JP7696568B2 - Control device, control method, and program for rotary screen printing machine - Google Patents

Description

The present invention relates to a control device, control method, and program for a printing machine that performs rotary screen printing.

In a rotary screen printing machine, low ink viscosity is preferable for printing high-definition images at high speed. Patent Document 1 proposes a rotary screen printing machine equipped with a printing mechanism in which the squeegee faces upward and contacts the inner surface of a cylindrical screen cylinder. With this printing machine, by adopting an upward squeegee mechanism, it is possible to obtain suitable printing quality while controlling the amount of ink.

In a rotary screen printing machine that uses an upward squeegee mechanism, the temperature of the ink may rise due to friction between the squeegee and the screen cylinder and heat generated by the printing machine, or the temperature of the ink may fall due to the influence of the outside air. In this case, it is expected that the viscosity of the ink will change and its printability will be impaired. For this reason, the printing machine described in Patent Document 1 is also equipped with an external tank that is connected to the inside of the screen cylinder and has a temperature adjustment mechanism. Furthermore, in order to circulate the ink between the inside of the screen cylinder and the external tank, a supply pump that supplies ink from the external tank to the inside of the screen cylinder and a discharge pump that discharges ink from the inside of the screen cylinder to the external tank are also installed. The operation of the supply pump and the discharge pump are controlled according to the amount of ink in the screen cylinder.

JP 2009-137094 A

To ensure good printing quality, it is desirable to constantly supply ink adjusted to a temperature suitable for printing from the external tank described above into the screen plate cylinder, while also constantly discharging the ink in the screen plate cylinder into the external tank and not fluctuating the amount of ink in the screen plate cylinder.

For example, if the amount of ink supplied per unit time when the supply pump is operating is equal to the sum of the amount of ink discharged per unit time when the discharge pump is operating and the amount of ink consumed per unit time by transferring ink to the printing substrate, then suppressing fluctuations in the amount of ink in the screen cylinder can be easily achieved by constantly operating the supply pump and discharge pump continuously.

However, in reality, the image area differs for each printing design, so the amount of ink transferred to the printing substrate differs each time. Also, the change in ink temperature caused by the room temperature when printing is carried out and the temperature change of the screen cylinder over time since printing started may not be able to be fully controlled by the temperature adjustment mechanism of the external tank. When this happens, the ink flow characteristics change, causing a corresponding change in the balance between the supply amount and the discharge amount.

The amount of ink in the screen cylinder increases or decreases depending on the difference between the supply and discharge amounts of each pump. In addition, the operation and stoppage of each pump is switched on and off based on a set value. Therefore, fluctuations in the amount of ink are kept within a certain range by switching the pumps on and off based on the set value.

However, switching each pump on and off results in an alternating increase and decrease in the amount of ink, which is different from the ideal stable state in which the supply and discharge volumes are in balance. Furthermore, when the ink volume alternates between increasing and decreasing, the amount of ink supplied to the tip of the squeegee also inevitably increases and decreases.

When the amount of ink inside the screen cylinder is increased and decreased frequently over a short period of time, printing defects such as missing lines and roughness are more likely to occur on the printing substrate.

The present invention aims to provide a control device, control method, and program that can reduce printing defects in a rotary screen printing machine.

The control device according to the present invention is a control device for a rotary screen printing machine including a cylindrical screen cylinder, a squeegee that contacts the inner surface of the screen cylinder with its upper surface facing upward, an ink recovery means that recovers ink inside the screen cylinder, an ink amount sensor that detects the amount of ink remaining in the ink recovery means, a discharge pump that discharges ink from the ink recovery means, an external tank that stores the ink discharged by the discharge pump, and a supply pump that supplies the ink stored in the external tank into the screen cylinder. The control device includes a memory unit that stores ink amount change data that indicates the change over time in the ink amount detected by the ink amount sensor and status change time data that indicates the time when the status of the discharge pump and/or the supply pump changes based on the ink amount, a data processing unit that calculates the ink change rate inside the screen cylinder using the ink amount change data and calculates the frequency of status changes of the discharge pump and/or the supply pump using the status change time data, and a drive control unit that controls the discharge pump and the supply pump based on the ink amount, the ink change rate, and the frequency.

