TIJ vs CIJ: Thermal Inkjet and Continuous Inkjet Compared

You are specifying a coding station, and someone asks the question the whole project hangs on: thermal inkjet or continuous inkjet?

In a brochure the two look interchangeable. On a running line they are not. Start with one structural fact and the rest falls into place: in a TIJ cartridge the printhead travels with the ink; in a CIJ system the printhead is a permanent part of the machine and the ink arrives separately.

Almost everything people argue about — resolution, character height, line speed, running cost, who maintains it — follows from that. A cartridge carrying its own nozzle plate has to be light enough to handle, cheap enough to throw away, and sealed well enough that the ink survives a weekend. A permanent head can be built for a far harder duty cycle, but only if ink and make-up solvent can be fed to it continuously and held in condition.

This page is written by a company that makes TIJ cartridges. The boundaries are stated at the end, including the applications where we will tell you to buy something else.

The five questions that decide it

Answer these in order before comparing any specifications. They are also the questions we ask before we quote.

1. Does the code sit on the surface or soak into it?
2. How tall is the character, and how dense is the code?
3. How fast is the line, and what has to move?
4. What does the code have to survive afterwards?
5. Who is going to look after the printer, every day?

Surface and ink

A water-based ink needs somewhere to go. On paper, board and other porous surfaces it soaks in, dries quickly and holds. On PE, PP, PET or coated metal there is nowhere to soak in, so the formulation has to change: a fast-dry solvent ink, an oil-based ink, or a surface treatment applied to the substrate before printing.

Continuous inkjet leans on a solvent carrier that flashes off quickly, which is one reason it became the default on non-porous and awkward surfaces. The trade-off is the solvent itself. It evaporates, it has to be topped up continually, and in many markets it brings ventilation and VOC handling with it.

If the surface is the thing blocking you, the useful document is not a printhead datasheet — it is how we match ink to material.

Character height and code density

This is where the two technologies separate most visibly.

A CIJ head prints from a single nozzle whose droplets are deflected, so character height comes from how far the droplet is allowed to travel before it lands. A standard head covers roughly 1.5 mm up to about 10 mm, and larger nozzle sizes extend the top of that range. The characters are built from a dot matrix, and the strength of the technology is reach: large codes, read at a distance, on surfaces and shapes that are hard to present to a head.

A TIJ head prints from a whole row of nozzles at a fixed pitch, so the height of one pass is the print width of the cartridge — on the cartridges we supply, print widths of 12.7 mm and 25.4 mm. Inside that band, TIJ places many more droplets per unit area, which is why it produces dense high-contrast codes rather than a coarse dot matrix.

What you need to print	TIJ	CIJ
Small, dense Data Matrix or QR	Native strength	Possible at lower density
Two or three lines of small text	Within the print width	Comfortable
Characters taller than one print width	Needs more than one print width or head	Native strength
Text read from several metres away	Not the tool	The usual choice
Marking on a curved or uneven surface	Needs a close, even gap	More tolerant of a stand-off

Neither column is a ranking. A line that needs a 3 mm date code on a carton is not waiting for CIJ, and a line that needs a 15 mm batch number on an extruded pipe is not waiting for TIJ.

Line speed and how the head moves

In a TIJ system the product usually moves past a fixed head, or the head traverses while the product indexes. Because the cartridge is light it can be carried on a moving carriage; that is the same mechanical fact behind handheld units, inline coders and overprinters. What limits speed is how fast the controller can fire the nozzle row and how the code is laid down, which is why the DPI figure on a datasheet is a hardware property and not a printing specification — we went through that in detail in DPI and resolution in thermal inkjet. Width is the other half of that picture: one half-inch head covers 12.7 mm, and four one-inch heads stitched together cover 76.2 mm.

CIJ wins when the line is simply faster than the product can be stopped, or when the substrate will not sit still. Extruded cable, pipe and profile run at speeds that make intermittent printing impractical, which is why that sector is traditionally CIJ territory. Where we can help there, we would rather have the honest conversation than a sale — see coding on cable and pipe.

What the code has to survive

A code that has to come through a retort cycle, a pasteurisation tunnel, a caustic wash or a solvent wipe is a materials problem before it is a printing problem.

Both technologies can be made to work. The question is whether the ink supplier can show you test results for your combination of substrate, surface treatment, process and time. This is where a claim is worth nothing and a sample is worth a lot. Adhesion is specific to the ink, the material, the treatment and what happens downstream; a supplier who tells you by email that their ink “works on PE” has told you almost nothing.

Who runs it every day

Maintenance is where the two differ in kind rather than in degree.

A TIJ cartridge has no recirculation loop and no solvent top-up. Its failure mode is drying: a nozzle that dries out during a long stop stays dry, and the fix is to replace the cartridge. The daily routine is short and needs no consumables beyond cartridges — but the printhead sits inside the consumable budget, so every head is paid for again.

A CIJ system keeps ink circulating through the nozzle all day, which is what allows a permanent head to survive. The same circulation brings viscosity control, make-up solvent, a gutter to catch unused droplets, filters and a cleaning routine. Running cost is dominated by solvent consumption rather than by the head.

Neither is cheaper in the abstract. A line that runs a few hours a day, several days a week, will usually find the cartridge model cheaper to own, because nothing has to be held in condition between shifts. A line running three shifts, six days a week, will usually find the CIJ model cheaper per code once the volumes are real. Which side you land on is an arithmetic question about your line, not a question about which technology is better.

When continuous inkjet is the answer

• The line runs faster than the product can be stopped or indexed.
• The marking position is curved, irregular or recessed, or the head has to stand off from the product.
• The code is large — a batch number or a date read from several metres away.
• The product goes through a process that no practical ink-and-treatment combination on your line will hold up to.
• The same head has to mark a wide range of products without being changed.

When thermal inkjet is the answer

• The code is small and dense: a Data Matrix, a QR code, or several lines of text in a small area.
• The line stops, indexes, or runs at a speed a traversing head can keep up with.
• Capital cost and simplicity matter more than cost per code at very high volume.
• The ink has to be a specific chemistry rather than a general-purpose black. We make, among others, a UV-invisible ink that is invisible in daylight and reads only under ultraviolet light (365 nm), which is used for marking and authentication rather than for reading — see the cartridge range.
• The marking is intermittent by nature: a unit that is carried to the product rather than built into a line.

What we make, and what we do not

This article is written by a company that makes TIJ cartridges and their inks, so it is worth being explicit about the boundaries. The long version is on the manufacturer page; the short version is here.

We make the cartridge body, and we formulate and fill the ink. The printhead inside the cartridge is one we qualify and buy, not one we manufacture. We do not build printers, and we do not supply CIJ ink or CIJ systems at all.

That has a practical consequence for you. When the right answer is a continuous inkjet system, we cannot sell it to you. We can tell you that we think you need one, and we can help you work out what to ask a CIJ supplier for. What we will not do is sell you a thermal inkjet setup for a line we already believe it will disappoint on.

What to send us for a real answer

If you are still choosing, the useful things to send are: the substrate, with any coating or treatment noted; a sample of the actual material or product; the code content, its size and the height you need; the line speed and whether the product stops; what happens to the product after marking; and a photograph of where the mark goes.

With those, the answer usually arrives as a sample rather than as an opinion. If your application is a date, batch or lot code on a pack, start with date and batch coding. If it is something else, send us the details and we will come back with the two or three options worth testing.