Can Wire EDM Services Meet Surface Finish Requirements?
One of the most common misconceptions about wire EDM is that because it’s a burning process, it produces a surface finish that won’t meet the requirements for certain parts.
Let’s debunk this myth once and for all. The truth is that wire EDM can easily achieve surface finishes smooth enough for even aerospace and medical applications.
A Primer on Wire EDM Services and Surface Finish
Wire EDM removes material by creating microscopic arcs of electricity between the machine’s cutting head and the workpiece. These electric shocks vaporize the material, and an insulating fluid washes it away, leaving behind a small pit only a few microns deep. Wire EDM machines create thousands of tiny pits per second.
Surface finish is determined by measuring the height of the bumps between the pits. The higher the roughness average (Ra), the rougher the finish. At Arbiser Machine, we can achieve an Ra of 112-10 µin with wire EDM.
How to Control Surface Finish with Wire EDM Services
The surface finish of a wire EDM part depends on how many passes we make with the wire. Most parts require 1-4 passes to achieve the desired accuracy and finish. Here’s an overview of the different levels of cuts:
Rough cut (first pass). The first cut is the most intense, and its main job is to remove the slug—the scrap produced by the cut. Like any manufacturing method, wire EDM has an inverse relationship of cutting intensity to surface roughness: a hotter, more intense cut yields a rougher finish. Still, about 90% of our wire EDM parts only need a rough cut, which can achieve an Ra of 112 µin and tolerances within +/- .002”.
Finish cut (second pass). Some parts require a smoother surface finish and tighter tolerances. A second pass with the wire can refine the part geometry to +/- 0.0005” and produce a surface finish of 72 µin.
Surface finish cut (third or fourth pass). At this point, the accuracy of the part won’t improve much, but a third and fourth cut will bring the surface finish as low as 35 µin and 10 µin, respectively. Surface finish cuts are most common for medical applications, such as the x-ray machine components we make for one longtime customer. But many parts don’t require such a fine finish.
Communicating Surface Finish Requirements
When you provide part drawings to a precision machine shop, be sure to call out the surface finish requirements in the title block. If needed, your shop can help identify the right surface finish for a specific part’s application and appearance. The shop will then decide internally how many passes of the wire are necessary.
It’s important to note that material type can affect the surface finish potential of a part. Materials that have already been hardened have a uniform grain structure and tend to yield the best surface finishes during wire EDM. However, with materials like untreated aluminum, the smoothest surface finish we can usually achieve is 39 µin.
We’ll always do what it takes to meet your surface finish requirements, whether we’re leveraging our wire EDM services or one of our many other capabilities. Request a quote today!