Inkjet technology
The basic form of the inkjet was a single nozzle with either fluid forced through under pressure, pulled from it by electrical potential or pushed out with the help of a piezo.
Inkjet technology was pioneered by Teletype Corporation[3] in the 1960s which introduced the "electronic pull", high voltage drop extraction from a nozzle, Inktronic Teleprinter in 1965 printing at 120 characters per second (cps) from a row of 40 inkjets using the Charles R. Winston patent, Method and Apparatus for Transferring Inks, 1962, US3,060,429.
[3] Howtek was started as R.H Research in 1982 by Robert Howard after successfully growing Centronics,[3][4] the first dot-matrix solenoid-driven wire ribbon impact printer company in 1968.
Howard had tested making dots on paper by using ultrasonic sound in the late 1960s but did not advance the idea until some 20 years later in 1984 with Howtek when he hired 6 key employees from Exxon to develop his hot-melt color inkjet printer idea.. Exxon Office Systems(EOS), Brookfield, Ct plunged into the non-impact printer business in the late 1970s and invested as much as $2 billion.
Ken went on to work at UARCO business forms and made associations with developers of On-Demand inkjet, including Steve Zoltan at Gould and Silonics under Ed Kyser and Stephen Sears.
Within 6 months of joining R.H Research(name changed to Howtek) the Alpha jet print samples with hot-melt ink were being shown at COMDEX, in Las Vegas.
J. McMahon went on to work at Sanders Prototype(Solidscape) 3D printer manufacturer and is now employed at Layer Grown Model Technology supporting On-demand single-nozzle inkjets and claims to be the godfather of 3D Inkjet single-nozzle technology as a historian who worked in the field since 1978 with Steve Zoltan and Ken Bower at Exxon.
3D Inkjet single-nozzle printing has a direct path from Teletype hot-melt inks (Wax and metal alloy) to Steve Zoltan's single-nozzle jetting technology that never developed at Exxon with glass nozzles but became reality at Howtek with Teflon molded nozzles and heated printheads in 1984.
An ex-Howtek employee, Richard Helinski is credited for the patent using two materials to produce particle deposition articles in 3D using Howtek style inkjets and thermoplastic inks.
These same Howtek inkjets and materials were used in the Ballistic Particle Manufacturing, Personal Modeler and the Visual Impact Corporation, Sculptor 3D printer businesses that have since closed.
Single nozzle jets are still in use today in Solidscape 3D printers and are considered to produce a very high quality model.
Various drop formation technologies exist, and can be classified into two main types: continuous inkjet (CIJ) and drop-on-demand (DOD).
Released drops either fall vertically without any trajectory manipulation or require special fire timing when projected horizontally from a rotary printhead spinning at 121 RPM to form characters (Howtek color printer 1986).
Arrayed Inkjet Apparatus (John G Martner patent 4468680, 1984 Exxon Research and Engineering Co) was invented after testing a Piezo DOD epoxied on the end of a piano wire 30 inches long and inserted into an ink fluid chamber leading to a nozzle.
The object of the invention was to build a printhead to reduce crosstalk (sound or any energy into closely placed nozzles for text printing).
Howtek style inkjets and Thermoplastic materials were created to print documents and images and later Braille characters.
The CIJ formed ink drops are either deflected by an electric field towards the desired location on the substrate or collected for reuse.
Since this method is based on electrostatic deflection, ink additives, such as potassium thiocyanate, may deteriorate the performance of the printed devices.
Howtek produced its own full-color thermoplastic- ink material printing letterhead sheets in the rotary-head Pixelmaster printer in 1986 with 32 single nozzles (eight for each primary color).
The ideas for the design came from a book discovered by Jim McMahon in 1972, Harry F Olson's Music, Physics and Engineering.
[29] Earlier inkjet designs with glass nozzles were also resonance sources and when packed with vibration dampening material could never eliminate spray.
The square wave pulse leading edge triggered a sound wave in the fluid that reflected off the tail end of the nozzle tube and was reinforced when the lagging edge of the drive pulse was passing under the center of the piezo to boost the fluid pressure sufficiently to expel one single drop.
The speed of sound for each of the two inks (wax and Thermoplastic) differs resulting in two maximum resonance frequencies for the same inkjet nozzle structure.
It originally had a hex-shaped metal nozzle-end structure with an offset-nozzle orifice that allowed the jet drops to be (aimed) directed toward a target to align properly for the best print quality when it was previously installed in the Howtek Pixelmaster.
Over 1500 Howtek style inkjets were acquired by early Sanders Prototype, Inc when production of the Modelmaker 6 Pro was first started in 1994.
The original prototype 3D printer, the Sculptor by Visual Impact Corporation, using Howtek nozzles, printed horizontally in 1989.
The Pixelmaster also projected the drops horizontally from a 121 rpm rotating printhead to print 2D characters or images on paper.
It may be a deposition of a precursor followed by a catalyst, sintering, photonic curing, electroless plating etc., to give the final result.
See Ballistic Particle Manufacturing(BPM)which uses a Solid ink single nozzle, heated to 125C and a 5 axis printing technique that required no other process for fabrication.
Each inkjet assembly will have a slight variation in drop size and maintaining all material and jet parameters is necessary for optimum performance.
