Gravimetric dosing

During this process, the dosing machine continuously measures weight loss. The hopper, or the complete dosing unit, is placed on a weighing cell, and during the dosing process the entire dosing unit, including the products, becomes lighter and lighter.

However, there is no control over the flow of the natural during this process as only the additive or masterbatch is added, and if deviations occur during gravimetric dosing due to screws, cavities or dosing tubes, there is no possibility to compensate. In theory, the accuracy should be higher because of a feedback loop, but in many systems, this feedback loop causes even more deviations because the control constantly adjusts the requirements and creates even more uncertainties. Often the weighing cell in the dosing machine is larger than 15 or 20 kg, making it impossible to measure small quantities.

Economic reasons: the economic reasons are considered average, as the units with loss in weight are more expensive, but do not offer much more.

Logistical reasons: little stock is needed during gravimetric dosing according to the weight loss principle.

Flexibility: There is no batch, which makes for great flexibility.  

Reproducibility: Theoretically, reproducibility should be high as everything is weighed. However, these machines are often not as accurate as of the manufacturer claims, resulting in greater uncertainty about the actual material dosed, making it more difficult to reproduce exactly the same product.

Traceability: In theory, the reasons for traceability should be great. However, our research shows that the most commonly used systems do not do what they say they will. Therefore, we consider this to be average.

The dosing machine weighs the dispensed product. Think of the gravimetric dosing of a product in a bucket that is placed on a weighing platform. This weighing platform weighs the weight increase.

This principle is also often referred to as batch blending. It works quite differently from the other methods because not only the additives and masterbatch are dosed and weighed, but also the natural. Ferlin's batch blenders, such as the FBG NECS, FBG MECS and the FBG FLECS eliminate the pulsating effect because they do not work with screws. Each component is dosed one by one in a weighing pan. When each component has been dosed, they fall into a mixing chamber to create a homogeneous batch.

Economic reasons: the flow of each component is monitored, allowing the dosing machine to anticipate deviations from the first component. The second component is often the natural or milled product which is very easy to dose. In addition, the smart operating options make it possible to optimise the use of the crushed product. Further,
it is possible to measure small quantities by using a separate weighing pan. This results in the option of measuring very small quantities.

Logistical reasons: gravimetric dosing according to the principle of weight increase requires less stock compared to the use of compounds.

Flexibility: The flexibility is average, as these dosing machines prepare a batch.

Reproducibility: Reproducing the same end product with the same settings is very likely when using a gain-in-weight unit. It measures everything that happens in the mix and can adjust component demand based on deviations.

Traceability: Traceability is considered to be high because the dosing machine measures all components one by one. This makes it easy to store all data and to see at a later stage which materials have gone into each batch.