Labeling Machine Troubleshooting for Label Applicators

Most calls we take are one of about a dozen things, and a good share of them get solved on the phone before anybody drives anywhere. This page is those dozen things, written down, so your own team can work through them at six in the morning.

This labeling machine troubleshooting guide covers label applicators, print and apply systems and the product handling around them, symptom by symptom, on any brand. Marapack Services services labeling and coding equipment from a base in the Pacific Northwest, on Altech, Label-Aire 3100 applicators and 5100 systems, PackLeader, CTM and Tach-It machines.

If you work through this page and it is still wrong, call 253-709-5566 with what you found and it will be a much shorter call. If the same fault keeps coming back on more than one line, book an equipment audit and have the whole line looked at.

How do you troubleshoot a labeling machine?

Troubleshoot a labeling machine by changing one thing at a time, and by first finding which half is broken: the label half (the roll, the web, the peeler bar and the label sensor) or the product half (the conveyor, the gap, the product sensor and the applicator stroke). Nearly every symptom belongs to one half.

Two rules before you start, and they save more time than everything below.

Rule one: change one thing at a time. The fastest way to turn a ten minute fault into a two day fault is to adjust the sensor, the speed, the air pressure and the peel position together and then not know which one mattered.

Rule two: find out which half is broken. A labeling system has a label half and a product half. The label half is the roll, the web, the peeler bar and the label sensor. The product half is the conveyor, the gap, the product sensor and the applicator stroke. Nearly every symptom below belongs firmly to one half, and knowing which one you are in eliminates most of the list immediately.

Why are labels lifting, curling or falling off after application?

Labels that lift, curl or fall off after application are very often a surface or adhesive problem rather than a machine problem: condensation on a cold case, waxed or dusty board, an adhesive not rated for the conditions, too short a wipe down, or handling before the adhesive has built bond strength. Check those before touching the applicator.

This is the most common complaint in the category and it is very often not the machine.

Check in this order.

1. The surface. Waxed corrugate, recycled board with a high dust content, moisture on the face, a cold case coming out of a cold room into a warm packhouse. Condensation forms on a chilled surface in seconds and no pressure sensitive adhesive bonds to a film of water. If the case is cold and the room is warm, that is your answer and no adjustment will fix it.
2. The adhesive. Standard permanent adhesive is not the same as a cold temperature or freezer grade adhesive, and it is not the same as an adhesive rated for recycled or waxed board. If the labels changed supplier, or the season changed, or the product moved from ambient to chilled, the adhesive specification is the first suspect.
3. The wipe down. After the label lands, something has to press it. Too short a brush or roller, or none at all, leaves the label lying on the surface rather than bonded to it. Corner lift almost always traces here or to the adhesive.
4. Dwell time before handling. Pressure sensitive adhesive needs time to build bond strength. A case labeled and immediately stacked, wrapped or dropped will lift at the corners.
5. Application pressure and squareness. A tamp that touches at an angle bonds one edge properly and the other barely.

When to call: if the surface, adhesive and wipe down are all right and it still lifts, the applicator geometry needs looking at.

Why does the labeling machine miss labels?

A labeling machine misses labels when it cannot see the label gap or cannot see the product in time. On the label side that means a dirty, drifting or mistaught label sensor, clear labels on a clear container, changed stock or web slip. On the product side it means sensor position, products arriving without a gap, or line speed.

A product goes past unlabeled. This is the failure that gets past everybody, because an unlabeled product looks obviously wrong to a person and completely normal to a conveyor.

The label half:

• Label sensor not seeing the gap. The most common single cause. A standard gap sensor reads the difference between the label and the liner, and it drifts, gets dusty, or was never taught properly for the current stock.
• Clear labels on a clear container. Standard gap sensing fails on transparent stock, reliably, eventually, and usually mid season. This is not a calibration problem, it is the wrong sensor for the job. A label tracing sensor built for transparent product exists precisely because this is universal. We supply it among the spare parts for Altech heads.
• The stock changed. New liner, different opacity, a printed backing, a different gap length. A sensor taught on the old roll may not read the new one.
• Web tension or slip. If the web slips at the drive, the machine dispenses less than it thinks it did.

The product half:

• Product sensor position. Too close to the applicator and the machine has no time. Too far and the label lands late.
• Products arriving nose to tail. Without a gap, the machine cannot separate one product from the next, and it will skip. The fix is a spacer, a timing screw or a gapping conveyor rather than a faster head.
• Line speed above what the head can do for that label length. A head rated for a given web speed applying a long label at a fast cycle is a different machine from the same head wiping a short label on.

When to call: if the sensor is clean, the stock is unchanged and the gap is consistent, the fault is usually a sensor at the end of its life or a drive issue.

Why are labels crooked, skewed or in the wrong place?

Where the label lands tells you the cause. Consistently in the wrong place is a setup problem. Randomly in the wrong place is a product presentation problem. Skewed rather than offset points at squareness between the product and the head. Drifting slowly over a run points at web tension, a slipping drive or an off-center roll.

