1, Overview of auto rack plating machine:
Auto rack plating machine is in accordance with certain technical requirements, various plating tank-related traffic, racks, electrical systems, power equipment, ventilation system, filtration system, temperature control heating systems, air mixing system, level control systems, cathodic mobile devices form a complete multi-functional automatic control system. This production line is suitable for rolling, hanging plating dual.
2, Working process:
Plating production line using straight cantilever crane, while the crane equipped with lifting hook. Crane and hook each driven by motor separately, and motors speed controlled by inverter. There are proximity switches and sensors in suitable position on crane, and the sensors will be installed according to positioning rail, thus crane translation and hook lifting will be all positioned by sensors. For simplicity in explanation of Crane operation for plating line, now will simplify 30 station 30 to 5: loading station, pre-processing station, plating bath station, after-processing station, unloading station. Following picture shows the working process.
Loading and unloading station are beginning and end of crane running. On loading position, hung plating workpiece manually, then return loading station to hang electroplating products, i.e. cycle the plating work. Lift the hanging workpiece and not stop until sensor close to the upper limit. Go to the next step: move crane to right until sensor approach the 2nd, then stop, at this moment, the hook just above on the pre-processing station;
Down hook and do not stop until sensor close to the lower limit, then put plating workpiece into plating bath, according to specific process requirements to deal with plating products on timing period;
When the timing period reached, lift the hook to rise electroplating product and not stop until sensor arrive at the upper limitation, after that, continue to the next step;
Continue to the move crane right until sensor close to the 3rd sensor then stop, at that time, the electroplating product is just above the plating bath station;
Still drop hook and do not stop until sensor close to lower limit, then put the plating piece in to plating bath, according to specific requirements to deal with plating parts on timing period;
After plating process finished, rise the hook and not stop until sensor close to upper limit, continue to the next step;
Continue to move crane on right direction, until sensor close to the 4th sensor, then stop, at this moment, the part is just above the after-processing bath station;
Then down hook and don’t stop until sensor close to the lower limit, then put the parts into after-processing bath to proceed bath solution recycling, and wash cleaning with water;
After the hook rising in place, continue to move the crane on right side to approach unloading station to unload the electroplated parts, and then return to the loading station to repeat the previous step one by one.
3, Mechanical design:
This time we take straight line cantilever structure type as our sample. Mechanical structure mainly includes rack structure, cranes and variety kinds of plating baths.
Considering larger acid and alkali corrosive for environment on plating production, we use high quality stainless steel profiles for integral part of the rack, in order to improve equipment corrosion resistance, and also achieve the required device strength and rigidity. In the mean time, for easy installation, the rack each part adopts screw join, then maintenance is simple, and the appearance is compact.
Except manual loading and unloading workpiece the entire production process is full automatic operation. The crane driving relies on primary and secondary rail along with the side of the rack. While lift arm slide along with the rail on crane rack, using method of rolling or sliding to replace directly elevate or drag, then to reduce the bearing.
3.3 Cathode moving:
When in plating there are bubbles generated on the cathode, if these gas stick on to the cathode surface, then will prevent metal irons continue deposition, resulting in coating surface mottling, micropore, thereby affecting products quality. In order to eliminate this phenomenon, we adopt cathode moving devices. These devices is horizontal movement type, which movement number: 15-20 times/min, moving stroke 60ram, driven by single phase DC power: 370w. And equipped with position sensors in cathode one side, so that the crane movement compatible with cathode moving, to prevent accidental operation, then affect normal processes operation.
4, Electrical design section:
As per features of complex running, circular motion, auxiliary equipment, various types of positioning detection, so many signal picking up for electroplating production line, and based on different technological demands, the tasks need to be achieved are different. This will require the ability to modify technical processes and operating parameters at any time, so the whole control system should have strong adaptability and adjustability, also require the system safe, reliable, accurate and stable performance. Therefore we choose PLC, IPC, inverter, touch screen as mainly control system.
