into the machine by the conveyor body 11 and placed in the work position. Next, the circuit board P is clamped by the circuit board clamping mechanism 12. 【0042】 Figure 4 is an explanatory diagram of the operation of the circuit board clamping mechanism 12. When the circuit board P is placed in the working position (top figure a), the lifting table 171 rises, and the circuit board P is transferred from the conveyor body 11 to the backup pin 172 (middle figure b). Then, the clamping plate 121 moves from the retracted position to the operating position and clamps the circuit board P from both sides (bottom figure c). As a result, the circuit board P is clamped by the circuit board clamping mechanism 12. 【0043】 The upper surface of each clamp plate 121 is a fairly flat surface, and when the substrate P is clamped, the upper surface is positioned flush with the upper surface of the substrate P. The upper surface 121a of each clamp plate 121 is the mask mounting surface on which the mask body 141 is superimposed together with the upper surface of the substrate P. 【0044】When the substrate P is clamped, the substrate P supported by the substrate support portion 17 is overlaid on the lower surface of the mask 14 by the operation of the table drive mechanism 19. 【0045】 When the substrate P and the mask 14 are overlaid, the squeegee unit 20 is disposed at a predetermined movement start position. At this position, the print head 22 descends, and the squeegee 24 is pressed against the upper surface of the mask 113 at a predetermined attack angle θ and printing pressure. In this state, as the squeegee unit 20 moves, the squeegee 24 moves in the Y direction at a predetermined moving speed. Along with this movement, the solder S is printed on the substrate P through the pattern holes of the mask 14. 【0046】 When the squeegee unit 20 moves to the movement end position, the substrate P together with the substrate support portion 17 is reset to the original position by the operation of the table drive mechanism 19. As a result, the substrate P is separated from the mask 14. Thereafter, the clamping of the substrate P by the substrate clamping mechanism 12 is released, and the lift table 171 is reset to the home position, whereby the substrate P is delivered from the backup pin 172 to the conveyor main body 11. Then, the substrate P is carried out of the apparatus by the conveyor unit 10, and a series of printing processes in the apparatus main body 2 are completed. 【0047】 Returning to FIG. 1, the display unit 5 (corresponding to the "notification unit" of the present invention) is constituted by an output device such as a liquid crystal display. The display operation of the display unit 5 is controlled by a display control unit 33 described later. 【0048】 The input unit 6 is constituted by an input device such as a keyboard, a mouse, or a touch panel provided on the display unit 5. The input unit 6 receives input operations of various commands to the control unit 3 by an operator. 【0049】The control unit 3 consists of a CPU (Central Processing Unit), ROM (Read Only Memory) for storing control programs, RAM (Random Access Memory) used as the CPU's workspace, and the like. The control unit 3 controls the operation of each component of the main unit 2 by having the CPU execute the control programs stored in the ROM. In other words, the control unit 3 functions as a printing control unit 31, a setup control unit 32, and a display control unit 33. 【0050】 The print control unit 31 controls the operation of the series of printing processes in the main unit 2 of the device described above. 【0051】 The setup control unit 32 controls the operation of each part of the main unit 2 of the device that is necessary for setup work. Setup work is the preparation work to start the printing process. For example, setting the mask 14 to be used for printing in the mask holder 15 and setting the backup pins 172 in positions on the lifting table 171 corresponding to the size of the substrate are examples of setup work. 【0052】 The setup control unit 32 performs an inspection process for the setup work. The inspection process checks whether the arrangement of the mask 14 set in the mask holder 15 and the backup pins 172 set in the lifting table 171 is suitable for the substrate to be produced. This inspection process includes a mask inspection process, which measures the thickness of the mask 14 set in the mask holder 15 and checks whether its thickness is suitable for the substrate to be produced. This mask inspection process will be described in detail later. 【0053】 The display control unit 33 controls the display by the display unit 5 to display various information related to the printing process and setup process of the main unit 2. 【0054】 The memory unit 4 stores various types of information that are referenced when controlling the operation of the printing process and setup process. This information includes substrate data D11 and printing condition data D12. 【0055】The board data D11 contains information about the boards to be produced (component-mounted boards). The board data D11 includes information such as the type (ID) of the board P to be produced, the printing position (coordinates of pads and lands) on each type of board P, and the type (ID) and shape (size (area), thickness) of the mask 14 used for printing on each type of board P. 【0056】 The printing condition data D12 contains information about the printing process conditions (reference values). The printing condition data D12 includes information such as the attack angle of the squeegee 24, printing pressure, travel speed, and the arrangement of backup pins 172 in the substrate support section 17. 【0057】 [Control of Mask Inspection Process] The control of the mask inspection process by the setup control unit 32 will be explained with reference to Figures 5 and 6. The mask inspection process is a process that determines whether the mask 14 set in the mask holder 15 by the setup work is suitable for the substrate to be produced, based on the thickness of the mask body 141. 【0058】 Figure 5 is a flowchart showing an example of mask inspection process control. This control flow starts when the operator operates the input unit 6 according to the display screen of the display unit 5, prior to setting the mask 14 into the mask holder 15. 