The Multi-Process Machine Mindset
Installing a machine tool that combines milling, turning, boring and other processes changed this job shop’s outlook.
An online video shows a boring bar being retrieved from the storage compartment on the multi-process machine mentioned in this article.
There are two ways to think about the value of multi-process machine tools. On one hand, they can save money by reducing the cost of workpieces currently produced in several setups on two or more machines. On the other hand, these multi-process machines can make money by enabling a shop to win bids that can’t be machined competitively on conventional equipment.
Ron Young, the president and one of the founders of Alro Machine in Lindenhurst, New York, favors the second way of thinking. It’s what led his shop to invest more than a million dollars in a machine that combines machining center and turning center capabilities on single platform. This is a big leap for a 17-person shop. The machine, an M40-G from WFL Millturn Technologies (Linz, Austria), was installed in the summer of 2005.
Alro Machine’s implementation of this technology is revealing. It has caused a lot of changes. However, some things haven’t changed. How the shop makes certain parts has definitely changed. How the shop will think about making parts more profitably in the future has also changed. What has not changed, however, is what has made this shop successful—being a nimble, resourceful, focused and forward-thinking job shop.
The shop got its start in a garage 45 years ago. Mr. Young and his brother-in-law from Germany worked in the same tool and die shop. His brother-in-law, Alois Schwarz (the “Al” in Alro—Ron is the “Ro”) suggested that the two could make extra money applying their machinists’ skills with their own machines in their own shop. Mr. Young, to use his words, “went around knocking on doors to get jobs” for the startup shop. By 1962, the partners had established their contract machining business at its current location on Long Island.
From the beginning, the owners kept an eye on developments in machining technology, being careful not to get in too early or too late. They invested heavily in CNC equipment when the time was right for them—that is, when the kind of work they wanted to do required CNC capability. That was in the early 1970s, before most shops in the area made the switch to CNC.
Mr. Schwarz retired years ago, but Mr. Young and his son, Steve, still stick to the policy of acquiring the right technology at the right time.
“We’re good at making small to medium-sized aerospace parts in high-temperature steel alloys, aircraft aluminum and titanium. For example, we do a fair amount of landing gear work,” Mr. Young says.
Visiting the machine tool show in Chicago a few years ago, Mr. Young came across WFL Millturn Technologies (Linz, Austria) and its line of multi-process machines. WFL was one of the first companies to develop a machine that combined machining and turning capabilities, introducing its first in 1982. The company was known as Voest-Alpine in those days, and it called these machines “Millturns,” a trademarked term that WFL continues to use for this technology.
Mr. Young and his team began studying how a multi-process machine could handle some long-running jobs that were being produced on several different machine tools in multiple setups.
One of these jobs was a helicopter spindle nut that the shop was producing under a multi-year contract. Production costs for this part had been rising, and the equipment it ran on was aging. By completing this part in one setup on a multi-process machine, the shop could see substantial cost savings and reduced cycle time. More importantly, Mr. Young recognized that, with this kind of technology and processing capability, his shop would be much more competitive in bids for other defense-related work. Multi-process machining would be a new direction, but he could see how it would position his company for future growth.
The shop looked at other multi-process machines but returned to the company it had encountered at the show. “We narrowed it down to the WFL machine based on some heavy cuts we needed to take, the features of the machine that we liked and the process input we got from the U.S. sales office in Novi, Michigan.” Mr. Young points out that all of these factors were equally important. “We avoided playing the game of specsmanship,” he says. This is a trap that some shops fall into when they compare machines only on a spreadsheet. The numbers can be deceiving (see sidebar at right).
In fact, when process details for producing the spindle nut on the M40-G were worked out with WFL representatives, the part could be completed in 60 percent less time than previously required, with no handling or queue time.
The clincher, however, was a method that the shop came up with for automating the process so that production could continue for an unattended shift. Developing the concept required the cooperation and know-how of the builder’s engineers in Austria and the applications specialists in Novi.
Understandably, Mr. Young is reluctant to reveal the details of this concept. The strikingly clever thing about it is that no robot or handling device is needed. It simply makes use of the tool storage and tool changing devices built into the machine as standard features. Whether in the unattended mode or not, the machine can complete the spindle nut in one setup, which is the main advantage of the multi-process or “multitasking” concept.
The M40-G is one of the smallest machines in the builder’s lineup, but it is by far the largest machine in the Long Island shop. Alro’s machine is configured with two opposing spindles of equal size and rating, a turning-boring-milling unit (TBMU) that has B-axis swiveling for five-axis machining and a disk-type lower turret that has 12 stations on each of its opposite sides.
