When having to commercialize their products in powder or granulate form, industrial companies often adopt a small packaging format that will allow them to sell to individual customers in supermarkets or e-commerce for example. Food manufacturers (coffee powder, spices, cereals...), pharma, or chemical companies (detergents...) typically chose to pack their products in sachets (few dozens gram) or pouch (few hundred grams to few kg). The operation of packing the material is actually very sensitive as it must be done very quickly, while being accurate (do not underdose which would not be compliant from a regulatory point of view, nor overdose which would represent a loss for the manufacturer) and not damaging the product.
This page is focusing on the most common technologies that can be proposed by filling packing manufacturers for filling powders in packaging designed for retail business. The filling of bulk product, in 25 kg bags or in bigger supersacks is not discussed here.
One of the most widespread type of filling machine is probably the Auger filling machine. With this type of filler, the powder is dosed towards the pack (sachet, pouch, sometimes stick) with an Auger (an archimedes screw). One part of the Auger is within a hopper containing the powder to dose and one part of the Auger is within a tube (filling tube) in order to be able to make the dosing.
Such a filling machine is volumetric which means that the dosing is done only on the number of rotation of the Auger which then delivers a volume, corresponding to a weight (what interests the customer) thanks to the material bulk density.
The hopper can have different shapes, typically a cone shaped hopper when there is only one Auger (1 filling head) for pouch filling machine or very small sachet machines, to a wedge shape hopper when there are several Auger (several filling heads).
The rotation of the Auger is bringing material to the filling tube, which allows a dosing to the packaging positioned just below (there is a complete mechanism to form the pack from reels of laminate). The filling is sequential, not continuous. The machine is bringing a new pack in position (more exactly, it is forming it), then the Auger runs to dose the product, that falls in the open packaging, then the packaging is closed and moved away. The cycle can then restart.
In order to have a volumetric dosing as precise as possible, and make sure that the dosing of product stops sharply, the Auger fits very tightly in the filling tube. This may be a source of concern if the Auger is not manipulated properly, especially during cleaning and maintenance as the very narrow gap in between the screw and the tube means that it can lead to metal metal contact if the Auger is little bit bent for example.
The basic design for a cup filler is to have a hopper whose bottom is equipped with rotating plate having small cups. When rotating, the cup is filled with product when passing below the material hopper, then the tube is blinded and then emptied towards the open packaging.
The volume of the cup is adjustable in order to fit the requirement for the filling volume and then weight. It must be noted that the system, compared to Auger filling, is rather passive, the powder has to flow by itself in and out of the cup. It means that this kind of dosing is particularly well adapted to very free flowing products but will lose some accuracy if the product is cohesive, do not flow well in the cup, or on the contrary get compacted in the cup and do not empty well towards the packaging.
On the other hand, the filling process is here very gentle and particularly adapted when there are pieces that should not be broken (which would be the case for a screw conveyor).