In 60 seconds
- When a roll will not run, the printing is rarely the problem — the reel specification is. Five things have to match: unwind direction, core diameter, maximum outside diameter (and roll weight), gap and sensing method, and liner width.
- "Normal wind" is not a specification. Unwind direction is two independent choices multiplied: face out or face in, and which edge leads (top, bottom, right, left) — eight standard positions. Most applicators accept exactly one of them.
- The gap is not just white space, it is the sensor signal. 3 mm is the common default; printer specifications usually say 2–4 mm. Too small and the sensor cannot separate label from liner at line speed; too large and you waste liner and shorten every roll.
- Eye marks (black marks) are only needed when the liner cannot be read through: clear or dark faces, metallised stock, continuous media, irregular die-cuts. They have hard numbers: 2.5–11.5 mm long, at least 9.5 mm wide, density above 1.0 ODU, printed on the back of the liner in a fixed lateral position.
- The fastest way to order: send the applicator model, core I.D., maximum O.D., maximum roll weight, a photo of the unwind path and the sensing method in one message. We answer with a roll specification sheet you can check against the machine.
1. Why a technically correct label still fails on the line
A converter ships a reel of material; an applicator consumes a set of geometry. Five mismatches account for most failures:
- Wrong unwind direction — the label leaves the roll on the wrong edge, so the peel plate cannot release the leading edge, or the print arrives upside down.
- Core off by 1–2 mm — the roll will not seat on the mandrel, or seats loosely and wobbles, which destabilises tension.
- Outside diameter too large — the reel does not fit the unwind magazine at all and has to be rewound before use. This is the classic "arrived, but unusable".
- Roll too heavy — the shaft and tension control cannot hold it; the reel creeps down and the registration drifts.
- Sensing mismatch — gap too narrow, liner too transparent, or a black mark that should have been printed and was not.
All five can be settled with one page of questions before quoting. The cost of asking is zero; the cost of discovering it at the dock is a re-run plus air freight.
2. Unwind direction: eight positions, and one photo
Two independent parameters: face out (print on the outside of the roll) or face in, multiplied by which edge leaves the roll first — top, bottom, right or left. Four times two gives the eight standard positions (position 1–8).
| Position | Facing | Leading edge | Typically used on |
|---|---|---|---|
| 1 | Face out | Top | Many desktop thermal printers, hand dispensers |
| 2 | Face out | Bottom | Label heads with the peel plate above the web |
| 3 | Face out | Right | The most common default on automatic applicators |
| 4 | Face out | Left | Mirrored infeed, or products that must sit to the left |
| 5–8 | Face in | Top / bottom / right / left | Machines whose peel plate or print head approaches from the other side |
- Face out is the default, but do not assume it. Face in exists precisely because some machines run the liner side as the web path.
- The communication that never fails: one photo — a label already lifted on the peel plate with a corner still attached to the liner, taken so the machine direction and the printed face are both visible — plus make and model. "Normal wind" tells a converter nothing.
- Front and back labels may differ. Lines that apply both often need one roll face out and the other face in; specify them separately.
- Keep direction and dimensions apart. "3-inch core, face out, right edge leading" is a complete sentence. "3-inch normal roll" is not.
3. Reel geometry: core, outside diameter, weight, liner width
| Item | Typical values | Why the machine cares |
|---|---|---|
| Core I.D. | 25 mm (1") / 40 mm / 50 mm / 76 mm (3") | Industrial applicators and printer rewinders are usually 76 mm; desktop thermal printers 25 or 40 mm. Some machines accept a 76/100 mm adapter. |
| Maximum O.D. | About Ø107–127 mm on desktop units; Ø205 / 300 / 305 / 356 mm on applicators | A physical limit of the magazine. Example: Shibuya L410A 14" (356 mm); HERMA eco Ø300 mm. |
| Maximum roll weight | Roughly 15–17 kg (cab HERMES Q with 205/305 mm unwind) | Shaft and tension capacity; overweight rolls creep and drift. |
| Liner width | At least 6 mm wider than the label | Guides and rollers must press on liner, not on adhesive — some machines state a 6 mm minimum overhang. |
| Labels per roll | Calculated from O.D., pitch and material thickness | Drives changeover frequency and waste; specify "at least N labels", not "about". |
| Core type | Notched core for locking mandrels, returnable or not | Some pneumatic shafts need a notch; without it the roll slips. |
Capacity maths: doubling the outside diameter does not double the label count — count scales with the annular cross-section, i.e. O.D.² minus core I.D.², so a Ø300 mm roll does not hold twice the labels of a Ø150 mm roll.
