Continuous weighing solids
Loss-in-Weight vs. Gain-in-Weight
Correct weighing of ingredients is essential for reaching the required product quality. If the various raw materials are not dispensed in the correct quantities to begin with, it will never be possible to produce a correct product. Therefore, Sobatech dedicated decades of time and effort in developing the most accurate feeding technologies available.
VOLUMETRIC VS. GRAVIMETRIC
Dry ingredients can be either dosed volumetrically or gravimetrically. A volumetric dosing system doses a given volume of material per time unit. The dosing speed of a volumetric feeder should be selected manually, which may vary based on the nature of the raw material input. A volumetric feeder is open-loop in a sense that it does not corrects to variations in the material’s density. A gravimetric dosing system doses the actual given weight of material per time unit. The weight is measured by using load cells which form the foundation of the entire system. In a self-calibrating gravimetric feeder system, the motor automatically alters its speed when a change is detected in the material flow. When using a gravimetric feeder to dose, you are in complete control of the quality of your final product.
LOSS-IN-WEIGHT VS. GAIN-IN-WEIGHT
Sobatech only works with loss-in-weight dosing systems which are gravimetric feeders ; the most accurate weighing solutions available. The systems ensure an accurate flow of ingredients during both loss-in-weight (normal operation) as well as gain-in-weight (during refilling). The feeders are located on digital load cells that constantly measure the weight reduction per time unit. Based on that information, the speed of the dosing screws is constantly controlled. To optimize dough homogeneity, Sobatech generally separates the major ingredients (e.g. flour) from the minor ingredients (e.g. premix).
OPEN SOURCE SOFTWARE
Sobatech developed its own tailor made open source software to control the feeder-pumps and other hardware involved in the continuous dosing of the ingredients. Put differently, in Sobatech’s continuous mixing systems there are no hidden programs nor protected passwords. The complete system is open and accessible to the customer.
THE WEIGHING BELT
A weighing belt operates by continuously weighing a moving bed of material on a short conveyor belt and controlling that belt speed to result in the desired flow rate at discharge.
Unlike most loss in weight feeding systems whose physical size must typically be increased to accommodate higher flow rates, weight belt feeders can achieve high rates while remaining compact. The system is flexible in regards to the quantities it can dose; it can feed between 20 and 10.000 kg of powder per hour.
Gain in weight (refilling)
There is an open connection between the receiving hopper and the weighing belt system meaning that the challenges of compressibility related to the gain in weight process do not apply to this system.
GRAVIMETRIC WEIGHING HOPPER
The well-known gravimetric dosing hoppers are located on loadcells that constantly measure the weight reduction per time unit.
The gravimetric weighing hoppers are offered in a variety of different sizes and designs. Please contact one of our team members to learn which design fits your process best.
Gain in weight (refilling)
The hopper design shown on the top of this page is called the flat bottom and has significant advantages in relation to the gain in weight process. As the location of the dosing screws is different from the location of refilling – compressibility of powders is, as a result of an increased headload, minimized. This allows for a more accurate dosing during refilling.