Not all UV curable, rigid board printers were created equal


Well-known member
How to choose the printer that best fits your needs
Randy Paar
Marketing Manager, Display Graphics
Canon Solutions America

UV curable rigid board printers, commonly referred to as “flatbed” printers have been around for over a decade and continue to be an area of growth for print service providers due to the wide application range and the relatively higher profit margins for large format graphics compared to other graphics segments.
Commercial printers from large to small are either presently outsourcing large format graphics or taking the plunge and purchasing their first flatbed printer to produce these graphics in-house.

If this sounds like you then read on… for the uninitiated, buying a flatbed printer can represent a daunting task fraught with uncertainty and fear. How do you know if you’re buying the best solution for the applications you want to produce today but also suitable for the applications you may want to produce in the future?

Buying the wrong printer can tie up your capital for years, potentially causing you to lose customers due to unsuitable quality, or cost too much to operate, or may limit your versatility to produce new applications. In this article we identify different approaches in printer design, the importance of inks and which applications are best suited for each type of system. Additionally we give you some tips on how best to kick the tires during your sales cycle so you avoid an unpleasant surprises down the road.

Two types of printers
In the beginning there was roll-to-roll printing… and it was good! Until someone thought that instead of printing onto a roll and then mounting that onto a board that printing directly onto the board would save time, materials and waste. That’s when someone decided to open up the print gap on a roll-to-roll inkjet and push a board through to create a direct-to-board inkjet print.

That led to what today we call a “hybrid” printer. A hybrid printer could generally print on both a rigid board or on roll media allowing for great flexibility for shops that had a mix of work.
Eventually, certain manufacturers less concerned with roll-to-roll support started devising a new style of printer that featured a stationary flatbed table on which the board rested while being printed. That started a different tangent in printer development – the true, stationary flatbed printer!

What’s the difference?
Both the hybrid and the stationary flatbed operate very differently and that has significant implications in the types of applications you can produce, the labor required, the physical footprint and the overall print quality and repeatability. Let’s take a look at the basic operation and the pros and cons of each design in more detail.

The Hybrid printer
Operation can be quite simply summed up as “trying to hit a moving target”. The operator loads a square or rectangular board onto a feed table in the front of the printer ensuring that the board edge is registered against a flat guide and fed straight into the printer where a belt then transports the board past the print zone. As it prints, the operator may often check that the board doesn’t skew.
Then, before another board is loaded, the operator must run around to the other side of the printer and remove the printed board from the rear take-up table and then run to the other side of the machine to continue production of the next board.
For roll-to-roll printing, the operator must remove the two tables used for rigid board printing and store them away and then re-attach them again when they need to switch back from roll to rigid work.
Hybrid systems, having evolved from roll-to-roll printers, often have the roll-to-roll capability built-in resulting a lower system cost than a stationary flatbed with an additional roll option.
Because rigid board printing requires tables on the front and back of the printer, the overall footprint is considerably larger than a stationary flatbed.
Switching between roll and rigid printing requires removing, storing and re-attaching the tables
Printing onto a “moving target” means that image placement relative to the board is going to be different every time
Unless the work you do is always single sided printing onto square or rectangular substrate, you’re not effectively able to produce higher margin graphics such as texture printing, double-sided work with accurate front/back registration, printing onto irregular shaped objects with first building a jig, printing full bleed, etc.
True, Stationary Flatbed
Printing on a stationary flatbed printer is relatively straightforward. A board is placed on the table and usually registered against some registration pins or positioned by eye in relation to some fixed reference points on the table surface. A vacuum is then switched on to hold the board securely in place and the gantry and inkjet carriage system moves across the board to print the graphic. During printing, there is nothing the operator is required to do. Once the board is printed, the vacuum is turned off, the board removed and the entire process is repeated.
For roll printing, the device needs some form of roll printing option. Some manufacturers systems stretch the roll media across the flatbed table while others offer a dedicated Roll Media Option that has its own print platen leaving the table open to stage the next rigid job. Switching between roll and rigid is then accomplished with the push of a button
Greater range of applications including printing to irregular shapes without requiring a jig, texture printing, accurate double-sided printing, full-bleed printing.
Unattended printing. Once the printer starts printing, the operator can walk away and perform other tasks.
The stationary flatbed printer has a significantly smaller footprint
Switching between roll and rigid printing does not involve any tables
Usually a higher price than a similarly productive hybrid printer due to a more demanding manufacturing process.
Roll printing capability is an option, rather than standard.