In the above control device, the discharge pump stops when the ink amount falls below a lower limit and starts when the ink amount exceeds an upper limit, and has a data processing unit that calculates the ink reduction rate using the ink amount change data and calculates the stop frequency of the discharge pump using the state change time data, and when the stop frequency exceeds a predetermined number of times and the average value of the reduction rate exceeds a predetermined value, the drive control unit may control the supply pump to increase the amount of ink supplied.

In the above control device, the supply pump stops when the ink amount exceeds an upper limit and starts when the ink amount falls below a lower limit, and has a data processing unit that calculates the ink increase rate using the ink amount change data and calculates the supply pump stop frequency using the state change time data, and when the stop frequency exceeds a predetermined number of times and the average increase rate exceeds a predetermined value, the drive control unit may control the discharge pump to increase the amount of ink discharged.

The control method according to the present invention is a control method for a rotary screen printing machine including a cylindrical screen cylinder, a squeegee in upward contact with the inner surface of the screen cylinder, an ink recovery means for recovering ink within the screen cylinder, an ink amount sensor for detecting an amount of ink remaining in the ink recovery means, a discharge pump for discharging ink from the ink recovery means, an external tank for storing the ink discharged by the discharge pump, and a supply pump for supplying the ink stored in the external tank into the screen cylinder,
Ink amount change data indicating the change over time in the amount of ink detected by the ink amount sensor is stored, status change time data indicating the time at which the status of the discharge pump and/or supply pump changed based on the ink amount is stored, the ink amount change data is used to calculate the ink change rate in the screen cylinder, the status change time data is used to calculate the frequency of status changes of the discharge pump and/or supply pump, and the discharge pump and supply pump are controlled based on the ink amount, ink change rate, and frequency.

In the above control method,
The discharge pump may be stopped when the amount of ink falls below a lower limit and activated when the amount of ink exceeds an upper limit, the ink amount change data may be used to calculate the ink reduction rate, and the state change time data may be used to calculate the stop frequency of the discharge pump, and if the stop frequency exceeds a predetermined number of times and the average rate of reduction exceeds a predetermined value, the supply pump may be controlled to increase the amount of ink supplied.

In the above control method,
The supply pump may be stopped when the amount of ink exceeds an upper limit and activated when the amount of ink falls below a lower limit, the ink amount change data may be used to calculate the ink increase rate, and the state change time data may be used to calculate the supply pump stop frequency, and if the stop frequency exceeds a predetermined number of times and the average increase rate exceeds a predetermined value, the discharge pump may be controlled to increase the amount of ink discharged.

The program according to the present invention is a program for causing a computer to execute a process for controlling a rotary screen printing machine including a cylindrical screen cylinder, a squeegee in upward contact with the inner surface of the screen cylinder, an ink recovery means for recovering ink within the screen cylinder, an ink amount sensor for detecting the amount of ink remaining in the ink recovery means, a discharge pump for discharging ink from the ink recovery means, an external tank for storing the ink discharged by the discharge pump, and a supply pump for supplying the ink stored in the external tank into the screen cylinder,
Ink amount change data indicating the change over time in the amount of ink detected by the ink amount sensor is stored, status change time data indicating the time at which the status of the discharge pump and/or supply pump changed based on the ink amount is stored, the ink amount change data is used to calculate the ink change rate in the screen cylinder, the status change time data is used to calculate the frequency of status changes of the discharge pump and/or supply pump, and the discharge pump and supply pump are controlled based on the ink amount, ink change rate, and frequency.

The present invention makes it possible to reduce printing defects in rotary screen printing machines.

1 is a front view showing a schematic configuration of a control device according to a first embodiment of the present invention; FIG. 4A is a diagram showing an example of ink amount change data, and FIG. 4B is a diagram showing an example of state change time data. 4 is a flowchart showing an example of a procedure of a control operation by the control device of the first embodiment. 5 is a timing chart showing an example of the relationship between the operation of a pump controlled by the control device of the first embodiment and the amount of ink retained in the retention tank. 10 is a flowchart showing an example of a procedure of a control operation by a control device according to a second embodiment of the present invention. 10 is a timing chart showing an example of the relationship between the operation of a pump controlled by a control device of a second embodiment and the amount of ink retained in a retention tank.

Embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments described below, and various other embodiments are included within the scope of the technical ideas described in the claims.

First Embodiment
Fig. 1 is a diagram showing a schematic configuration of a rotary screen printing machine according to a first embodiment of the present invention. The rotary screen printing machine 1 shown in Fig. 1 includes a printing mechanism 10, an ink circulating mechanism 20, and a control device 30. In addition to these, the rotary screen printing machine 1 also includes a paper feed unit (not shown) that feeds a printing substrate to the printing mechanism 10, a paper discharge unit (not shown) that discharges the printing substrate from the printing mechanism 10, and the like.

First, the printing mechanism 10 will be described. The printing mechanism 10 has a screen plate cylinder 11, a squeegee 12, a retention tank 13, and an ink amount sensor 14. The screen plate cylinder 11 is a cylindrical member, and a through hole is formed in its outer periphery. During printing, the screen plate cylinder 11 rotates in one direction (clockwise in FIG. 1). This causes ink to be ejected upward from the through hole. The ejected ink is transferred to the printing material sandwiched between the screen plate cylinder 11 and an impression cylinder (not shown).

The squeegee 12 is provided inside the screen plate cylinder 11. The squeegee 12 is fixed to a support (not shown). The tip of the squeegee 12 faces upward and contacts the inner surface of the screen plate cylinder 11 so that the ink is ejected upward. The squeegee 12 pushes ink E into the through holes of the screen plate cylinder 11 and scrapes off excess ink. The pushed-in ink E is transferred to the substrate as the screen plate cylinder 11 rotates. This forms an ink pattern on the substrate.

A retention tank 13 is also provided within the screen cylinder 11. The retention tank 13 is an example of an ink recovery means, and recovers the ink E that is scraped off by the squeegee 12 without being transferred to the printing substrate.

The ink amount sensor 14 detects the amount of ink retained in the retention tank 13. The ink amount sensor 14 is composed of, for example, a pressure sensor. As the amount of ink retained in the retention tank 13 increases, the pressure value measured by this pressure sensor increases. In other words, the ink amount sensor 14 detects the amount of ink retained in the retention tank 13 by converting the measured pressure value into an ink amount. Note that the method of detecting the amount of ink is not limited to pressure, and other methods may be used.

Next, we will explain the ink circulation mechanism 20 that is installed outside the screen cylinder 11. The ink circulation mechanism 20 has a discharge pump 21, an external tank 22, and a supply pump 23, which are connected to the retention tank 13 via a pipe 24.

The discharge pump 21 is connected to a recovery port 131 provided in the retention tank 13 via a pipe 24. The discharge pump 21 discharges ink from the retention tank 13. The discharged ink is stored in the external tank 22 via the pipe 24.

In the external tank 22, the ink E discharged by the discharge pump 21 and unused ink are stored. A temperature control mechanism (not shown) is provided in the external tank 22. The temperature control mechanism is, for example, a band-shaped heater installed on the inner side and bottom surface of the external tank 22. The shape of the heater is not limited to a band shape, and may be any shape that can be installed inside the external tank 22. In addition, it is preferable that the temperature control mechanism has a function of controlling the temperature of the ink stored in the external tank 22 so that the viscosity of the ink stored in the external tank 22 is maintained at a preset value (for example, a value of 2 Pa·s or less). For example, the temperature of the ink in the external tank 22 is monitored, and the heater is operated in response to the temperature change to cool or warm the ink in the external tank 22. In addition, the relationship between the temperature change and the viscosity change of the ink may be grasped in advance, and the temperature of the ink may be controlled in a temperature range where the desired viscosity is obtained.

The supply pump 23 supplies ink stored in the external tank 22 into the screen plate cylinder 11 through a pipe 24. The supply pump 23 and the discharge pump 21 can adjust the amount of ink fed per unit time by inverter control by the control device 30. That is, the supply pump 23 can adjust the amount of ink fed per unit time into the screen plate cylinder 11, and the discharge pump 21 can adjust the amount of ink discharged per unit time from the retention tank 13.

Next, the control device 30 that controls the ink circulation mechanism 20 will be described. The control device 30 has a memory unit 31, a data processing unit 32, and a drive control unit 33. The control device 30 is configured, for example, by a PLC (Programmable Logic Controller) that controls the ink circulation mechanism 20 by a predetermined program.

