Published 4/7/2017

Adding Context to Advanced Milling

For all its focus on machines, cutters, parameters and tool paths, an expo hosted by Methods Machine Tools demonstrated that competitive hard milling increasingly requires looking beyond the workzone and even beyond traditional machining.

High-Speed Machining

Matt Danford

Former Senior Editor, Modern Machine Shop

This automated Yasda PXi30 machining center, now awaiting shipment to a customer, was touted as an example of the future of hard milling for job shops. These machines are designed for the highest levels of precision. More emphasis, however, was placed on the labor cost savings gleaned from the machines' five axes of motion and, especially, the multi-pallet system—attributes that aren't unique to Yasda.

Dale Mickelson, specialist in die-mold and precision machining, touted whisker-reinforced ceramic cutting tools as a good option for difficult materials like Inconel (though not titanium, which burns). That’s largely because these tools can take more heat than carbide without breaking down. As the tool wears, the ceramic breaks away and leaves what is essentially a fresh cutting edge in its wake. This kind of wear is visible on the edges of this model from Kennemetal, which ran dry (no coolant) in a hard milling demonstration on the Yasda machine in the previous picture. Mr. Mickelson added that silicon chrome and chromium tool coatings can be particularly useful in “gummy, sticky” hard materials because they maintain a sharp edge and prevent workpiece material adhesion.

Mr. Mickelson also advised looking beyond spreadsheets and brochures when evaluating a potential new machine tool. That is, machine tool technology in general has advanced to the point where it can be difficult to find major differences in rapids, positioning capability and other commonly listed specifications. Although such specifications are important, he also urges manufacturers to take a close look at the machine’s structural design and other attributes. For instance, Yasda machines like these feature hand-scraped ways; axis roller guides aligned to ensure precise motion of the hybrid box ways; pallet-changing repeatability of less than 2 microns; and a spindle that’s decoupled from the motor. The decoupled spindle motor is said to reduce thermal growth and maximize the benefits of the Big Plus spindle interface, which maintains dual points of contact between the spindle face and flange face of the tooling.

The Methods event also revealed the value of tracking the continued advance of additive manufacturing technology—not as a threat to milling, but as a potential complement to it. For example, conversations in the Boston-area facility’s new additive lab focused on reducing assembly work by 3D printing metal parts in one piece and then finish-machining them, as opposed to machining multiple parts from stock. Highlighted examples included aerospace fuel injectors and food processing machinery with critical seals.

Advanced mold manufacturers are already leveraging additive manufacturing technology for conformal cooling: that is, designing cooling channels to snake closely along the contours of the tool’s geometry. Despite the way it looks upon emerging from the machine (left), company representatives insist that the tool steel in this example offers similar properties of a non-3D-printed insert, down to the machining parameters employed to finish it (middle). In addition to saving customers time on mold cooling cycles, 3D printing inserts in this way can reportedly reduce manufacturing times. Both the metal insert and plastic representation of the conformal coolant channels (right) were printed on 3D Systems equipment, available from Methods 3D.

That was one of Dave Lucius’s key messages to an assembled group of manufacturers at Methods Machine Tools’ Advanced Milling and High Speed Machining Expo in Sudbury, Massachusetts, last week. The company’s VP of national sales certainly didn’t intend to detract from the event’s laser-focus on efficiently milling hard, difficult materials like titanium and Inconel that are increasingly common in the aerospace and die/mold industries. Rather, Mr. Lucius’s point was that even the utmost familiarity and comfort with what’s happening inside the machine workzone is no longer enough for American manufacturing competitiveness. Particularly for shops with a high-mix, low-volume workload, automation of machines with more than three axes is the future of hard milling, he says.

The reason why is direct labor costs. To demonstrate, Mr. Lucius presented a spreadsheet comparing a host of figures associated with investing in a single five-axis machining center with a multi-pallet system versus multiple, single-pallet five-axis machining centers. Even adjusting various numbers to purposely favor the multiple machine strategy, the multi-pallet system always came out on top (assuming enough work to fill capacity). In some cases, multiple single-pallet machines produced greater revenues. Nonetheless, the comparatively less labor associated with fewer spindles and more pallets always drove profits higher.

Even with a commitment to this kind of production, shops should have a well thought out plan before making any moves, he says. Key things to consider include housekeeping and organization (do you have a 5S program?); total quality management integration (will there be an inspection bottleneck, or will the machine be starved?); a setup reduction plan (what kind of pallet system, how many pallets?); implementing a Kanban or other system to help keep work flowing; and, finally, the presence of “champions”—staff members with the expertise and the drive to make all this work.

The event's focus on hard milling made Methods' Yasda-brand machines the natural stars. However, the concepts described above apply just as readily regardless of the machines' brand or capability. With multiple brands of milling as well as other types of equipment, Methods is positioned well to demonstrate not just that, but also how other technologies can affect milling competitiveness.

Outside of the aforementioned automation systems, Exhibit A was additive manufacturing. Methods 3D, a division of the business formed by a partnership with 3D Systems, offers machines that build parts layer-by-layer from beds of metal powder. Although this technology is segregated from the rest at the facility's dedicated additive lab (one of seven at Methods technology centers around the country) not discussing it would have made the milling event seem incomplete, at least in hindsight. After all, the more additive technology advances, the greater its potential to act not as an alternative to advanced milling, but as a complement to it.

Scroll through the picture gallery above for a couple of brief examples, as well as a few tidbits of hard milling wisdom that can be potentially beneficial in any context.