【0059】 When the control flow starts, the setup control unit 32 loads the substrate P into the machine and places it in the work position (step S1), and moves the substrate P to a predetermined printing height position (step S3). Specifically, after clamping the substrate P with the substrate clamping mechanism 12, the table drive mechanism 19 is activated to move the substrate P to the printing height position. The printing height position is the height position at which the upper surface of the substrate P is aligned with the lower surface of the mask 14, assuming the mask 14 is set in the mask holder 15. 【0060】 When the substrate P is positioned at the printing height, the setup control unit 32 controls the squeegee unit 20 and performs a first measurement process to measure the height of the conveyor top surface, specifically the top surface 121a of the clamp plate 121, i.e., the mask mounting surface (step S5). 【0061】Figure 6 is a flowchart showing the control of the first measurement process by the setup control unit 32. First, the setup control unit 32 sets the attack angle θ of the squeegee 24 to a predetermined measurement angle θo (step S21), and then positions the print head 22 at a predetermined measurement start height Ho (step S23). 【0062】 The measurement angle θo of the squeegee 24 is, for example, the angle at which the squeegee 24 makes line contact with the upper surface 121a of the clamp plate 121 at its edge. Specifically, the measurement angle θo can be 45°. The measurement start height Ho is, for example, the end of the upward stroke in the lifting stroke of the print head 22. 【0063】 Next, the setup control unit 32 moves the squeegee unit 20 so that the squeegee 24 is positioned above a predetermined measurement position Po in the Y direction (step S25). The measurement position Po can be the center of the upper surface 121a of the clamp plate 121 in the Y direction. 【0064】 When the squeegee 24 is positioned above the measurement position Po, the setup control unit 32 lowers the print head 22 (step S27) and determines whether the squeegee 24 has come into contact with the upper surface 121a of the clamp plate 121 based on the electrical signal from the load cell 225 (step S29). Specifically, the setup control unit 32 determines whether the load value detected by the load cell 225 has reached a preset threshold. The threshold is preset to a value equivalent to the load value when the squeegee 24 comes into contact with the upper surface 121a of the clamp plate 121. Therefore, the setup control unit 32 can detect that the squeegee 24 has come into contact with the upper surface 121a of the clamp plate 121 based on the electrical signal from the load cell 225. 【0065】 Figure 7 is a side view of the main body of the device 2 during the first measurement process, showing the state in which the squeegee 24 is in contact with the upper surface 121a of the clamp plate 121 at the measurement position Po. 【0066】If the process in step S29 determines Yes, the setup control unit 32 stops the print head 22, measures the height of the upper surface 121a of the clamp plate 121 based on the electrical signal from the encoder 231b, and stores the result (step S31). Specifically, the amount of displacement of the print head 22 in the Z direction from the measurement start height Ho to the stopping position is calculated, and the height of the upper surface 121a of the clamp plate 121 is determined based on the calculation result. 【0067】 Once the first measurement process is complete, the setup control unit 32 resets the print head 22 to the measurement start height Ho and moves the squeegee unit 20 to a predetermined retracted position. The retracted position is, for example, the position of the stroke end of the movable stroke of the squeegee unit 20. With the squeegee unit 20 positioned in the retracted position, the operator can easily set the mask 14 against the mask holder 15. 【0068】 Returning to Figure 5, the setup control unit 32 determines whether or not the mask 14 has been set inside the machine (step S7). If it determines Yes, the setup control unit 32 executes a second measurement process to measure the height of the top surface 141a of the mask (step S9). The determination in step S7 is made based on whether or not an input indicating completion of mask setting has been made, for example, by the operator's input unit 6 after the mask 14 has been attached to the mask holder 15. 【0069】 The control of the second measurement process is basically the same as the control of the first measurement process. That is, the setup control unit 32 sets the attack angle θ of the squeegee 24 to the measurement angle θo and positions the print head 22 at the measurement start height Ho above the measurement position Po. Next, the setup control unit 32 lowers the print head 22, and when the detected load value by the load cell 225 reaches a preset threshold (a value equivalent to the load value when the squeegee 24 contacts the upper surface 141a of the mask), it stops the print head 22. Figure 8 is a side view of the main part of the device body 2 during the second measurement process, showing the state in which the squeegee 24 is in contact with the upper surface 141a of the mask at the measurement position Po. 【0070】The setup control unit 32 then calculates the amount of displacement of the print head 22 in the Z direction from the measurement start height Ho to the stop position, and determines the height of the upper surface 141a of the mask based on the calculation result. 【0071】 Once the second measurement process is complete, the setup control unit 32 moves the squeegee unit 20 to the retracted position. 【0072】 Next, the setup control unit 32 calculates the thickness dimension of the mask 14 based on the results of the first measurement process and the second measurement process (step S11). Specifically, the thickness dimension of the mask 14, that is, the thickness dimension of the mask body 141, is calculated by subtracting the height value of the upper surface 121a of the clamp plate 121, obtained in the first measurement process, from the height value of the upper surface 141a of the mask obtained in the second measurement process. 