With auger dosings, the often “dusty” product is found in a supply hopper. Under the hopper is a dispensing tube in which the auger filler rotates. The dispensing tube can be closed at the bottom by a valve ball, or a clam shell, etc.
An agitator causes the product to move from the supply hopper to the auger filler. The auger rotates the powder downwards. An amount of product is transported during every revolution of the auger and transfers a certain amount of product with each revolution.
Auger dosings are volumetric dosings, like cup fillers. The volume depends on the speed and the inclination of the auger, or the auger movement. These elements determine how much product fits between the wall of the dispensing tube and the screws of the auger.
By setting how many revolutions the auger makes per dispensing, one can determine how much product volume will end up in each bag. The filling weight of the bag is determined by the speci c gravity of the product. The precision of an auger dosing depends on the degree of filling required from the auger filler and of the consistency of the product volume.
After every time it dispenses, the auger filler stops briefly. In order to prevent product running out of the dispensing tube at that point, the tube is closed with a valve or ball for easy owing products (such as corn starch, for example). For ground coffee, pancake mix and other products that do not flow as easily, a restrictor is used at the bottom of the dispensing tube. That could be a ring or a screen for example.
The combination of dispensing tube, auger ller and closing mechanism is placed in the forming tube of the VFFS machine. The diameter of the dispensing tube is a determinant for the packaging speed. The greater the diameter, the more product that can be transported in one revolution. The diameter is always reduced by the space that any closing mechanism takes, therefore reducing speed.
The operation of a dispensing pump is comparable to that of an auger dosing. The pump carries the desired amount of product with a filling tube to the bottom of the forming tube. This filling tube is closed after each time dispensing not with a valve, but with a filling nozzle that depends on a product. This keeps product from falling out of the filling tube between dispensing. There are different types of pumps, such as hose pumps, displacement pumps and rotation pumps. The selection of pump is determined by the product characteristics.
All consumer packages must have a weight designation that meets the speci cations of the Fair Packaging and Labeling Act (FPLA). In short, this decree states that on average no less than the speci ed weight can be in the packaging, with the average taken of the packages made during a certain period (for example a half hour). Deviations in the specified weight can remain within strict limits.
When using weight, count and especially volumetric dispensing systems (auger fillers, cup fillers), it is recommended to set up a check weigher behind the VFFS machine. This weigher checks each bag and knocks or blows bags that are underweight or overweight off of the conveyor belt.
The check weigher also documents systematic weight changes. For example, the specific gravity of coffee can exhibit differences within one batch. If that is the case, it is possible to pass on to the dosing that the filling volume must be adjusted accordingly (tendency control).