Advanced Precision Machining

Milling and Machining Trends - The Growth of Multi-Axis CNC Milling Machines

[November 12, 2019] The precision machining sector of the manufacturing industry is dynamic, rapidly evolving, and unprecedented growth is forecasted in the very near future. Machine shop operations today are in the midst of resurgence thanks in part to improving economic conditions, reshoring of manufacturing jobs, and increased demand for products that drive our economy and improve our way of life. Recent advances in precision manufacturing technology, most notably in the form of computerized numerical control (CNC), computer-aided design and manufacturing (CAD/CAM), and cutting-edge tooling machines featuring even greater multi-axis capabilities, have led to revolutionary design and production improvements for precision machined parts.  

At Advanced Precision Machining’s (APM's) a leading Colorado machine shop, we make every effort to keep up to date with new milling and machining trends, and lately a topic generating some buzz has been the increased use and demand for multi-axis CNC milling machines, and how these precision manufacturing marvels may become favored over more conventional and cost-effective 3-axis or 5-axis CNC mills. A big question that will need to be answered and put to the test will be; “Is this technology an improvement over traditional and currently relied upon methods of machining a part, and how can machine shops justify the complexity involved in having one extra axis of rotation?” An Interesting topic of conversation to be sure, and we'd briefly like to share some of our thoughts with readers of this blog.

While by no means new technology, the utilization of multi-axes has permeated part fabrication, and the incorporation of 3-axis and 5-axis milling machines are now common and have proven themselves to be a monumental improvement over conventional horizontal or vertical CNC mills throughout the past decade. Today, the direction that high-speed machining tools are taking is a trend towards updating and improving upon existing designs. This means adding additional axes, allowing for improved throughput, and the ability to produce more complex parts with higher tolerance capabilities.

Today’s milling machines are rooted in a long history, with their simplest and earliest designs dating back to the 1800s. Technology advanced of course, and today we are routinely able to machine a wide array of intricate parts across 3 (X,Y & Z), 4 (X,Y,Z & C or Q) or even 5 (X,Y,Z &C and Q) axes with CNC movement and other CAM devices. By the early 2000s, hexapod actuated milling machines opened machinists up to the possibilities of adding further dimensional axes (more than 5) by utilizing robotic legs and creating more "freedom of movement". The system is based upon a type of parallel robot known collectively as a "Stewart Platform" that uses 6 hydraulic actuators, or legs. A part to be machined sits on a platform affixed to the actuators allowing the part to be milled in essentially, 6 dimensions - the X,Y & Z axes, and pitch, roll & yaw rotations. So, three linear movements and three rotational movements. The results were impressive, and the groundwork was laid to enhance the ability to machine parts with continuous motion producing more complex and contoured workpieces. 

Commercial acceptance of multi-axis, hexapod CNC milling machines was slow, but the techniques utilized led today’s advanced 6-axis, and more, milling centers that are no longer reliant on “Stewart-type” robotic actuators. Everything is maintained in the machine head. The addition of another rotation axis, usually about the Z-axis, now allows for turning from both the ends of the fixture without multiple fixtures and defects in the final machine. Set up and handling time is greatly reduced, and most importantly, the additional axes often result in a significant improvement in speed compared to 5-axis configurations. The use of the 6-axis also enables for complex work like drilling holes of different diameters and shapes and allows for more variable cutting speed and patterns. 

So, the big question remains; Are additional rotation axes worth the investment given their relatively high cost? Today’s technological marvels create motions in the X, Y and Z dimensions and are performed by three parallel axes resulting in greater stiffness and accuracy, improved flexibility, and a larger cutting area. This gives the CNC machinist a distinct advantage when it comes to speed, more complex shapes, and difficult parts, but to date, 5-axis machines are able to handle most workloads. So, the jury is still out. Making, using, and maintaining such complicated, multi-axis machines is no cheap task! However, the increasing demand for enhanced productivity and reduced process time from industries like the automotive and aerospace sectors is prompting manufacturers to step up their game. Barriers to full entry and acceptance do include the cost and availability, and not everyone is willing to go all-in just yet. But who knows though, by the end of this decade we might see a changing of the guard. Stay tuned!

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About the Author

Gerry Dillon is a co-founder, current owner and certified CNC machinist at Advanced Precision Machining (APM), a full-service machine shop located in Longmont, Colorado. Before making his home in the United States in 2000, Gerry was born and raised on the emerald isle of Ireland and took an interest in milling and machining from an early age, ranking #1 in the Irish National Apprenticeship Program. In 2005, he and a partner began what’s grown into a leading Colorado machine shop. Gerry brings over 30 years of machining experience to the shop floor and is certified in all aspects of geometric dimensioning and tolerancing.

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