We adopt Siemens PLC or Mitsubishi PLC which based on customers’ requirements. Use sensor to control solution liquid level. On condition of communication with IPC, to control crane movement, cathode moving, spray system, air agitation system.
PLC and IPC via serial communications to conduct real-time monitor of production process, and the preparation and operation all operated under WINDOWS. The system has function of power-off protection, which can timely protect on-site data and station, to ensure that the system can continue to operate safely.
When start computer, will appear control software welcome interface, then click the button to enter into management menu. In this menu to select technology, complile technical, storage technology, delete process, power management, cathode movement on/off and exit menu. After call in the technical management menu, then can modify the technical parameters.
In power management function modules: power control mode divided into remote mode and local mode, the plating current and voltage can be adjusted by these two modes.
4.3 Touch Screen:
After IPC setting parameters and reading in PLC data, but can not take effect immediately. For solving this problem, we use touch screen, to display various parameters and operating functions. Conditions take it force: press initialization button on touch screen, and then successful complete initialization. Parameters will be effective immediately after setting, then been replaced until IPC parameters conditions meet the demands. Operator can flexibly use machine in accordance with this characteristic. In standby state, if this is not alarm. The initial menu of touch screen functional blocks shown in as following figure:
1) Automatic and manual modes. Crane movement will auto running according to parameters set based on process automatically;
Manual mode, by means of control box to control crane moving, and emergency brake stop button can be used to stop any movement.
These two modes can be switched with each other, which provides the necessary means for facilitate maintenance, operations, and the safe operation of the machine.
2) Initialize the module: it is premise for crane normal operation, only in initialization state read PLC parameters can take effect.
3) Barrel and Rack plating: two ways can be switched depending on demands of products.
4) Start module: initialization is completed, you can press this button to start running the program, crane will run accordance with the technological process.
5) Process parameter module : this module is pressed to switch to process parameter setting screen, ease for user check IPC parameters, and modify process time.
6) Crane parameter module: in this module, crane accelerate and decelerate time, rinse bath station, spray time, enter bath time with electricity and cathode movement stop and moving time can be set.
In addition, if alarm occurs. Touch screen display alarm figure, and display alarm cause. After troubleshooting pressing the release button to display initialization interface. Recover normal state.
In order to locate small car accurately, it is necessary to control crane speed. When the inverter has a positive output, the motor forward, crane move left, hook rise; When the inverter has a reverse output, motor reversal, crane right move, hook dropping.
In order to prevent plating workpieces shaking and can’t reach destination when crane working, we required, when crane translation, first fast speed, when approaching the station turn into a slow speed, in order to reduce braking torque, and improve positioning accuracy, as well as rails wearing.
5, Key auxiliary machine:
5.1 Spray equipment:
In order to thoroughly wash and clean the workpiece in bath, there equipped with spray device in each plating rinse bath. After crane arriving at rinse bath according to technical process and finishing the washing, the workpiece will be lifted, the magnetic valve controlled by PLC will be opened immediately, and shut down after periodically washing the products.
5.2 Plating power supply:
From principle knowledge, we know electroplating power supply must be DC power or pulsed power supply. While various types of plating bath, the power requirements are not same, so in electroplating production the electric current, voltage should be controlled within a certain error range. Therefore, use high-frequency switching power supply with features of constant voltage, constant current , constant current density control, IGBT module and unique driving protection method. Via PLC to conduct local and remote control and their conversion, to bring convenience for actual production.
5.3 Temperature control system:
Since high temperature demands of electrolytic degreasing and plating bath, which directly affects the quality of the plating products, therefore we use temperature control systems. This system is composed by temperature controller, temperature sensor, heating tube and electrical relay.
Temperature control system working principle:
When bath solution temperature measured by sensor below the set temperature, temperature controller output signal to drive relays, then heating tube continue to heat;
When the measured temperature is higher than the set temperature, temperature controller stop to output signal, then heating pipe stop heating.