Food & Drink Processing & Packaging Issue 36 2021 | Page 26

Controlling the Bake of the Perfect Loaf

Bread . Just thinking of the word pushes your olfactory senses to imagine yeastbased delights at the counter of your favorite bakery . But baking the perfect loaf , and in large enough quantities , demands furnaces that accurately control the process from beginning to end . This was precisely the task faced by Mechatronics Ltd ., a system integrator and official distributor of Delta Motion , Drive , Control , and Robotics products based in Bulgaria .
The requirements for the bread furnace machine defined four temperature zones . The first zone is especially powerful to compensate for the cooled conveyor belt and the relatively cool loaf entering the oven . At this step , steam is also injected into the furnace to give it that freshlybaked sheen . It is followed by three temperature-controllable baking zones that are carefully controlled for baking the optimal loaf . The conveyor belt of this traveling oven design must also be held at the correct speed throughout the process . Rounding off the specifications was a human-machine interface ( HMI ) to configure the baking process , deliver temperature status of each zone , and output any error status information .
For the HMI , the team selected the Advanced HMI DOP-107WV from the DOP-100 Series . This touch-based control panel features a 16:9 7 » color TFT screen with a modern-looking , narrow frame . Its multilingual support meant it was well-suited for the target market , while user-friendly editing software ensured that the final user interface was easy to navigate . With several RS-485 capable COM ports , it integrated perfectly with the other components selected for the furnace . Considering the operating environment , the flat , wipeable surface of the DOP-107WV proved the ideal choice for a dusty bakery . Control for
26 FDPP - www . fdpp . co . uk the conveyor was implemented using an MS300 Series inverter . This AC motor variable frequency drive ( VFD ) also supported the RS-485 Modbus interface and is ideal for open-loop control of IM and PM motors .
Of course , the quality of the bake is ultimately defined by the furnace . Special attention was given to selecting the optimal control approach for the seven heating elements used . After careful deliberation , the DTC1000 Temperature Controller was selected as the main controller , with DTC2000 controllers used in parallel for the remaining six heaters . These are also connected to the Modbus . The selection of established , reliable components , along with the careful programming , were critical in delivering a low-maintenance design that could be operated 24 / 7 .
To provide optimal temperature regulation , the auto-tuning function of the DTC1000 / 2000 was used . The inputs are acquired from third-party PT100 temperature sensors while control of the heating elements is implemented with solid-state relays . Auto-tuning uses a training process to configure the closedloop PID controller once the sensors and heaters are installed in this 250 kW furnace . Further complicating the implementation is the dual heating and sensing of the last three baking zones .
With one heater above the conveyor and the other below , each needs to be set to a different temperature . Spare outputs from the Delta Temperature Controllers were available and linked to relays for audible and visible alarm signals . These signals were also replicated in the DOP- 107WV HMI .
Closely coupled with the quality of the bake is the speed control of the conveyor belt . The MS300 VFD is linked to an inductive proximity sensor that is easy to clean and remains accurate in the dusty baking environment . Installed closed to the gears , the built-in programmable logic controller ( PLC ) of the MS300 is configured to monitor and calculate the conveyor speed . This is continuously compared it to the setpoint defined in the HMI . Thus , the end-customer only needs to set the desired baking time , the required temperature , and then press run to start baking .
The Mechatronics Ltd . team benefited from the broad range of industrial automation solutions in the Delta portfolio . Integration of the VFD , HMI , and Temperature Controller was simplified thanks to the out-of-the-box interoperability and connectivity of the components selected .
Most people would assume that baking bread is very simple . On the contrary , the bread furnace project has highlighted the skill required of both bakers and engineers to create a machine that delivers the perfect loaf . The auto-tuning function of the DTC1000 / 2000 played a large part in ensuring that bakers can deliver a quality product every batch , by providing excellent temperature control ,» said Victor Ogedegbe , Field Application Engineer at Delta .
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