How Toner is Used
Other Factors impacting LaserJet Print Cartridge Yield
The ISO/IEC yield methodologies allow the customer to compare the declared yield of cartridges from many different manufacturers. The printing style of the customer (type of documents printed, number of color pages, size of print jobs, image density, simplex v. duplex, etc.) will have a substantial impact on the cartridge’s actual page yield. Accordingly, actual yield may vary considerably from the declared yield and HP cannot guarantee that a customer will always achieve the declared page yield. Many customers will find that their print cartridge provides more pages than this declared yield and other customers will find that their printing style results in the cartridge providing less pages.See LaserJet page yields for more detail
HP designs its LaserJet printer systems to deliver outstanding value and print quality over the life of the printer. In order to accomplish this, the LaserJet printer system is made up of the printer itself and the HP LaserJet print cartridge/s. These print cartridges (which are sometimes called ‘toner cartridges’) contain far more than toner. These print cartridges are complex multipart systems, one part of which is toner.
The design details of the print cartridge/s used in HP LaserJet printers differs between printer models to reflect the different customer needs being addressed by different printer models. For example, a LaserJet monochrome printer can have a different cartridge design than an HP color LaserJet printer. Color printing is more complex than monochrome printing and the cartridges used in color printing can differ significantly between different HP color printer models. These design differences are driven by HP’s goal of delivering the best value, printing experience and outstanding print quality for a variety of customers who have different printing needs.
All LaserJet cartridges contain a number of mechanical parts in addition to the toner. These components—such as developer, photoconductor (PC) and cleaning blade—wear during the printing process as the toner is used. While these components are designed to be durable, different printing styles can cause different parts within the cartridge to wear at different rates. For example, in some laser printers, the printing of mostly low coverage pages may result in other cartridge components wearing out before the toner is depleted. In another case, printing mostly on narrow paper like envelopes can cause the PC to be the first component to reach end of life.These worn components will ultimately lead to print quality degradation just as toner depletion can lead to print quality degradation.
In addition, the toner itself is a complex chemical formulation designed specifically to work with the other printer system components to deliver consistent high print quality. Because it is physically impossible to extract all of the toner in a LaserJet print cartridge for printing purposes, some residual toner will always remain in the cartridge, but whether this toner is useable and the amount of this residual toner will differ depending upon customer printing styles and cartridge design. Because toner is subject to physical movement (stirring) during printing, the toner can actually become ‘worn’ during the printing process to an extent that it can become unusable. This wear can limit the ability of the toner to develop the image properly and cause print defects. Other factors can also impact print cartridge yield. For example:
- Stop and start printing – Each time a print job is started there are several rotations of the printing system before and after printing is complete. These rotations cause wear to all components in the printing system, including the toner.
- Environmental issues at the customer site – HP designs its printing systems to provide quality and reliable printing over a wide range of environments, but some environments can cause the system to use more or less toner, impacting the yield. For example, very humid environments can cause print cartridge yields to decrease.
- Alienation issues and alienation formulas – On color printers, there are special modes that disengage the color cartridges from the system when monochrome only documents are printed. This is called alienation. Depending on the frequency of monochrome and color documents being sent to the printer, the alienation system may not disengage the color cartridges in some instances. Customers value fast printing speeds so the alienation system is designed to strike a balance between printer speed—which is faster when cartridges are not alienating frequently—while minimizing the wear on the color cartridges. The frequency of alienation can impact the life of the color cartridges due to increased wear on the cartridges rather than use of toner.
- Toner as cartridge lubricant – In the printing process, there are systems where a very small amount of toner is used for lubrication. Contact areas between cleaning blades on the PC and on the transfer systems require a small amount of toner to reduce friction and increase life. Use of this toner is taken into account when conducting ISO yield testing (stated differently, ‘extra’ toner has been included in the cartridge during manufacture to account for lubrication).
- Underprinting – To improve the “blackness” or overall PQ of some areas of a print, HP may use some colored toner along with black toner to generate certain black areas on the page. This is done to provide the highest print quality possible for the customer.
- Manufacturing variances – As with all manufactured systems, there will be some variation in all of the parts of the printing system. Some of this variation can be accounted for with calibration of the printing system—so from time to time the HP printers will calibrate themselves. Other manufacturing variance can not be accounted for with calibration and may impact the yield of the printing system. To ensure this variation is minimal, HP uses multiple printers and print cartridges when measuring yield. The ISO testing methods that HP uses require a minimum of 3 printers each using a minimum of 3 cartridges/cartridge sets.
- Composite black – For black and white images and photos, a blend of colors called “composite black” may be used to achieve significantly better image quality and smoother gray tones than can be accomplished with black toner alone. For users who wish to print images using just black toner, many HP color printers offer customer configurable options enabling the customer to print using only black toner. For example, by selecting “print in grayscale” in the printer driver specifies printing using only black toner.
- Duplex printing – in order to print on both sides of a page, the paper must travel a longer distance while the printed side of the page is reversed. This can cause more rotations and mechanical wear on the cartridge and lead to reduced cartridge life and page yield.