Stress-Free Machining with PECM
Conventional machining processes – and several more high-tech methods – can apply stress on the part, creating microcracks, geometric or thermal distortion, and can even change the composition of the material itself. These processes also put stress on the tool, which increases machining time, increases cost, and decreases repeatability of the part-- crucial when machining advanced materials.
Pulsed electrochemical machining (PECM), however, is a non-contact, non-thermal method that introduces no wear to the tool.
Result from Energy-Dispersive X-Ray Spectroscopy (EDS) of a PECM sample of electroless nickel deposit. These results illustrate that the surface of the PECM’ed part is identical to the bulk material properties.
Inlay: Image of nickel surface after PECM.
In PECM, there is no contact between the tool and the part to be machined. Instead, the electrode tool moves toward the workpiece surface and regulates the gap to less than 100μm (.004”). An electrolyte solution is pumped between the tool and the part while a pulsed DC current is applied to dissolve the metal. The electrolyte solution also clears away waste materials, preventing unwanted contact between the tool and the workpiece. Therefore, no mechanical stress is introduced to the part in PECM.
Other machining processes, such as ones that use abrasives or cutting tools, can create brittle microfractures and/or burrs. PECM, however, does not introduce any mechanical stress to the part and is burr-free, which makes for more durable, reliable parts with greater longevity. Not only is machining with Voxel “pixel perfect,” but it also stays that way.
Voxel’s electrochemical machining process is not heat-based and introduces no substantial thermal load the part, eliminating the influence of thermal stresses to the part. The electrolyte solution must maintain a temperature of <100°C to prevent boiling of the water-based electrolyte and can often be held to a <40°C depending on the operation.
On the other hand, machining processes such as electric discharge machining (EDM) and laser cutting or machining use heat to shape the workpiece. This heating creates recast layers, heat-affected zones, and microcracking – all of which are detrimental to the part performance. Even conventional machining processes such as milling, turning, and grinding can introduce unwanted heat into the part. The non-thermal PECM process preserves the material’s makeup and the intended shape of the part, and prevents compromising its strength.
NO TOOL WEAR
Because PECM is a non-contact and non-thermal process, not only does the workpiece avoid damage, but also the tool. No tool wear leads to inherently high process repeatabilities. In comparison, a sinker EDM electrode wears continuously during operation and can require a continuous replacement of electrodes to achieve tight tolerance features. This lack of tool wears means PECM is particularly well suited for high aspect ratio features, repeated features on a single part, or high quantities of parts.
When using other conventional machining processes, such as grinding or milling, the tool steadily wears away from contact with the workpiece. Many machine tools try to compensate for this wear through in-process measurements. However, at some point, the tool dulls, chips, or wears far enough that replacement is required. If you are machining high-temperature aerospace alloys, these milling tool replacement costs can be $30-$150/hr, depending on the operation.
On the other hand, Voxel’s PECM process operates independent of tool wear, giving you easily repeatable parts without needing to remake and replace the tool.
Stress-free machining expands the options for designers and engineers in incredible ways. High aspect ratio or thin-walled features, machined surfaces free of stress or microcracks, parts without thermal distortion, and high feature-to-feature or part-to-part repeatability are all areas where PECM can add value to your operations. These benefits can be used to replace an existing process and may help enable new designs that would not otherwise be possible or cost effective. With PECM, it’s all in a day’s work.
In short, Voxel’s Pixel-Perfect Machining is also stress-free machining. With no contact, no thermal impact, and no tool-wear, a part made with pulsed electrochemical machining lasts longer, works better, and can be made identically over and over again.
If this sounds like something you want, contact us! We’re ready to use PECM to make your job a little more stress-free, too.