3 Flavors of Five-Axis Machines

The concept of a five-axis machining center is straightforward. Five axes of motion — three axial and two radial — are used to enable access to multiple areas of a part in one setup. In most cases, tools and/or workpieces are oriented and then fixed into an angled position for machining (often referred to 3+2 or 4+1 machining). That said, there are applications in which the motion of all five axes — X, Y and Z axially; B and C radially — occurs simultaneously when complex contouring work is required.

How that motion occurs differs depending on the machine design. But there are also other differences besides that. Here, we look at one designed for micromachining, a second that’s bar-fed and a third offering workpiece pallet-loading capabilities.

Micromachining

Although the Precision Machining Technology Show (PMTS) is commonly associated with high-volume turning technology, there was a healthy presence of advanced milling machines at the 2023 event. One example is the compact, five-axis Micro5 from Chiron Group, a machine that is new to the U.S. market and can complement a shop’s small-part turning capabilities.

This machine, part of the company’s Factory5 brand offering, is described as having a “5:1 ratio of machine to workpieces,” five-times lower weight and a much lower energy consumption than conventional machines at 500 W. Having a 50 by 50 by 50-mm working area, it is said to be well suited for small workpieces for industries, including medical (surgical devices, orthopedics, implants and so on), watchmaking (casings, movements and so on), jewelry and small electronics.

The company says the Micro5 offers substantial rigidity, static stiffness and thermal stability, helping enable it to achieve 0.5-micron repeatability, 2-micron accuracy and quality surface finishes. It can achieve acceleration of 2 g, comes standard with a 60,000-rpm spindle (an optional 80,000-rpm spindle is available) and noise level during operation is less than 50 decibels.

A tower-design automatic tool changer can accommodate as many as 60 tools with ATC 15-W tapers. This can enable multiple different tools to be installed to accommodate different parts or redundant tooling to run multiple similar parts. Parts can be machined dry (with air blast) with oil or using minimum quantity lubrication (MQL). A cart stored under the machining workzone is used to catch machined chips.

The Micro5’s intuitive human-machine interface (HMI) monitors parameters such as feed rates, overall air pressure, power supply, spindle temperature, spindle current draw, DC bus and oil level. Alerts can be sent when a given parameter falls out of specification (such as air pressure is too low).

A variety of workholding devices are available, including zero-point clamping for manual or automatic workpiece clamping, a centric vice for automatic workpiece clamping and collet chucks.

Bar Feeding

Traditionally a Swiss machine shop, Swiss Precision Machining (SPM) notes that an automated, bar-fed, five-axis machining center platform has led the company to substantial growth.

The company purchased its first five-axis machine, a Willemin-Macodel 408MT, in 2012. The shop needed a more optimized process for running a part used for meniscus surgery that was being manufactured on one of its CNC Swiss-type lathes. According to SPM, that part, along with other complex parts, is machined complete on the five-axis machining center with better finishes than when created on the Swiss-type. This machine platform also enabled the machining of a broader range of medical parts unattended thanks to the bar feeder, which expanded SPM’s customer base. It now has numerous such models as well as a 508MT2.

SPM’s five-axis machining centers, which can perform turning, milling, drilling and boring, are all bar-fed primarily with stainless steel and titanium stock. The smallest parts the company produces are 0.250 inch in length and 1.5 inches in diameter. Batch sizes vary from tens of thousands of parts a year to 100 to 200 parts a year. However, some of the machining centers are churning out prototypes that can include batch sizes of 5 to 250 parts. The completed parts are ejected from the machine by a conveyor belt as well as some carousel collection systems.

According to SPM, the machining centers’ normal cycle times are anywhere from a few minutes to 30 minutes. The shop recognizes that cycle times oftentimes are not faster than if those parts would be produced on CNC Swiss-types. However, it recognizes that producing short cycle times is not always the most critical aspect of machining, especially when running complex parts such as those that the five-axis machines are producing that require more processes than turning. And the machines can hold tolerances as tight as ±0.0001 inch, which is necessary for some of its customers’ parts.