【0073】 Next, the setup control unit 32 determines whether the thickness dimension of the mask 14 matches the thickness dimension of the substrate data D11 stored in the storage unit 4, that is, whether it is suitable for the substrate to be produced (step S13). If the determination is Yes, the setup control unit 32 turns on the mask setup flag to indicate that the setup work for the mask 14 has been performed correctly (step S15), and then terminates this control flow. 【0074】 On the other hand, if the process in step 13 determines "No", the setup control unit 32 causes the display unit 5 to notify the display control unit 33 of predetermined error information (step S17), and then terminates this control flow. In this case, the display control unit 33 displays an image indicating the abnormality, along with information on the display unit 5 indicating that the mask 14 set in the mask holder 15 is not compatible with the substrate to be produced. 【0075】 [Control of Printing Process] Next, the control of the start of the printing process by the print control unit 31 will be described. Figure 9 is a flowchart of the start of operation control in the printing device. 【0076】 When this control flow starts, the print control unit 31 determines whether the operator has turned on the automatic operation start button (step S41), and if it determines Yes, it further determines whether the mask setup flag is ON or OFF (step S43). 【0077】 If the result in step S43 is determined to be Yes, the printing control unit 31 starts the automatic operation of the printing process of the main unit 2, that is, the series of printing processes described above, from loading the substrate P into the machine to unloading it (step S45). 【0078】 On the other hand, if the result in step S43 is determined to be No, the print control unit 31 executes a process to prohibit the start of automatic operation of the print process and also causes the display unit 5 to notify predetermined error information via the display control unit 33 (step S27). In this case, the display control unit 33 displays an image indicating the abnormality, along with information on the display unit 5 indicating that the mask 14 set in the mask holder 15 is not compatible with the substrate to be produced. 【0079】 [Effects] As described above, in the printing apparatus 1 according to the embodiment, as shown in the measurement process of Figure 10, a first measurement process is performed to measure the height Hc of the upper surface 121a of the clamp plate 121, which is the mask mounting surface of the conveyor unit 10, before the mask 14 is held in the mask holder 15, and a second measurement process is performed to measure the height Hm of the upper surface 141a of the mask after the mask 14 is held in the mask holder 15. The difference (Hm - Hc) of the measurement results of these first and second measurement processes is obtained as the thickness dimension t of the mask 14. For this reason, the printing apparatus 1 of the embodiment can appropriately measure the thickness dimension of the mask 14 that is actually set in the printing apparatus 1. 【0080】 Furthermore, in the printing apparatus 1 of this embodiment, substrate data D11, which associates the thickness dimensions of the substrate to be produced with those of the mask 14, is stored in the storage unit 4. If the thickness dimension t of the mask 14 set in the mask holder 15 does not match the thickness dimension of the substrate data D11, the display unit 5 is used to notify the user of the error. This alerts the operator, allowing them to quickly replace the mask 14 with the correct one. As a result, it is possible to prevent the use of an incorrect mask 14 with a different thickness dimension in the printing process. 【0081】In particular, in the printing apparatus 1 of this embodiment, if the measured thickness dimension t of the upper surface 141a of the mask does not match the thickness dimension of the substrate data D11, the start of the printing process is forcibly prohibited, thereby ensuring that the printing process is not started using an incorrect mask 14 with a different thickness dimension. 【0082】 Furthermore, in the printing apparatus 1 of this embodiment, the print head 22 is raised and lowered by driving a motor 231 having an encoder 231b. Then, in the first measurement process and the second measurement process, the squeegee 24 is used as a measuring probe, and the heights Hc and Hm of the upper surface 121a of the clamp plate 121 and the upper surface 141a of the mask are measured based on the output signal from the encoder 231b when the detected load value of the load cell 225 reaches a threshold value after the print head 22 is lowered. 【0083】 The squeegee 24, motor 231, and load cell 225 are essential equipment for the printing apparatus 1 for controlling the raising and lowering of the squeegee 24 and the printing pressure. In other words, dedicated equipment for measuring the heights Hc and Hm of the upper surface 121a of the clamp plate 121 and the upper surface 141a of the mask is unnecessary. Therefore, according to the printing apparatus 1 of this embodiment, the heights Hc and Hm can be measured, and consequently the thickness dimension t of the mask 14, in a rational configuration using existing equipment. 【0084】 [Second Embodiment] Next, a second embodiment of the printing apparatus 1 will be described. 【0085】 Figure 11 is a side view showing the squeegee unit 20 of the printing apparatus 1 according to the second embodiment. The second embodiment has the same basic configuration as the first embodiment, except for the following differences. Therefore, the following description will mainly explain the differences from the first embodiment. 【0086】 In the first embodiment, the measuring probe used in the first measurement process and the second measurement process is a squeegee 24. That is, the squeegee 24 is shared as a measuring probe. 【0087】In contrast, in the second embodiment, as shown in Figure 11, a measuring probe unit 26 is provided separately from the squeegee 24 as a measuring element. The measuring probe unit 26 is positioned adjacent to the squeegee 24 of the print head 22, specifically, adjacent in the Y direction to the center of the longitudinal direction (X direction) of the squeegee 24. 