Are two-axis lathes going the way of the dinosaurs? Maybe not, but here are some reasons why turn-mill, multitasking, and Swiss-style turning centres are often a better investment.
By Kip Hanson
Any shop that has purchased a five-axis milling machine will tell you they can now produce more parts with fewer operations. There’s less work-in-process (WIP), better part quality, lower operating costs, and the shops enjoy significantly greater efficiency overall. These advantages are just as true for parts requiring simultaneous, five-axis interpolation as it is for simpler, five-sided workpieces. In most cases, there are no secondary operations to deal with (and therefore no fixture costs), and because cycle times are generally longer, those tending the machine are free to work on more value-added activities. Five-axis machining, it seems, is a winner all around.
Now, replace the terms “five-axis milling machine” with those in the article’s headline: turn-mill, multitasking, and Swiss-style turning centres. The advantages just described are equally true. Andy McNamara, director of sales at Doosan Machine Tools America, notes that multitasking machines—those with a true milling spindle and machining centre-style toolchanger—are among the fastest-growing segment of new machine tool sales.
“Much of this activity is in the aerospace segment, but even many job shops and general manufacturers have begun to see the advantages of these machines,” he says. “This is why we’ve recently expanded our SMX multitasking lineup with several new models and continue to move in that direction. That’s because multitaskers offer distinct advantages over basic turning centres due to their having a true milling machine spindle and ATC, not to mention the ability to utilize parallel processes and new machining techniques not possible in the past.”
When asked what’s driving this growth, McNamara pointed to two factors. The first of these is no different than any other new technology introduction: the buying public has become more comfortable with the idea of multitasking and turn-mill machines. Further, those who’ve adopted it have begun to pull ahead as they learn how to leverage it and incorporate it into their processes.
The second is ease of use. “When five-axis machining centres first came out, the lack of good CAM postprocessors was a major deal,” says McNamara. “Now it’s a non-issue. The same is true with multitaskers and other types of advanced machine tools. The CAM people have done a great job of keeping up with the technology, and as a result, programming what is clearly a complex machine tool has become much easier than it once was.”
Synched for success
Gonzalo Serrano says that some machine builders are also doing a great job. An applications engineer at Index Corp., he points to the company’s WinFlexIPS and WinFlexIPSPlus (designed for Traub equipment) and VirtualPro (which supports Index machine tools) programming and simulation software as three notable examples.
Says Serrano: “Each of them makes even challenging operations like pinch milling and turning, five-axis machining, and other synchronous, multi-channel processes easy to program. The simulation is really accurate as well, which helps to detect and avoid collisions. This last part is an important consideration on any machine tool, but especially when you have multiple axes and spindles to keep an eye on.”
In addition, the company is making its products Industry 4.0 capable, says Index proposals engineer Randy Carlisle. “As CNC machinery becomes more capable, more of their users want to collect operational and performance data. Our INDEX iXpanel HMI [human machine interface] does that. It runs on the latest Siemens control—the S840D—and provides all the hardware needed to communicate with other equipment, with the customer’s network, and to capture data for use in 3rd party analytics packages.”
Like most machine tool builders, Index is also addressing the need to keep what are admittedly more expensive machine tools running as much as possible. For instance, its iXcenter is an integrated cell that houses a Fanuc LR Mate robot that can not only load and unload parts, but also adjust tool offsets based on feedback from a Renishaw or comparable gauging system.
Okuma America Corp. offers a similar system. Lathe specialist David Fischer explains that the Armroid machine-mounted robot also provides load/unload capabilities, as well as a work support and a directed, programmable coolant nozzle. Such integrated automation is one more example of why multitaskers and the like are gaining steam in a competitive machine tool environment.
“I think a lot of shops still don’t appreciate the value of producing a complete part in a single operation,” says Fischer. “By avoiding multiple handlings, you eliminate all the variables and chance for human error that would otherwise be present. You also gain larger clocks of uninterrupted cycle time, which is both more predictable and easier to schedule. And during this time, the operator is free to take care of QC functions, prepare for the next job, work in documentation, and so on. It’s about letting machines do what machines do best and people do what people do best, right?”
To those who argue that a pair of two-axis lathes can produce more than a twin-spindle live-tool lathe or multitasking machine—and cost less to boot—Fischer suggests that this way of thinking is obsolete. The advantages outlined thus far easily outweigh any pure cycle time considerations, especially inlight of the industry’s increasing demand for smaller job quantities and greater flexibility. In addition, some machine models can perform skiving and deep hole drilling, operations once reserved for specialty equipment.
“We had a case recently where the customer’s part required a total of eight hours to set up several operations on more conventional CNC machine tools,” says Fischer. “Their quantities were initially in the 1,000 to 1,200 range, however, so it was no big deal, at least until the lot sizes began to fall to 100 or 150 pieces. By moving to a multitasking machine from our Multus line, they were able to complete these smaller quantities in less time than they once spent on setup time alone, even though the cycle time itself was a bit longer.” SMT