Behind-the-scene stories about the development of the imagePROGRAF TX Series of large-format printers
Printing out CAD drawings of buildings at architectural design offices, making enlarged prints of photographs, and producing posters at shops and schools; large-format printers are tasked with outputting a variety of printed materials on such paper sizes as A0 and B0. Until now, Canon’s lineup of large-format inkjet printers was comprised of models dedicated to a specific use, such as graphic arts and photos, posters, and CAD drawings.
One day, we were asked to take on an almost impossible mission: to develop an unprecedented, large-format printer, which Canon technologies had not yet covered, a single unit that would be capable of outputting sharp and beautiful lines even on inexpensive plotter paper as well as handling not only conventional inkjet-use plain paper but also photo-quality glossy paper. In short, we were tasked with creating a printer compatible with both CAD and poster printing at a high level, which had never been achieved before.
But that wasn’t all. We were also tasked with achieving our fastest ever print speeds and simplifying the setting of roll paper, which had long been a niggling problem with large-format printers.
One kind of ink?the design of which typically varied from one type of paper to another?had to be compatible with multiple types of paper. Would we be able to pull it off? For our team of five facing this “impossible” task, we were faced with challenges day after day.
Chikanobu Ikeda
in charge of: firmware
Kenji Moribe
in charge of: materials development
Hajime Nagai
in charge of: process design
Tomohito Abe
in charge of: mechanics
Masaharu Shimakawa
in charge of: electrical systems
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Ikeda:Canon started with the development of the BJ-W9000 in 2001; the company’s first large-format printer, built from the ground up for the high-quality printing of such output as photos. I was involved in its creation as a member of the development project. As this was Canon’s first large-format printer, which set the standard for models to follow, and because my colleagues and I worked so hard on it, I have a bit of a personal attachment to this product. Actually, I privately refer to it as a “legendary device.”
BJ-W9000
For the BJ-W9000 printer, we made every effort on image processing, a field that Canon excels in, to achieve the best possible image quality. From 2002 onwards, Canon has launched several printer models aiming to fill out its lineup.
Shimakawa:The “iPF” series released in 2006 was particularly noteworthy. This series was comprised of three models for photographic and graphic art uses and three for CAD and poster uses. Efforts to expand the printer line-up continued in the ensuing years, which included the “PRO” series that realized high productivity as well as superb image quality high enough to satisfy the needs of professional photographers.
Ikeda:Our mission was to create a totally new-concept large-format printer: a single model capable of both CAD- and poster-use printing, even on plotter paper and other types of plain paper. What’s more, the printer was expected to be able to perform at high speed and output outstanding image quality.
Nagai:It was indeed a big mission. In addition to being able to reproduce fine lines of design drawings, cleanly and free of ink bleed, whether on inkjet plain paper or plotter paper, the printer needed to exhibit excellent color development performance not only when printing photos on glossy photo paper, but also when printing on plain paper.
Abe:It wasn't just that. High-speed performance was also a must in order to respond to the needs of the plotter market, where large volumes of drawings have to be output at high speeds. For large-format printing, the thing that takes the most time is moving the print head. So we focused on increasing print head scanning speed.
Shimakawa:On top of that, we were also asked to improve the printer’s overall ease of use. As you know, a paper roll is bulky and heavy, which makes even just setting it on the printer a pain in the neck. With conventional models, the user had to take the trouble of setting the paper roll on the machine by pulling out the paper edge then putting it into the paper feeding port. So, we aimed to simplify this process as much as possible.
Moribe:The key difference is the Inks. Conventional inks are designed to print cleanly according to the types of paper they are used for, such as inkjet plain paper and glossy paper. Inks for plain paper are made to quickly coagulate to prevent bleeding. Conversely, inks for glossy paper are designed to settle smoothly on the paper surface to give off a glossy sheen. As such, if you use an ink meant for plain paper to print on glossy paper, it will harden unevenly and make the paper surface rough, resulting in the loss of that sheen.
Our current mission was to create a so-called “multi-functional” ink capable of cleanly printing on any type of paper. In the beginning, I felt it was almost impossible to create an ink that could both reproduce CAD lines accurately and be used for poster printing. But I went back to square one and began to think about how I could approach this challenge.
Nagai:For this mission, the ink had to be able to reproduce sharp black lines whether it was being used for printing on inkjet plain paper or on less expensive plotter paper. When a conventional ink based on a combination of dye and pigment inks is used to print on plotter paper, the ink permeates into the paper, resulting in blurred lines. To overcome this problem, we had our ink development team design an ink that performs in a manner unheard of until now.
