Valve Jet Printers and Large Character Coding Explained

Large character coding is how manufacturers print the big, readable codes you see on shipping cartons and outer cases: batch numbers, best-before dates, pallet identifiers and product descriptions, printed in characters tall enough to scan from a distance in a warehouse. Two machines do this job: the valve jet printer and the hot melt wax printer. This guide covers how each works, which substrates suit them, and where they sit alongside the other coding technologies on a production line.

What a valve jet printer is

A valve jet printer is a non-contact inkjet technology used for marking, coding and labelling. A series of electronically controlled valves open and close to release precise droplets of ink onto the surface, forming characters. Because nothing touches the product, it prints on cartons as they move past on a conveyor with no need to stop or index the line.

The defining feature is character size. Where a continuous inkjet printer produces small codes suited to individual retail items, a valve jet produces large characters designed to be read across a warehouse aisle or from a forklift. Valve jet is one of two common ways to do large character coding; the other is a hot melt wax printer, covered below.

How it works

Each valve in the printhead is an individually controlled gate. Opening a valve for a set interval releases a droplet of ink onto the passing surface, and firing the valves in the right pattern as the product moves builds up the character. Droplet size is larger than in continuous inkjet, which is what produces the bigger print and also what limits the resolution: valve jet is built for legibility at size, not for fine detail.

What it prints on

Valve jet suits porous surfaces such as cartons and paper. That is a real constraint rather than a preference. The ink relies on absorbing into the surface to dry and stay put, so it is at home on corrugated board and kraft paper and out of place on glass, metal or film. If your code needs to go onto a plastic bottle or a foil pack, a different technology applies.

Markem Imaje valve jet printers use either water-based or solvent-based consumables to suit different substrates, and print from low up to high speed applications.

What it codes

• Batch or lot numbers for product traceability.
• Expiry dates for perishable goods.
• Manufacturing dates for time-sensitive products.
• Serial numbers for individual product identification.
• Warning labels and safety instructions.
• Variable data for personalised packaging.
• Alphanumeric characters at carton-legible size.

The other large character option: hot melt wax

A large character hot melt wax printer heats a wax-based ink to a liquid, deposits it on the surface, and the ink cools and sets to form the print. It covers the same large character job as valve jet and differs in two ways that usually decide between them.

First, substrate range. Valve jet needs a porous surface. Hot melt wax prints on coated and uncoated paper, cardboard, corrugated boxes, synthetic materials, plastics, wood and some metal surfaces, so it handles coated cartons and non-porous packaging that valve jet cannot. Second, print quality. The wax printer produces higher-quality output, including barcodes, QR codes, logos and graphics, where valve jet is built for plain alphanumeric characters.

Valve jet stays the simpler and cheaper option when the job is dates and batch codes on plain corrugated board. Once the carton is coated, or the code has to include a barcode or logo, hot melt wax is the one to look at. Markem Imaje large character printers run from low up to high speed applications either way.

Valve jet against the other coding technologies

Technology	Character size	Typical substrate	Usual position on the line
Valve jet	Large	Porous: cartons, paper	End of line, outer case
Hot melt wax	Large	Coated and uncoated board, plastics, wood, some metals	End of line, outer case
Continuous inkjet (CIJ)	Small	Paper, plastics, glass, metal, film	Primary pack, high speed
Thermal inkjet (TIJ)	Small to medium	Porous and some coated surfaces	Primary and secondary pack
Laser coding	Small to medium	Plastics, glass, metal, cardboard, film	Permanent codes, no consumables
Print and apply	Label	Any, label carries the print	Cartons and pallets, barcodes

Most lines that run valve jet also run something else. The typical arrangement is a CIJ or laser coder marking the primary pack at speed, and a valve jet marking the outer carton once products are cased. Our comparison of inkjet versus laser coding covers the primary pack decision in more detail.

Valve jet or print and apply for cartons?

Both mark cartons at end of line, and they solve different problems. Valve jet prints ink directly onto the board: cheaper per carton, fewer consumables to manage, nothing to run out of except ink, and no label to peel off in transit. Print and apply produces a printed label and sticks it on: better where the code must include a scannable barcode, where print quality has to survive a supply chain scanner, or where a customer or retailer mandates a specific label format.

The practical rule is that human-readable information favours valve jet, and machine-readable barcodes on cartons favour print and apply. Plenty of sites run both, with direct-printed dates and batch codes plus an applied logistics label.

What to check before specifying

• Carton surface. Confirm the board is uncoated and porous. Coated or waxed cartons point to hot melt wax instead.
• Character height needed. Driven by how the code has to be read: at arm's length, or across a warehouse.
• Line speed and carton spacing. Determines throughput and printhead positioning.
• Which face gets the print. Side, top or both, which decides how many printheads you need.
• Ink type. Water-based or solvent-based, chosen against the substrate and the storage conditions.

Frequently asked questions

What is a valve jet printer used for?

Printing large characters such as batch codes, dates and product identifiers directly onto cartons and other porous packaging, without contacting the product.

What is the difference between valve jet and continuous inkjet?

Valve jet releases ink through electronically controlled valves to form large characters and works on porous surfaces such as cartons. Continuous inkjet fires a continuous stream of charged droplets to produce small, high resolution codes across a much wider range of substrates including plastics, glass and metal.

What is the difference between valve jet and a hot melt wax printer?

Both do large character coding. Valve jet fires ink through electronically controlled valves and needs a porous surface such as plain corrugated board. A hot melt wax printer melts wax-based ink onto the surface, handles coated board, plastics, wood and some metals, and gives higher print quality including barcodes and logos.

Can a valve jet printer print barcodes?

Its strength is large human-readable characters rather than fine detail. Where a carton needs a reliably scannable barcode, a hot melt wax printer or a print and apply system is generally the better fit.

Does valve jet printing work on plastic or film?

No. Valve jet is for porous surfaces such as cartons and paper. Plastics and coated board are handled by hot melt wax, and glass, metal and film by continuous inkjet or laser coding.

What consumables does a valve jet printer use?

Water-based or solvent-based ink, selected to match the substrate. There is no ribbon or label to replace.

Related machines and guides

• Valve jet printers from Nexus Australia
• Large character hot melt wax printers
• Continuous inkjet (CIJ) printer guide
• Thermal transfer overprinting explained

Code your cartons the right way

Nexus Australia supplies Markem Imaje valve jet and large character hot melt wax printers Australia-wide, alongside the full coding and marking range, and can match the technology to your substrate, character size and line speed. Contact our team to talk through your carton coding requirements.