A stored energy printer is a

computer printer In computing, a printer is a peripheral machine which makes a persistent representation of graphics or text, usually on paper. While most output is human-readable, bar code printers are an example of an expanded use for printers. Differ ...

that uses the energy stored in a spring or

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

to push a hammer through a ribbon to print a dot. As compared to

dot matrix printer A dot matrix printer is an impact printer that prints using a fixed number of pins or wires. Typically the pins or wires are arranged in one or several vertical columns. The pins strike an ink-coated ribbon and force contact between the ribbon ...

s that print a single column of dots at a time, this printer generally creates an entire line of dots at a time. Therefore, it is also known as a

line matrix printer A line matrix printer is a computer printer that is a compromise between a line printer and a dot matrix printer. A line matrix printer prints page-wide lines of dots, building up a line of text by printing lines of dots. Applications Line matri ...

. This technology produces premium impact printers that print for millions to billions of dots per hammer. The advantage of this technology is that it has the lowest known cost of ownership: ink is transferred by conventional typewriter-style ribbons.

Technology and use

The most common printer to use this technology was the line-matrix printer made by

Printronix Printronix is an American supplier of line matrix printers. Printronix is based in Irvine, California, and operates across 14 offices worldwide. Products Printronix's printers are primarily used in industrial environments for printing high-volum ...

and its licensees. In this type, the hammers are arranged as a "hammerbank"; a type of comb that oscillate horizontally to produce a line of dots. A character matrix printer has also been produced. In this printer, the

hammer A hammer is a tool, most often a hand tool, consisting of a weighted "head" fixed to a long handle that is swung to deliver an impact to a small area of an object. This can be, for example, to drive nails into wood, to shape metal (as w ...

s are machined from an oval of magnetically permeable stainless steel, and the hammer-tips form vertical rows. The original technology, patented by Printronix in 1974, has the top of a stiff

leaf spring A leaf spring is a simple form of spring commonly used for the suspension in wheeled vehicles. Originally called a ''laminated'' or ''carriage spring'', and sometimes referred to as a semi-elliptical spring, elliptical spring, or cart spring, it ...

held back by a

magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...

ic pole-piece. A

tungsten carbide Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...

hammer is

brazed Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal. Brazing differs from we ...

to the center-top of the leaf spring. When it produces a dot, a coil (

electromagnet An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the ...

) wrapped around the pole-piece neutralizes the magnetic field. The leaf spring snaps the hammer away from the pole-piece, pushing the hammer out against a ribbon and placing an image of a dot onto the paper. Recent designs have performed complex optimizations in the magnetic circuit, and eliminated unwanted

resonance Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillatin ...

s in the spring. The result was a near-doubling of speed. Other improvements include the use of

electrical discharge machining Electrical discharge machining (EDM), also known as spark machining, spark eroding, die sinking, wire burning or wire erosion, is a metal fabrication process whereby a desired shape is obtained by using electrical discharges (sparks). Material i ...

to produce complex, three-dimensional hammers that trade-off the magnetic circuit, mechanical resonances, and printing speed. Normal wear usually occurs when the spring rubs against the pole-piece as it returns. This causes the pole-piece to wear, eventually requiring the pole pieces to be reground and recertified. Hexavalent

chrome plating Chrome plating (less commonly chromium plating) is a technique of electroplating a thin layer of chromium onto a metal object. A chrome-plated item is called ''chrome''. The chromed layer can be decorative, provide corrosion resistance, ease ...

on the pole-piece, combined with careful design, more than doubles speeds and improves life-span. It produces approximately a billion impressions per hammer. Computer peripherals Computer printers Impact printers {{writingsystem-stub