Sauce filling machine accuracy is harder to hold than most liquid fills suggest. Sauces and dressings change viscosity with temperature, with each batch and with particulate content, and every change alters how much product a filling head delivers. Lines manage this by setting the target above declared quantity and adjusting heads by hand, which means overfill on most packs and frequent intervention by operators.
How overfill builds up on a liquid line
The typical pattern on a multi-head sauce filler is:
- Fill weights that differ between heads, so the target is set to keep the lightest head above declared quantity
- Weights that drift as product temperature changes between the start of a batch and the end
- A step change in fill weight at each new batch or after a hold in the balance tank
- Operators adjusting heads after periodic check-weighs, with adjustments that vary between shifts
Because the target is set by the lightest-filling head, every other head overfills. On a line filling tens of thousands of bottles a day, a few grams per bottle becomes a significant volume of product.
Why liquid fill weights drift
Most sauce fillers are volumetric. A piston filler draws a set volume and dispenses it; a flowmeter filler opens a valve until a set volume has passed. Declared quantity is by weight or by volume at a reference temperature, so any change in density or in how completely the product is drawn and dispensed changes the result.
Viscosity is the main driver. Thicker product fills piston cylinders less completely at speed and clings to nozzles and valves. Temperature affects both viscosity and density. Particulates add random variation. Wear in piston seals and valves adds slow drift that differs from head to head.
Improving sauce filling machine accuracy
Closed-loop control uses the checkweigher downstream of the filler as the measurement and the filler’s head adjustments as the control. Each container’s weight is matched to the head that filled it, and each head is corrected individually.
How it works
- 1
Track
The controller follows each container from the filler to the checkweigher, so every weight is tied to the head that filled it.
- 2
Average
A rolling average is kept for each head, filtering out the random variation caused by particulates and splashing.
- 3
Trim
When a head average moves away from target, its piston stroke or flowmeter setpoint is adjusted by a small, limited amount.
- 4
Alarm
A head that needs repeated correction is flagged, pointing maintenance to a worn seal or valve before it affects compliance.
With every head held close to the same average, the target can be set for the line rather than for its worst head. Packaged goods sold by measure are regulated under the Average Quantity System, administered by the National Measurement Institute: the average of a sample must not be less than the declared quantity. Holding averages stable is therefore both a cost and a compliance measure.
The value of reducing overfill
The benefit depends on line speed, current overfill and product value.
Overfill cost calculator
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- Overfill per year
- 28,800 kg
- Cost of overfill per year
- $172,800
Other approaches
- More frequent manual checks. Reduces drift but adds labour, and adjustments still vary by operator.
- Temperature control of the product. Worthwhile where batch temperatures vary widely, and complementary to fill-weight control, but it does not address head-to-head variation.
- A new filler with integrated weighing. Appropriate at the end of a filler’s life. Where the filler is sound, feedback control achieves much of the benefit for a fraction of the cost.
- A large systems integrator. Suited to new lines. For a single filler and checkweigher, the overheads are rarely justified.