In the widespread application of robotic polishing, there are some particularly challenging materials—titanium alloys, high-temperature alloys, composite materials, and 3D-printed parts—that pose significant difficulties. Thanks to their unique physical and chemical properties, these materials have become critical components in high-end manufacturing—but they also frequently stump conventional polishing techniques. So how can we equip robots with the right “tools” and “strategies” to effortlessly tackle these hard-to-process materials? This article will provide you with an in-depth analysis.

Titanium Alloy Grinding: Challenges and Breakthroughs

Titanium alloys, with their high strength, corrosion resistance, and excellent biocompatibility, are widely used in the aerospace and medical fields. However, during the grinding process, they face... Huge challenge Poor thermal conductivity causes grinding heat to be difficult to dissipate, leading to easy burning of the workpiece surface. The material has high viscosity, causing grinding swarf to easily adhere to the abrasive grain surfaces and clog the grinding wheel.

Faced with these issues, Selection of New Tools It is of paramount importance. Studies have shown that multilayer brazed diamond grinding wheels perform exceptionally well, boasting advantages such as high abrasive retention strength, ease of dressing, ample chip space, and self-sharpening capability. When these grinding wheels were used for dry grinding of titanium alloys, the results were highly encouraging: the wheels did not become clogged or stuck, the grinding temperature remained low, and the surface showed no signs of burning. The surface roughness Ra value could be precisely controlled at around 0.8 μm, fully meeting the requirements for dry grinding processes applied to aerospace-grade titanium alloy parts.

For titanium alloys Process Plan Studies have explored the use of spherical consolidated abrasive grinding heads for grinding TC4 titanium alloy. By optimizing process parameters—specifically, a grinding head rotational speed of 2,000 r/min, a grinding angle of 30°, and a grinding time of 10 seconds—it was possible to achieve a material removal rate of 22.2 mg/min while attaining a surface roughness Ra value of 0.7 μm, thus balancing both efficiency and quality requirements.

High-Temperature Alloy Grinding: Striking a Balance Between Efficiency and Quality

Superalloys (such as nickel-based superalloys) operate under high-temperature and complex stress conditions, and are prized for their high hardness, high strength, and excellent wear resistance. Difficult to process These materials have extremely low grinding efficiency, making it difficult for conventional grinding wheels to meet the requirements.

For high-temperature alloys Tool Selection CBN (cubic boron nitride) grinding wheels demonstrate significant advantages. CBN abrasive grains possess high hardness, high strength, and high chemical inertness, making them ideal for high-speed grinding. Experimental studies have employed three types of CBN grinding wheels—ceramic-bonded, electroplated, and brazed—to perform high-speed grinding on the GH4169 high-temperature alloy. By optimizing process parameters, these studies achieved efficient deep grinding while ensuring surface integrity.

From Process innovation From a technical perspective, some researchers have proposed a “combined process of electrochemical spark machining and mechanical grinding,” which aims to significantly enhance the grinding efficiency of high-temperature alloys while achieving high grinding quality. This method addresses the characteristics of high-temperature alloys—such as their high toughness, plasticity, and strong adhesion—and represents a promising exploration from the perspective of improving the grinding efficiency of difficult-to-machine materials.

Taking the grinding of N09907 high-temperature alloy bars as an example, the grinding process requires... Comprehensive consideration In the pre-processing stage, annealing is used to relieve stress. During rough grinding, a large depth of cut and low spindle speed are employed to rapidly remove material. In fine grinding, a micro-feed rate combined with high-frequency oscillation is utilized, ultimately achieving a surface finish of Ra 0.2–0.4 μm.

Composite Material Grinding: Addressing the Challenges of Anisotropy

Carbon fiber/resin-based composites, with their anisotropic properties, low interlaminar strength, high carbon fiber hardness, and poor thermal conductivity, are prone to defects such as burrs, delamination, and tearing during machining. Traditional machining methods and manual work practices are not only inefficient but also highly susceptible to machining defects.