【0088】 The measuring probe unit 26 is fixed in a position hanging down from the lower surface of the lower frame 222 and is configured to extend and retract in the vertical direction. Specifically, the measuring probe unit 26 comprises an air cylinder 262 fixed downward to the lower frame 222 and a measuring head 261, for example, cylindrical in shape, fixed to the tip of the rod of the air cylinder 262. The measuring head 261 forms the tip of the measuring probe unit 26 and is displaced vertically by the operation of the air cylinder 262. This causes the measuring probe unit 26 to extend and retract in the vertical direction. 【0089】 The measuring head 261 has a measuring surface 261a, which is a flat surface, at its lower end. The measuring probe unit 26 is configured to switch between a rod-retracted drive state (solid line in Figure 11) in which the measuring surface 261a of the measuring head 261 is positioned above the lower end Le of the movable range of the squeegee 24, and a rod-extended drive state (dash-dot line in Figure 11) in which the measuring surface 261a is positioned below the lower end Le of the movable range of the squeegee 24, by the operation of the air cylinder 262. The measuring probe unit 26 is controlled to be in the rod-retracted drive state except during the first and second measurement processes. 【0090】 The control of the mask inspection process in the printing apparatus 1 of the second embodiment is basically the same as the control of the first embodiment described with reference to Figures 5 and 6. However, in the second embodiment, a measuring probe unit 26 is used instead of the squeegee 24, so the specific processing differs from the first embodiment in the following respects. 【0091】 First, in the process of steps S21 to S25 in Figure 6, the setup control unit 32 sets the squeegee 24 so that the attack angle θ is, for example, 0° (see Figure 11), and in this state, positions the measuring probe unit 26 above the measurement position Po. 【0092】Furthermore, during the processing of steps S27 to S31, the setup control unit 32 switches the measuring probe unit 26 from a rod retraction drive state to a rod extension drive state, and lowers the print head 22 in this state. That is, the print head 22 is lowered with the measuring surface 261a of the measuring head 261 protruding below the lower end Le of the movable area of ​​the squeegee 24. As a result, as shown in Figure 12, the measuring head 261 comes into contact with the surface to be measured (the upper surface 121a of the clamp plate 121, the upper surface 141a of the mask). Figure 12 is a side view of the main part of the device body 2 showing the state during the second measurement process. 【0093】 As described above, the printing apparatus 1 of the second embodiment is equipped with a dedicated measuring probe unit 26 as the measuring probe. With this configuration, solder S does not come into contact with the measuring probe, which is advantageous in improving measurement accuracy. That is, when the squeegee 24 is shared as the measuring probe, if solder S adheres to the squeegee 24, it is possible that errors will occur in the measurement results. However, according to the second embodiment, since solder S does not come into contact with the measuring probe unit 26 at all, there is no room for errors in the measurement results due to the influence of solder S. For this reason, the printing apparatus 1 of the second embodiment is advantageous in improving measurement accuracy. 【0094】 Furthermore, as previously described, the measuring probe unit 26 is extendable and retractable, and during the first and second measurement processes, the measuring probe unit 26 is set to the rod-extended drive state (extended state). That is, the measuring surface 261a of the measuring head 261 is positioned below the lower end Le of the movable range of the squeegee 24. Therefore, the measuring head 261 can be brought into contact with the object to be measured without being affected by the squeegee 24. On the other hand, during normal printing, the measuring probe unit 26 is set to the rod-retracted drive state (retracted state). That is, the measuring surface 261a of the measuring head 261 is positioned above the lower end Le of the movable range of the squeegee 24. Therefore, the measuring probe unit 26 does not get in the way during the printing process. 【0095】 [Third Embodiment] Next, a third embodiment of the printing apparatus 1 will be described. 【0096】Figure 13 is a front view showing the squeegee unit 20 of the apparatus body 2 according to the third embodiment, and Figure 14 is a side view showing the squeegee unit 20. The third embodiment has the same basic configuration as the first embodiment, except for the following differences. Therefore, the following description will mainly explain the differences from the first embodiment. 【0097】 In the third embodiment, the print head 22 is provided with a buffering mechanism that buffers the collision between the squeegee 24 and the upper surface 141a of the mask during the printing process, and a locking mechanism 28 is provided that can disable the function of this buffering mechanism. 【0098】 Specifically, a pair of connecting shafts 224 are provided so as to be displaceable in the vertical direction (axial direction) relative to the upper frame 221 (corresponding to the "first movable part" of the present invention). Furthermore, by attaching coil springs 226 to each connecting shaft 224, the squeegee 24 is biased downward relative to the upper frame 221. As a result, when the squeegee 24 contacts the upper surface 141a of the mask, the squeegee 24, the lower frame 222 (corresponding to the "second movable part" of the present invention), the load cell 225, and the intermediate frame 223 rise relative to the upper frame 221, and the collision between the squeegee 24 and the mask 14 is cushioned by the coil springs 226. 【0099】 In other words, the cushioning mechanism of the print head 22 consists of a connecting shaft 224 that is provided so as to be displaceable in the vertical direction relative to the upper frame 221, and a coil spring 226 attached to the connecting shaft 224. 