Curing system, ink and printhead technologies
One major change that has been happening over the past five years is the increasing adoption of UV-LED curing systems in place of the traditional Mercury vapor lamps. Each approach also has its unique features and benefits.
Mercury vapor lamps produce an abundant range of usable wavelengths of curing energy and have been used in the printing industry for many, many years. As a result, formulating compatible inks is a relatively well known process and ink chemists are presented a wide range of suitable chemical components to choose from, depending on the characteristics they are trying to achieve.

Because the light source is an analog bulb, the upfront lamp cost is relatively low which helps keep the initial machine price and subsequent lamp replacement costs down. However, since these are high intensity UV lamps that need to first warm up and stay on during the print cycle, they do consume more electricity than UV-LED and depending on printer design and bulb used, can produce considerable heat on the media surface and eventually need replacement.
There are several notable benefits that UV-LED curing brings. Because LEDs are electronic components, they can be switched on and off instantly from zero to full intensity or anywhere in between. This means that there is no warm up time or mechanical shutters to block the light when it’s not required. UV-LED is also long lasting and not requiring replacement under normal circumstances. Compared to one competitive Mercury vapor system, over a typical 5-year lifespan of a printer, this can represent a cost savings of about $4,000 in Mercury vapor lamp replacement costs. Not a huge amount but still more than is required with UV-LED.
Electrical use is also a benefit with UV-LED as they can draw significantly less power than conventional Mercury vapor bulbs. This is exacerbated by the fact that the Mercury vapor lamps must first warm up and then be constantly on throughout the entire print cycle.
The last benefit is the perception of lower heat generated on the substrate’s surface by UV-LED curing. While in theory this sounds true it’s important to point out that a UV-LED array still generates a considerable amount of heat. With some heat sensitive substrates, this heat can deform the substrate causing a range of issues including permanent deformation, head strikes, dimensional distortion resulting in multi-panel misalignment, etc. Meanwhile, certain Mercury vapor systems have significantly improved on their heat management to actually compete if not exceed the performance of LED systems.
In addition to heat and humidity, latex printers give off VOCs, which can have unwanted effects if not properly addressed. This may require further investment in HVAC improvements that should be identified early on in the sales cycle.
Latex systems also print additional substances besides just the visible CMYKcm or White inks. A “primer” must be used on all substrates to “optimize” ink adhesion. Additionally, if you are not planning on applying a protective laminate film, a protective “coating” is also recommended to be printed overtop the ink to provide some improved level of abrasion and chemical resistance.

Both the primer and top-coat add to the cost per square foot of the printed graphics. In addition, the Latex system also requires users to purchase costly Maintenance Kits to be used every 20 liters of ink.
The printhead technology is also very different in Latex printers compared to UV curable printers. Latex printers use disposable thermal printheads compared to semi-permanent piezo-electric printheads used in UV curable printers. There is a misperception that these semi-permanent piezo printheads are as much as seven to eight times the cost of a $600 thermal printhead. On the surface, this would be true however the semi-permanent nature of a piezo head makes the need replacement far less frequent, if at all compared to an absolute need to replace thermal printheads. (Thermal printheads are only guaranteed by the manufacturer for 8-12 liters of ink.) As a result, the yearly printhead costs on a Latex printer can far exceed those on a UV printer.

Another important aspect about printheads is the drop size they can produce. In this case smaller is generally better because smaller drops mean finer detail and smoother vignettes. Many piezo printheads used in todays UV curable printers are greyscale printheads meaning they can produce a range of different size ink drops from as small as 6 picoliters (six one-trillionth of a liter). This is possible due to a piezo crystal in each nozzles ink chamber in the print head is capable of rapid firing multiple, single sized ink drops in quick succession that combine in mid-air before striking the media surface thereby producing varying sizes of drops on-the-fly. This is beneficial because not every image consists of only fine detail but also areas of solid, saturated color. Here the large ink drops provide good coverage.