Consistently in the wrong place is a setup problem: peel position, applicator position, product sensor timing or a stored recipe that no longer matches the product.

Randomly in the wrong place is a presentation problem: the product is moving, bouncing, or arriving at a slightly different position each time. Guide rails, side belts and a stable product path fix this and a machine adjustment does not.

Skewed rather than offset points at squareness: the product is not square to the head, or the applicator pad is not parallel to the face.

Drifting slowly over a run points at web tension, a slipping drive or a roll that is wound off center.

Why does the label wrap, wrinkle or fold?

A label wraps, wrinkles or folds when it leaves the web badly presented: the wrong peel angle or peel position, a peeler bar that does not suit the product, web tension too low, static from dry air and plastic film, or, on a non contact applicator, air blow settings that are too strong or too weak.

• Peel angle and peel position. The peeler bar is what separates the label from the liner, and the peel angle decides whether the leading edge is presented flat.
• The wrong peeler bar for the product. On the Altech ALritma labeling heads and ALstep heads, the range runs from rigid to adaptive to spring loaded to quick change. A product whose height varies wants a spring loaded bar, and a rigid bar on a variable height product produces exactly this symptom.
• Web tension too low, letting the label leave the web before it is presented.
• Static. Dry air, plastic film and a fast web produce static, and a statically charged label goes where it likes.
• Air blow settings on a non contact applicator: too much air folds the label, too little leaves it short.

Why does the web break, or the machine keep stopping on a web fault?

Web breaks and web faults usually trace to the roll or the tension rather than the machine: a roll diameter or core size the machine was never specified for, a full or binding rewind, unwind tension too high or a dragging brake, splices and joins hitting the peeler bar, or a damaged edge on the roll.

• Roll diameter or core size the machine was never specified for. This is a real and common one. Roll diameter, core size and web tension are machine specifications, and a roll your converter can happily make is not automatically a roll your machine can take. Check the roll against the machine before assuming the machine is faulty.
• Rewind full or binding. On a machine with an integrated rewinder, a full rewind stops everything. On one without, somebody has to empty the waste bin.
• Tension too high at the unwind, or a brake that is dragging.
• Splices and joins in the roll hitting the peeler bar.
• A damaged edge on the roll from handling or storage.

Our page on label rewinders and unwinders covers the roll handling side in more detail.

Why does the applicator fire but not place the label?

When a tamp or tamp blow applicator fires but does not place the label, check the air first: low pressure or water in the air line. Then check for blocked vacuum holes on the pad, a worn or wrongly sized pad, a stroke length that is wrong for the product height, and a sticking cylinder or valve.

On a tamp or tamp blow applicator:

• Air pressure low, or water in the air line. Compressed air quality is a chronic issue in a wet packhouse. Check the filter and the drain before the machine.
• Vacuum holes on the pad blocked with adhesive or dust, so the pad cannot hold the label.
• The pad is worn or the wrong size for the label.
• Stroke length wrong for the product height, especially where product height varies.
• Cylinder or valve sticking.

On an air blow applicator, the same list in a different order: air supply first, then the blow plate and holes, then the distance to the product.

How do you troubleshoot a print and apply label printer?

Troubleshoot a print and apply label printer by catching a label at the peel position before it is applied. If the print is already bad, the print engine is at fault and the kind of defect points to the part. If the print is clean but the content is wrong, check the data feeding the printer before opening anything.

If your system prints as well as applies, first separate the two halves. Catch a label at the peel position before it is applied and look at it.

If the print is bad, it is the print engine, and the type of bad tells you a lot: a consistent vertical line of missing dots is a printhead; overall lightness is printhead pressure, platen wear, a ribbon mismatch or a darkness setting somebody changed; a fade across the label width is pressure or platen; creased print is the ribbon path; smearing is a ribbon and stock mismatch or a contaminated printhead. When the engine needs more than an adjustment, see our page on print engine rebuilds.

If the print is clean but the content is wrong, it is data and format rather than hardware. Check what is feeding the printer before opening it.

If the print looks fine to you but a customer's scanner rejects it, that is print quality as a measured property rather than a visual one, and a handheld scanner in your plant is not a test of it. On the equipment side that usually points at the printhead, the ribbon and stock pairing, or where the label is landing. Our print engine page and our GS1-128 and SSCC pallet label guide cover both sides.

Why is the machine slower than it used to be, or slower than it was sold as?

A machine that has slowed down over time is showing wear: belts, drives, bearings, an applicator cycle that has lost its edge, or air supply that is not what it was. A machine that was slow from day one usually has a specification mismatch, because head speed and products per minute are not the same number.

Two different problems that get reported the same way.

Slower than it used to be is wear: belts, drives, bearings, an applicator cycle that has lost its edge, or air supply that is not what it was. This is a maintenance finding.

