What is the practical difference between volumetric and gravimetric filling?
A volumetric system repeats a measured volume, displacement or calibrated flow; a gravimetric system measures the mass delivered to the container or receiving vessel. Volumetric control follows the dosing device, while gravimetric control follows the weighing signal and must account for tare, settling and material still in flight.
The terms describe the control basis, not one universal machine design. Piston, pump, cup, flow-meter and weighing systems each introduce different product-contact, cleaning, cut-off and line-handling requirements.
How does density variation affect the decision?
Density matters when a volume target is expected to deliver a consistent mass. If density changes with formulation, aeration, temperature or batch condition, the same volume can represent a different weight. A weight-controlled process measures mass directly, but the weighing result can still be affected by vibration, tare variation, drips, product in flight and unstable containers.
Record density under production conditions rather than relying on a nominal laboratory value. If the declared quantity is by volume, also define how volume is established and checked; if it is by mass, define tare and check-weighing responsibilities.
Is weight filling the same as checkweighing after filling?
No. Weight filling uses a weighing signal to control or end the dose. Checkweighing measures a completed pack after filling and normally accepts, rejects or records the result. A project may use one or both functions, but the control loop, timing, accuracy evidence and legal quantity-control responsibilities are different.
State whether the weighing device controls the filler, verifies the pack, provides feedback to a separate filler or only collects process data. Do not assume that an end-of-line checkweigher corrects a poor filling process.
Which method is more suitable for high-value or variable products?
The suitable method is the one that controls the quantity that matters to the product and commercial requirement with acceptable waste, cycle time and maintenance. Weight control can be useful where mass is the primary target or density varies; volumetric control can be effective where the product and dosing displacement are stable and the required quantity is volume-based.
High value alone does not decide the method. Include start-up loss, line clearance, overfill strategy, nozzle cut-off, residual product, cleaning loss and the cost of holding or rejecting non-conforming packs.
How do container tare and line vibration affect gravimetric filling?
Gravimetric filling depends on a stable tare and a reliable weight signal. Container-weight variation, conveyor vibration, product movement, draughts, contact with guides and material still travelling after the shut-off command can all change the result. The mechanical handling and weighing sequence therefore form part of the dosing specification.
Test the lightest and heaviest containers, known supplier variation and all fill ranges. Define how tare is established, whether each pack is tared individually, and what happens if a container is missing, unstable or outside the expected tare window.
What should a comparison trial prove?
A comparison trial should prove repeatability with the real product and container across the intended range, normal starts and stops, product refill conditions, temperature or density variation, changeover, cleaning and the agreed measurement method. Results should identify the control basis, sample method and any excluded conditions.
Provide enough product for stabilisation and representative running, not only a handful of doses. Agree whether the test evaluates net weight, gross weight, volume, average quantity, minimum quantity or another customer-defined criterion.
Discuss the application with Lancing.
Send the product, density information, target quantity, container tare range, required output and acceptance method so both control routes can be reviewed.
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