【0100】 As shown in Figure 14, the locking mechanism 28 consists of a locking piece 281 driven to move back and forth in the Y direction by a solenoid 282, and a locking member 227 having a locking hole 227a which is an engagement hole for the locking piece 281. The solenoid 282 is fixed to the upper frame 221 via a bracket 228, and the locking member 227 is fixed to the intermediate frame 223 at a position opposite to the locking piece 281 in the Y direction. 【0101】In the forward drive state, when the locking piece 281 is advanced, the locking piece 281 is inserted into the locking hole 227a, as shown by the dashed line in Figure 14. As a result, the locking mechanism 28 is locked, that is, the intermediate frame 223 is locked to the upper frame 221 so that it cannot be displaced, and the cushioning function of the print head 22 is disabled. 【0102】 On the other hand, in the retracted drive state where the locking piece 281 is retracted, the locking piece 281 detaches from the locking hole 227a, as shown by the solid line in Figure 14. As a result, the locking mechanism 28 is released, that is, the intermediate frame 223 becomes displaceable relative to the upper frame 221, and the cushioning function of the print head 22 is activated. 【0103】 The locking mechanism 28 is controlled to be in the unlocked state except during the first and second measurement processes. 【0104】 The control of the mask inspection process in the printing apparatus 1 of the third embodiment is basically the same as the control of the first embodiment described with reference to Figures 5 and 6, but the specific processing differs in the following respects. Specifically, in the process of step S27 in Figure 6, the setup control unit 32 first switches the lock mechanism 28 from the unlocked state to the locked state, and lowers the print head 22 with the buffering function of the print head 22 disabled. 【0105】 In the printing apparatus 1 of the third embodiment, during normal printing, the locking mechanism 28 is controlled to be in an unlocked state, thereby cushioning the collision between the squeegee 24 and the mask 14. As a result, it is possible to suppress or prevent damage caused by the collision between the squeegee 24 and the mask 14, contributing to improved durability of the printing apparatus 1. 【0106】On the other hand, during the first and second measurement processes (step S27 in Figure 6), the locking mechanism 28 is controlled to a locked state, thereby locking the lower frame 222 to the upper frame 221 so that it cannot be displaced. In other words, the squeegee is constrained so that it cannot be displaced in the vertical direction, and the buffering function described above is disabled. As a result, there is no extra vertical displacement of the measuring element, the squeegee 24, and it becomes possible to perform the first and second measurement processes more quickly and accurately. 【0107】 [Modifications] The embodiments described above are for illustrative purposes only, and therefore various changes, substitutions, additions, omissions, etc., can be made within the scope of the claims or their equivalents. For example, the following configuration can also be adopted. 【0108】 (1) In this embodiment, the heights Hc and Hm of the upper surface 121a of the clamp plate 121 and the upper surface 141a of the mask are measured based on the electrical signal output from the encoder 231b. That is, the encoder 231b is provided as the measurement unit of the present invention that outputs a signal corresponding to the vertical height of the object to be measured. However, as shown in Figure 15, a non-contact type displacement sensor 29 can also be provided as the measurement unit. The non-contact type displacement sensor 29 (hereinafter abbreviated as displacement sensor 29) is a measurement device that irradiates light onto the object to be measured and receives the reflected light to output a signal corresponding to the vertical height of the object to be measured. 【0109】 In the example shown in Figure 15, the displacement sensor 29 is fixed to the lower frame 222 of the print head 22. In this configuration, the measurement process in steps S5 and S9 of Figure 5 is performed using the following control method instead of the control method shown in Figure 6. Specifically, the setup control unit 32 moves the squeegee unit 20 so that the displacement sensor 29 is positioned at a predetermined measurement start height Ho above the measurement position Po. Subsequently, the height of the object to be measured (the upper surface 121a of the clamp plate 121 and the upper surface 141a of the mask) is measured using the displacement sensor 29. 【0110】According to the configuration shown in Figure 15, there is no need to raise or lower the print head 22 for height measurement. Therefore, the measurement process in steps S5 and S9 of Figure 5 can be performed more quickly. In addition, since the print head 22 does not move during height measurement, there are no measurement errors caused by such movement, and the height can be measured with greater accuracy. 【0111】 (2) In the embodiment, in the measurement process of step S5 in Figure 5, the height of the upper surface 121a of the clamp plate 121 is measured as the mask mounting surface. However, the height of the conveyor upper surface is not limited to the upper surface 121a of the clamp plate 121. The conveyor upper surface to be measured can be any part of the conveyor unit 10 as long as it is the surface on which the masks 14 are superimposed. However, the upper surface 121a of the clamp plate 121 is the surface that supports the lower surface (back surface) of the mask 14 at a position adjacent to the substrate P. For this reason, by measuring the height of the upper surface 121a of the clamp plate 121, the reliability of the measurement results and, consequently, the reliability of the final determined thickness dimension t of the mask 14 can be improved. 【0112】 (3) In this embodiment, the substrate P is brought into the machine in step S1 of Figure 5, but the substrate P in this case may be either a product substrate or a dummy substrate. Alternatively, the process in step 1 of Figure 5 may be omitted, and the measurement processes in steps S5 and S9 may be performed without bringing the substrate P into the machine. However, if the measurement is performed with the substrate P actually clamped by the substrate clamp mechanism 12, the clamp plate 121 and mask 14 will be more stable when the measuring probe (squeegee 24, measuring probe unit 26) is brought into contact with it. For this reason, in order to improve the measurement accuracy, it is preferable to actually bring the substrate P into the machine and perform the height measurement process as in this embodiment. 