When you are shopping around for a new UV-cured ink printer, there are some basic questions you should ask about its printheads.
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WHICH BRAND AND WHICH MODEL OF PRINTHEADS ARE BEING USED?
Most printer spec sheets do not list the printhead. When you ask what printhead, you are usually told the brand, but not the model of the printhead; but in a few hours research you can find out on your own.
Once you know the name and model number of head, you can go onto the company website and see all the specs of the head (all the information that most printer manufacturers don’t have in their own spec sheets). We highly recommend IMI conferences in USA, EU, and Japan as a good place to learn about printhead systematics is an IMI conference: www.imiconf.com and www.imiEurope.com
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IS THIS PRINTHEAD ADAPTED FROM SOLVENT INK OR A NEW DESIGN MADE ESPECIALLY FOR UV INK CHEMISTRY?
Some heads just were not made originally to handle UV-cured inks. Early model Epson heads are an example (made for photo printers and fine art giclee, water-based inks). This does not mean they can’t jet UV-curable inks, it just means they may require special inks. So it does help to learn whether the heads you are about to end up with, whether they are made to handle UV-inks from the beginning. Epson itself makes no UV-curing printers; Epson makes only water-based and solvent-based printers, so their heads are tuned to these inks.
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HOW MANY OTHER PRINTERS UTILIZE THE SAME PRINTHEAD? HAVE THEY SHOWN ANY PROBLEMS?
Konica Minolta, Ricoh, Kyocera, XAAR, and Dimatix Spectra are piezoelectric printheads. These are industrial strength piezo printheads, as compared to Epson piezo printheads; which are more for home and hobby printers.
Fujifilm Dimatix Galaxy 256/30 HM printhead.
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HOW MANY NOZZLES PER PRINTHEAD?
This may help you know how fast, or slow, your printer will be.
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HOW MANY TOTAL NUMBER OF PRINTHEADS?
Some individual printheads can be divided, and jet more than one color (half of the jets one color; the other half another ink). More expensive printers have 6 heads, per color.
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HOW MANY PRINTHEADS PER COLOR?
This will tell even more about how slow, or fast, your printer can jet ink.
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WHAT IS THE PICOLITER DROP SIZE? IS THERE VARIABLE DROPLET CAPABILITY?
The smaller the drops, the better the quality achieved in print. However, smaller drop sizes can reduce the speed of a printhead system. Likewise, printheads that produce bigger drop sizes do not offer the same print quality, but their print speed tends to be better.
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IS THERE A SPECIAL HEAD FOR WHITE INK OR VARNISH? OR THE SAME MODEL AS FOR CMYK?
Since white ink may do better with a larger nozzle, some printers have a “white ink drop size favorable head” just for the white ink. Other printers use the same head for any and all colors. For varnish, best ask an experienced printer operator and printer designer whose head is best for varnish. To handle varnish is not as easy as handling inks. On comparable grounds, be sure your white ink has a recirculation system (otherwise the white particles will settle and clog the nozzles).
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IF THIS PIEZO HEAD FAILS, WHO IS RESPONSIBLE FOR PAYING FOR REPLACEMENT HEADS? WHAT ARE THE MOST COMMON CAUSES OF PRINTHEAD FAILURE? WHICH OF THESE CAUSES OF FAILURE ARE COVERED BY THE WARRANTY? WHICH CAUSES OF PRINTHEAD FAILURE ARE NOT COVERED BY THE WARRANTY? IS THERE A LIMIT TO THE NUMBER OF PRINTHEAD FAILURES THAT ARE COVERED OVER A UNIT OF TIME?
Most warranties do not pay for the replacement of printheads if it was a user error that caused the failure. Most failures are indeed user error; the most common cause is a head strike.
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HOW OFTEN CAN YOU EXPECT HEAD STRIKES? WHAT CAUSES THEM?
Head strikes are the most common cause of premature head failure (Improper loading of the media, which make cause buckling, because the media rubs up against the fragile nozzle plate, or not going through the printer properly). A single head strike may wipe out only a few nozzles or may kill the entire printhead. Another cause is constant flushing; the flushing seemingly wears out the nozzle system.
Memjet printhead.
CONCLUDING REMARKS
When we are at a signage expo, or textile printer trade show, or an expo for glass or printers for ceramic tiles, we have learned over the last 20 years that only about 10% of the booths put an emphasis on which printhead is used. In fact, often over 25% of the sales reps and booth personnel tell us they don’t know the brand or the model of what printhead is in the printers in their own booth.
In other words, there is sadly not much excitement about what printhead is being used.
This results in or are encouraged by, a comparable focus by the print shop owner or manager (who comes to the booth to make a decision of which printer brand and which model to buy). Their #1 question is the price, and then another dozen questions (which we will cover in a subsequent article “Ten Crucial Questions to ask BEFORE you buy a UV-curing printer.”
Yet we recognize that the printhead is indeed important. The brand and model of RIP software is also crucial. But since this article is on the printheads, we can say that some printheads are significantly better than other printhead brands: speed differs astronomically; longevity (how long before the printhead fails) is also variable among brands.
As the first example, Dilli uses Konica Minolta printheads on some models; but newer models feature the speed benefits of Kyocera printheads.
EFI VUTEk printers in the past used Seiko heads. But gradually more EFI models are using Ricoh heads.
These three brands (Kyocera, Konica Minolta, and Ricoh) are respected brands. You do not tend to find these professional head brands in entry-level printers, for example. Every head has special features, and these heads are all well accepted.