It is important to understand that certain types of coated wire can degrade the accuracy output from the machine.  Part accuracy can be reduced with coated wire as a result of the wire’s outer coating eroding and vaporizing more quickly than a standard brass wire. This deviation is most easily seen as tapered error in the part from the additional wire electrode wear. Some types of coated wire have an outer coating that can also affect the machine’s pick-up cycle accuracy due to an oxide layer or from the flaking and rougher surface of the coated wire.

There are wires that are designed for high accuracy applications. These wires tend to provide less of a machining speed increase than high-speed type coated wires.  One of the most common and oldest type of coated wire still in use today is A-type wire, which is ideal for high accuracy applications.  A-type wire has a distinctive bright silver color that is often shiny.  It provides a minimal machining speed increase over brass wire, but typically provides more reliable AWT performance while achieving the highest level of surface finish and accuracy.  Many machine OEMs recommend the use of A-type wire to achieve the highest part quality. It’s also considered the industry’s “go-to” wire in achieving the best possible surface finish, especially on carbide materials.  A-type wire is typically produced to a higher tolerance level than traditional plain brass wire, providing an accuracy advantage.