The storage unit 31 stores the above programs and various data. Here, an example of the data stored in the storage unit 31 will be described with reference to Figures 2(a) and 2(b).

Figure 2 (a) is a diagram showing an example of ink amount change data. The ink amount change data 311 shown in Figure 2 (a) shows the change over time in the amount of ink stored in the ink reservoir 13 by storing the ink amount detected by the ink amount sensor 14 in association with the detection time.

On the other hand, FIG. 2(b) is a diagram showing an example of status change time data. Status change time data 312 shown in FIG. 2(b) indicates the status change time of the discharge pump 21 and the supply pump 23. This status change time is the time when each pump changes from an operating state to a stopped state, or the time when each pump changes from a stopped state to an operating state. Note that the status change time data 312 stores the status change times of both the discharge pump 21 and the supply pump 23, but it is also possible to store the status change time of only one of the pumps.

The data processing unit 32 uses the ink amount change data 311 stored in the storage unit 31 to calculate the ink change rate (the ink increase rate or the ink decrease rate).
In addition, the data processing unit 32 calculates the frequency of state changes of the discharge pump 21 and/or the supply pump 23 using the state change time data 312 stored in the storage unit 31 .

The drive control unit 33 controls the discharge pump 21 and/or the supply pump 23 based on the amount of ink detected by the ink amount sensor 14, as well as the ink change rate and frequency of state changes calculated by the data processing unit 32.

The operation of the control device 30 according to this embodiment will be described below with reference to Figures 3 and 4. Figure 3 is a flow chart showing an example of the procedure of the control operation by the control device 30. Also, Figure 4 is a timing chart showing an example of the relationship between the operation of the pump controlled by the control device 30 and the amount of ink retained in the retention tank 13.

When the printing mechanism 10 starts printing, the discharge pump 21 discharges a fixed amount of ink from the retention tank 13 to the external tank 22 based on a control signal SG1 (see FIG. 4) input from the drive control unit 33 of the control device 30. At this time, the supply pump 23 supplies a fixed amount of ink from the external tank 22 to the screen plate cylinder 11 based on a control signal SG2 (see FIG. 4) input from the drive control unit 33 of the control device 30.

The data processing unit 32 of the control device 30 also periodically acquires the amount of ink detected by the ink amount sensor 14 (step S101). The acquired ink amount is stored in the memory unit 31 as ink amount change data (step S102).

As printing progresses, the amount of ink remaining in the retention tank 13 also decreases. Therefore, the data processing unit 32 determines whether the acquired ink amount is below the lower limit LL (see Figure 4) (step S103).

When the data processing unit 32 notifies the drive control unit 33 of the determination result that the ink amount has fallen below the lower limit LL, the drive control unit 33 outputs a control signal SG1 to command the discharge pump 21 to stop (step S104). At this time, the output time of this control signal SG1 is stored in the memory unit 31 as state change time data indicating the stop time t11 (see Figure 4) of the discharge pump 21 (step S105). Note that if the ink amount has not fallen below the lower limit, the drive control unit 33 maintains the operation of the discharge pump 21 and the supply pump 23.

While the discharge pump 21 stops in step S104, the supply pump 23 continues to operate, so the amount of ink retained in the retention tank 13 increases. Therefore, the data processing unit 32 determines whether the acquired ink amount exceeds the upper limit value UL (see Figure 4) (step S106).

When the data processing unit 32 notifies the drive control unit 33 of the determination result that the ink amount exceeds the upper limit value UL, the drive control unit 33 outputs a control signal SG1 to command the discharge pump 21 to operate (step S107).

The operations of steps S103 to S107 described above, i.e., the operation in which the drive control unit 33 controls the discharge pump 21 and/or the supply pump 23 based on the result of comparing the ink amount with the lower limit value and the upper limit value, are repeated to a certain extent as shown in FIG. 4. However, in this embodiment, during the above operations, the data processing unit 32 calculates the ink amount reduction rate p using the ink amount change data 311 read from the memory unit 31 (step S108). The reduction rate p can be calculated, for example, as ΔA/Δt as shown in FIG. 4. Here, Δt is the time elapsed from the time when the ink amount reached the maximum value MAX, i.e., the time when the ink amount reached the upper limit value UL, and is set in advance. Meanwhile, ΔA is the ink amount reduced during the period Δt.

