The dosage process: Differences between gravimetric and volumetric dispensers.

The dosage process distributes raw materials and additives in accurate quantities to get a good mixing with the correct requirements.

There are mainly two types, volumetric dosages and gravimetric dosages. These two types share components like the hopper, feeding throat, stepper motor and the screw feeder; and are used for the same functionality but, what is the difference?

The volumetric dosage: normally supply the volume of material for unit of time, in these types of dispensers the speed of dosage must be set manually and its speed is variable depending each raw material, the required time is different for example between a foaming additive or some specific masterbatch.

The gravimetric dosage: by calculating the weight and according to specific parameters, speed and quantity are set. In these dispensers the weight of the additives is measured with a load cell. One of the factors that differences the most these dispensers than volumetrics is that they have self-calibration function that produce speed change when detects a different material flow. Although these dispensers are more expensive, finally allows a big saving in large in additives.

At SCT-STRAW we have both technologies to be able to use the most suitable one in each situation, from volumetric dosing usually for masterbatch in tubes or PP parts that require colour, to gravimetric dosing used for example in PS mix for packaging or TPV in automotive parts.

                                                                                                                                                                            One of our gravimetric dispensers.