Most users of EDM wire only know their wires by the brand name used by their respective manufacturing or marketing company. It is very important to understand what is behind an individual brand or product before making a specific selection. One should know the technology behind each brand and what it has to offer. All of the available brands can be classified into two basic categories: Standard Brass EDM Wire and Coated Brass EDM Wire.
All standard brass EDM wires are composed of a homogeneous binary-copper zinc alloy with zinc contents ranging from 35 – 40 weight percent. It is known that EDM electrodes benefit from increased zinc content because of zinc’s low energy of vaporization and to a lesser extent are hindered by lower electrical conductivity. It is also known from metallurgical principles that alpha phase brass is easier to deform than beta phase brass so it is no accident that the most common binary Cu/Zn alloys have 35% (Asian) and 37% (European) zinc contents. They contain the maximum zinc content available in alpha phase brass which has a balance between optimum vaporization and electrical conductivity. The two phase brass (40% Zn) alloy typically cuts 3 - 5 % faster than the single phase alpha brass alloys, but generally costs more because of the added processing costs required by additional process anneals and in some applications can be subject to brittleness issues.
Zinc Plated Wire
Historically the first attempt to attain higher cutting speed than standard brass EDM wire was to electroplate a thin pure zinc coating onto the surface of a single phase alpha brass alloy core. Such wires became known as “A-Type” wires and are still in use today. Unfortunately the thin coating thickness limited the height of the workpiece to 3 – 4 inches for appropriate applications since the low melting point of the zinc (420⁰C) allows the coating to be softened and literally blown off the surface of the core wire by the intensity of the spark discharges and the hydraulic forces of high pressure flush systems.
Diffusion Annealed Coated Wire
The workpiece height limitation faced by “A-Type” wires was overcome by diffusion annealing which is a well-known metallurgical phenomenon where two elements intermix, driven by a concentration gradient, when heated to an elevated temperature.
The first diffusion annealed wire type introduced was a beta phase brass layer on a copper core which has become known as “X-Type” wire which typically is only used on Charmilles machine tool models due to the low tensile strength of the core. “X-Type” wires have the advantage of a zinc rich surface (approximately 45% zinc), a high conductivity, and the elevated melting point of beta phase brass (approximately 880⁰C).
The second diffusion annealed wire type introduced was a beta phase brass layer on an 80Cu/20Zn core and that product has become known as “D-Type” wire which has found application on a wide variety of machine tool types. It too has a zinc enriched surface (approximately 45% zinc), a higher conductivity core than standard brass, and the elevated melting point of beta phase brass (approximately 880⁰C).
Gamma Phase Coated Wire
Gamma phase brass is a brittle intermetallic alloy (Cu5Zn8) with a high zinc content (approximately 65% Zn) which can also be synthesized by a diffusion anneal. However when such coatings are wire drawn subsequent to the diffusion anneal, the coating will fracture due to its brittleness and redistribute around the wire circumference creating a discontinuous layer sometimes described as a “porous layer” which promotes turbulent flow enhancing the flushing of debris. However it is zinc enrichment created at the surface combined with the elevated melting point of CuZn gamma phase (approximately 800⁰C) which are the biggest factors contributing to the outstanding performance of Gamma Phase Brass coated wire types.
Multi-Phase Layered Coated Wire
In addition to the three previously mentioned brass phases (alpha, beta, and gamma phase), there is one more brass phase that has unique properties that can be utilized in EDM applications – epsilon phase brass (approximately 85% zinc content). All of these phases can be arranged in various combinations to take advantage of their individual physical and chemical properties. Examples of such combinations are Gamma X, Gamma D, and Epsilon (see discussion of Epsilon product in Portfolio Tab).
Complex Alloy Coating Microstructure
In 2016 Dr. Tomalin identified an innovative technology for manufacturing a complex alloy coating with a unique microstructure that incorporated beta phase brass precipitates interspersed within a host gamma phase brass coating layered on a beta phase brass intermediate layer. The resultant product which has been named Blaze wire has been extensively field tested in wide ranging applications where the performance of Blaze is characterized as reducing repetitive job cycle times by 10% - 30% through increased cutting speeds and/or reduced wire breakage. Patent applications are pending in the United States and Europe.
Electrolytic Plasma Technology
Late in 2017, Dr. Tomalin, developed a gamma phase nickel-zinc coated EDM wire with an essentially continuous coating with a zinc content in excess of 80% and with a melting point of approximately 800⁰C. Initial laboratory testing indicates the above combination of properties results in cutting speeds 15% faster than similarly constructed gamma brass coated wire types (i.e. gamma phase coating on an alpha brass core). A Meteor 80 wire product produced with this patent pending technology will be available in the second half of 2018.
GIP WIRE PORTFOLIO
GIP EDM wire portfolio only includes coated products which have been produced using unique proprietary and patented technologies.
KLEEN: Produced using a patented hot dip coating process.
PLASMA: A gamma brass wire produced using proprietary electroplating and hybrid diffusion annealing process.
EPSILON: Produced using patented “dual” coating gamma phase technology.
METEOR: Produced using a patented Nickel-Zin coating.
We have tested our products against all other coated wire including standard brass wires. As illustrated, each of the GIP products rank equal to or better than the other coated wires available in the market.