4. Gap and pitch: what the sensor actually reads
- Pitch = label length in the machine direction + gap. The machine stores pitch, not single-label length; change the gap and every machine parameter moves with it.
- Common values: 3 mm is the industry default; printer specs typically read "2–4 mm, preferably 3 mm" (Zebra ZT411: inter-label gap 2–4 mm, preferably 3 mm).
- Too small: at line speed the sensor cannot separate label from liner — skipped labels, print landing on the gap, double feeds. Clear and glossy faces make it worse.
- Too large: wasted liner, fewer labels per roll, more changeovers, longer cycle time. Small labels suffer most.
- Put registration tolerance in writing: industrial printer specs quote ±1.0 mm (Zebra ZT411: ±1.0 mm vertical on non-continuous media, ±1.0 mm horizontal within a roll). Your application accuracy requirement starts from that number.
- Irregular shapes: keep the gap constant in the machine direction and make sure the sensing line falls on bare liner, never beside a sharp corner — otherwise the detected position shifts every label.
- Alternatives: a sensing notch (commonly 6 × 3 mm) or a Ø3 mm hole, useful when the artwork leaves no room for a usable gap.
5. Eye marks: when they are mandatory, and how to specify them
A black mark is printed on the back of the liner and read by a reflective sensor. Because it does not rely on light passing through the face material, it is far more reliable when:
- labels or liner are clear or translucent (too little contrast at the gap)
- the face is dark, metallised, foil or holographic
- the liner is opaque, or both sides carry print
- the material is continuous and cut to length by the machine
- the die-cut is irregular so the gap is not a clean straight line
- the gap has to be under about 2 mm
| Parameter | Published specification | Note |
|---|---|---|
| Mark length (machine direction) | 2.5–11.5 mm (Zebra ZT411); 6–10 mm (Toshiba BV420D) | Below the minimum it is not detected; above it can cover the previous detection window. |
| Mark width | ≥9.5 mm (Zebra ZT411); ≥8 mm (Toshiba BV420D, TSC MH240) | Width sets the lateral alignment tolerance. |
| Density | >1.0 ODU | Media itself should be ≤0.5 ODU, otherwise contrast is insufficient. |
| Position | Back of liner, one per label, fixed lateral position | Must not wander left or right; distance to the label's leading edge must also be constant. |
| Relationship to the gap | One sensing method per roll | With a black mark, the machine is set to black-mark mode — do not ask for gap sensing as well. |
Practical warning: print the mark in the same pass as the labels (pre-printed liner or simultaneous printing). Hand-applied marks land within 1–2 mm of target, which is exactly the range where sensors start misreading.
6. Die-cutting and waste stripping: cut the face and adhesive, never the liner
- Cutting through the liner means the web breaks on the line. Cutting depth must go through face and adhesive only — basic craft, and still the most common cause of export returns.
- Strip the waste cleanly. Adhesive left on the edge builds up on the peel plate and stalls the web.
- Agree splices in advance. How many joins per roll, and how they are flagged (coloured tape, splice tab). Undeclared splices stop a production line.
- Replace missing labels. Without a missing-label detector, one empty position becomes a batch of rework.
- Rewind tension: too tight and adhesive oozes at the edges — worse with hot-melt adhesive and hot transit — then the roll blocks on unwind; too loose and the web wanders and the labels wrinkle. This is rewinder craft, not press work.