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Moribe:There are two types of inkjet printer ink: dye ink and pigment ink. Dye ink is suitable for outputting beautiful images on glossy paper, but it lacks water resistance. So, for this model, our first choice was pigment ink, which would enhance the water resistance of printed materials.
Comparison of water resistance between dye ink and pigmented ink
Image is for illustration purposes.
As I just mentioned, the most important thing for CAD is whether or not the printer can reproduce sharp black lines. Inkjet plain paper has various means to prevent the ink from bleeding. But cost-oriented plotter paper does not, allowing the ink to blur very easily. When thinking about what could be done, I decided to approach the problem by thinking about it from the ink side of things.
Bleeding occurs when the ink gradually permeates into the paper. To prevent this phenomenon, the ink needed to have some kind of property that would stop it permeating. So we created a so-called “tapered ink.”
Moribe:I began by observing the phenomenon of bleeding. I prepared a type of paper in which the ink was most likely to bleed to create the most stringent conditions for the ink. I combined with a microscope with a high-speed camera to observe what was happening after the ink lands on the paper surface and to see just how ink bleeds. Then I repeated these tests to see how bleeding would change when different types of paper and differently designed inks were used.
As a result, I found that black dots with the least blur were formed on the intended positions if the ink stayed there for at least a certain period of time without permeating the paper. Thinking it might be possible to draw a clean, sharp line by connecting these dots, I narrowed down the points into two key elements. One was surface tension. Take alcohol for example. Alcohol has low surface tension while water has high surface tension. So, when the same amount of alcohol and water are put on paper, the alcohol quickly permeates into paper whereas the water will remain in a ball for a while. Any liquid will be slow to permeate if its surface tension is increased. The other element was to raise ink viscosity. The more viscous a liquid, the harder it becomes to permeate. Naturally, it is hard to discharge a highly viscous liquid from a nozzle. Therefore, I made adjustments so that the ink has a low viscosity when it is ejected, but its viscosity increases after it has landed on the paper through such phenomena as water evaporation.
By controlling both surface tension and ink viscosity, it finally became possible to create a matte black ink that can realize sharp and clean black lines regardless of the types of paper. This ink has been adopted in our newly developed five-color full pigment LUCIA TD ink.
Comparison of matte black inks
Image is for illustration purposes.
Moribe:We decided to use pigment inks for cyan, magenta and yellow. Thanks to their low surface tension, these inks make it possible to output images cleanly on glossy paper. However, because color inks have a lower surface tension, when they come into contact with the matte black ink, which has higher surface tension, the color inks are drawn into the black, which results in blurring.
Nagai:By inserting another black ink with the same surface tension as the color inks, it becomes possible to prevent both types of ink from bleeding into each other. Of course, black inks with different surface tensions will bleed into each other, but they are both black so they look the same in the end. As a result, black and colors are separated clearly, enabling blur-free images to be created. To develop the imaging process design, I identified the area where colors and black came into contact and became prone to blurring, and I inserted another black ink into that area.
The mechanism behind why LUCIA TD ink does not bleed
Image is for illustration purposes.
Moribe:It was the development of “tapered ink,” which is totally different from conventional inks. Moreover, the tapered ink needed to be properly ejected from the print head. Designing an ink to produce clean images is different in nature from designing ink that’s easy to eject the ink from the print head. I knew it wouldn’t be so hard to create an easily ejectable ink if I slightly compromised on image quality. However, making such a compromise was the last thing on my mind as an ink developer. So I asked the print head development group to carefully consider the possibility of designing a dedicated print head that would be compatible with the tapered ink. And they came up with just the right design, one that also realizes high image quality.
Nagai:As someone working in process development, I felt the same way as Mr. Moribe. In order to achieve the targeted image quality, I teamed up with the print head development group and solved problems one by one. We worked on making ink ejection stable and highly reliable. The vivid color inks in question had a weakness: clean images could be achieved if they made an ideal landing on the paper, but if their landing was off, differences in ink density could occur, making the colors look different. So we looked for a dot arrangement that would make variances less visible on the off chance the ink landed out of place. However, there was one other problem. Typically, the print head moves at a maximum speed of about 70 inches per second, but the higher the printing speed, the more difficult print head braking becomes. As a solution, I asked the mechanical engineering group to design a carriage (a unit loaded with a print head that scans the paper width-ways while printing) that ensures high image quality is achieved even with the print head moving at such high speeds. Thus, it became possible to control not only dot arrangement but also the print head so that it could output optimal images accurately even at high speed.
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Abe:The mechanical designs of conventional carriages vary from one model to another because each model is designed to achieve optimal performance based on their intended purpose; either for CAD or posters. This time, our mission was to achieve a good performance balance between those two purposes while also realizing the highest-ever print head speed. When I first heard this incredible request my mind went blank--or rather, "black" like ink! (laughs). Despite such circumstances, the carriage design team members came up with one creative idea after another, and we were able to jump-start the design process.
