Multi Head Weighing Machine
A ‘typical target’ weight per pack might be 100 of a product. The product is fed to the top of the multihead weigher where it is dispersed to the pool hoppers. Each pool hopper drops the product into a weigh hopper beneath it as soon as the weigh hopper becomes empty.
The weigher’s computer determines the weight of product in each individual weigh hopper and identifies which combination contains the weight closest to the target weight of 100g. The multihead weigher opens all the hoppers of this combination and the product falls, via a discharge chute, into a bagmaker or, alternatively, into a distribution system which places the product, for example, into trays.
Dispersion is normally by gravity, vibration or centrifugal force, while feeding can be driven by vibration, gravity, belts, or screw systems.
An extra layer of hoppers (‘booster hoppers’) can be added to store product which has been weighed in the weigh hoppers but not used in a weighment, thus increasing the number of suitable combinations available to the computer and so increasing speed and accuracy.
Fresh meat and fish, whether in a sauce or not, poultry and cheese (including grated cheese) can be moved along by using belts or screw feeders rather than vibration.
Granules and powders
While free-flowing, fine-grained powders can be weighed more cheaply by other means (such as cut-gate or linear weighers, or volumetric feeders), granules such as coffee granules and products such as loose tea can be weighed on today’s multiheads.
Weighers with more shallow angles of descent and various cushioned inserts have made it possible to pack delicate and brittle items such as hand-made chocolates and gourmet biscuits.
Using mix-weighing combined with a distribution system tailored to deliver separate components into a tray, a ready meal can be assembled with just the right quantities of, say, rice, meat and vegetables in the appropriate compartments.