What is a weigh filler user requirement specification?
A weigh filler user requirement specification is a controlled description of what the machine and complete filling route must achieve for the buyer’s products and packs. It should define outcomes, interfaces and acceptance evidence without assuming that one particular weighing technology is already correct.
Include the operating context: manual, semi-automatic or automatic presentation; normal production hours; product refill method; required cleaning access; downstream sealing or container handling; and any site constraints. A supplier can then identify where assumptions still need a product trial or drawing review.
Which product information belongs in the URS?
The URS should identify every materially different product family and describe particle size, shape, fragility, dust, static, moisture sensitivity, stickiness, abrasiveness and loose bulk density where known. A trade name alone is not enough because two batches sold under the same name can feed and settle differently.
State which batch represents normal production and which represents the difficult limit. Include photographs and representative samples when possible. For blends, note whether segregation or fines accumulate during handling, because the product reaching the feeder at the end of a run may differ from the product at the start.
How should target weight and tolerance be written?
Define the smallest, routine and largest target net weights, the pack tare method, and the acceptance rule for each important format. Avoid a single unsupported “accuracy” number. State whether the decision is based on individual limits, average weight, sample standard deviation, giveaway or a combination of these measures.
The URS should distinguish machine display resolution from proven process performance. It should also state the reference scale and test conditions used to judge results. Where packaged-goods law or legal metrology applies, the buyer’s competent quality or metrology adviser should confirm the applicable obligations for the product and market.
How should production output be specified?
Specify output as accepted finished packs over a defined sustained period, including normal product refill, pack presentation, discharge, closure handover and routine operator duties. A theoretical discharge rate can help compare machines, but it does not prove the complete line will achieve the required sellable output.
Record the expected product and pack combination for the output test, because a smaller target weight may not be the fastest if the product flows poorly or the pack is difficult to present. Identify planned breaks, cleaning intervals and downstream constraints that could limit the effective rate.
Which line interfaces should the URS include?
The URS should define the physical and control boundary between the weigh filler and every connected machine. That normally includes product infeed, hopper-level control, discharge height, bag or container support, sealer or VFFS timing, conveyors, checkweigher signals, coding and fault-stop behaviour.
For each interface, identify who supplies the equipment, who owns the final design and what signal or mechanical condition proves readiness. A simple interface schedule prevents gaps such as a filler that can discharge before the pack is present or a conveyor that continues after a downstream reject system has stopped.
What should the URS say about trials and factory acceptance testing?
The URS should define the products, packs and operating states that must be demonstrated, the data to be recorded and the acceptance decisions that follow. It should require consecutive results and normal operating interruptions rather than a selected set of successful fills.
Agree sample quantities, preparation, target weights, hopper-level conditions, changeovers and reporting before the trial. Separate a machine factory acceptance test from site acceptance, because utilities, product feed, operators and downstream equipment may be different after installation.
How should mandatory and preferred requirements be separated?
Mark each requirement as mandatory, preferred or information-only, then give every mandatory item a measurable acceptance method. This prevents a useful machine route being rejected for a preference while ensuring that critical product, safety, quality and line-integration requirements remain visible.
Where the buyer does not yet know the answer, state the decision that must be made and the evidence required. For example, “discharge method to be confirmed by trial using production pouch” is more useful than inventing a chute size before the pack and product have been tested.
