PECM And Next-Gen Manufacturing
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Engineers have implemented a variety of advanced technologies to improve the efficacy and efficiency of critical parts, such as parts within high temperature engines or surgical equipment. These advancements include, but are not limited to:
Miniaturization of critical parts, and
Implementing additive manufacturing in production operations
However, problems will grow if manufacturers continue to pair conventional machining methods with these advancements. The abrasiveness of certain advanced materials, more challenging part geometries, and the inadequacies of conventional machining methods will reduce efficiency in producing the next generation of critical parts.
Voxel Innovations is a pioneer in the research and implementation of pulsed electrochemical machining (PECM), an alternative machining process. This article will showcase how Voxel Innovations & PECM can provide an effective solution to current manufacturing challenges, such as part miniaturization and machining advanced materials.
Voxel seeks to both educate and encourage open discussion on PECM, and this article seeks to highlight ways PECM can alleviate some current manufacturing issues.
PECM & Advanced Metals
It is likely that the next generation of critical components for some engines and power generation equipment will be required to withstand enormous temperature fluctuations and extreme environments. These extremes can include 1700°C (3000°F) heat within scramjet engines, or 800°C (~1500°F) and 20MPa (~3000psi) within supercritical CO2 heat exchangers.
Alternatively, low temperatures of 4°K (-269°C, or -452°F) within pulse-tube cryocoolers and -125°C (-195°F) for Mars missions require specialty materials. Materials scientists have been tasked to develop materials with advanced properties, such as superalloys, metal matrix composites or bulk metallic glasses, to name a few. These advanced properties can include improved corrosion resistance, higher tensile strength, and a wider temperature resistance range.
Many of the unique qualities of these advanced materials are what makes them challenging to machine. For example, most advanced materials have relatively low machinability compared to conventional materials as a result of high tensile strength and abrasive surface qualities.
Tensile strength and material hardness are irrelevant to PECM. Conductivity, rather than hardness, determines the machinability of a material to PECM. Voxel has developed technology to machine a nickel superalloy at a similar rate to copper.
Another example of an advanced material advantage that simultaneously poses a challenge is corrosion resistance. This feature is particularly troublesome to electrochemical machining operations. PECM relies on the oxidization of metal materials to dissolve the workpiece to the desired geometry. However, many advanced materials can still qualify for PECM, such as certain metal matrix composites.
How PECM Will Aid Miniaturization
Engineers are constantly tasked to miniaturize a wide variety of crucial parts. Ultimately, their objective is to design smaller-sized parts, while simultaneously maintaining (or even improving) the part’s original capabilities. Generally, there are three primary incentives for manufacturers to encourage part miniaturization:
• Miniaturization can reduce manufacturing time
• Miniaturization can improve the form, fit and function of the part
• Miniaturization reduces the materials required
Miniaturization offers other industry-specific advantages. For example, aerospace engineers reduce aircraft weight by miniaturizing critical components, leading to improved range or fuel efficiency. Ultimately, the ability to machine thin-walled structures and intricate part geometries is vital for the implementation of part miniaturization across all manufacturing. Voxel’s unique PECM process can machine thin-walled features with micrometer-precision, while simultaneously finishing surfaces as low as 0.005 - 0.4μm Ra (0.2-16μin) (Data from Voxel Innovations).
Miniaturized parts comprised of advanced composites will be a crucial aspect of next-gen aerospace engineering for both commercial and military aircraft.
Heat transfer components, for example, will continue to play a vital role in aerospace engineering, as the material, features, and surface finish are crucial to heat transfer components --and thereby the entire aircraft’s-- overall efficiency. Vital components of jet engines are continuing to decrease in size, requiring increasingly smaller, thinner components but with increasing tolerance challenges to maintain engine performance.
PECM has the ability to allow a variety of critical aircraft components to be manufactured with improved resolution, smaller sizes, and smoother surface finishes.