The 408MT and 508MT2 models are equipped with a swiveling powered spindle fitted on a B-axis and an A-axis spindle, enabling up to 6,000 rpm in turning mode. However, the 508MT2 is capable of simultaneous machining with the pickup device/vice that grabs the parted-off part for backworking. This provides two more axes other than the main five. Therefore, it is sometimes called a seven-axis machining center.

The five-axis machines also have eased the pain of the facility’s skills gap. For example, they have eliminated secondary processes that used to take an operator time to move unfinished parts to the next process or machine on the shop floor.

Operators are also freed up to lightly attend these machines because of their efficiency — one operator might run four machines. The machines also have created a lights-out shift overnight at the shop, facilitating even more productivity. Besides the tool detection system in place on the machines, tool counters and sister tools are used to enable lights-out machining. SPM uses statistical process control (SPC) data to know when the optimal time is to run lights-out.

Workpiece Pallet Loading

Blaine, Minnesota’s Challenge Machine specializes in machining small, complex parts — some exceedingly small. It does this using a range of equipment, including B-axis Swiss-type lathes, VMCs with trunnion tables that provide fourth- and, in some cases, fifth-axis rotation, as well as high-speed, true five-axis machining centers.

Although the shop has been able to realize long stretches of unattended machining with its bar-fed Swiss-types, its milling equipment previously required manual part loading. However, its five-axis machine which features an integrated workholding pallet changer and high-capacity automatic tool changer (ATC) can run unattended during the day and lights-out during the evening. In addition, CNC functionality combined with touch-probing routines simplifies programming because operations are created based on one kinematic point that creates one work coordinate system.

The automated five-axis machine is a Micro Pro from Germany’s Kern Microtechnik (known in the U.S. as Kern Precision, located in Addison, Illinois). Challenge Machine purchased this model because it was experiencing accuracy, repeatability and surface finish issues for a growing number of medical parts the ISO 13485-certified shop was running on some of its five-axis trunnion machines. Plus, features such as cooling channels throughout that mitigate thermal growth also facilitated reliable machining for complex parts that typically have long cycle times. This, in addition to other machine capabilities, gives the shop the confidence to set it up to run on its own for days or even weeks.

According to Kern, the Micro Pro — which features hydrostatic guides, linear drives and a single-casting base made from ultra-high-performance concrete (UHPC) — achieves better than 2 microns positioning accuracy and better than 1 micron repeatability. It was designed with small-parts machining in mind, offering XYZ travels of 350 by 220 by 250 mm, while its swiveling B axis rotates 220 degrees. It also has small footprint of only 43 square feet.

The Micro Pro uses an Erowa zero-point workholding system with power chuck that provides repeating positioning accuracy of less than 0.0001 inch. The machine can store 30 pallets and 109 toolholders in its enclosed, multilevel racks along one of its sides. The integral workpiece changer automatically delivers pallets with raw material (commonly round stock held in collets in Challenge Machine’s case) to the chuck, and removes and stores pallets once parts are completed.

The workpiece and tool storage capacity offers the shop versatility in the types of jobs it runs across the machine. For example, redundant tooling can be loaded into the machine when batch sizes of the same or similar parts are high. (Batch sizes for this machine typically tops out at 100 to 300 pieces.) Conversely, various different tools (and pallets with raw material) can also be loaded so it can concurrently run a mix of low-volume jobs.

To offer further confidence to run the Micro Pro unattended, Challenge Machine takes advantage of the Blum-Novotest laser probe which is mounted on the side of the machine’s swiveling B-axis casting for tool presetting and, during unattended machining cycles, to check for tool breakage and track tool wear (for some applications).

Learn More

Our website, productionmachining.com, offers numerous other articles highlighting five-axis machine tools as well as other CNC milling machine technologies. Click on the “topics” pulldown at the top of the page to start your search.