Optimizing 5-Axis Machining: The Impact of Block Processing Time-Based Programming on Speed and Precision

High-speed precision machining has come a long way, especially with the rise of 5-axis technology, which now handles creating complex, high-quality parts for industries like aerospace, medical, and automotive. But there’s still a tough challenge: balancing speed with precision. Push the machine for faster output, and precision can slip. Slow it down, and productivity falls. This balance has driven researchers to find CNC programming techniques that deliver both efficiency and accuracy. One challenge in 5-axis CNC work is managing what’s known as “block processing time”. Each block provides precise instructions for movement. In high-speed work, the machine must process these commands almost instantly to keep the tool path smooth and precise. If it falls behind, the machine slows down to prevent errors, especially with the intricate paths common in 5-axis machining. Things get even trickier with commands that need the rotary and linear axes to move together smoothly. Recognizing the limitations of traditional methods, Dr. Toshiaki Otsuki and Dr. Hiroyuki Sasahara from Tokyo University of Agriculture and Technology took a fresh look at this problem. Their research, published in Precision Engineering, delves into block processing time (Tb)-based programming as a solution. Unlike earlier studies that mainly focused on simpler 3-axis setups, the authors zoomed in on 5-axis machining, which requires greater coordination across additional rotary axes to keep precision high, even at faster speeds.

To see if block processing time (Tb)-based programming could genuinely improve speed and precision, the researchers set up a series of experiments. They tested two different control styles: Tool Center Point (TCP) control, which keeps the tool’s contact with the workpiece highly precise, and Non-TCP control, where each machine axis works independently. Their aim was to see if syncing each block’s instructions with the machine’s processing ability could outdo traditional programming, which tends to max out in either speed or accuracy.  Their testing focused on machining flat surfaces, carefully observing how the tool path and cut quality varied under each programming approach. Early on, they needed to identify the block processing time for each control type. Traditional method typically ramps up the machine’s feed rate until it hits what’s called the “saturation speed.” However, newer CNC machines make this saturation harder to find due to their advanced capabilities, so the team developed a new method to pinpoint the maximum feed rate where speed consistently matches programmed commands, giving them a precise Tb value to guide block length and speed.

With these identified Tb values, the team set up two machining paths for each control method: one adjusted for Tb and the other using a traditional linear approach with a 5-micrometer tolerance. The results were striking. For Non-TCP control, the Tb-based path let the machine maintain high speeds without the slowdowns and machining error common with traditional paths. This adjustment smoothed out waviness on the surface, particularly in complex areas, resulting in a more pricise finish. TCP control saw similar improvements. With Tb-based programming, the machine’s movements stayed close to the intended feed rate, avoiding sudden shifts. Conventional programming often faltered here, especially with sharp turns, leaving rough, wavy surfaces. Tb-based programming, by contrast, kept tool pressure steady, yielding a high-quality, precise finish with fewer inconsistencies. Additionally, the Tb-based approach minimized errors from rotary movements, maintaining stable, accurate cuts even at high speeds. Surfaces machined with Tb-based programming consistently showed lower waviness, reflecting better precision. The fact that Tb-based paths were faster is clearly demonstrated in “Appendix A. Supplementary videos” included in the online article (Precision Engineering, Volume 88, 2024, Pages 497-515). The increase in precision is clearly shown in the figure below. Under Non-TCP control, Tb programming yielded surfaces with fewer irregularities than the traditional method, which surpassed the 5-micrometer tolerance. With TCP control, Tb programming held closer to the intended path, showing superior precision.

In conclusion, Dr. Otsuki and Dr. Sasahara’s findings hold real promise for industries that rely on high-speed, high-precision 5-axis CNC machining. By Tb-based programming, they tackled a long-standing issue: the trade-off between speed and precision. Traditionally, machining has required a choice between faster machining and pinpoint precision, with one often sacrificed for the other. Their study shows that by adjusting block length to the machine’s processing speed, both can be achieved, resulting in smoother, higher-quality surfaces without slowing production. In sectors that need precise parts—like turbine manufacturing, prosthetics, or high-performance optics—this approach could cut production times and eliminate delays for fine-tuning. It’s also a win for sustainability, as better machining control reduces material waste, making the process more efficient. With modern CNC machines, Tb-based programming fully leverages advanced features like enhanced look-ahead and movement control, not only boosting performance but also adding flexibility to meet various production demands without sacrificing quality. Overall, the new research lays a strong foundation for future studies on block processing time across different materials and geometries, pointing toward exciting new possibilities in CNC programming.