To put it simply, all you need to make a carriage move faster is to enlarge its motor. But that entails a sharp increase in costs, so we had to rule out that option. Instead, we looked into other possibilities such as making the carriage itself lighter and reducing friction.
With the first prototype model, we could achieve higher speeds, but the carriage showed unstable behavior due to poor balance. To make it lighter and better balanced, I once even made a request, which I knew would be too demanding, to the electrical system team: “Please make a circuit board this small, whatever it takes!” But it soon became evident we could improve balance by establishing the center of gravity around the print head. So we made such adjustments as lightening the rear side of the carriage and successfully increased the carriage speed by 20 percent compared to conventional products.
Ikeda:When it comes to firmware (software embedded into devices), I thoroughly checked the flow of internal processing related to the printing speed. Of course, prior to this point I had also made painstaking efforts to eliminate unnecessary processing. This time, however, I looked even deeper. For example, I made improvements to aspects where processing time could be shortened by as little as one-hundredth of a second.
Shimakawa:Previously, it was typical for the electrical systems team to measure electric signal waveforms of motor movement and ink discharge, and to inquire of the firmware staff about any problematic parts where processing inefficiency was likely. For our new mission, however, we set up an investigative group dedicated to printing speed. Personnel from mechanics and process development teams also participated in this group, joining forces to scrutinize each and every process. I can proudly say that what we have achieved for high-speed operation represents the sum of our collective efforts and never neglecting even seemingly minor problems.
Abe:At the start, we concentrated our efforts on high speed. Once we'd achieved that, we were able to realize improvements in image quality with relatively less difficulty. Success in slimming down the carriage led to a simpler shape, which allowed us to incorporate technologies formerly used exclusively in either photo- and poster-use models or in CAD models. Looking back at the approach we took, I think our success in realizing high image quality was possible because we first focused on high speed, instead of aiming to achieve both goals at the same time. I felt the way we worked was something like doing a crossword puzzle; if one line on the grid was filled, it in turn makes it easier to fill other lines throughout the puzzle.
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Shimakawa:Office multifunction devices and printers found in offices use cut paper; in other words, rectangular sheets of A4- and A3-size paper. On the other hand, large-format printers use rolls of paper, which makes it hard to locate the paper feeding port as intuitively as with cut-sheet devices. Because of this, some users complain that it takes them a long time to get accustomed to loading paper rolls. Our aim, then, was to ensure that anyone could load these paper rolls with ease.
Our ultimate goal was to develop a printer that could load the paper automatically once the user had placed it in position. We succeeded in our goal, ultimately creating the industry's first*1 “automatic roll paper setting system” that automatically feeds papers rolls; users need only to place the roll and press a button.
*1 Among large-format printers (A2 paper size or larger). Based on Canon research.
Shimakawa:After the device has confirmed that the paper is in place and the paper loader unit cover is properly closed, the roll begins to rotate in the direction opposite to the feeding direction. As the edge of the paper touches the flapper, it slides off the flapper, allowing the edge to fall away from the paper roll under its own weight.
Then, a proximity sensor attached to an arm detects that the edge of the roll of paper has fallen, the roll reversed direction and guides the paper edge into the feeding port. This system features an algorithm based on a combination of our original gravity separation mechanism and a simple proximity sensor.
Mechanism of automatic paper roll loading (as viewed from the side)
The roll rotates toward the machine.
The edge of the paper roll pushes the flapper.
The paper edge comes off the flapper, allowing the paper to fall under its own weight.
The proximity sensor detects that the edge of the paper roll has come off the flapper.
Rotation is reversed, and the paper is guided into the feeding port.
Proximity sensor unitThis proximity sensor detects when something comes close to it. Proximity sensing is a familiar technology used in such everyday tools as smartphones, allowing them to turn off the screen display in order to prevent it from being mistakenly operated when pressed against the ear, or to prevent a telephone call from being interrupted.
Shimakawa:At first, I thought of using a shock sensor. After the edge of the paper pushes the flapper, the paper falls down and the flapper returns to its starting position. So I thought, "Wouldn’t it be possible to use a sensor to detect the shock that's produced at that time?" However, after further consideration, I came to realize that the way the paper edge leaves the flapper can vary significantly and the level of shock varies according to a number of factors such as paper hardness and the amount of paper on the roll--all of which affects the behavior of the flapper.
Developing a new component for this particular product was not a realistic approach because it would require a considerable amount of investment. Furthermore, large-format printers are long-lasting products, so we had to choose components that would ensure a long lifespan. As such, it was one of our priorities to develop original technology that utilized as many ready-made components as possible. While examining familiar products, we came upon the idea of using a proximity sensor. But despite this progress, there was still a long and difficult road ahead to complete the final design.