After calculating the decrease rate p as described above, the data processing unit 32 then calculates the stop frequency f of the discharge pump 21 using the state change time data 312 read from the memory unit 31 (step S109). The stop frequency f is the number of times that the ink amount reaches the lower limit LL within a predetermined period T, for example as shown in FIG. 4. This number can be calculated by counting the number of stop times t11 to t14 indicated in the state change time data 312.

Then, the data processing unit 32 determines whether the stop frequency f exceeds a predetermined number N (step S110). In step S110, it is determined whether the stop frequency f of the discharge pump 21 between the present time and a time a predetermined period T back from the present time is within an acceptable range. If the stop frequency f exceeds the predetermined number N, the data processing unit 32 determines whether the average value m of the reduction rate p of the ink amount within the predetermined period T exceeds a predetermined value P (step S111).

If the average value m exceeds the predetermined value P, the data processing unit 32 notifies the drive control unit 33 of the determination result. In this case, as shown in FIG. 4, the drive control unit 33 outputs a control signal SG2 to the supply pump 23, which indicates a command to increase the ink supply amount during the operation period D1 of the discharge pump 21 (step S112). As a result, the reduction rate p of the ink amount is suppressed.

Therefore, according to the present embodiment described above, the supply pump 23 appropriately increases the ink supply amount while the discharge pump 21 is operating in response to fluctuations in the amount of ink in the screen plate cylinder 11, thereby preventing a sudden decrease in the amount of ink in the screen plate cylinder 11. This makes it possible to avoid frequent increases and decreases in the amount of ink, thereby reducing printing defects in the rotary screen printing machine.

In addition, in this embodiment, if the frequency of increases or decreases in the amount of ink in the screen cylinder 11 increases, the control device 30 can automatically handle the situation, eliminating the possibility of the operator erroneously operating the pump.

Furthermore, even if conditions such as ink type, ink pattern, pump type, and ink path length are changed, optimal ink circulation can be provided by automatically controlling the discharge pump 21 and/or supply pump 23 based on various parameters set each time.

Second Embodiment
A second embodiment of the present invention will be described below. The configuration of the rotary screen printing machine according to this embodiment is the same as that of the rotary screen printing machine 1 according to the first embodiment described above, and therefore a description thereof will be omitted. In this embodiment, the operation of the control device 30 is different from that of the first embodiment. Here, the operation of the control device 30 of this embodiment will be described with reference to Figs. 5 and 6.

Figure 5 is a flow chart showing an example of the procedure of the control operation by the control device 30 of the second embodiment. Also, Figure 6 is a timing chart showing an example of the relationship between the operation of the pump controlled by the control device 30 of the second embodiment and the amount of ink retained in the retention tank 13.

When the printing mechanism 10 starts printing, the data processing unit 32 of the control device 30 periodically acquires the amount of ink detected by the ink amount sensor 14 (step S201), in the same manner as in the first embodiment. The acquired ink amount is stored over time in the memory unit 31 as ink amount change data (step S202).

While the printing mechanism 10 is printing, as in the first embodiment, the drive control unit 33 repeatedly controls the discharge pump 21 and the supply pump 23 based on the results of comparing the ink amount obtained from the ink amount sensor 14 with the lower limit value LL or the upper limit value UL.

However, in this embodiment, the data processing unit 32 determines whether the acquired ink amount exceeds the upper limit value UL (see FIG. 6) (step S203), and if the ink amount exceeds the upper limit value UL as a result, the drive control unit 33 outputs a control signal SG2 to the supply pump 23 to command it to stop (step S204). In this case, the output time of this control signal SG2 is stored in the memory unit 31 as state change time data indicating the stop time t21 (see FIG. 6) of the supply pump 23 (step S205). Note that if the ink amount does not exceed the upper limit value, the drive control unit 33 maintains the operation of the discharge pump 21 and the supply pump 23.

While the supply pump 23 stops in step S204, the discharge pump 21 continues to operate, so the amount of ink retained in the retention tank 13 decreases. Therefore, the data processing unit 32 determines whether the acquired ink amount is below the lower limit value LL (see FIG. 6) (step S206).

