Gloss and colour, print mark and reflex sensors for coffee pad filling

The Optima Group is an internationally active, mid-sized family company headquartered in Schwäbisch Hall, Germany. It offers industry oriented packaging and filling machines for the foods, pharmaceuticals, chemicals, air and water filters, cosmetics and non-wovens sectors.

The systems dose and package liquid and dry foodstuffs (from low viscosity to paste-like, powders and granulates and chunky and flaky products) and fill them into containers.

All of the systems have wenglor sensors installed to ensure smooth operations. Design engineer Waldemar Salwasser, was convinced by the user-friendliness and functionality of the sensors when developing the coffee pad filling system. “When we decided to use gloss sensors several years ago, wenglor was the only manufacturer who offered them,” said Salwasser. The wenglor Color Sensor had a number of competitors, but it’s distinguished by a compact format.

Optima’s systems are comprised of modules and are matched to individual customer requirements. The little round plastic cups, which are later filled with coffee or tea powder, are set into cavities via a magazine in the CFL2 machine. Filters are then added if required. The next module doses the coffee or other foodstuff into the cups via a funnel. The tricky part, for sales engineer Matthias Roski, involved regulating the quantity of coffee in the funnel with a wenglor sensor to ensure that there’s always enough powder in the filling funnel.

“Thanks to the CMOS line array in the CP35 Reflex Sensor for Measuring Tasks, I found a solution for the application,” he explained.

The Reflex Sensor measures the fill-level and regulates it autonomously. It functions in accordance with the principal of angular measurement. For this reason, the object’s colour, shape and surface characteristics have practically no influence on measurement results. The output signal of the Reflex Sensor with CMOS line array technology is practically independent of brightness, colour and surface characteristics of the object to be measured.

The measured value can be read out as a voltage value within a range of 0-10 V, as a current value within a range of 4-20 mA, or in digital format via the RS232 interface. A rising or falling characteristic curve can be selected. High speed, speed mode or the high resolution mode can be selected as required. Teach-in, filter functions, an error output and an RS-232 port are included. The measuring range can be selected individually within the sensor’s working range.

When the product is filled into the cups, aroma can be added via the liquid dosing unit, if desired. The cups are then advanced to the foil unrolling module, where they’re sealed with a glossy foil. The wenglor Print Mark Sensor detects the position of the foil and reads out a signal as soon as the foil is located at the right position for stamping and application to the cups so that the round lids sit firmly on the cups. The sensors have been specially designed to recognise printed markings. They have a very small spot and use a white light LED with a long service life. Only one sensor is required for the recognition of all colour combinations, as well as differences in brightness between printed markings and the background.

The foil which comes from the unrolling module is one single piece, but it may be comprised of several individual foils which are joined by a blank foil. This unprinted joining foil is either red, green or white. These colours are taught in in advance and detected by the wenglor Color Sensor, which prevents the joining foil from being stamped onto the cups by generating a switching signal. The colour combinations can be individually defined, and the type of white light source can be selected as required.

wenglor Gloss Sensors then check to make sure that each cup has a foil lid before it leaves the system. Gloss Sensors are capable of differentiating between surfaces with glossy and matte finishes. Due to the fact that the foil lids are glossy, this type of sensor is ideally suited for the application. The degree of gloss is adjustable and is nearly independent of distance.

The coffee pads are then automatically weighed. If they fulfil all of the specified criteria they leave the machine, otherwise they’re sorted out. 400 pads are produced per minute in this way.