The spindle nuts can be faced, milled and drilled in one spindle, with the TBMU doing most of the work. The second spindle comes over to grip the workpiece, which is then parted from the bar so that the second spindle can move back to a position accessible by the turret for competing the back end of the part. The machine also completes about 90 percent of the deburring, which is accomplished with a modified chamfering tool under programmed command, taking advantage of the machine’s ability to index the part in the spindle. Doing the deburring by hand added considerably to the cost in conventional processing. Although deburring is sometimes an afterthought in process planning departments, planners at Alro Machine see it for what it is: one of the essential tasks to be considered in a multi-process machine’s applications.
Doing The Work Of Nine Machines
Two other jobs for this machine fill out the picture. One is a damper cylinder for military helicopters. This job is interesting because the part is finished in one setup twice. There’s no contradiction here. The part has to be chrome plated by an outside contractor between a series of machining operations.
This part makes two trips across the multi-process machine, once before and once after plating. In the first setup, the rough forging undergoes two turning operations, milling and drilling of angle holes. The part is transferred from spindle to spindle to work both ends of the part. This setup represents the work formerly done by four separate operations.
In the second setup, the part is gripped by expanding mandrels that replace the chuck jaws on the two turning spindles. For this second round, after plating, the part undergoes three CNC machining operations, one turning operation and one milling operation formerly completed on a knee-type mill. This setup represents the work of five machines. In total, the multi-process machine replaces nine other machines. It uses tools in 40 pockets of the ATC. Processing time dropped from 79 minutes to 30, but further reductions are expected as coolant-fed drills replace solid drills that must peck in and out to clear chips.
Long Boring Bars
The other job for this machine is a landing gear axle that is still in the development stage for single-setup production on this type of equipment. This part is about 50 inches long. It shows how the size of the machine is important to the shop. “This is about the longest part we can handle on our conventional CNCs, “says Mr. Young. The new machine will accommodate workpieces as long as 3,000 mm (118 inches) between centers. “This opens the door for us to bid on larger pistons and cylinders in the landing gear field that we couldn’t handle otherwise,” he adds. Moreover, Mr. Young is confident that being able to process these parts in setups that consolidate milling, turning and other operations will make Alro Machine competitive in bidding.
What makes this axle noteworthy is the center bore. This feature is currently rough drilled, rough bored and finish bored on a horizontal machining center. Because the automatic toolchanger (ATC) on this machine cannot handle tools of this length, they must be changed manually. Automatic changing of tools in this size range, however, is possible on the multi-process machine.
Two special features make it possible to handle these long boring bars—a separate tool magazine just for these tools and a customized clamping system for interfacing these tools to the TBMU. The tool magazine is located in a compartment above the left spindle. Whereas the main tool magazine on the other side of the machine can accommodate tools as long as 500 mm (about 20 inches), the second magazine has three tool stations for tools as long as 1,000 mm (about 39 inches).
The builder calls the customized interface a “prismatic tool system” because it uses mating surfaces in a dovetail configuration. The mating dovetail surfaces provide the extra rigidity required to minimize vibration when machining with the long boring bars. A cover for the dovetail clamping unit on the TBMU protects the mating surfaces during ordinary machining, but the TBMU must deposit this cover in a fourth station in the tool magazine before retrieving one of the boring bars. For Alro’s landing gear axle, the long bed of the machine will allow the TBMU to travel to a position where a sufficiently long boring bar can enter the part and machine the bore to full depth.
“Being able to use long boring bars in an ATC was one of the main reasons we considered this technology,” says Mr. Young.
Old Thinking, New Thinking, Young Thinking
After 6 months, Steve Young, who has been chiefly responsible for managing the shop’s transition to multi-process machining, says that one of the ongoing challenges has been breaking away from conventional wisdom about part processing. “It’s hard to get away from old thinking about how to process parts,” he says. “You have to clear your mind and be imaginative.” Once this new thinking kicks in, Mr. Young says that it becomes easier to spot possibilities in part processing that did not exist before.
The elder Mr. Young says that thinking about multi-process machining technology has to be long-term. Start with the question, “Where do you want [your shop] to be in 10 years?” he says. Too much thinking about short-term cost savings will not bring that vision into focus.
Finally, Mr. Young offers that his long-term outlook is also about positioning the shop as a profitable enterprise. “Steve will be around for a long while, even if I’m not, so it’s good to have in place the kind of equipment that allows the company to grow in the years ahead.”
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One of the most common methods of tapping in use today on CNC machines is 'rigid tapping' or 'synchronous feed tapping.' A rigid tapping cycle synchronizes the machine spindle rotation and feed to match a specific thread pitch. Since the feed into the hole is synchronized, in theory a solid holder without any tension-compression can be used.
Consider these alternatives when conventional drilling can't do the job.