WMH beefs up Yorkshire pudding line
26 Nov 2010
Cornish machine builder Western Mechanical Handling (WMH) UK Ltd has recently developed a new technology for depositing Yorkshire pudding batter into baking moulds for a frozen foods manufacturer.
Previous methods have proved inconsistent and temperamental, causing variation in final weight of the end product and stoppages to production. These were based on standard motors running for a set time.
To overcome the various issues, WMH Automation has developed a servo based system which irons out the inaccuracies of batter pumping whist increasing throughput. Other requirements of the brief included cost effective design and ease of service and support.
Using peristaltic pumps the batter delivery is now accurate to +/- 0.1g. The batter is fed through a flexible tube fitted inside a circular pump casing, in which rollers rotate to squeeze the tube and cause the batter to flow forward.
To achieve the steadiest flow possible WMH has mapped the pump into discrete operational zones where the batter flow rate varies and is using servo technology from Mitsubishi Electric to ensure total accuracy.
The system comprises of a 10-axis J3 servo drive arrangement. Each servo is linked together with Mitsubishi Electric’s high speed SSC net. Nine of the axes are dedicated to the depositors, each driving 32 pump chambers.
The servos are each programmed with a map of known volume to be dispensed and the required number of rotations can be calculated depending on the required product settings.
An anti-drip mechanism was also designed into the system which stops excess product causing cleaning issues later in the production cycle. The servos suck excess batter back into the nozzle at the end of each cycle.
The tenth axis drives the depositor heads carriage which synchronises with the conveyor speed, as detected via an encoder feedback. This helps increase throughput and reduce waste.
All the servo motor functions and controlled by the latest Mitsubishi Q170M motion controller running on a Q series PLC.
WMH control systems engineer Matt Hurley has used function blocks to control multiple applications in the past using the GX IEC Developer software tools. He explains this project:
“Each servo drive has a common function block calculates the required amount of batter to be dispensed, based on the recipe in use, the position of the pump and the type of batter. It also selects the number of dispensing heads to be used. This method of programming has lead to efficiencies of programming time and reduced commissioning time on site.”
The servos configuration also benefits from a dedicated motion design tool, MT Designer, which allowed WMH to parameterise the motion requirements and follow on to programming, monitoring and system test monitoring and maintenance.
Operator control and information is provided by one of the latest HMI products from Mitsubishi a GOT1555. This displays current status, alarms and diagnostics, including recipe management with selection for CIP and Priming modes at just a finger touch for the operator.