The motivation to miniaturize parts for the medical industry differs from that of aerospace manufacturing. Smaller surgical equipment, for example, may not only reduce manufacturing costs, but may result in quicker, less invasive procedures. Manufacturing the next generation of medical equipment will prioritize its compatibility with robotic instruments, as they are capable of considerably higher precision than humans, thereby allowing the use of smaller components.
Voxel’s PECM technology provides an ideal solution for miniaturizing high-volume production of medical parts. By processing multiple parts in parallel, PECM can reduce the per-part cost of surgical tools which is particularly valuable in a market with more single-use medical devices. PECM’s unique surface finishing qualities also have particular benefits for medical parts as smooth surface free of microcracks are more resistant to. bacterial growth and may improve the part’s biocompatibility.
The evolution of pacemakers is a good example of the miniaturization of medical technology over time. Researchers continue to innovate this technology; pacemaker manufacturing is expected to rise as the number of individuals suffering from heart attacks in the United States slowly rises, and the pressure to miniaturize will grow with this trend.
However, medical device manufacturers are facing obstacles, such as integrating smaller, more powerful batteries and thin-walled flexures composed of tough materials like Titanium. PECM can be a viable solution, as it can easily machine thin-walled, burr-free features otherwise sensitive to thermal distortion that may affect the part’s functionality.
Stent manufacturing is another example of medical device manufacturing challenges that PECM can alleviate; manufacturers are challenged with improving stents’ radial strength and corrosion resistance for biocompatibility, while simultaneously attempting to miniaturize parts. An important motivation for stent miniaturization is assisting cardiologists in treating smaller vessels that often can’t be treated with current stent technology during PCI (percutaneous coronary intervention).
As the next generation of stents is researched and developed, especially drug-eluding stents, demand is expected to grow, and manufacturers will need a high-volume, scalable manufacturing process create components with smaller or thinner features, requirements that PECM can excel at. PECM may also be able to machine more complex geometries of stent or other intravascular devices while simultaneously finishing the product.
The Future of Additive Manufacturing & PECM
Growing popularity of lean manufacturing methods encourages manufacturers to improve material usage by machining parts with features closest to their final shape, also known as near-net manufacturing. The exponential growth of additive manufacturing (AM) is a direct result of this trend, as a 3D printed part has little to no material waste.
Benefits of AM include reduction of material waste, consolidation of multiple components into a single part, topology optimized designs, and reduced cost for design iteration. The growth of additive manufacturing is most prevalent in aerospace, medical, defense, and energy applications but it is not without its drawbacks.
A crucial disadvantage of AM is its rough surface finish. These surface irregularities can be due to support structure remnants or downskin surfaces. Surface roughness can create flow or sliding friction in crucial joint or heat exchanger parts, promote bacterial growth in medical devices, and cause fatigue failures in aerospace applications. PECM can be employed as a secondary finishing operation to eliminate both the macro and micro surface roughness.
AM is also limited in its ability create thin-walled features, such as sharp leading edges on turbines engine airfoils. These features are often also sensitive to thermal distortion or are impacted by the vibrating tool of conventional machining methods. PECM offers a fast, secondary machining process of additively manufactured metal parts requiring more precise features of thin walls. This application of PECM is especially ideal for high-volume production of 3D printed parts due to high repeatability of the process.
AM engineers have prioritized material quality and resolution over speed as the process was validated for critical applications. As AM processes improve and mature into higher volume production applications, the cost of metal AM is a growing impediment. Instead of printing slowly with high resolution, high speed but lower resolution metal AM paired with a secondary machining operation like PECM may provide a lower total part cost while still achieving critical surface finish and geometries.
Voxel Innovations has ongoing research in the field of secondary processing of metal AM parts with PECM and is exploring ways to better meet the needs of this growing industry. The PECM process is another tool in the toolbox for design engineers working with metal AM and can help additive manufacturers improve form tolerance and surface quality of parts.
Contact Voxel Innovations to learn more about pulsed electrochemical machining, or see our education portal.