Machines Master Complex Parts
Automation adds flexibility to EDM
By Robert B. Aronson
"EDM is growing applications in the medical and aerospace industries," explains Hirschmann Engineering (Elgin, IL) President Peter Knowles. Integrating a Hirschmann submersible B axis to a wire or sinker EDM allows automatic indexing as well as "turn and burn" applications. This more versatile positioning capability reduces the need for multiple setups. The part can be completed while mounted on a single pallet.
"Because of a growing demand for automation, we have made a number of installations using Fanuc robots for loading and unloading EDM machines, CNC machining centers, and CMMs," explains Knowles.
Also noted is an increase in demand in some areas for sinker EDM machines.This may be due, in part, to some work returning from China, or US manufactured products going to Europe due to our declining dollar," says Knowles.
To meet the need for small round parts, the company offers submersible high-speed spindles (with variable and programmable ranges up to 1500 rpm) for machining in wire EDMs. When turning small parts, one of the major problems is that the pressure of the tool can deform the part being made. One answer is to turn the part using a wire EDM in a lathe-like operation where the part rotates and the wire acts as a "cutting tool." Because spark erosion removes the material without contacting the workpiece, there is no part deflection due to tool pressure. Hirschmann axes (H80 series) can be used to make part diameters down to 0.002" (0.05 mm), with a runout of 0.002 mm.
The growth of the aerospace and medical industries has proven tremendously beneficial for the EDM market. New materials, such as titanium alloys, are expensive and very difficult to cut via traditional milling or grinding machines. "As cutting tool evolution is lagging behind the rapid development of hard materials, EDM is often the most effective means to produce parts," explains Gisbert Ledvon, Business Development Manager, GF Agie Charmilles (Lincolnshire, IL). "Furthermore, wire EDM produces large slugs that can be used to create smaller components. With milling processes, large quantities of materials are lost to chips."
To retain a competitive edge over foreign manufacturers, many US shops are moving towards the production of smaller, more complex components with high accuracy requirements. EDM technology has shifted to meet this growing need. "The GF AgieCharmilles Vertex 1F, for instance, can thread wires down to 0.0008" [0.002 mm]," says Ledvon.
The development of five-axis wire EDM has proven to be another highly beneficial innovation. GF AgieCharmilles offers the Turn-while-Burn feature, which rotates a part during cutting to produce complex geometries. To further expand the applicability of EDM, diesinkers are being designed with additional axes, to make cooling holes in jet engine blades.
Twin-wire systems have improved cutting efficiency. A brass wire makes a roughing cut, followed by a coated wire for finishing. GF AgieCharmilles also has introduced Direct Cut, a generator technology that makes both a roughing and finishing cut in one pass. "Benefits include reduced wire consumption, 20% less filtration, and increased consumable life by up to 40%; the entire process is made more environmentally friendly," Ledvon concludes. — Bob Aronson
This article was first published in the August 2008 edition of Manufacturing Engineering magazine.