Servo drives speed fish finger packaging

When Youngs Bluecrest Seafood decided to upgrade a packing line for fish fingers, it opted to "do it itself" using the M'Ax servo system with SLM technology from Control Techniques.

When Youngs Bluecrest Seafood decided to upgrade a packing line for fish fingers, it opted to "do it itself" using the M'Ax servo system with SLM technology from Control Techniques.

The result was the removal of a production bottleneck, a saving of some GBP 180,000 per year and an increase in production.

The line takes frozen fish fingers and packs 50 at a time into five cardboard boxes.

Previously, this had been a hand-picking line, employing some 27 people.

"We looked at the options available to us and realised that we could build a fully automatic machine ourselves for the same cost as buying in a semi-automatic", says Factory Engineer, Stuart Baker.

"But it all hinged on the servo system", he added, "and, after we undertook a technical appraisal, we chose Control Techniques M'Ax with four-wire SLM, because of its flexibility, ease of programming and greatly reduced wiring".

The system comprises a Control Techniques MC216 motion controller, with its capability of 16-axis control, eight M'Ax single-axis servo drives and eight Unimotors with SLM technology.

"To reduce our spares requirement, we standardised on one rating of servo drive and motor", explained Baker.

As a result, at a time when the plant has increased from 12 hours to 20 hours a day operation, just 13 people are needed on this line, allowing the remaining 14 to be redeployed elsewhere in the plant.

This has given a saving of some GBP 180,000 a year and an increase in line capacity.

"This area was previously a bottleneck, with a maximum throughput of 1.2 tonnes per hour", says Baker.

"Now, with half the people, we are working towards a target of 1.7 tonnes an hour on all products".

Frozen fish fingers are fed across a vibrating deck, which collates them into 50 lines of product.

Five packs at a time are indexed into the packing machine, using the registration input to measure the carton distance to the pneumatic stop.

This replaces 14 packers.

As the fish fingers move down the deck, a servo motor provides a finger lifting and separating action from underneath to prevent them sticking.

Servos then provide indexing into a collating plate, which pushes the blocks of fish fingers into the correct width for the box and a vacuum pick and place unit picks up five carton loads at a time and places them in their boxes.

Finally, an acceleration conveyor rapidly clears the boxes ready for the next batch.

"To simplify the mechanical design of the machine, we have used three of the six axes paired (two servomotors on each shaft)", says Baker.

Overall control of the system is from a Control Techniques MC216 modular motion controller, that is expandable to 16-axis control with the addition of daughterboards.

With high-speed multi-axis control (1ms per axis), the MC controller is able to perform tasks such as cam indexing and complex acceleration/deceleration profiles and variants are available to cover every conceivable feedback.

Control Techniques' new M'Ax servo drives are a big step forward in servo technology and have been designed to help the machine builder, cutting setup times and giving exceptional dynamic performance.

M'Ax is the first servo to provide "easy-start", with auto loading of the motor map - virtually plug and go.

M'Ax is also extremely compact, using less cubicle space than most servo drives and, using SLM technology, wiring is drastically reduced too.

Particularly important for complex installations is the fast synch between drives, with performance unaffected by the number of axes involved and the ultrafast acceleration compensation.

In this case, working with M'Ax servo controllers and Unimotors with SLM technology, the package is particularly straightforward to build into a machine because of the simplicity of programming and the reduced number of wiring connections.

SLM technology uses the motor-mounted SinCos encoder and DSP technology which provides very high resolution control.

Cabling costs are cut by two thirds and an error-free signal is ensured through a high-speed dedicated bus system.

The Unimotor range of brushless AC servomotors from Control Techniques gives extraordinary torque per unit volume with industry-leading thermal performance.

The single-piece integral construction, which gives increased torsional stiffness, also permits accurate and consistent bearing to housing alignment and maintains air-gap concentricity.

This arrangement optimises torque output and reduces cogging to less than 1%.

The SL motors feature a module with built-in speed loop electronics and a specially developed encoder interface and is designed to provide highly accurate speed and position control when used in conjunction with the M'Ax range of servo drives.

This speed and position transducer provides a resolution of greater than eight million points per revolution, giving a greatly enhanced performance, with a digital link unaffected by noise.

Further, with intelligence centred on the motor, the update loop response is cut to just 125us and a staggering axis to axis synchronisation of 50ns.

The reduction in cabling with the SL Unimotor coupled with M'ax servo drive also gives major customer savings.

Not only does the package cost less than that of equivalent servos, but the installation time is reduced.

With half as many cables to connect, the chance of error is less and the ongoing costs of maintenance are reduced by improved reliability.

The final deciding factor for many users is the "plug-and-play" connectivity, with an ASIC on the motor sending set-up data to the drive on initial switch-on.

Even an inexperienced engineer can complete commissioning in around one minute.

"SLM was a key factor in our choice of the Control Techniques system", says Baker, "and we have found it greatly simplified not only the build and installation, but also, with its extensive diagnostics, has reduced maintenance time too.

We evaluated several systems and it was gratifying that the best was also British.

We went on a two-day training course and that was all we needed, although we do get excellent support from the Telford Drive Centre and they were particularly helpful during the development phase.

The system really is easy to use - we can even adjust gains whilst the machine is operating - we're all very impressed".

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