【0113】(4) In this embodiment, the setup control unit 32 detects when the measuring probe comes into contact with the object to be measured (the upper surface 121a of the clamp plate 121, the upper surface 141a of the mask) based on the electrical signal output from the load cell 225. In other words, the setup control unit 32 acquires the detected load value from the load cell 225 as information corresponding to the load when the measuring probe is in contact with the object to be measured. However, the information acquired by the setup control unit 32 is not limited to the load value. The setup control unit 32 may be configured to acquire data on physical quantities other than the load value and to detect when the measuring probe comes into contact with the object to be measured based on this data. For example, since the current value applied to the motor 231 is proportional to the load, the current value of the motor 231 may be acquired as the information. 【0114】 (5) In the embodiments, a printing apparatus 1 was described that has one swingable squeegee 24 and performs printing by changing the orientation of the squeegee 24 during forward and reverse movements. However, the present invention is also applicable to a printing apparatus 1 that has two squeegees with different orientations and uses the two squeegees during forward and reverse movements. In addition, in the embodiments, a printing apparatus 1 was described in which an operator manually attaches and detaches the mask 14 to the mask holder 15. However, the present invention is also applicable to a printing apparatus 1 that has a configuration for automatically attaching and detaching the mask 14 to the mask holder 15. 【0115】 The present invention, as described above based on the embodiments, can be summarized as follows. 【0116】The present invention relates to a printing apparatus for performing a printing process in which a coating material is printed on a substrate via a thin plate-shaped mask superimposed on the substrate. The printing apparatus comprises a conveyor for transporting the substrate to a predetermined work position, a mask holder for which the mask is detachably held, a measurement unit for outputting a signal corresponding to the vertical height of an object to be measured, and a control unit. The conveyor has a mask-loading surface on which the mask is superimposed together with the upper surface of the substrate, and the control unit performs a first measurement process for measuring the height of the mask-loading surface based on a signal output from the measurement unit with the mask-loading surface as the object to be measured, before the mask is held in the mask holder, a second measurement process for measuring the height of the upper surface of the mask based on a signal output from the measurement unit with the upper surface of the mask as the object to be measured, and a process for determining the difference between the measurement results of the first measurement process and the second measurement process as the thickness dimension of the mask. 【0117】 In this printing apparatus, a first measurement process is performed to measure the height of the mask load surface on the conveyor before the mask is held in the mask holder, and a second measurement process is performed to measure the height of the top surface of the mask after the mask is held in the mask holder. The difference between the mask top surface height obtained in the second measurement process and the mask load surface height obtained in the first measurement process is determined as the thickness dimension of the mask. Therefore, it is possible to measure the thickness dimension of the mask that will actually be set in the printing apparatus. 【0118】 In this printing apparatus, the conveyor may include a conveyor body for transporting the substrate and a clamping mechanism for holding the substrate at the work position, wherein the clamping mechanism includes a pair of clamping members that clamp the substrate from both sides in its width direction and have an upper surface on which the mask is superimposed together with the upper surface of the substrate, and the mask mounting surface may be the upper surface of the clamping members. 【0119】The upper surface of the clamp member is the surface that supports the lower surface (back side) of the mask at a position adjacent to the substrate. Therefore, by measuring the height of the upper surface of the clamp member as the mask mounting surface, the reliability of the measurement results for the mask mounting surface, and consequently the reliability of the final determined mask thickness dimension, is improved. 【0120】 In the above-described printing apparatus, the measurement unit comprises an encoder, and the printing apparatus further comprises a movable member including a motor equipped with the encoder and a lifting unit equipped with a measuring probe that can contact the object to be measured and moves up and down by the drive of the motor, and the control unit controls the operation of the lifting unit and acquires information corresponding to the load when the measuring probe is in contact with the object to be measured in conjunction with the operation of the lifting unit, and in the first measurement process, based on the information, it is detected that the measuring probe has come into contact with the heavily mounted surface of the mask and the height of the heavily mounted surface of the mask is measured based on the output signal from the encoder at the time of contact, and in the second measurement process, based on the information, it is detected that the measuring probe has come into contact with the upper surface of the mask and the height of the upper surface of the mask is measured based on the output signal from the encoder at the time of contact. 【0121】 With this configuration, the height of the conveyor's mask load surface and the top surface of the mask can be appropriately measured based on information corresponding to the load when the measuring probe is in contact with the object to be measured as the lifting unit operates, and information based on the output signal from the encoder, i.e., the rotational displacement of the motor that operates the lifting unit. 