Development of specialized tools It is the key to solving the challenging problem of grinding composite materials. A series of specialized tools designed specifically for machining carbon-fiber composites includes: a range of electroplated superhard abrasive (diamond) multi-blade core-drilling tools and their combined hole-making tools; electroplated superhard abrasive grinding wheels with controllably arranged micro-abrasive clusters; and ultra-thin cutting tools made from superhard abrasives. These specialized tools can effectively accomplish composite-material machining tasks that conventional processing methods cannot, overcoming defects such as burr tearing and delamination commonly encountered in traditional machining processes.

In Process Plan Moreover, ultrasonic milling and grinding technology demonstrates significant advantages. A patent indicates that using an ultrasonically assisted milling and grinding process to machine carbon fiber composites can markedly improve the surface quality of workpieces, reducing surface roughness by approximately 16% to 36%. At the same time, the force acting on the grinding wheel in the feed direction is reduced by about 44%, and the force acting on the grinding wheel in the downward pressure direction is reduced by about 46%. Additionally, the cutting temperature is lowered by 29%.

Polishing Metal 3D Prints: Breaking Through the Bottleneck in Surface Precision

Although metal 3D printing technology can freely create complex shapes, the issue of rough part surfaces cannot be completely resolved simply by optimizing the printing process. Post-processing of 3D-printed parts is therefore necessary; currently, the main post-processing methods include finishing and machining.

Facing multiple Finishing method We need to select based on specific requirements: Manual polishing quality depends on the operator's experience and suffers from poor repeatability and consistency; sandblasting and CNC grinding have limited accessibility when processing parts with complex, porous internal surfaces. For components with high surface quality requirements (complex structures with Ra ranging from 0.8 μm to 1.6 μm), finishing processes face significant challenges.

Innovative process technology Offers new possibilities for polishing 3D-printed parts:

— Shape-adaptive grinding (SAG) is a novel process designed for machining difficult-to-machine materials with free-form surfaces. Researchers employed a shape-adaptive grinding method using a spherical, flexible grinding tool to polish the free-form surfaces of 3D-printed titanium alloy parts. By performing both rough and fine polishing steps, they removed the defect layer on the additively manufactured surface, ultimately achieving a surface roughness Ra of less than 10 nm.

— Abrasive flow machining (AFM) is particularly well-suited for finishing internal surfaces, grooves, holes, cavities, and other areas that are difficult to reach with conventional polishing or grinding processes.

— Chemical polishing and Electrochemical polishing It can effectively improve surface quality. Taking porous implants as an example, this technology can reduce the surface roughness from 6–12 μm to 0.2–1 μm.

Future Outlook: Smartization and Green Development

As manufacturing continues to develop, robotic polishing technology is also moving toward intelligence and green practices.

— Green Grinding Technology Focusing on key challenges in dry grinding and polishing of difficult-to-machine materials—such as the easy occurrence of workpiece surface burns and the tendency of grinding wheels to become clogged and fouled—researchers have developed a new CNC-controlled, mobile, portable grinding and polishing device suitable for difficult-to-machine materials like titanium alloys and nickel-based alloys. They have also devised practical dry grinding and polishing process solutions applicable to a wide variety of materials and structural configurations.

— 3D-printed ultra-hard abrasive tools Emerging additive manufacturing technologies hold promise for breaking through the traditional barriers in the production of ultra-hard abrasive tools. 3D printing technology boasts high material utilization and enables the rapid, layer-by-layer fabrication of products with any desired shape from raw materials, opening up new possibilities for the manufacture of customized, complex-structured grinding tools.

Conclusion

When dealing with difficult-to-machine materials such as titanium alloys, high-temperature alloys, composite materials, and 3D-printed parts, robotic grinding is no longer simply a case of “replacing humans with machines.” Instead, it requires a deep understanding of material properties, the targeted selection of appropriate grinding tools, and the development of scientifically sound process plans. As new technologies and processes continue to emerge, robotic grinding will play an even more critical role in the high-end manufacturing sector, turning these “tough nuts” into “delicious delicacies.”

For manufacturing enterprises, mastering the grinding processes for these difficult-to-machine materials not only enhances product quality and production efficiency but also helps establish core technological advantages in the fiercely competitive market, enabling them to gain a head start in development.