Packaging
An end to downtimes
Tuesday 06. May 2008 - Condition monitoring in packaging applications
Unexpected machine downtimes due to unforeseeable failures are now a thing of the past. Condition monitoring and diagnostic systems monitor critical components as well as process states online and provide a timely warning of any deviations from a reference value. With sensors and electrical terminals for valve terminals from Festo for component and system diagnostics, OEMs and system operators can concentrate on their core business.
More and more packaging machine builders are recognising how important it is not only to look at low acquisition costs, but also to focus on the overall costs of a system throughout its service life. The reason for this is that acquisition costs are often one of the smaller cost factors over a systems life cycle. The magic words are total cost of ownership and life cycle management.
Expensive to maintain and service
A study by Rockwell Automation reveals some astounding figures: maintenance accounts for between 15 and 40 % of the indirect costs of a manufacturing plant. Around half of these costs could be avoided if strategically-oriented diagnostic and conditioning monitoring systems are used.
According to this study, repairs represent the largest item within indirect costs with 70 % of the expenditure; as unplanned follow-up costs they actually amount up to 10 to 28 % of the total life cycle costs of a system. And, according to a report in a financial paper, these follow-up costs should be multiplied by a factor of 4 or 5. Why? Because machine downtimes can also result in quality defects or the inability to deliver and can even damage a companys image. High commissioning costs when changing products and batches are further factors that can be reduced by monitoring and storing process and quality-related parameters.
Unplanned machine stoppages
can upset the high demands for short cycle times and productivity in the packaging industry. Thats why the VPP 250 bag forming and packaging machine from Wolf Verpackungsmaschinen GmbH, with a cycle rate of 100 bags per minute, is equipped with a diagnostic system from Festo. This provides continuous monitoring of the pneumatic components and direct monitoring of process-related parameters. The flow rate sensor MS6-SFE and the pressure sensor SDE1 – both from Festo – monitor deviations from a reference value for compressed air. The measured data and the available valve control and proximity switch signals are read into the electrical terminal CPX from Festo and processed in the controller module FEC.
Process parameters such as foil-dependent contact pressure and belt wear are monitored by means of position measurement of the pneumatic feed cylinders using the analogue sensor SMAT. The cooling air flow rate and pressure are also monitored as process and foil-related variables to avoid unnecessary use of compressed air. With transverse sealing, wear and tear to the blade is monitored via the positioning time of the cylinders; with longitudinal sealing, premature wear is monitored via the travel time of the cylinders. Stroke counters on the cylinders and switching cycle counters on the valves provide information on the service life and recommended replacement time. The electrical peripherals of the CPX monitor events such as short circuit, wire breakage, overvoltage and valve blockages.
Global access and integration into existing customer systems
Diagnostic characteristic values for detecting leaks and positioning times include, for example, air consumption and operating pressure. Malfunctions and the location of faults are detected via diagnostics. Functions such as counted valve switching cycles and executed cylinder strokes assist in preventative maintenance. The results are displayed on the touch panel FED from Festo. They are also made available to the machine controller via fieldbus.
This means the diagnostic solution is easy to integrate into an existing control concept and also that all diagnostic data can be accessed globally. Thus service staff of machine manufacturers, maintenance personnel of machine operators and external service providers can increase system availability and optimise maintenance processes.