When the data processing unit 32 notifies the drive control unit 33 of the determination result that the ink amount has fallen below the lower limit value LL, the drive control unit 33 outputs a control signal SG2 to the supply pump 23 to command it to operate (step S207).

In addition, in this embodiment, during the operations of steps S203 to S207 described above, the data processing unit 32 calculates the ink amount increase rate q using the ink amount change data 311 read from the storage unit 31 (step S208). The increase rate q can be calculated, for example, as ΔB/Δt, as shown in FIG. 6. Here, Δt is the time elapsed from the time when the ink amount became the minimum value MIN, i.e., the time when it reached the lower limit value LL, and is set in advance. On the other hand, ΔB is the ink amount that increased during the period Δt.

After calculating the increase rate q as described above, the data processing unit 32 then calculates the stop frequency f of the supply pump 23 using the state change time data 312 read from the memory unit 31 (step S209). The stop frequency f is the number of times that the ink amount reaches the upper limit value UL within a predetermined period T, for example as shown in FIG. 6. This number can be calculated by counting the number of stop times t21 to t24 indicated in the state change time data 312.

Then, the data processing unit 32 determines whether the stop frequency f exceeds a predetermined number N (step S210). In step S210, it is determined whether the stop frequency f of the supply pump 23 between the present time and a time a predetermined period T back from the present time is within an acceptable range. If the stop frequency f exceeds the predetermined number N, the data processing unit 32 determines whether the average value M of the ink amount increase rate q within the predetermined period T exceeds a predetermined value Q (step S211).

If the average value M exceeds the predetermined value Q, the data processing unit 32 notifies the drive control unit 33 of the determination result. In this case, as shown in FIG. 6, the drive control unit 33 outputs a control signal SG2 to the discharge pump 21 indicating a command to increase the ink discharge amount during the operation period D2 of the supply pump 23 (step S212). As a result, the ink amount increase rate q is suppressed.

Therefore, according to the above-described embodiment, the discharge pump 21 appropriately reduces the ink supply amount while the supply pump 23 is operating in response to fluctuations in the ink amount in the screen plate cylinder 11, thereby suppressing a sudden increase in the ink amount in the screen plate cylinder 11. This makes it possible to avoid frequent increases and decreases in the ink amount, thereby reducing printing defects in the rotary screen printing machine.

In each of the above-described embodiments, the drive control unit 33 controls the discharge pump 21 and/or the supply pump 23 to suppress either the rate of decrease or the rate of increase of the amount of ink in the screen plate cylinder 11, but the first and second embodiments may be combined to control each pump to suppress both the rate of decrease and the rate of increase. In this case, the frequency of increase and decrease in the amount of ink can be further suppressed, making it possible to further reduce printing defects in the rotary screen printing machine.

In addition, in this embodiment, the data processing unit 32 calculates the stop frequency of the discharge pump 21 or the supply pump 23, but the operation frequency may be calculated based on the operation time when each pump changes from a stopped state to an operating state. In this case, the drive control unit 33 controls the ink discharge amount through the discharge pump 21 and the ink supply amount through the supply pump 23 based on the operation frequency and the rate of change (rate of decrease or rate of increase) of the ink amount. In this way, by the drive control unit 33 appropriately controlling the discharge pump 21 and the supply pump 23, it is possible to reduce printing defects of the rotary screen printing machine.

It can also be realized by using a program that causes a computer having functions equivalent to the memory unit 31, data processing unit 32, and drive control unit 33 to execute control of the ink supply and/or ink discharge of the rotary screen printing machine described above.

1: Rotary screen printing machine 11: Screen plate cylinder 12: Squeegee 13: Retention tank (ink recovery means)
14: Ink amount sensor 21: Discharge pump 22: External tank 23: Supply pump 30: Control device 31: Memory unit 32: Data processing unit 33: Drive control unit

Claims (7)

