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Is a Multi-Axis Machining Center Right for You?

June/July 2012

It can be the key to higher productivity and untended operation

Would a multi-function, multi-axis machine handle this Midwestern manufacturer’s machining processes more efficiently?

The company, which makes consumer and industrial products, had a machining process that was begging to be automated. It’s not especially complex – it involves turning on both ends of small cylindrical parts and some milling – but it requires 0.0005 in. accuracy on both sides of a milled slot, and the turning is both internal and external on the same parts.

The machine has to turn, thread and mill the same parts. The workpieces are a family of approximately 20 parts with similar configurations, machined in batches. The company needed to update an old process for faster cycle times and minimum manual handling. Multi-axis machines typically are advertised to machine highly complex, often contoured parts. Here was one that is more typical of real manufacturing.

Compact, versatile and capable of many operations in a single setup, several of these machines from different builders can easily handle the configuration of such parts, automating loading and unloading, manipulating parts automatically for machining multiple features and even multiple sides of prismatic workpieces. But the 0.0005-in. tolerance for a slot is a challenge. “We looked far and wide to find a machine that would hold the tolerance,” says the general manager of manufacturing.

The company found what it was looking for in an Amada Wasino A12. It answers a key question about the capabilities of multi-axis machines. They are as accurate as modern conventional turning and milling machines. With four or five axes of motion that coordinate functions with manageable programming and with fully automated part handling, they look like the answer to a lot of prayers.

They also provide one-stop machining of many part configurations and hands-off processing. They are cost-effective for a few parts or for production-sized batches. Plus, they meet the demands for consistent part quality sometimes better than multi-machine cells that perform just one or two operations per machine.
Are they practical for a job shop

The questions for a shop that is focused more on sheet-metal fabrication, with a secondary interest in parts machining, are how practical they are, how much training they require and how they compete in terms of per-part costs. Answering these questions requires some careful shopping. One machine will potentially replace several, and a general answer is that it’s much less complicated than shopping for and coordinating several machines to do the same job. For example, there is only one overall cycle time to plug into the calculations.

“We just got our machine online about two months ago,” says the GM. “It’s given us what we were looking for – quick parts turnaround, unmanned machining, and the accuracy we needed.”

The multi-axis machine was not overkill at all for them, as it turned out.

They replaced a series of production turning machines from the 1970s with the A12. One way to look at it is that a modern machine is bound to produce better results, so his enthusiasm is to be expected. But the other is that his operators were trained on a 1970s Allen-Bradley control, and they’ve now jumped into a generations-newer operating environment.

“The operator just dumps in a basket of parts, pushes a button and moves on to other jobs. In two months, we’re still learning and tuning the process. But we’ve already moved on to a second shift with the machine. We have everything macro-programmed. We’re using quick-change tools, and we pre-set tools outside of the machine.”

The evidence is strong that modern CNCs and interfaces bring programming these multi-axis machines under control, and that training from the major builders is well attuned to the needs of operators. Talking to a few users is better than reading about it, given all of the variables and options available on these machines.

A lathe with milling, or a mill with turning?

What came first? To clarify the functions of available machines, it helps to recognize how they developed.

CNC turning machines with live tooling on the turrets was one step. Add a fourth axis – in and out for the tool-carrying turret – and you have a multi-function machine that can turn and then index and mill multiple sides of a part, using the main machine spindle as an indexer. It can also function as a full C-axis for multi-axis milling. This configuration is popular for smaller-sized parts or up to the largest parts you’d run on a mid-sized CNC lathe.

At about the same time, four- and five-axis mills, with tilting and rotating tables, approached the idea from the other direction. Simultaneous multi-axis machining was part of the these configurations from the beginning, but they also index for multi-side, two- and three-axes milling.

Eventually, a hybrid of vertical-spindle milling with a tool changer on a lathe-configured machine bed became the third type of multi-axis, multi-function machine tool. There is size overlap among the different types, but this last class of machines tends to focus on larger parts.

Amada Wasino

Amada Wasino builds on the lathe-configured machines with tools on the turrets. Compact, high-powered spindle motors give machines of this configuration considerable milling horsepower, up to 7.5 hp or more. With two spindles on one model and two turrets on another, plus full contouring in all axes, the parts configurations that such machines can handle are enormous.

Taking advantage of the lathe-centered parts holding, machines of this configuration lend themselves to the compact, built-in gantry loaders made popular by modern automated CNC lathes. Simple staging and simple offloading – onto a carousel or simply dropping parts into chutes – results in a self-contained, fully automated, multi-function cell in a compact floor space.

Amada Wasino also has a multi-function version of its small gang-tooled lathes. With powered spindles mounted on the cross-slide, these machines allow a variety of machining functions, including turning and grinding as well as drilling and milling, combined with fast, straight-line indexing between spindles.

Mazak

Mazak has such a variety of multi-axis machines (which the company calls “multi-tasking”) that it categorized them into five different levels of machine capability and complexity. They’re worth listing because they serve as a good description of the range of multi-axis, multi-function machines in general:

Level one is the turning-machine configuration with a drum-type turret and powered spindles. Machines of this type fall into five different product families; the sizes, options and configurations can address practically any machining requirements for this general machine class.

Level two is level one with another axis – an in and out Y-axis for the turret, which expands milling capabilities. One- and two-spindle models are available in this configuration, as well as two-turret models.

Level three includes certain models in the company’s Integrex line. These are among the hybrids described above, with an independent milling-spindle headstock on its own machine ways and a tool magazine, providing 4-1/2 axes of motion.

Level four is more complex. It provides five-axis simultaneous machining for larger parts. Barfeeders, gantry loaders and robots are available for different models in the line, and they can be integrated with an automated parts-palletizing system.

Level five is level four with special machining functions, including gear cutting, honing, grinding and polishing, among other possibilities.

Mazak’s line leaves no stone unturned – until someone finds another stone.

Okuma

Like Mazak, Okuma has multiple configurations of multi-function machines, including the hybrid type with a horizontal-lathe configuration and an independent milling head.

Several models include sub-spindles that oppose the main turning spindle, with the capability to grab the part from one spindle with the other to allow automatic handling of parts to be machined on both ends. The company has extended the multi-axis concept to handle large parts. The Multus and Macturn series include models that will swing parts of over 40 in. diameter.

Hurco

Hurco has adopted the milling-based approach, with rotating tables and trunnions that present multiple sides of a part to the milling spindle or that allow simultaneous five-axis machining. The company also has a line that has a swivel head and rotating table – something that Hurco says is quite popular in Europe, with the table and trunnion configuration more popular in the US.

Like the lathe-configured machines, their basic and more common function is to allow conventional milling on multiple sides. Hurco emphasizes the milling rigidity the company achieves with its vertical-mill configuration.

    These builders represent the range of multi-axis, multi-side machining available today. They were selected as representative of the field, and because the last three, particularly, have extensive illustration and videos of actual operations on each website. Describing them in words is no match for seeing how the combined and simultaneous functions complement each other to produce extraordinary geometric machining capability that translates into single-setup machining of both simple and complex parts. Some of those parts might look a lot like yours.

Amada Wasino
Hurco
Mazak
Okuma