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Volumetric fillers fill any volume without regard to container. They can fill 12 ounces as precisely into a 5 gallon bucket as into a 15 ounce bottle. One style of filler uses scales to fill by weight rather than liquid volume. Some products will change their specific volume during filling. Entrained air may be one cause. If they are filled by volume using a piston filler, this may result in underfills. Filling by weight eliminates this effect.

Scale fillers begin by placing the container on the scale and taring it or zeroing out the scale. This eliminates the effects of weight variation between containers. Taring is fast but does take some milliseconds in the fill cycle. If there is minimal weight variance between containers or high precision is not required a standard tare weight can be programmed and the product filled to a gross weight.

Once the container has been tared, product is introduced to the container. In the simplest system, the container is filled until the target weight is achieved. This triggers a signal to stop the product flow.

This will cause imprecision in the final volume for two reasons:

There will be inflight product. Inflight product is product that has left the filling nozzle but has not yet arrived in the container and has not been weighed. Inflight product should be consistent from cycle to cycle and can be adjusted for. Stopping flow slightly below target will allow the inflight product complete the final volume.

The second issue is fluid dynamics. The product is filled at a high flow rate to minimize filling time. This high flow rate causes turbulence in the bottle during filling and may cause weighing errors. These may not be consistent enough to be compensated for.

Bulk and dribble is the answer. Product is filled at a high “bulk” flow rate until about 98% of the target volume is reached. The flow rate is then reduced to about 10% and the last of the fill is “dribbled” into the container. This dual flow technique allows both his speed and high precision.

Scale fillers can be intermittent motion such as an inline filler or can be continuous rotary motion. Speeds can range from few containers per minute to several hundred. This is just one example of material handling equipment that Frain can help with.