Slower than expected from day one is usually a specification mismatch rather than a fault. Head speed and products per minute are not the same number. A head rated at a given web speed applying a long label with a tamp cycle produces far fewer products per minute than the same head wiping a short label on. If the number never matched, the conversation to have is about the label length, the application method and the gap, not about the machine being broken.

More on matching the head to the job: label applicator machines.

What causes labeling machine faults that come and go?

Intermittent labeling machine faults usually come from a sensor near the end of its life, compressed air that sags or carries water, product presentation that varies, a loose connector or a flexing cable, temperature and humidity where chilled product meets a warm room, or something upstream. Check them in that order.

Intermittent faults are the expensive ones, because they are the ones people chase. The usual sources, in the order we check them:

1. A sensor at the end of its life. Sensors drift before they fail. An intermittent fault that got gradually more frequent over a season is very often a sensor, and sensor refurbishment is one of the least expensive fixes on the machine.
2. Compressed air. Pressure that sags when another machine cycles, or water in the line.
3. Product presentation varying with operator, shift, product size or how full the line is.
4. A loose connector or a cable being flexed by a moving assembly.
5. Temperature and humidity, especially where a chilled product meets a warm room.
6. Something upstream that only happens sometimes. The labeler is where the fault shows up, not always where it lives.

What should you check before calling for labeling machine service?

Before you call, write down the exact fault message, pull ten consecutive labels, catch a label at the peel position, check the roll, clean the label sensor and check the product sensor, check air pressure at the machine, watch ten products go through, and note what changed. That turns a diagnostic call into a parts call.

A five minute check. Do these in order and write down what you find.

1. Read the fault on the screen and write down the exact wording.
2. Pull ten consecutive labels off the machine and look at them together. Ten tell you what one cannot.
3. Catch a label at the peel position before it is applied, if the machine will let you, and check whether the problem exists before application.
4. Check the roll: correct stock, correct core, correct diameter, wound the right way, undamaged edges.
5. Look at the label sensor and clean it. Check the product sensor is where it should be and that nothing has been knocked.
6. Check air pressure at the machine, not at the compressor, and drain the filter.
7. Watch ten products go through without touching anything, and note whether the fault is every time or sometimes, and whether it correlates with anything visible.
8. Note what changed. New label stock, new product, new operator, a cleaning shift, a move, a power event. Something changed. It is almost never nothing.

Then call us on 253-709-5566 with the machine model, the serial number, and what you found. If it needs a part, we can bring it rather than discover it.

Labeling machine troubleshooting FAQ

What is the working principle of a labeling machine? A labeling machine unwinds a roll of pressure sensitive labels, peels each label off its liner at the peeler bar once the label sensor has found the gap, and applies it when the product sensor sees a product arrive, by wiping, tamping or blowing it on. The empty liner is rewound. Every symptom on this page is a fault in one of those steps.

Why are our labels falling off cold cases? Almost always adhesive specification and condensation rather than the applicator. A chilled surface moving into a warm room grows a film of moisture in seconds, and pressure sensitive adhesive does not bond through water. The fixes are an adhesive rated for the temperature, applying before chilling where the process allows, or changing where in the line the label goes on.

Our clear labels keep getting missed on clear containers. Is the sensor broken? Probably not. A standard gap sensor reads the optical difference between the label and the liner, and on a transparent label there may not be enough difference to read reliably. There is a label tracing sensor built specifically for transparent product. This is a component change rather than a calibration.

The machine skips labels when the line is busy. Why? Usually because products are arriving without a gap. The machine has to see one product end and the next begin. Where the gap is the problem, the fix is a spacer, a timing screw or a gapping conveyor rather than a faster labeling head.

How do we know whether it is the printer or the applicator? Catch a label at the peel position, before application. If it is already wrong, it is the print engine. If it is perfect and lands badly, it is the head or the product presentation.

Our barcodes scan here and fail at our customer. What is going on? A handheld scanner is forgiving and a fixed receiving scanner is not. Print quality is a measured property with defined grades, and a symbol can be failing for reasons invisible to the eye, most commonly a printhead with a failing dot line, insufficient quiet zone, or a label applied over a wrap seam or a fold.

Can you help over the phone? Frequently, yes. Send a photograph of the fault screen, a photograph of the label and the machine serial number and we will tell you whether it needs a visit.

Is it worth repairing an older machine? Usually. Obsolete means the manufacturer stopped supporting it, not that the mechanics stopped working. Send the model and serial number. Our used and refurbished equipment page covers the repair, refurbish or replace decision.

Should we be doing scheduled maintenance instead of this? If your production is seasonal, yes, and it is the single change that most reduces the number of times you need this page. See our page on labeler preventive maintenance.

Still wrong

Work the five minute check, then send us what you found. The more of this page you have already done, the shorter and cheaper the call. For a fault you cannot clear, our labeling machine repair and service team takes it from there, and if it is happening on more than one line, have the whole line checked with an equipment audit.