Establish availability
Confirm that the weigher has the correct recipe, sufficient product, no active fault and an available completed or buildable dose according to the selected control philosophy.
Direct answer
A multihead weigher interface should define machine states, signal ownership, timing, fault recovery and the boundary between production control and safety.
The minimum interface normally identifies when the weigher is available, when a downstream machine requests a dose, when the dose is complete and what happens during faults or stops. The exact signals, protocol and data available depend on the selected equipment. Safety functions must be engineered and validated separately from ordinary production-data signals.
| Interface item | Purpose | Question to settle |
|---|---|---|
| Weigher ready | Indicates that the system is able to participate in the production cycle | Which conditions remove ready, and does the downstream machine stop or wait? |
| Dose request / packer ready | Tells the weigher when the receiving pack or machine is prepared for discharge | Is the request edge-triggered, held, queued or cancelled after a timeout? |
| Dose complete | Confirms that the selected dose has been released according to the agreed sequence | What proves completion, and when may the packer move to the next state? |
| Product low / feed demand | Coordinates the upstream feed system with the weigher product level | Who controls the elevator or conveyor and how is overfill prevented? |
| Fault / inhibit | Stops or pauses the sequence when the weigher cannot complete the requested action | Which faults require operator reset, recipe reload or controlled emptying? |
| Recipe and product identity | Aligns settings across weigher, packer, coder and inspection equipment | Which machine owns the master recipe and how are mismatches prevented? |
| Production data | Provides counts, weights, alarms, run state or other supported information | Which data are required, at what frequency and how will they be stored or used? |
| Safety circuit | Protects people through the validated safety architecture | Which equipment is inside the safety boundary and who is responsible for validation? |
State sequence
Write the normal cycle and the abnormal cycle before the PLC code is finalised.
Request the dose
The downstream machine confirms that the bag, pouch, jar, tray or other receiving position is ready and that a discharge will not contaminate the seal zone or miss the pack.
Release and acknowledge
The weigher discharges through the agreed chute or timing hopper. Dose-complete logic confirms the sequence rather than assuming a timed delay always represents a completed transfer.
Advance the packer
The downstream machine closes, seals or indexes only after the agreed completion condition. The weigher begins rebuilding portions for the next cycle.
Recover from stops safely
Define what happens to product in hoppers, chutes and open packs after an emergency stop, guard opening, power loss, packer fault or aborted request. Restart must not create a duplicate or missing dose.
FAT and SAT
Test the interface with normal cycles, waits, faults and restart conditions.
Normal-cycle test
Run representative product and pack formats through repeated cycles. Record ready/request/complete timing, product transfer and any waiting state that limits output.
Fault-recovery test
Simulate agreed faults and aborted cycles. Confirm the equipment enters a safe, understandable state and cannot release an unintended dose on reset.
Recipe-control test
Confirm how the line handles the wrong product, target, bag length, coder data or inspection recipe. The master/slave relationship should be documented.
Product-feed test
Check low-level demand, upstream refill, overfill prevention and the effect of feed interruptions on hopper population and pack output.
Data and counters test
Verify only the supported data points required by the project, including units, reset behaviour, timestamps and treatment of rejected or aborted cycles.
Site acceptance test
Repeat the critical sequence with the installed feed, utilities, support frame, packer, guarding and site controls. Factory evidence does not replace the installed-line check.
Controls questions
Questions integrators should settle before commissioning.
Should the interface use hard-wired signals or a network?
Use the interface supported by the selected machines and the project's reliability, diagnostic and data requirements. A network may provide more information, but it also needs agreed ownership, mapping, version control and fault behaviour.
Which machine should own the recipe?
There is no universal answer. The project should identify one master source or a controlled synchronisation method so the weigher target, bag or pouch format, coder and inspection settings cannot drift apart.
Who controls the timing hopper?
Control ownership depends on the mechanical design and selected equipment. Define whether the weigher, packer or line PLC commands the hopper, and what feedback confirms that product has transferred.
What must happen after an emergency stop?
The validated safety design determines safe stopping. The production sequence must also identify product already weighed, product in the transfer path and the pack state so restart cannot create an extra, missing or contaminated pack.
Should remote access be included?
Only if the selected equipment supports it and the site's cybersecurity and access-control requirements are defined. Remote support scope, approval, logging and responsibility should be agreed before commissioning.
What controls information is needed for a quotation?
Provide the line sequence, existing PLC/HMI platform, I/O or protocol requirements, safety boundary, recipe ownership, data points, network policy, remote-access policy and FAT/SAT expectations.
Controls review
Define the sequence before the equipment is ordered.
Send the current line layout, machine list, I/O expectations and restart philosophy.
Discuss the controls interfaceRelated guidance