【0122】 In this case, the measuring probe may be configured as a squeegee that moves the coating material along the mask on the mask. 【0123】 This configuration allows for the measurement of the height of the object being measured in a rational way, by sharing the squeegee as a measuring probe. In other words, the height of the mask-loaded surface and the top surface of the mask on the conveyor can be measured using existing equipment of the printing apparatus, such as the squeegee and the equipment for raising and lowering the squeegee. 【0124】On the other hand, the above-described printing apparatus may further include a squeegee provided in the movable part for moving the coating material on the mask and along the mask, wherein the measuring probe is configured to extend and retract between an extended state in which the tip is located below the lower end of the movable range of the squeegee and a retracted state in which the tip is located above the lower end of the movable range, and the control unit further controls the measuring probe, and in the first measurement process and the second measurement process, the measuring probe is controlled to be in the extended state. 【0125】 In this configuration, during the first and second measurement processes, a measuring probe, separate from the squeegee, is brought into contact with the object being measured. In other words, with this configuration, the coating material does not come into contact with the measuring probe. Therefore, the measurement results are not affected by the coating material adhering to the measuring probe, which is advantageous in improving measurement accuracy. Moreover, since the measuring probe is configured to be extendable and retractable, it is possible to avoid the squeegee getting in the way during the first and second measurement processes, and the measuring probe getting in the way during the printing process. 【0126】 The above-described printing apparatus may further include a load sensor that outputs a signal corresponding to the load, and the control unit may acquire the information based on the signal output from the load sensor. 【0127】 With this configuration, it is possible to detect when the measuring probe comes into contact with the object being measured based on the signal output from the load sensor. 【0128】 In the above-described printing apparatus, the movable part includes a first movable part that moves up and down by the drive of the motor, and a second movable part equipped with a measuring probe, connected to the first movable part so as to be displaceable in the vertical direction relative to the first movable part, and elastically biased downward relative to the first movable part. The printing apparatus further includes a locking mechanism that can switch between a locked state in which the second movable part is locked so as not to be displaceable relative to the first movable part, and an unlocked state in which the second movable part is displaceable relative to the first movable part. The control unit further controls the locking mechanism and controls the locking mechanism to the locked state during the first measurement process and the second measurement process. 【0129】 In this configuration, the second movable part is connected to the first movable part so as to be displaceable in the vertical direction and is elastically biased downward. This is particularly useful when the measuring probe is a squeegee. Specifically, during the printing process, the locking mechanism can be released to cushion the collision between the squeegee and the mask. On the other hand, during the first and second measurement processes, the locking mechanism can be switched to the locked state to lock the second movable part so as not to be displaceable relative to the first movable part. This eliminates unnecessary displacement of the squeegee, which is the measuring probe, making it possible to measure the height of the object being measured more quickly and accurately. 【0130】 In the above-described printing apparatus, the measuring unit may be a non-contact type displacement sensor that outputs a signal corresponding to the vertical height of the object to be measured by irradiating the object with light and receiving the reflected light. 【0131】 This configuration allows for the direct measurement of the height of the conveyor's masked surface and the top surface of the mask using a non-contact displacement sensor. Therefore, the first and second measurement processes can be performed with a simpler configuration. 【0132】 In each of the above-described printing apparatuses, the apparatus may further include a storage unit that stores substrate data relating the substrate and the thickness dimension of the mask used for printing the substrate, and a notification unit that can notify information related to the printing process, wherein the control unit further controls the notification unit, and if the thickness dimension of the mask obtained based on the measurement results of the first measurement process and the second measurement process does not match the thickness dimension of the substrate data of the substrate to be printed, the control unit may execute a process to notify error information via the notification unit. 【0133】 With this configuration, if the thickness of the mask held in the mask holder does not match the thickness of the substrate data of the substrate to be printed, the notification unit will notify the operator of the error. This will alert the operator and prevent the use of an incorrect mask with a different thickness in the printing process. 【0134】In this case, the control unit may be configured to perform a process to prevent the printing process from starting if the determined thickness dimension of the mask does not match the thickness dimension of the substrate data of the substrate to be printed. 【0135】 This configuration ensures that the start of the printing process is forcibly prohibited, thus reliably preventing the printing process from being initiated with an incorrect mask that has a different thickness dimension.

