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Thermal vs. continuous inkjet printers: What are the differences?

CIJ-vs-TIJ-printing

Thermal vs. continuous inkjet printers: What are the differences?

A fast, reliable, and accurate ink marking solution is highly valued across virtually all types of industries. In this article we will examine two of the most popular types of inkjet marking printers – continuous and thermal inkjet. In particular, we will assess how each printer works and what are the advantages or disadvantages of each machine. Let’s get started:

How does a continuous inkjet (CIJ) printer work?

First introduced in 1951, the technology behind CIJ printers has barely changed through the decades, which is a testament to how effective it is. The process starts with a high-pressure pump that delivers ink from a reservoir to the nozzle. A piezoelectric crystal attached to the nozzle vibrates as it receives a current supply, causing the stream of ink to break apart into regularly spaced microscopic droplets. By varying the supply of current to the crystal, the frequency of vibration, and the rate of droplet ejection can be controlled.

The droplets pass through an electric field created by a charged electrode. The electric field toggles on and off, resulting in an alternating series of charged and uncharged ink droplets. The uncharged droplets serve to minimize the effects of electrostatic repulsion between successive charged droplets.

The droplets then pass through another electric field created by a charged plate. The ink droplets are repelled from the charged plate according to the degree of their charge, therefore controlling where they will land in the substrate. Uncharged droplets pass through the second electric field unrepelled and go straight to a recycle stream.

How does a thermal inkjet (TIJ) printer work?

The first TIJ printer was developed in the 1970s, a good two decades after CIJ technology was created. Its relative simplicity and ease of use have made it the leading technology used in consumer inkjet printers, although it’s now developing a significant presence in industrial applications.

The principle behind TIJ printers is much simpler than that of CIJ printers. All the magic happens in the cartridge. Each cartridge has an array of ink chambers, with each one containing a heating element.

When the ink chamber receives a command to eject an ink droplet, a current is passed through the heating element. The heating element is simply a coil positioned right above the nozzle of the ink chamber. The current heats up the coil, resulting in rapid vaporization of the ink positioned right below it. The increase in pressure results in the ejection of a droplet of ink through the nozzle and into the substrate. Consequently, the bubble caused by the vaporization collapses and creates a vacuum, which pulls in more ink towards the chamber.

Print quality and resolution

TIJ printers have rapidly evolved in the past few years and have now come ahead in the contest for print resolution. While CIJ printers can still reliably produce clean dot patterns, TIJ printers are capable of a print resolution up to 600 x 600 dpi. You’ve probably seen how capable TIJ printers are even with your desktop inkjet printer. This same level of quality and resolution can now be achieved in an industrial setting.

Print speed

While both TIJ and CIJ printers are suited for rapid printing needs, the Rayleigh mechanism that breaks up the ink droplets in CIJ printers is still more capable of ejecting droplets at a higher rate – up to a maximum of almost 200 meters per minute.

TIJ printers, on the other hand, are capable of printing up to 100 meters per minute. In most cases, that is faster than the production line speed requirement.

Footprint

If you plan to integrate continuous printers into your production line, then you’re probably concerned about how much space they are going to take. The simple answer is that TIJ printers take less space than its CIJ counterpart.

TIJ printers designed for industrial use that basically look like a print head connected to a control panel. Thanks to its smaller footprint, TIJ printers can also be portable – something that is more difficult to do with a CIJ printer.

CIJ printers tend to be about the size of a mini fridge (approximately 40cm). The unit is connected to the production line via a cable, whilst a nozzle at the end of the cable ejects the ink droplets. Therefore, you do have some flexibility of where to position the CIJ printer by the production line.

Maintenance and ease of use

CIJ printers require an annual service to ensure that the machine is kept in an optimum condition. An engineer will ensure to change filters, check caliberation, check cable connections and more.

The cartridge-based design of a TIJ printer requires less maintenance and cleaning. Moreover, changing a print cartridge in a TIJ printer is a simple task.

Summary

Both CIJ and TIJ printers play important roles in rapid manufacturing industries: the economical CIJ printer that ejects ink droplets to produce marks or the TIJ printer that offers a cartridge system with high-res end product. Choosing one over the other requires careful consideration of the costs, print quality, speed, and maintanadce associated with each technology.

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