Shimakawa:When using relatively hard paper, the outer part of the roll, as opposed to the edge of the paper, tended to come close to the sensor and cause false positives. Also, if paper on the roll is loosely wound, the sensor would mistakenly detect the roll as being near. After considering a variety of algorithms, I came to the conclusion that it would be difficult for our electrical systems team to solve this problem on our own. So we asked the mechanics team for assistance. They came up with an exquisite design which involved adding a spring to the flapper so that it has slightly more strength. I'm sure we wouldn't have thought of this solution had we insisted on doing everything ourselves.
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Ikeda:I can say our teamwork was very good thanks to the positive attitude of our development team chief and the extensive knowledge of the other team members, who all demonstrated exceptional teamwork. Whenever a problem arose, we were able to quickly come together and solve it.
Abe:It was also important to have a flexible work environment in which everyone could freely express their ideas. Our team motto is "Don't hesitate to make bold suggestions for improvement." Refusal to back down because you don't want to be criticized for changing your mind can wind up causing critical delays. It's often the case that you make judgments as proceed with your work and things seem to be going well, then suddenly you stop and think "Wait, something's not right..." Our team culture is flexible enough to allow anyone to say “Sorry, I think I might have been mistaken. Let me rethink my decision." This helps us make quicker judgments and speeds up progress. That's definitely our greatest strength.
Moribe:When I'm working on a development project and I think something is impossible, instead of giving up, I take a step back, reevaluate conventional wisdom and think "Is it really impossible?" Instead of just deciding that it was impossible to, for example, combine ink that stays firm with more fluid ink, it's important to approach the problem from a different angle and challenge assumptions.
Nagai:I think it's important to maintain good communication with others so that we're all on the same page. In addition, I place a great deal of importance on understanding scientific principles. If we make an improvement by adjusting some parameter, I make sure to understand exactly why it improved before I proceed any further.
Shimakawa:In the field of electrical systems, we often design devices using products and parts commonly found on the market. Therefore, it's important to gather information and keep up with new developments. I'm always following the latest market trends and considering how to apply whatever useful products are out there to our own product designs. As such, I frequent trade shows and other industrial exhibitions because they're an excellent way to gather information.
Ikeda:The more advanced printers become, the more work firmware has to perform. Back around 2001, the firmware team comprised a mere handful of people, but now there are dozens of staff on hand. Each member is only directly responsible for a small portion of the firmware, and their areas of expertise are becoming more and more specialized. As a result, it becomes harder for individuals to maintain a view of the bigger picture in terms of functionality. Of course it's important to focus on one's specialty, but taking that too far risks losing the ability to see things from the end users' point of view. Therefore, I think we have to maintain a delicate balance between broad and detailed perspectives; to strive for perfection in our individual fields while maintaining a grasp of the overall workflow.
Abe:I attended the product announcement event in order to understand users' honest reactions. During demonstrations, guests were so impressed that they'd say things like "I can't believe it prints so quickly at this level of image quality!"
Shimakawa:When we demonstrated how easy it was to load the paper roll, people actually began applauding! That was an incredible feeling I'll never forget.
Nagai:Walking around town, I occasionally come across posters that I can say for certain were output by our printer. Seeing real-world applications like those is reassuring and makes me quite happy. Likewise, when I hear about the success of large-scale sales talks, I understand just how well our product is trusted. I want to experience more of these feelings in the future. I want to ensure that trust remains strong by working to create better and better products.
Shimakawa:When I use large-format printers for in-house presentations, I'm thrilled by what they're able to produce. I often hear feedback from customers who say "Wow! Large prints really make a difference." I'd like our customers to experience more of those moments. There is certainly a great difference in visual impact between smaller-sized prints and prints of A2 and larger sizes. Going forward I want to improve the ease-of-use of our large-format printers so that there are more opportunities to create large-size prints.
Moribe:There's always demand for greater speed and image quality, so I want to continue improving both. As someone in charge of inks, I plan to keep exploring new concepts and striving to deliver the high image quality that professionals are seeking.
I was pleasantly surprised by the precision and outstanding color that the TX-series could achieve using plain paper.
A breakthrough like this isn't possible if one were to simply give up and say "This is the only way," or "This is the best we can do." Instead, we persisted in our quest to find the best possible solution. Also important was the power of positive and forward-thinking teamwork, rather than everyone working on their own, that has resulted in this innovative new technology.
Thanks to its greater ease-of-use, this state-of-the-art large-format printer is sure to demonstrate its usefulness in many aspects of our lives.
