Posted to News on 27th May 2009, 18:32
Electronic cam controller suits labelling and capping machines
Inmoco's Elmo E-cam (electronic cam) for labelling and capping machines claims to double throughput, reduce complexity, and provide top-level performance, with high levels of reliability in demanding environments. Based upon Elmo Harmonica servo drives and servomotors, the product is designed for use with rotary carousels. These are traditionally mechanical cam systems employing magnetic clutches to regulate tightening torque.
However, mechanical cam systems have a number of shortcomings. First, they have reduced efficiency, due to the mechanical couplings that require complex and costly installation procedures and constant maintenance. Second, they are noisy. Third, they offer inadequate or no format flexibility. Fourth, there is limited scalability of the machine, both during the design stage of the installation and for machines already in service.
Recent technological advances have led to the replacement of the mechanical cam with an electronic cam. As a result, each platter or chuck is driven by an onboard electric motor. The use of an electronic cam offers advantages in terms of format flexibility, as the format is managed electronically, and allows modifications to the machine operating cycle, both during the design stage and for machines already in service.
Higher throughput
Inmoco's Elmo E-cam has an ECAM (electronic cam) operating table in each drive. This provides implementation flexibility on existing mechanics. It allows the bottle movement profiles to be changed by altering parameters without making a mechanical change, for example, changing the bottle turning speed based on the bottle's radius. In addition, the distribution of processing power using ECAM enables the network update rate to be increased from 4ms/point to 2ms/point, while reducing the network baud-rate from 15MHz to 500kHz. This enables the machine speed to be increased without affecting network robustness, which is assured by the ability of the small Elmo drives to absorb shocks.
With the ECAM system, all of the axes are slaves of the main axis in the carousel, with slave point 0 received by a camera through the central controller. Also included in the system is an HMI, which is linked to the central controller, and a master encoder that sits in the static part of the machine and provides the location information of the carousel's central axis - without additional general wiring - using CANopen communication.
In order to increase process reliability, the machine is assembled with two labelling systems, one after the other. Both systems are designed to attach the same label. If bottle inspection after the first system senses that there is no label on the bottle, the second labelling system is activated, and the bottle runs a second ECAM motion. The bottle is also inspected before the first labelling system, to determine its angle on the axis. The angle is measured by a vision system; it is then sent to the drive, which corrects its ECAM motion to align it according to the bottle itself.
Management of the ECAM motion, across the first and second labelling systems, is performed in every drive that is commanded by the central controller. In this system flexibility of feedback is provided by the ability to operate with resolvers in compact drives. Moreover, the ruggedness and compact nature of the system enables motors to be placed in the bottle axes without timing belts. Although the motors are shock-loaded when a bottle is pressed, their rugged construction enables them to withstand these conditions and provides high levels of reliability in operation.
Compact servo drives
The Harmonica range of servo drives that control the capping/labelling motors are miniature units that offer OEM machine builders all the performance and features of much larger digital servo drives in a smaller and more cost-effective package, which measures just 82 x 25.4 x 75mm. Providing levels of flexibility that are claimed to be unmatched, the Harmonica is available as a fully digital velocity- or current-mode amplifier, as a network drive in distributed motion systems using the CANOpen interface, or as a standalone motion controller for single-axis servo control.
Furthermore, the combination of small size, ease of set-up and commissioning, simplicity in mounting (panel or DIN rail), and communication facilities offered by the Harmonica and Harmonica Plus models mean that they are particularly suitable for OEM machine builders. Although very compact, the drives sacrifice nothing in functionality, offering all the dynamics, precision and functionality of much larger servo drives with a specification that integrates position loop, and both digital current and digital velocity loops, all with auto-tuning adjustment. Conveniently for the user, adjustments to these loops can also be undertaken using Windows-based Composer software, which is part of the automated set-up, start-up and tuning package that supports the amplifier.
Many onboard facilities of the Harmonica Series provide OEMs with the widest range of operating possibilities, including point-to-point positioning, dual-loop operation (which compensates for mechanical backlash), PT1, PVT2, follower and pulse-and-direction modes, and ECAM. ECAM is an operating mode that is well suited to periodic operations, especially in applications such as flying shears, rotating knives and packaging systems, where varying gear ratios are required along the motion cycle.
