Author: Bill Faber, Head of Delta Electronics Industrial Automation Team
When a company decided to build a new generation of independent packaging film processing machine modules, its control engineering group considered two things: slimmer control architecture and flexible design to meet the growing demands of the packaging market. In order to minimize costs, the number of components must be reduced without affecting machine performance. In addition, new systems must provide more functions and higher functions, so the natural evolution of next-generation designs will not be limited.
The core of the module consists of four motion axes: two for driving the nip rollers that control the operating speed and tension; two for linear flight, stamping and engraving processes. The control system must also meet two operating modes: continuous operation (with and without registration) and intermittent indexing related to the registration mark. An operator interface is required for machine settings and information storage.
The pre-processed film is pulled by one of the pressure rollers (machine host). In continuous operation mode, it must input its speed command from the upstream floating roller analog position reference. Therefore, the tension between the two nip rollers must be strictly controlled. This is achieved by accurately slowing down the second nip roller by an operator-defined percentage (allowing the film to slide at the second nip roller). Due to the elasticity and memory properties of the material, this hysteresis difference may change. Therefore, the HMI must be able to manually adjust the ratio in real time (+/- 1% to 3%).
Since the motion control is controlled by the built-in functions and motion macros of the ASDA-A2 servo drive, no PLC is required
While maintaining proper tension between the two pinch rollers, the linear actuator connecting the two separating rollers must advance the shuttle at the speed of the web by 80% of the total travel distance, and then return to the starting position for its next cycle . This action actually stops the web, allowing the fixed indenter to drop, touching the film and engraving a logo. In order to prevent the film from being damaged, stretched or torn by the die, the engraving action must be controlled and adjusted according to the size of the die and the required force and time. This operation may require a continuous pattern without registration marks, which represents the length of the repeated part. There is also a registration matching mode that needs to be synchronized with the mark on the film.
Using HMI, the operator should be able to load new recipes. The machine settings can be arbitrary; and there may be situations where the predefined electronic cams are not preloaded. The machine axis must be automatically adjusted according to the position feedback of the film positioning mark.
Since this is an independent machine module, it does not require a lot of input/output (I/O) and all are triggered closely based on the axis position or speed, so the customer wants to cancel the programmable logic controller (PLC) and use the I/servo drive The available operating system reduces system costs and improves local I/O responsiveness. In addition, the customer hopes to use the built-in functions of the servo drive to fully operate the machine, thereby eliminating the need and cost of the central upper motion controller.
Delta Products Corp. (Booth S-8078) is located in the North Carolina Research Triangle Park's industrial automation business group's solutions to meet application needs and provide additional functions. The entire system control scheme can use four parameterized motion intelligence ASDA-A2 servo systems and a DOP-B07P professional HMI to run. The distributed control of ASDA-A2 makes it possible to cancel the upper controller, and the software wizard speeds up the setting speed. Since Delta manufactures ASDA-A2 servo and DOP-B HMI, additional functions are added to make these two products even better. Work together effectively.
The Dancer control system consists of four motion intelligent A2 servo drives and a DOP-B07P professional HMI.
Spindle operation includes two modes: continuous and intermittent. The continuous mode runs the system according to the speed command from the floating wheel, which is directly fed to the spindle. Since the machine does not have an external main encoder, the spindle encoder is used as a reference for other axis movements: tensioner nip rollers, shuttles and presses.
Intermittent mode runs the system at index intervals based on film positioning marks. In this mode, the distance between registration marks may not be consistent, but the index distance must be operator-defined and a very precise distance from the registration marks. Since the host is actually a servo axis that drives the nip roller, after starting to move and capture the positioning mark, the index target distance is actually redefined internally by the axis. The spindle uses ASDA-A2's 5 microsecond fast capture registration function, which can internally change the moving target reference to the actual registered capture position, eliminating any communication delay with the upper controller. Therefore, even if irregular marking distances occur at high-speed film speeds, the machine host can accurately index so that the printer can engrave within the precise distance from the marking. According to the customer, "It is a real game changer for us to change the target position instantly based on the internal calculations of the drive."
In order to control the section tension and maintain the same speed reference level as the position feedback command of the dancer roller, the encoder output from the main shaft is scaled and then passed to the second nip roller. The operator can use the HMI to manually override this zoom ratio instantly to increase or decrease the film tension to match the specifications of the material used.
Since all machine axes use spindle encoder feedback, the ASDA-A2 drive bypass function is used, which allows the encoder signal to be amplified and re-sent to the next drive, each with only 50 nanoseconds of propagation delay. At a maximum machine speed of 240 feet per minute, the 100-nanosecond delay between the main shaft and the fourth axis only reflects one-half of the encoder count for feedback of 100,000 counts per motor revolution.
The DOP-B Professional series HMI includes pre-designed eCAM editing and downloading functions.
In order to stamp and engrave correctly at high speeds, the shuttle must match the film speed within at least 80% of the total stroke of the actuator. In the non-registered mode, the operator can set the required speed to match the area distance between the engraved marks. The DOP-B07P professional series man-machine interface is used to graphically set and generate the electronic cam profile and download it to the ASDA-A2 servo axis of the shuttle, and run continuously according to the main feedback. This allows the electronic cam profile to be customized without the need to plug in a personal computer.
In the registration matching mode, the shuttle movement must be coordinated with the registration mark position, which may cause challenges due to mark printing errors and/or material stretching. The synchronized axis macro function compensates and implements the necessary corrections. When the parameter setting is less than five, this macro is turned on, and the ASDA-A2 servo drive will continuously automatically capture and compare the registration marks, and make necessary adjustments to the electronic cam profile in real time.
This synchronized axis macro can also be used to ensure that the engraving axis is printed in the correct position. However, in order to ensure that the shaft is pressurized at the correct pressure, the operator must also be able to adjust the amount of torque and determine the window in which the torque limitation will occur during the press's electronic cam cycle. In response to this requirement, the output range I/O function of the ASDA-A2 drive is used to dynamically limit the torque output according to the operator's setting.
The ASDA-A2 servo drive provides two additional options. If the user wants to implement slip compensation operation through an external encoder, ASDA-A2 has a second encoder feedback input for full closed-loop control operation. If the graphics on the film interfere with the registration mark operation, the registration mask range function allows the user to specify a distance window within the cam cycle, in which the ASDA-A2 synchronous axis operation will ignore any operation on the registration input.
Delta Products meets the customer's machine function and production model requirements, and in the process reduces the system components in the scalable independent system to accurately control all four axes of complex motion-without the need for a PLC. Instead, the motion control is controlled by the built-in functions and motion macros of the ASDA-A2 servo drive, such as synchronized electronic cams, electronic gears, position capture and comparison, dynamic end point changes and the second full closed loop, and DOP-B with downloadable users Define the PE series of the cam.
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