7. One-page specification sheet you can forward as-is
| # | Item | What you fill in | Why it matters |
|---|---|---|---|
| 1 | Applicator model | Make + model (e.g. HERMA eco, cab HERMES Q4, Shibuya L410A) | Sets the limits for core, O.D., direction and sensing |
| 2 | Unwind direction | Face out/in + leading edge (or position 1–8) + a photo | Get it wrong and the line stops |
| 3 | Core I.D. | 25 / 40 / 50 / 76 mm — measure the tube | If it does not fit, the roll is scrap |
| 4 | Maximum O.D. | Largest roll the magazine accepts, minus 5–10 mm clearance | Too large and it must be rewound |
| 5 | Maximum roll weight | kg — from the manual or a scale | Overweight rolls slip and drift |
| 6 | Liner width | Label width + 6 mm or more | Guides press on liner, not adhesive |
| 7 | Gap | mm (3 mm default) | The sensor signal, and it defines pitch |
| 8 | Sensing method | Gap (transmissive) / black mark / notch / hole | Decides whether a mark is printed, and where |
| 9 | Labels per roll | At least N | Changeover frequency and waste |
| 10 | Splices | Maximum N per roll, and how flagged | Avoids line stoppages |
| 11 | Shelf life | Use within N months of receipt | Adhesive ages, especially in heat and humidity |
8. Five line faults and what they usually mean
| Symptom | Most likely cause | Fix |
|---|---|---|
| Labels applied upside down or rotated 180° | Leading edge opposite to the machine's web path | Rewind to the correct position; do not compensate in machine software |
| Double feeds, or print landing on the gap | Gap too narrow / liner too transparent / sensor not calibrated | Widen to 3 mm+, or add a black mark and switch to black-mark mode |
| Drifts halfway through a roll | Loose rewinding, unnotched core slipping, overweight roll | Tighten rewind, use a notched core, make rolls smaller |
| Adhesive build-up at the peel plate | Waste not stripped, die cut into the liner, adhesive too soft | Correct the cut depth, strip cleanly, move to a firmer or low-temperature adhesive |
| Edges lift after application | Adhesive mismatched to surface energy, or applied cold | Higher initial tack, add a nip roller, let material come to room temperature before running |
9. What you are paying for, and how long it takes
- Proof (digital): small quantity, rewound to your direction and gap. Most of the cost is set-up — the point is to run it on the machine once.
- Production (rotary / flexo): adds tooling and waste stripping; unit price falls with quantity, while roll size and count decide your downtime.
- Lead times: proofs about 24 hours; small production runs about one week; bulk (offset / rotary) about 15 days.
- Recommended sequence: do not scale up first. Run two or three "line trial" rolls for one shift, confirm direction, gap, sensing and release, then talk volume.
10. FAQ
Q1: I do not know which unwind direction my machine needs.
Send three things: the machine's rating plate (make and model), a photo of a roll currently running with a label lifted on the peel plate and still attached to the liner, and the core I.D. measured with a caliper. From those, direction, core and maximum O.D. can all be fixed.
Q2: Can I order one or two rolls just to test?
Yes — small runs go digital, so the unit price is higher because set-up is spread over few labels, but it is the cheapest possible validation. It is far cheaper than a full run in the wrong direction.
Q3: Do I always need a black mark?
Only when the liner cannot be read through and gap sensing is unreliable. On coated-paper faces with translucent glassine liner, a normal 3 mm gap is enough and the mark is money you do not need to spend.
Q4: Can a roll wound the wrong way be rewound?
Yes, if you have rewinding equipment — but rewinding changes tension and roll evenness, and clear or thin faces wrinkle easily. In practice a new roll is cheaper than the rework, which is why the specification should be fixed the first time.
Q5: Will rolls deform in transit to Hong Kong or Southeast Asia?
They can — heat and stacking are the causes. Use five-ply corrugated cases, foam end caps or bubble wrap per roll, never stack more than two high, and keep rolls away from the container ceiling. Let them stand at room temperature for 24 hours before running; tack recovers.
Request a quote: six details, and the file formats we accept (one message, not three)
- Artwork: AI, PDF, EPS or PSD with fonts outlined or embedded; include the die line if you have one; 20MB per file. A photo or screenshot is fine if the design is not final.
- Finished size and shape (round, square, custom; a die-line file is ideal).
- Quantity: how many versions, how many per version, and whether it ships in rolls or cartons.
- Material and where the label sits: paper, synthetic paper, PE or PET; outside the pack or inside.
- Destination market and the standard to meet (Hong Kong, Southeast Asia, EU food-contact rules).
- Required delivery date: samples and digital work about 24 hours, small runs about one week, bulk about 15 days — confirmed against the actual schedule.
Your contacts: quotations Ms Zeng +86 180 1199 6161 | sales Mr Hong +86 189 2511 1128. We reply within the working day (Monday to Saturday); for urgent work please call.
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