Claims

1. A printing apparatus that performs a printing process for printing a coating material onto a substrate via a thin plate-shaped mask placed on top of the substrate, comprising: a conveyor for transporting the substrate to a predetermined work position; a mask holder for detachably holding the mask; a measurement unit for outputting a signal corresponding to the vertical height of an object to be measured; and a control unit, wherein the conveyor has a mask-loading surface on which the mask is placed together with the upper surface of the substrate; the control unit performs: a first measurement process for measuring the height of the mask-loading surface based on a signal output from the measurement unit with the mask-loading surface as the object to be measured before the mask is held in the mask holder; a second measurement process for measuring the height of the upper surface of the mask based on a signal output from the measurement unit with the upper surface of the mask as the object to be measured after the mask is held in the mask holder; and a process for determining the thickness dimension of the mask as the difference between the measurement results of the first measurement process and the second measurement process.

2. A printing apparatus according to claim 1, wherein the conveyor comprises a conveyor body for transporting the substrate and a clamping mechanism for holding the substrate at the work position, the clamping mechanism includes a pair of clamping members that clamp the substrate from both sides in the width direction and have an upper surface on which the mask is superimposed together with the upper surface of the substrate, and the mask superimposing surface is the upper surface of the clamping members.

3. A printing apparatus according to claim 1 or 2, wherein the measuring unit comprises an encoder, the printing apparatus further comprises a movable member including a motor equipped with the encoder and a lifting unit equipped with a measuring probe that can contact the object to be measured and which moves up and down by the drive of the motor, the control unit controls the operation of the lifting unit and acquires information corresponding to the load when the measuring probe is in contact with the object to be measured in conjunction with the operation of the lifting unit, in the first measurement process, detects that the measuring probe has come into contact with the heavily mounted mask surface based on the information and measures the height of the heavily mounted mask surface based on the output signal from the encoder at the time of contact, and in the second measurement process, detects that the measuring probe has come into contact with the upper surface of the mask based on the information and measures the height of the upper surface of the mask based on the output signal from the encoder at the time of contact.

4. A printing apparatus according to claim 3, wherein the measuring probe is a squeegee that moves the coating material on and along the mask.

5. A printing apparatus according to claim 3, further comprising a squeegee provided in the lifting section for moving the coating material on and along the mask, wherein the measuring probe is configured to extend and retract between an extended state in which its tip is located below the lower end of the movable range of the squeegee and a retracted state in which its tip is located above the lower end of the movable range, and the control unit further controls the measuring probe, and in the first measurement process and the second measurement process, controls the measuring probe to be in the extended state.

6. A printing apparatus according to any one of claims 3 to 5, further comprising a load sensor that outputs a signal corresponding to the load, wherein the control unit acquires the information based on the signal output from the load sensor.

7. A printing apparatus according to any one of claims 3 to 6, wherein the lifting section includes a first movable section that moves up and down by the drive of the motor, and a second movable section equipped with the measuring probe, connected to the first movable section so as to be displaceable in the vertical direction relative to the first movable section, and elastically biased downward relative to the first movable section, the printing apparatus further includes a locking mechanism that can switch between a locked state in which the second movable section is locked so as not to be displaceable relative to the first movable section, and an unlocked state in which the second movable section is displaceable relative to the first movable section, the control unit further controls the locking mechanism, and controls the locking mechanism to the locked state during the first measurement process and the second measurement process.

8. A printing apparatus according to claim 1 or 2, wherein the measuring unit comprises a non-contact type displacement sensor that irradiates light onto the object to be measured and receives the reflected light to output a signal corresponding to the vertical height of the object to be measured.

9. A printing apparatus according to any one of claims 1 to 8, further comprising: a storage unit for storing substrate data relating the substrate and the thickness dimension of the mask used for printing on the substrate; and a notification unit capable of notifying information related to the printing process, wherein the control unit further controls the notification unit, and if the thickness dimension of the mask obtained based on the measurement results of the first measurement process and the second measurement process does not match the thickness dimension of the substrate data of the substrate to be printed, the notification unit performs a process to notify error information.

10. A printing apparatus according to claim 9, wherein the control unit performs a process to prohibit the start of the printing process if the determined thickness dimension of the mask does not match the thickness dimension of the substrate data of the substrate to be printed.

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