Test, test and test
So, let’s say you’ve narrowed it down to a couple of vendors and now want to get them to produce a benchmark. It’s important you test these in an apples-to-apples comparison as best as you can AND test them on a wide assortment of substrates and in all the published print modes. Ideally, you are there when they print the files so you can confirm print times.
First, based on your primary applications, make a list of all the objectives you have in the new printer. This might include what number of boards you need to produce per day or month and at what level of quality is required to be sellable to your customer.

Use the same benchmark image between the vendors and have each print the image at the same size and in all the different modes across a full range of standard media that you will be using. Ideally this is a good test image that shows off all the attributes of a printer. Any printer test image such as the ONYX Quality Test Print distributed with the ONYX Thrive RIP is a good example of an image that will test any printer and show its strengths and weaknesses.

Ensure that the vendor labels all the prints with substrate name, the print mode used, total print time from when the RIP’ed print was released from the print controller to when the print was completed and if possible, the amount of ink used.

Now it’s a matter of comparing print quality and finding which mode produced the most desirable results. From there you now want to compare the related print speeds that produced the desired quality. You may find that some printers have to print slower than others to match a particular quality yet their price doesn’t reflect this. Consider if the printer can keep up with print volumes using that print mode. Is there still room for growth or to handle peak periods?

Now look at the cost of operation. Not only the ink cost per square foot printed but what additional costs need to be considered such as maintenance kits, printheads, electricity, additional primers/coatings and labor.
Finally, take the important step and evaluate the prints for adhesion and abrasion resistance. Many inks look like they perform well until you cut through the ink in a cross-hatch pattern, apply tape and quickly peel it back at 180 degrees and see how much ink comes off. This “tape test” is a quick way to check the quality of the ink adhesion on a particular media. Additionally, you could use a rotary abrader and see how many cycles the ink will last before it gets worn away. Also, like the rotary abrader, a rub resistance device can also wipe a printed test sample multiple times with common cleaners and solvents ranging from ammonia based cleaners to acetone to see how long it holds up.

Perhaps your application uses White ink. Before you go too far down the path evaluating a particular vendor’s product, ask if White is always online or if it needs to replace the light cyan and light magenta inks. This can have a detrimental effect on the CMYK image quality that you may have already accepted in the previous testing. Also, flushing out light inks so you can load White ink is both time consuming and wasteful. Make sure to ask how long that takes to perform and at what cost.

You’re buying more than just a printer
It’s easy to get too focused on the printer and forget to take into account the company that you‘re buying it from. You could have the best printer on the market but eventually all devices will at some point break down. That’s when it’s important that you’ve partnered with the right vendor so that your downtime is minimized. Some questions you should ask them/yourself:

  • Do they provide direct Service and Support
  • How many factory certified, trained technicians do they have and how many units are installed in the country
  • Where do the technicians have to travel from and what is the response time
  • What local parts availability is there
  • Is there an escalation path to the factory
  • Who provides the training? The Technician or an Applications Specialist?
  • Is there a Help Desk to call for support
  • How long is the warranty period and what is covered? Parts? Travel? Labor?
  • Are they a true end-to-end solutions provider or just a box mover selling only one component of the overall workflow
  • Do they sell compatible, tested media
  • Do they provide a growth path in their portfolio as my business grows
  • Do they finance internally or use a third party that either holds the lease, just sells the paper, or do they require you to find your own financing
  • Is there any trade-in value in 2, 3, or 5 years to move into newer technology?
In conclusion
The purpose of this article was to show how implementing a common sense, methodical approach will help minimize issues down the road and help ensure you get the most value from your investment.
What we have not touched on is the emotion involved in buying a large format UV printer that could cost as much as a house! It’s not uncommon to feel uncomfortable, or uncertain - that you’re perhaps overextending yourself, that maybe you should consider the “cheaper” solution.
But consider whether the cheaper option will meet your needs now and in the future? We’ve seen many first time buyers underinvest out of fear, and regret it later – even if the more expensive solution could in reality have been paid for perhaps in printing just one or two more boards per day.
A good vendor can show you the ROI based on your application using your costs and your selling prices to determine how long it will take to recoup not only the investment in a minimal system but also how much it will take to recoup investing in an optimal system. It may surprise you! The difference may only be a few weeks.

The world of flatbed printing continues to grow with many new applications and substrates being dreamed up constantly. Hopefully, we’ve at least given you some things to ponder and armed you with some good questions to minimize any unpleasant surprises as you go about deciding what to purchase in this exciting market segment.


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