Just What You Knead To Save Dough

The Bäcker Schmidt KG bakery company based in Heideck in Middle Franconia, Bavaria, Germany, has been proving for many years that traditional bakery skills and advanced automation technology mix well (in every sense of the words). Master baker Georg Schmidt, who has managed the mediumsized family company since 1972, has always had a weakness for technology—provided it makes work easier and improves productivity and especially, quality.

For example, he has relied for almost 20 years on automation and RFID (radio frequency identification) technology from Siemens in the form of a bakery control system from Borntraeger GmbH, in order to keep a check on the preparation of dough.

The recipe for success: offer variety and bake everything centrally. These help them to deliver the best fresh quality four times a day.

There is intense activity in the bakery seven days a week. On a constantly changing basis and following recipes to the letter, ingredients must be weighed, mixed and kneaded, and after resting for a specified time, the dough must be ready at the correct one of eight processing lines.

This happens between 80 and 120 times a day, with the trend still rising and only one baker being responsible for the entire production of dough. This has been possible with reliable, non-contact identification of mixing vessels—using wireless technology—which improves the variety and quality of bakery products and helps a bakery control system to maintain an overview of all mixtures.

This includes automatically checking recipe data, kneading times, temperatures and resting times of all dough mixtures without any errors. This is all achieved in spite of the difficult wireless operating conditions created by the stainless steel environment.

The entire production of dough used to require three bakers, at a time when production quantities and variety were significantly more limited. However, with the aid of a recipe control system and in connection with RFID technology, this has enabled the baker to make savings of over 60 percent in dough production in recent years.

At various locations in the dough preparation process there are RFID readers with external antennas linked by cable. Two RFID readers are at the floor scale of a central dosing station where small quantities of ingredients are added by hand and ‘monitored’, plus one RFID reader at each of the eight kneading machines.

Mobile data memories, also called transponders or ’tags‘, uniquely identify each mixing vessel and these are attached to every movable mixing vessel trolley. Each tag has a permanently assigned identification (ID) that is read without contact each time a new batch of dough (recipe) is loaded at the dosing station and linked (married) electronically to the mixing vessel.

By simply reading the tag ID, the higher-level control system can then uniquely identify every mixing vessel at each station. When a recipe is complete, the mixing vessel is advanced to a kneading machine whose controller in turn determines the required kneading time and the maximum temperature on the basis of the tag ID, and then starts the process. If the permissible dough temperature is exceeded, the system automatically adds dry ice.

After kneading, the baker returns the mixing vessel to the respective product line, where the forming process can begin once the resting time specific to the dough mixture has elapsed.

According to Mr Schmidt, the crucial advantage of the bakery control system in conjunction with the RFID system is that a single employee can easily manage the entire dough production, without experiencing any stress. The system knows at any time which types of dough are circulating so that these can be prepared and put aside at any time. The call is made via the baking line, on which the mixing vessel arrives at the corresponding kneader, taking into account the dough resting time.

After almost 20 years, the company felt it was time to modernise the tried-and-tested Moby RFID system. Advances in RFID technology now allow the use of passive ultra-high frequency (UHF) tags that require no battery and therefore no maintenance. This means they can be completely encased in plastic, which significantly simplifies the cleaning and maintenance process for the bakery.

The challenges for a UHF system however are seen in the metallic environment, where a reading distance of at least seven centimetres between tags and antennas must be achieved securely and reliably in an environment containing stainless steel and other metal components. On the other hand, the reading distance must not be too great, in order to reliably rule out the possibility of accidentally reading the wrong tag within the range of a reader (or its external antenna).

The Simatic RF600 RFID system from Siemens enabled the company to overcome these difficult ambient conditions with its new RF620A antenna, a small, linear-polarised antenna with special properties for metal environments. Due to its small size, it can be installed neatly beneath the kneading machines and the scales. In conjunction with the reader, it allows the use of UHF in the production environment, something that was previously the preserve of high-maintenance HF systems.

Suitable passive transponders were selected for the demanding conditions in terms of cleanliness and harsh industrial environment. These mobile tags can generally be used on any metal surface.

The compact, battery-free tags (50 mm diameter x 8 mm depth) require no maintenance and can therefore be totally encapsulated in plastic and therefore even better protected against external influences such as dirt, impact or hot water and steam that are encountered during the regular cleaning of the system. Mounted in sturdy stainless steel frames on the chassis of the mixing vessels, they can be read from the required distance without contact or line of sight.

This requires the RFID antennas to be installed on every station. Each is mounted under a cover of stainless steel, likewise reliably protected against mechanical damage (from the heavy mixing vessels moved manually by the baker) and against dirt and moisture. The UHF antennas permit the use of the very precisely defined limits of the radio field in order to prevent accidental reading of data from an incorrect neighbouring mixing vessel and thereby reliably preventing faulty batches.

The passive transponders therefore allow for reliable communication of information to be achieved. A metal environment is generally counterproductive for controlled transmission, so much so that normal tag reading distance is reduced from three metres to a few mere centimetres, but the transponders have allowed for the bakery’s equipment to work securely and reliably since the first trials.

In the bakery, a total of 11 external antennas forward the data to the actual read/write devices, six of which are mounted under the bakery roof. Each reader can consequently process the data from two reading stations, which makes the installation and integration easy, straightforward, and cost effective.

The readers are connected to the main controller via the internal interface and communication modules, which are mounted next to the readers. Connected between them is a data logger. The expansion of the system leaves sufficient freedom in the existing architecture and creates optimum conditions for future expansions of the entire automation system of the bakery.

With the full support of the Siemens technical consulting service, it was possible to integrate the new RFID system while production was in progress in March 2010. The system has been in operation on a daily basis since then, maintaining stability and being free from faults.

“The processes of dough-making have become even more reliable because several sources of potential errors have been eliminated. And more maintenance friendly of course, since the tags no longer have to be checked, cleaned and replaced,” concluded Mr Schmidt.