A control device for a rotary screen printing machine, comprising: a cylindrical screen cylinder; a squeegee in upward contact with an inner surface of the screen cylinder; ink recovery means for recovering ink within the screen cylinder; an ink amount sensor for detecting an amount of ink remaining in the ink recovery means; a discharge pump for discharging the ink from the ink recovery means; an external tank for storing the ink discharged by the discharge pump; and a supply pump for supplying the ink stored in the external tank into the screen cylinder,
a storage unit that stores ink amount change data indicating a change over time in the amount of ink detected by the ink amount sensor, and status change time data indicating a time at which a status of the discharge pump and/or the supply pump changes based on the ink amount;
a data processing unit that calculates an ink change rate in the screen printing cylinder using the ink amount change data, and calculates a frequency of state changes of the discharge pump and/or the supply pump using the state change time data;
a drive control unit that controls the discharge pump and the supply pump based on the ink amount, the ink change rate, and the frequency;
A control device comprising: the discharge pump stops when the amount of ink falls below a lower limit and operates when the amount of ink exceeds an upper limit;
the data processing unit calculates a reduction rate of the ink using the ink amount change data, and calculates a stop frequency of the discharge pump using the state change time data;
The control device according to claim 1 , wherein when the stop frequency exceeds a predetermined number of times and the average value of the decrease rate exceeds a predetermined value, the drive control unit controls the supply pump so as to increase the amount of ink supplied. the supply pump stops when the amount of ink exceeds an upper limit value and operates when the amount of ink falls below a lower limit value;
the data processing unit calculates an increase rate of the ink using the ink amount change data, and calculates a stop frequency of the supply pump using the state change time data;
3. The control device according to claim 1, wherein when the stop frequency exceeds a predetermined number of times and the average value of the increase rate exceeds a predetermined value, the drive control unit controls the discharge pump so as to increase the discharge amount of the ink. A control method for a rotary screen printing machine including a cylindrical screen cylinder, a squeegee in upward contact with an inner surface of the screen cylinder, an ink recovery means for recovering ink within the screen cylinder, an ink amount sensor for detecting an amount of ink remaining in the ink recovery means, a discharge pump for discharging the ink from the ink recovery means, an external tank for storing the ink discharged by the discharge pump, and a supply pump for supplying the ink stored in the external tank into the screen cylinder, the method comprising the steps of:
storing ink amount change data indicating a change over time in the amount of ink detected by the ink amount sensor;
storing state change time data indicating a time when a state of the discharge pump and/or the supply pump has changed based on the ink amount;
Calculating an ink amount change rate in the screen printing cylinder using the ink amount change data;
Calculating a frequency of state changes of the discharge pump and/or the supply pump using the state change time data;
controlling the discharge pump and the supply pump based on the ink amount, the ink change rate, and the frequency;
Control methods. the discharge pump stops when the amount of ink falls below a lower limit and operates when the amount of ink exceeds an upper limit;
Calculating a rate of decrease of the ink using the ink amount change data;
Calculating a stop frequency of the discharge pump using the state change time data;
The control method according to claim 4 , further comprising controlling the supply pump so as to increase the amount of ink supplied when the stop frequency exceeds a predetermined number of times and the average value of the decrease rate exceeds a predetermined value. the supply pump stops when the amount of ink exceeds an upper limit value and operates when the amount of ink falls below a lower limit value;
Calculating an increase rate of the ink using the ink amount change data;
Calculating a frequency of stopping the supply pump using the state change time data;
6. The control method according to claim 4, further comprising controlling the discharge pump so as to increase an amount of the ink discharged when the stop frequency exceeds a predetermined number of times and the average value of the increase rate exceeds a predetermined value. A program for causing a computer to execute a process for controlling a rotary screen printing machine including a cylindrical screen cylinder, a squeegee in upward contact with an inner surface of the screen cylinder, an ink recovery means for recovering ink within the screen cylinder, an ink amount sensor for detecting an amount of ink remaining in the ink recovery means, a discharge pump for discharging the ink from the ink recovery means, an external tank for storing the ink discharged by the discharge pump, and a supply pump for supplying the ink stored in the external tank into the screen cylinder,
a means for storing ink amount change data indicating a change over time in the amount of ink detected by the ink amount sensor;
a means for storing state change time data indicating a time when a state of the discharge pump and/or the supply pump has changed based on the ink amount;
a means for calculating an ink amount change rate in the screen printing cylinder using the ink amount change data;
a means for calculating a frequency of state changes of the discharge pump and/or the supply pump using the state change time data;
A program for causing the computer to function as a means for controlling the discharge pump and the supply pump based on the ink amount, the ink change rate, and the frequency.

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