Schwahr PLC application in UV coating production bus control

May 30, 2020

I. Introduction

With the accelerated development of the concept of Industry 4.0 and smart manufacturing, informatization and big data monitoring production methods are rapidly popularizing, UV roll coating production automation is also accelerating the process transformation of the traditional roll coating industry with the advantages of high roll coating quality and high return on investment. . At this stage, most of my country's roller coating production is still dominated by single-machine equipment control. Although there is connected production, it does not have the function of joint control and debugging of the whole line, resulting in high labor intensity for workers. When equipment fails, no linkage interlock is formed. Downtime results in high equipment damage rate and high maintenance costs. In addition, factors such as changes in the human resource structure of today's society, which have led to difficulty in recruiting workers, and rising wage levels, have plagued the roller coating industry. To solve the above problems, we must consider upgrading the automation and intelligence of the roller coating line to improve production efficiency and product quality and reduce operating costs.

2. Overview

In order to realize the centralized control of the UV production line and ensure the linkage and adjustment of the entire line, this plan is formulated according to user requirements. In this plan, there are a total of 15 sets of stand-alone equipment, including 2 dust collectors, 1 heavy-duty soil filling machine, 2 double-wheel coating machines, 2 double-lamp drying machines, 1 triple-lamp dryer, and 5 conveyors , 2 sanding machines. The sanding machine is a self-purchased product by the user and is included in the control scheme of this system. The sanding machine needs to provide a communication control interface for this system to control.

plc application cases

3. Control system and network configuration

  1. The PLC adopts the Schwahr brand and is equipped with an optional Ethernet interface. The bus communication adopts industrial Ethernet for communication. The communication protocol is MODBUS/TCP protocol. The transmission speed is fast and the control is real-time. Each stand-alone device selects the corresponding model according to the actual points and needs. PLC.
  2. In principle, the conveyor is not equipped with PLC control and must be controlled by nearby equipment.  Therefore, the PLC system of the  nearby equipment must reserve the control interface of the conveyor to reduce bus control costs.
  3. In order to improve the reliability and stability of the system, as well as data processing capabilities, communication speed, etc., this    system uses a high-end PLC as the master control PLC to process all data.
  4. The stand-alone equipment of this system is equipped with a human-machine interface for monitoring, and any stand-alone machine can     be controlled and adjusted on the spot.
  5. The total monitoring system uses a 10-inch touch screen and PLC for monitoring. It can also be configured with a cloud box (CBOX) +         large screen controller (TVBOX) + (large screen) solution to achieve centralized control. In this system, cloud box + large screen Screen     controller solution, the master control system has cloud control function, which can perform remote debugging programs, remote                  monitoring of equipment status via mobile phone and other functions.
  6. The network communication uses a 12-16 port industrial grade Ethernet switch, and the network cable uses an industrial grade shielded       Ethernet communication cable. The switch needs to be installed in a special electrical box. During on-site installation, the network cable       needs to be routed through iron pipes or independent wire troughs. Improve anti-interference ability.

PLC master control system

4. Process control system functions

(1) Routine functions of process system

  • The bus control system has memory and recipe functions. When producing different products, the recipes of different products can be directly called. The recipes include setting speed, height and other parameters. To call the recipe, you can measure the plate thickness through the product thickness gauge at the entrance of the production line, then confirm and save the data to the corresponding formula, and then call it when producing this plate type.
  • It has whole-line linkage, one-click start and stop. When starting, start the end equipment first, and then start the front-end equipment one by one in sequence. The order of shutdown is exactly the opposite. Avoid simultaneous start-up causing impact on the power grid.
  •  When a faulty machine occurs, the conveying equipment of the faulty machine to the entrance must be stopped immediately, but the roller coating wheel does not stop and rises to a safe height on its own. The equipment maintains normal operation toward the exit. After the fault is reset, it automatically drops to the set value. high. Fault types are divided into conveying faults, card board faults, dimmer faults, inverter faults, limit over-limit alarms, etc.
  • When linked, you can control the operation or non-operation (disabled) of any roll and raise it to a safe height.
  • The UV dryer uses an electronic light source, which can infinitely adjust the light source. It runs at full power when there is a board, and runs at 30% power when there is no board in standby. The light source power can also be adjusted in real time. After fine-tuning the on-site lifting height, the data can be directly transferred to the main control PLC after being saved, and saved and memorized in the formula for easy recall next time.
  • Install a set of material presence detection device at the entrance of the production line as a basis for system operation and standby state switching. This device also serves as a plate thickness detection alarm signal. When the plate thickness exceeds the set thickness, a switching signal is sent to The main control PLC issues an alarm and stops conveying.
  • Install a detection device on the dryer to determine whether there is a jam in the dryer. Stop the dryer immediately to avoid fire accidents.
  • Since the production line is long when the entire line is controlled, a three-color indicator light is installed on each machine to better monitor the operating status of the entire line, green for operation, yellow for standby, and red for failure.
  • The background monitoring system functions include equipment operating status monitoring, fault alarm information display, one-click start and shutdown functions, output statistics, recipe setting and calling, user login and logout, etc.

PLC on-site production line

(2) Energy management functions

  • The dryer of this system is equipped with an electronic dimmer. The dimmer can adjust the frequency conversion speed of the cooling fan according to the power of the light source to achieve the purpose of energy saving and consumption reduction.
  • Each set of rollers of the roller coating machine is equipped with a paint weighing device and a gap adjustment device between the rubber wheel and the steel wheel. The weighing device can monitor the weight of the paint in real time. It has an upper limit to stop oil feeding, a lower limit to refuel, an upper limit to alarm, and a lower limit to Lower limit alarm and other functions. In addition, the amount of paint can be directly determined by adjusting the gap between the steel wheel and the rubber wheel, thereby converting the paint consumption.
  • Each device can be equipped with a smart meter, or a smart meter can be installed on the entire line to monitor the power consumption of each shift every day, so as to monitor power-saving behavior.
  • For forward and reverse roller equipment, the reverse roller lift automatically adjusts the lifting height according to the position of the plate to ensure that the plate does not hit the roller when it enters the reverse roller, because when the reverse roller hits the roller, the paint will pile up and fall onto the conveyor belt, affecting the equipment's performance. Hygiene and maintenance, while also reducing paint loss.

(3) Equipment maintenance functions

  • The electronic dimmer is equipped with a running time record. When the UV lamp reaches the use time, an alarm will prompt the lamp to be replaced for equipment maintenance.
  • Use the solenoid valve that supplies oil to the roller as a timing basis to determine the usage time of each rubber roller, thereby reminding the user when to change the roller so that the equipment can be better maintained.

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