Continuous ink system

A continuous ink system (CIS), also known as a continuous ink supply system (CISS), a continuous flow system (CFS), an automatic ink refill system (AIRS), a bulk feed ink system, or an off-axis ink delivery system is a method for delivering a large and practically unlimited volume of liquid ink to a comparatively small inkjet printhead. Many business and professional grade printers incorporate a continuous ink system in their design to increase the speed and volume of printing capacity. Some aftermarket companies also build retrofit accessories to convert certain models of consumer-grade printers into continuous flow systems.

Comparison to the tank-on-printhead design

Most low-cost consumer printers place small ink tanks directly on the carriage with the printheads. These tanks can have extremely small liquid volumes, as low as 10 mL, and consequently require frequent replacement. More expensive business-grade printers use progressively larger ink tanks on the printhead, but as the platen width and speed of the printer increases it eventually becomes impractical to have the tanks integrated with the printheads due to the high mass and inertia the liquid volume adds to the printheads and the reduced accuracy of printing that occurs.

Separating the ink storage from the printhead also allows the tank to be refilled or replaced while a print job is in progress. With ink tanks located on the printhead, replacement typically requires repriming and alignment checks that necessarily require aborting any current print job. Separated ink tanks can be refilled or reprimed without disrupting a very large or expensive printing task, such as printing a 2 meter wide by 10 meter long outdoor banner.

Retrofit accessory kits

Many CIS systems have been developed to cover most Epson, HP, Canon, and other printers. These bulk feed systems also allow users to use inexpensive aftermarket inkjet inks as well as specialty inks for T-Shirt transfers or Black and White inks for B&W printing. These options have allowed users to produce specialty prints at a fraction of the cost of purchasing special cartridges or using more expensive printing solutions.

Retrofit continuous ink tanks designs vary, and most incorporate a constant level, barometric pressure design. Constant level CIS delivers a smooth flow of ink to the cartridges as needed. The front tank is vented to atmosphere, and negative gauge air pressure in the back tank delivers ink to the cartridges.

Retrofit ink tanks   Retrofit ink tubes suspended from the T-shaped plastic support   Retrofit ink tubes connected to a standard printer cartridge   Retrofit ink tank design

Limitations of retrofitting

Some printer manufacturers explicitly state that use of third-party inks and/or aftermarket continuous ink systems will void their product warranty.

Many consumer grade printers are designed with close-fitting and sometimes fully enclosing shrouds over the print carriage. It may be difficult or impossible to install a retrofit kit because there is no room to install the flexible tubing that must flex and bend as the printhead moves back and forth. Jamming may occur if the tubing droops into the path of the printhead and is crushed underneath the printhead or between the printhead and cover. It may be necessary to modify the printer by removing the cover or cutting slots into the body to provide an open space for the tubing.

Some tank-on-carriage printers such as Epson use a fold-over clamping system over the tank to secure it in place on the print carriage. This clamp blocks the path of tubing from a continuous flow system feeding the tanks, and the print carriage may need to be modified by removing the clamp, cutting holes in the clamp, or installing a retrofit open-top clamp.

Typically any modifications to a product's intended design purpose, such as using the product with an aftermarket CIS, will void all manufacturer warranties against defects and fitness for use. However, there are US Anti-Trust Laws that may prohibit this practice.

United States Code Annotated – Title 15 Commerce and Trade. Chapter 50 Consumer Product Warranties 15 Section 2302.

(c) No warrantor of a consumer product may condition his written or implied warranty of such product on the consumer’s using, in connection with such product, any article or service (other than article or service provided without charge under the terms of the warranty) which is identified by brand, trade or corporate name; except that the prohibition of this subsection may be waived by the Commission if:

1. The warrantor satisfies the Commission that the warranted products will function properly only if the article or service so identified is used in connection with the warranted product, and

2. The commission finds that such a waiver is in the public best interest.

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