Front and back labelling guide
Plan front and back label reel changes, run-out response, splice handling, incomplete-pack control and restart checks before specifying a labelling line.
Application guidance
Front and back rolls do not always finish together. Plan the material event and the affected containers as one recovery task.
When a front or back label supply is exhausted, a twin-side labelling line needs a defined response that prevents incomplete packs being released as finished production. That may be a controlled stop or an engineered inspection-and-reject sequence. Specify which packs remain between the heads, how they are identified and how the first complete packs after restart will be approved.
A low-reel warning, a missing-label detector and a splice detector are different functions. A warning gives time to prepare a roll; label detection controls dispensing; splice handling deals with a join in the liner. None should be assumed to be included merely because a machine has two label heads.
The workflow below is a specification and acceptance checklist. Operators must use the machine’s approved procedure; it is not permission to join moving webs, reach past guards or alter safety controls.
Application guidance
Ask for the behaviour required by the process, then confirm which sensors, controls and operating steps provide it.
| Low roll or roll end | Define the alarm, remaining-material warning method where fitted, stopping point and responsibility for replacing the correct roll. |
|---|---|
| Missing label on intact liner | Establish how the applicator responds to a gap without a label and how the resulting container is inspected or contained. |
| Supplier splice | Ask the converter to define permitted joins, their identification and whether labels around the join are usable. Agree detection, removal or handling before production. |
| Liner break or loss of tracking | Stop and recover under the approved procedure. Inspect threading, web path and the affected packs before returning to automatic operation. |
Application guidance
Define recovery before the trial, not after an unlabelled or doubly labelled pack appears.
A stop can leave a container after front-label application but before the rear label. Another pack may be waiting at the first trigger. Restarting both heads does not by itself identify which label each pack still needs. Document the product positions, whether tracking survives the stop and how ambiguous packs are segregated for inspection.
The vision inspection and reject guide explains the separate finished-pack decision. The FAT and SAT checklist provides the wider acceptance context.
Application guidance
Splices, roll changes and missing labels must each have an agreed production outcome.
A splice joins two lengths of label liner. Its thickness, alignment, tape position and nearby missing labels can change how that section travels through the label path. Agree the permitted splice construction and a clearly identified test piece with the converter and equipment supplier; do not introduce an improvised join simply to test the machine.
Automatic label splicing is a separate engineered capability. NJM’s automatic-splicing system illustrates that it requires dedicated equipment and controls. It is not a standard capability claimed for the Lancing machines on this website. Compare its cost and integration requirements only when reel-change downtime is a demonstrated constraint.
| Before the join | Establish a normal label feed and identify the test event. Record the label roll, liner and approved splice method. |
|---|---|
| At the detector | Confirm whether the join is detected deliberately, ignored safely or causes a controlled stop. A gap-sensor signal alone is not an acceptance result. |
| At the peel and drive | Observe the approved test under guarded conditions for web tracking, clean label release and safe response to a fault. |
| At the finished pack | Verify both labels, artwork identity, position and rejection of incomplete or uncertain packs. |
| After recovery | Repeat the normal output and first-off checks. Record any setup changes so the result can be reproduced with the next roll. |
Buyer questions
Not necessarily. Replacing both may simplify scheduling but can waste usable labels; changing one requires reliable pairing and restart control. Compare measured downtime, remaining material, job length and artwork-change risk. The decision should use the actual front/back roll quantities and production sequence.
A larger reel may reduce change frequency, but it must remain within the applicator’s approved diameter, core, weight, clearance and unwind capability. Do not assume that a reel fits safely because its web width is correct. Confirm the full material specification before changing reel size.
No. A gap sensor identifies a physical label or gap, not whether the printed design belongs to the selected job. Artwork or code checking needs a separate material-verification process or an appropriate inspection system, with the accepted reference tied to the production order.
Measure from the last accepted pack before the planned stop to the first accepted pack after recovery. Record waiting, safe access, threading, checking and rejected packs separately. Include the event in sustained-output calculations rather than quoting only the uninterrupted running speed.
Stop and follow the machine’s documented safe recovery procedure. Do not pull material from moving rollers or defeat an interlock. After recovery, account for the affected containers and approve both label positions before restarting normal production; the equipment-specific instructions determine the safe access method.
Project scope
Send the label counts and usable quantities for each reel, normal batch length, known converter splice policy, existing alarm and inspection functions, and the stop/restart behaviour of connected machinery. Identify who approves artwork pairing and releases first-off packs. The aim is a quoted recovery process, not an unspecified promise of uninterrupted operation.
Use the ROI and payback guide to compare measured downtime costs, and the booklet-label application guide where one head handles a layered label with different roll capacity or feed behaviour.
The references explain label construction, sensing or equipment principles. The selection steps here are application-planning guidance, not a recorded Lancing trial or confirmation of a fitted option.
Include the container, both label constructions, target output and any existing line constraints.