Product category:
Position, speed and torque measurement
News Release from: Festo | Subject: Festo DNC cylinder
Edited by the Processingtalk Editorial
Team on 21 April 2005
Festo servo-pneumatic drives "the
obvious choice"
Festo cylinders provide variable stroke and positioning rates to accommodate a wide range of product dispense requirements, in particular on the Optifill self-clean depositor from Burntwood Unitech
Burntwood Unitech Filling Systems has chosen to base its latest-generation filling machine on servo-pneumatic technology from Festo Accurate velocity and position control capabilities make the technology ideal for product dispensing applications
This article was originally published on Processingtalk on 3 Feb 2004 at 8.00am (UK)
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In this case, the filling machine accommodates an exceptionally wide range of product parameters and deposition rates, making it suitable for diverse applications in the food processing, pharmaceutical and cosmetics manufacturing industries.
Unitech Filling Systems specialises in equipment for processing liquids, pastes, semi-solids and particulates.
The company has grown rapidly in recent years, doubling both sales revenue and size since moving to new premises in Burntwood, Staffordshire, in 2002.
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After acquiring the Optima line of depositors and filling systems a couple of years ago - which it re-branded 'Optifill' - Unitech has expanded its product offering significantly, and now manufactures a wide range of single and multi-lane depositors, hopper systems and tanks, depositing nozzles and decorating heads.
A key feature of all Optifill products is that they are specifically designed for operator friendliness, which necessarily involves automating as much of the process as practicable, and for minimum component count to help keep manufacturing and maintenance costs as low as possible.
The latest addition to the range is a mobile depositor, intended to maximise production flexibility by combining highly versatile dispense capabilities with built-in self-cleaning facilities.
Housed in a compact, small footprint package, the depositor is intended as a general-purpose filling solution, and is available in high and low level configurations to simplify integration with conveying systems and other processing equipment.
According to Dennis Wood, Group Design Manager for Unitech, "Festo servo-pneumatic drives were an obvious choice for our new Optifill self-clean depositor.
The technology is now sufficiently mature to be used with confidence, and costs significantly less than electrical drives and servos.
It is also much easier to physically accommodate, making it ideal for small footprint volumetric dispensing applications such as this.
And because we already have extensive experience of pneumatic drives, the transition to closed-loop control techniques didn't pose too much of a design challenge." The piston in the product dispense cylinder of the Optifill self-clean depositor is driven by a standard 80mm diameter Festo DNC cylinder, fitted with a custom displacement encoder to provide position feedback to a Festo SPC200 smart positioning controller.
The pneumatic feeds for this cylinder are routed via directional proportional valves controlled by the SPC200, which executes previously-stored motion control sequences in response to commands from the system host PLC; communications between the PLC and the SPC200 are handled via an industry-standard fieldbus network.
At the end of a filling cycle, the piston in the main product dispenser is automatically returned to its start position, ready for the next production batch.
A key feature of the Optifill self-clean depositor is that, aside from removal of the hopper and dispense nozzle, it does not need dismantling for cleaning, which facilitates fast and easy product changeover.
All machine control functions, such as dispense rates and volumes, are controlled via an HMI linked to the PLC.
The HMI menu structures are easy to understand, enabling even relatively unskilled people to operate the system, and the PLC can also be networked to a third party controller for customers who wish to download fill settings such as speed, weight, etc, from a remote system.
The ability to accurately control the position and speed of the DNC cylinder driving the dispense piston enables the Optifill self-clean depositor to accommodate fill volumes from as low as 6cc to as much as 660cc, making it suitable for an exceptionally wide range of products.
In the cosmetics industry, for example, the depositor can handle anything from low viscosity face cream through to much denser substances.
The machine is equally versatile in the food processing sector, where it can be used for dispensing a wide variety of products, including batters, sauces and mashed potato.
Deposition rates depend upon product type and volume, but as a typical example, the machine is capable of depositing 500g portions of mashed potato at a rate of 30 per minute; for smaller volumes or more fluid products, the deposition rate can be as high as 40 portions per minute.
Even 'problem' products such as highly aerated decorative cream - which is easily compressible and hence difficult to dispense accurately - can be accommodated easily, because the machine's use of servo technology allows the deposit rate to be varied during the deposition cycle.
This is a key advantage, as Dennis Wood points out, "we recently had an application that involved feeding measured quantities of decorative cream to a 3-axis servo system for placing the zig-zag ornamentation on 'banana boats'.
The ability to dynamically switch the travel profiles of the DNC cylinder driving the main product dispense piston enabled us to achieve highly accurate and repeatable results, much to our customer's satisfaction." The PLC software features a built-in fail-safe procedure to prevent operation if a cleaning cycle has not been carried out since the machine was last used, to help customers maintain full HACCP (Hazard Analysis Critical Control Point) compliance.
The machine's built-in self-clean capabilities make this a very simple procedure.
Unitech has developed a unique combined rotary sleeve valve and product cylinder - driven via a rack and pinion system by a DNC cylinder - which reduces the number of wash cycles to a minimum.
The valve block, rotary valve, product cylinder and piston can all be cleaned in-situ, using a three-stage cycle comprising a cold water flush, sanitiser wash-through and final hot water rinse.
Depending upon the type of product, a complete wash cycle typically takes just 10 to 15 minutes.
The system automatically maintains date and time-stamped records of cleaning cycles, together with other pertinent data such as throughput, for customers who wish to maintain an audit trail for quality control purposes.
Optifill self-clean depositors are already generating considerable interest in the industry, and Unitech is now in the process of ramping up production. Request a free brochure from Festo ...
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