Leadtech Printer-Leading Manufacturer in the Coding & Marking Industry since 2011.
Industrial Coding and Marking Solutions for Different Packaging Materials: A Selection Guide
A batch code may look perfect on a carton but smear on a plastic bottle. Move the same job to a foil pouch, and the problem changes again. The film may shift while printing, or the code may end up too close to a seal after the pouch is formed.
These are packaging problems, not just printer problems. PET, glass, coated metal, flexible film, and corrugated board all behave differently during coding. This guide looks at these materials one by one and explains which industrial coding solutions can be considered for each packaging job.
What Does Your Packaging Surface Look Like at the Coding Point?
Before selecting a coder, take a few packs directly from the line. Check them at the point where printing will take place. A bottle may be wet there, a can may have a coated surface, and a pouch may not sit in the same position every time.
Is the Surface Porous or Non-Porous?
Paper and corrugated board take in ink. On a rough board, small characters can spread and lose their sharp edges. This needs attention when printing small text or barcodes.
Glass, metal, PET, and other non-porous materials are different. The ink stays on top of the surface, so drying and adhesion need checking. Print several samples and rub the code after the normal drying time. If it smears or comes off easily, that ink and surface are not a good match.
Is It Dry, Wet, Coated, or Printed?
Check the condition of the pack when it reaches the printer. Bottles coming from a filling process may have water or condensation on them. Cans can have lacquered surfaces. Cartons may have varnish or printed graphics over the coding area.
Plastic Packaging: Check the Exact Plastic, Not Just “Plastic”
PET, HDPE, PP, and LDPE should not be grouped under one coding setup. The plastic grade, surface finish, colour, and package shape can change the result. Identify the actual material before testing the code.
PET Bottles
For PET bottles, first decide where the code will sit. Avoid ribs, moulding lines, label edges, and sharp changes in bottle diameter. These areas can affect print position or leave part of the code difficult to read.
HDPE and PP Bottles and Containers
With HDPE and PP, check adhesion on the finished container. Don't qualify the ink on a different bottle just because the resin name is the same.
Use containers with the actual surface finish. Print the required date or batch code, allow the normal drying time, and rub the printed area. Any smearing, missing characters, or easy ink removal needs to be resolved before production approval.
Flexible Packaging Moves While You Are Trying to Code It
Flexible packs are rarely as simple as a flat piece of film. The material runs through the machine, gets formed, filled, and sealed. A code placed correctly on the web can end up near a fold or partly around the side of the finished pack.
Film and Foil Before Forming
When you code the film before forming, work from the finished pack position. Find where the date or batch code needs to appear, then trace that area back to the flat web.
Web movement matters here. If the film wanders sideways, the print moves with it. Fix the film tracking first instead of trying to compensate by moving the printhead.
Laminated and Pre-Printed Film
For laminated film, find out which layer forms the outside surface. That is the surface being coded.
Artwork also needs room for variable information. A dark date code over dark graphics may be difficult to read even when the print itself is good. Set aside a clear coding area in the packaging design where possible.
Match the Coding Method to the Package
The package material narrows the choice, but it does not decide it alone. The size of the code matters too. So does whether you need ink on the surface or a permanent mark made into it.
When CIJ Fits the Packaging Job
CIJ is mainly used for small variable codes such as production dates, expiry dates, batch numbers, and lot numbers. Since the printhead does not touch the product, it can code bottles, cans, jars, tubes, and other packs as they move along the line.
The ink has to match the surface. An ink selected for PET may not give the same adhesion on PP, glass, or a coated metal can. Drying time also matters when packs contact conveyor guides soon after printing.
Where Laser Marking Makes Sense
Laser does not put ink onto the package. It produces the code by changing the material or its surface layer. This makes the material response the main part of the selection.
CO₂ lasers can be evaluated for paper, board, glass, and compatible plastics. Fiber lasers are used more often with metals and certain plastics. UV lasers can produce fine marks on compatible plastics and films where the material responds well to the wavelength.
Packaging Material Selection Table
| Package | Coding Requirement | Method to Evaluate |
|---|---|---|
| PET bottle | Date, batch or lot code | CIJ / compatible laser |
| HDPE or PP container | Small variable code | CIJ / compatible laser |
| Glass bottle | Date or batch code | CIJ / CO₂ laser |
| Metal can | Variable or permanent code | CIJ / compatible laser |
| Flexible film | Variable code on moving film | CIJ / compatible laser |
| Corrugated case | Large text, barcode or graphics | Piezo inkjet |
Run a Packaging Trial Before You Approve the System
Use the same pack, code, and line conditions planned for production. Keep one approved sample after the trial so operators have something to compare against later.
Send the Actual Package
Send production packs to the supplier. If you use a 500 ml PET bottle with a specific label and cap, send that bottle rather than an unlabelled PET sample.
The same applies to printed pouches, lacquered cans, laminated films, and coated cartons. Include the finished surface that will pass the coder.
Put the Sample Through Normal Handling
After coding, let the pack follow its normal route. Run bottles along the conveyor and through packing. Put coded pouches through forming and sealing if the code is applied beforehand. Fold and close cartons as they would be during packing.
If the production bottle reaches the coder wet, test it wet. If a code normally touches conveyor guides shortly after printing, let that happen during the trial instead of protecting the sample.
FAQs About Industrial Coding Solutions for Packaging
What Coding System Can Print on Plastic Bottles?
For small changing codes such as expiry dates and batch numbers, CIJ is commonly used on PET, HDPE, and PP bottles. The ink must hold on the bottle and dry before the printed area touches a guide rail or another bottle. If you need a permanent mark, a compatible laser can be considered. The exact laser depends on how that plastic reacts to marking.
How Do You Code Wet Glass Bottles?
First, see how much water is actually on the bottle when it reaches the coder. Light condensation and a bottle covered with water are different conditions.
Print under that same condition. Let the bottle continue along the conveyor, then rub the code at the packing point. If it transfers onto your finger or another bottle, the ink has not dried well enough for that position on the line.
Can One Coding Machine Handle Bottles, Cans, and Cartons?
Only if the printing jobs fall within what that machine can handle. For instance, one CIJ printer may handle a two-line batch code on a PET bottle and a similar code on a can. That does not mean it is the right machine for a 50 mm barcode on a shipping carton. Compare the code size and content first, then the packaging material.
Let LeadTech Check the Actual Coding Job
Send LeadTech Printer your package sample together with the code you need to print. Include the material, code position, and basic line details. LeadTech can then match its industrial coding solutions to the actual packaging job rather than working from the package name alone.
