EDMing thin ribs is a difficult application. High-speed machining of the elec-trodes has made it possible to fabricate these electrodes from grades that are not capable of maintaining the detail in the cavity. The ideal graphite grade for thin ribs should have a flexural strength above 10,000 psi. […]
High-speed machining centers have made it possible to machine intricate detail into almost any grade of graphite, a task that would have been impossible using manual or CNC machining equipment. The high-speed spindles, making multiple passes with smaller chip loads, allow thin ribs to be machined without putting pressure on the rib. Materials with low [...]
The physical properties of each grade of graphite determine the ranking within classifications. The properties that influence performance are particle size, flexural strength and shore hardness. These properties along with a photomicrograph of the microstructure are the best tools for predicting graphite performance. […]
The graphite industry is constantly striving to produce higher quality grades. Graphite materials have continued to evolve along with the other aspects of the EDM industry, but at a less dramatic pace. Advancements have been made in the microstructure of the graphite materials, as this is the key to performance. […]
Graphite selection is critical to the success of the job. It is important to understand the characteristics and physical properties of the different manufactured brands and grades produced. The various grades should fall within one of the four EDM classifications: Angstrofine – Less than one-micron particle size material is used when extremely fine surface finishes [...]
The machined, natural EDM finish is the surface that the EDM process leaves on the metal at the end of the finishing cycle. The finishing cycle puts the most stress on the graphite electrode. Finish settings are high frequency cycles with more sparks, or discharges, per second due to the short on and off times [...]
A mold with a good EDM finish is ready to use right out of the machine (tank-to-part technology), while a mold that needs to be etched or polished to get the desired finish requires extra steps that increase cost and extend production time. […]
Graphite is a highly abrasive material, and tends to wear out cutters quickly. One of the greatest difficulties encountered when machining graphite is that cutter wear can reach unacceptable levels within the time required to machine a single, multi-featured electrode. As such, advanced tool coatings offer a significant benefit when producing graphite components. [...]
The advantages of laser engraving are described below: […]
Disposable inserts with a 1/64- to 1/32-inch nose radius are most effectively employed for turning graphite. A positive rake insert without a chip control groove is preferred. Cutting fluids and/or coolants are not recommended. Adequate and well-maintained fixturing, rigid tool setup and well-adjusted machine tools always provide superior results. […]