This is a recent paper I had to do for a Digital Print Processes Class I am taking at RIT
Cannon Image Press C6000
The Cannon Image Press C6000 print engine is very similar to the process of electrophotography. These steps are as follows – the charging of the photoreceptor, discharge of the image areas, developing of image areas, the transfer of toner to substrate and finally fusing of the image to the substrate.
Canon U.S.A. Incorporated, promises that the C6000 press will provide “image quality, productivity, and versatility” (Cannon 2). The first step that occurs within the C6000 engine is the charging of the photoreceptor. Then, the discharge of the image areas occurs using a twin red laser. Cannon claims that this special red laser allows for resolutions up to 1200 by 1200 dpi (C6000 Video). The next step within the process is the developing of the image using toner. The C6000 uses a four-color toner system, which does not allow for Pantone colors. However, much like other presses, the C6000 uses the Digital Front End to store CMYK equivalent colors in its library to allow for reproduction of these colors. Toner is placed on what Cannon calls an E Drum, a compact roller that helps carry the developed toner to the Advanced Image Transfer Belt (AITB) (Eddy par 4). The Advanced Image Transfer Belt is the main difference from the typical electrophotography process. The AITB is the intermediary that transfers the toner to substrate, instead of transferring the toner one color at a time, the AITB “transfers all four colors to the page in a single pass for a better impression on a wider range of coated, uncoated, and specialty stocks” (Cannon 7). Toner on the Cannon is known as a quick fix toner (often referred to as “V” toner) and allows for the fusing process to be faster than on a typical machine (Eddy 5). Lastly, the C6000 uses the fusing process to secure toner to the substrate. Cannon uses a “dual fusing system,” which is a method of heat pressure fusing, common in many digital printers (Cannon 6).
HP Indigo s5500 Digital Press
In contrast to the C6000, the HP Indigo varies more from the traditional electrophotography process. The most noticeable difference in this process is the use of liquid ink known as Electroink. This ink contains only two percent toner, imaging oil and an imaging agent, unlike that of the dry powder toner that is used in typical digital printer (Vogl Lecture). Just like a typical photoreceptor, also called the PIP or Photo Imaging Plate, is given a negative charge (Influence Graphics Video). Next, the image area is discharged using a laser on the PIP, which leaves a latent image area. The electroink is then attracted to the image area via the Binary Ink Development unit (BID), leaving electroink on the image areas of the PIP (Hewlett Packard Video). This is when the “inked image is then transferred to the electrically charged Intermediate Transfer Drum (ITM)” (Vogl Lecture). The Indigo is similar to the original process of electrophotography in that the image is not directly placed on the substrate with toner, but the process does differ in the fusing process of ink to the substrate. The impression cylinder makes a single rotation for each color instead of a traditional process, and the Intermediate Transfer Drum (ITM), which is electrically charged, transfers the image to the substrate. The inks on this printer dry almost immediately to the surface, allowing for prints to come out of the printer dry. This is due to the high heat that the ITM reaches, which causes the imaging oil to be refracted and the toner to bond and become solid (Print Applications Lab Video). The substrate “then passes between the ITM and the impression drum” (Vogl Lecture). The toner is transferred to the substrate, and the PIP rotates past the cleaning station, which removes any residual ink and charges (Vogl Lecture).
Xerox iGen 4
The Xerox iGen 4 utilizes a unique way to build an image, using as its base the steps of the traditional electrophotography process. However, it adds a slight twist, utilizing a belt mechanism to image the substrate being printed. The iGen contains four developer housings for each of the four colors of CMYK. The image is created on the photoreceptor belt, by charging, imaging it and recharging the photoreceptor for each separate color (Xerox Video). A scorotron charge is then released onto the photoreceptor belt. After this occurs, a laser will release the toner onto the belt, which is then developed. This occurs for each color in the order of Magenta, Yellow, Cyan and Black respectively (Xerox 7). The image is developed by a cloud of toner in between two donor rollers, which are then transferred to the photoreceptor belt (QDoxs Video). The donor rollers help to protect the toner on the photoreceptor belt, allowing for all four colors to be printed with out disruption of another toner layer. The transfer step occurs when the Pretransfer Erase Lamp exposes the belt to loosen toner and then a “hybrid Air Knife removes carrier beads and agglomerated toner particles from the belt” (Vogl Lecture). What is known as the pretransfer belt then uses a charge to help remove the toner from the photoreceptor, and a “Transfer Assist Blade presses substrate to the photoreceptor belt” (Vogl Lecture). What is known as the Detack Dicorotron applies a negative charge underneath the substrate to ensure limited friction between itself and the photoreceptor belt. The image is then transferred in a reverse order of KCYM. A front erase lamp erases any residual charge on the photoreceptor to ensure a clean area for image creation for the next pass. Finally, the image is fused using a contact fuser to create a final product.
Ricoh Pro C550EX
Of all the print engines explored in class, the Ricoh Pro C550EX truly encompasses the original electrophotography process. This is printer is geared towards small business and small print on demand jobs, so it is more user friendly and closer to electrophotograhpy.
The first step in the C550 EX is the charging of the photoreceptor. The printing process uses a scorotron charge to create a uniform charge on the photoreceptor (Ricoh Video). Using a laser, the image area is then selectively discharged just as was shown in class. The toner is then taken up with carrier beads and adheres to the image area. Ricoh has a unique system of toner that allows for finer details – “Sharpen every image with new PxP toner technology. Smaller toner particles ensure smooth, even distribution, which enhances edge definition, coverage and density while improving color matching” (Ricoh 3). This actually appears to be a major selling point of this printer according to many print blogs online (ESRI Forums Web). Also, within the development stage, the C550 runs a “parallel calibration to ensure consistent color quality over long job runs,” to assist with correct color management (Ricoh 3). The image is then developed. The next step in the process requires a transfer of the image to the substrate. The transfer of the image occurs on a belt system to make sure that the substrate receives toner is a smooth and efficient fashion. During the transfer stage, the printer is equipped with a registration sensor to make sure that paper stays in line when the substrate moves through the machine (Gregor Communications Video). This carries through to the fusing process, where the “system incorporates a smaller, more precise mechanism for moving paper in and out of the fuser unit” (Ricoh 3). By allowing for this, heaver stocks of substrate are able to move more easily through the fusing unit, which allows for more of a variety of jobs to be done on this machine.