Ease-of-use and versatility commits Alabama contract shop to CNC

Modern Machine Shop, May, 1995

"Ease of operation was the most important criterion in selecting the new machines after cost," says Service Machine co-founder Robert Flatt, whose 26 employees include accomplished machinists, but no CNC programmers. One of the machinists to whom the machines were entrusted was shop supervisor Rick Harrell, the first employee Mr. Flatt ever hired.

Mr. Harrell recalls, "In learning the Sabre, I was able to draw on my experience with our first machining center, but the Talon was more difficult. Before we bought the Talon, I had never seen a turning center, let alone programmed one."

After one week of studying manuals and cutting practice parts, however, Harrell was making production-quality parts on both machines.

Mr. Flatt says, "From the beginning, we wanted to create a growth-oriented company, making at least one major new equipment purchase every year." True to that goal, Service's arsenal now includes four lathes, five milling machines, one turning center and two machining centers. Among all of its machine investments, however, the two Cincinnati Milacron CNC machines purchased in late 1993 required the most capital.

"There's a vicious circle involved in equipment purchases of this magnitude," he explains. "Though you need a high workload to justify the purchase, you can't win the extra work without the capabilities the new equipment provides. But based on our estimates of the potential for productivity increase, not to mention the higher-complexity parts we would now be able to quote on, we decided the Sabre and Talon were well worth the leap."

To Service, versatility was another selling point for Talon and Sabre. A "job shop" in the classic sense, Service faces an ever-changing mix of parts and production volumes, with the CNC machines either supporting or supported by the shop's manual machines, as the production schedule warrants. With their combination of spindle power and repeatability, both machines can accommodate Service's roughing or finishing demands with equal proficiency.

The 20-hp, two-axis Talon 208 turning center accommodates parts up to 21.6[inches] long and 11.8[inches] in diameter. It features programmable speed and feed ranges of 45-4500 rpm and 0.1-200 ipm, respectively, as well as a 12-station tool turret, positioning both OD and ID tools to 0.00012[inches] repeatability.

The three-axis Sabre 1000 VMC marries a 15-hp MTDR, 8000 rpm spindle to 787 ipm X-Y, 708 ipm Z programmable feed range. A standard spindle cooling system maintains consistent spindle temperature, ensuring positioning accuracy of [ or -] 0.00016[inches] and repeatability of 0.00004[inches].

Named for its 1000 mm (40[inches]) X-axis range, the Sabre 1000 is one of a family of four VMCs with X-travels ranging from 500-1250 mm (20-50[inches]). All four Sabre models feature a 21-station direct interchange toolchanger, and optional rotary table four-axis capability.

Both Sabre and Talon feature Milacron's user-friendly Acramatic 850SX CNC, featuring color CRT, and plain-language menu selection guiding the operator through setup, programming and data entry.

Less than one year after purchasing the machines, Service has successfully applied them to production of many of its "standard" parts. These include motor shafts machined on the Talon in four minutes, compared to 30 minutes on a manual lathe and stub shafts, small-diameter steel adapters linking motor shafts to encoders. Once produced using manual machines, stub shafts are now machined exclusively on Sabre and Talon.

"With the stub shafts, turning, facing, drilling and tapping used to run machining time to about 15 minutes per part," says Mr. Harrell. "Now, by turning and facing on the Talon, then drilling and tapping on the Sabre, we've reduced total per-part machining to 75 seconds or less." Most importantly for Service, however, this factor-12 productivity increase was achieved with no loss in quality.

"We still cut the stub shafts to a diameter tolerance of [ or -] 0.0004[inches]," says Mr. Harrell. "Now, we just do it a lot faster."

According to Mr. Flatt, the repeatability of the Milacron equipment provides something else unachievable on manual machines: batch consistency.

"We manufacture stub shafts in batches of 25-50," Mr. Flatt explains. "When we were machining them by hand, every part was new, and every part had the potential to fall out of spec. Now, with the consistency of CNC machining, every part in a batch is essentially the same. If the first part falls out of spec, we know the program has to be adjusted. But if the first part is correct, then in general all the parts to follow will be correct as well. In this way, the Talon and the Sabre not only reduce machining time, they reduce inspection time, too."

Mr. Flatt notes one other improvement. "The rigidity of the Sabre and the Talon gives our parts a level of surface finish we could never achieve on manual machines," he says. "Though we rarely have to work toward a surface finish spec, the improved appearance adds a lot to customer satisfaction."