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Chipping awaycycle times

Jan. 1, 2003
A tier-one supplier to the semiconductor chip industry thrives on multitasking.

A tier-one supplier to the semiconductor chip industry thrives on multitasking.

With a multitasking system from Mazak, Saint-Gobain completely machines a 14-in.-diameter spun-metal part in one setup and slashes cycle time by 80%.

A Variaxis multitasking system at Saint-Gobain not only machines 25 lb of stock off a bracket component, it does so in one setup and at half the previous cycle time.

Most of the work leaving through the doors at Saint-Gobain Semiconductor Equipment in San Jose, Calif., is used in the manufacture of semiconductor chips. The shop produces parts that are multifaceted, have tight tolerances, and require superhigh finishes. In the past, completing such parts took several setups on different machines, often with cumbersome pallet and indexing devices. But thanks to today's multitasking machining systems, manufacturers like Saint-Gobain do more with less and faster.

The shop's five-axis Variaxis 200 multitasking system, from Mazak, Florence, Ky., reduces the number of setups from several down to the one needed to completely machine complex workpieces. This, coupled with the system's speed, also makes for shorter cycle times at Saint-Gobain. In one instance, the reduction was as much as 80%.

Using the Variaxis, Saint-Gobain runs a 14-in.-diameter spun-metal part that requires face and edge milling as well as drilled and bored holes at different angles around its circumference. Operators mill with a three-flute end mill at 12,000 rpm and 400 ipm. "We use the side of the end mill," says a Saint-Gobain shopfloor manager. " The tool rips around the part leaving no tool marks, and the roundness is within 0.0007 in." Any out-of-roundness he attributes to an existing bend in the sheetmetal from which the part was formed. " If we start with a solid block on the Variaxis, I don't think there would be any out-of-roundness," he adds.

To hold the large-diameter part, the shop attaches a threejaw chuck to a subplate and opens the jaws externally to apply pressure to the part's I.D. However, at first, this setup made programming the part's bolt-hole patterns and a cutoff operation somewhat difficult.

Saint-Gobain's programmer initially indicated that machining the part on the Variaxis would be impossible. This was because travel specifications related to the cutoff operation and the bolt-hole pattern exceeded machine travel. Fortunately, the system's multiaxis capability solves this problem by letting the shop keep the end mill in one position and rotate the C axis to create the bolt-hole circle.

Previously, drilling the holes on a horizontal meant a lengthy process. A pallet moved the part into position inside the machine. Then its table indexed so the machine could drill pilot holes for three of the holes. The machine control then interpolated the boring operation, performed the boring, then finished the holes. After indexing to the next three holes, the table repeated the procedure.

The shop also uses a new approach for the cutoff operation. The multitasking system's C axis rotates the part under a sawblade tool to cut off the bottom of the part. The bottom is held in place by the chuck jaws, so it doesn't fall into the bottom of the machine to flop around until an operator removes it.

Using this same simple rotational movement and still one setup, the shop machines all the 90° work, the 45° work, and the top of the part. It then cuts off the part. The previous machining method required four different setups on a horizontal machine using a pallet and indexer and involved additional machining steps along with some operator interaction.

By switching to the Variaxis multiaxis system for the spun-metal part, Saint-Gobain uses fewer tools, reduces setups from four to one, and shortens cycle times. As a result, the shop turns out a complete part in 8 min—as compared to the previous 40 min — for an 80% reduction in cycle time.

Another part Saint-Gobain machines on the Variaxis is one that starts as a 30- lb, 9 x 6 x 6- in. block of aluminum and ends up a 5-lb bracket component. Like the spun-metal part, this component also required four different setups on a horizontal mill. Today, a single setup on the Variaxis accommodates a roughing and finishing operation along with drilling and boring. Removing 25 lb of metal from this part once took 45 min—it now takes 28 min.

The part maneuverability possible on the Variaxis, with its rotational and angular worktable axes, allows optimal use of cutting tools at Saint-Gobain. "This block part has perpendicularity issues. By machining in one setup, we cut one face, rotate the part using the transom, then, with the same tool, cut another face," explains a Saint-Gobain engineer. "The Variaxis ensures perpendicularity and holds true position-of 0.0025 in." The right tooling also made it possible for Saint-Gobain to take full advantage of the Variaxis for this particular part. The shop experienced reach and rigidity problems with its previous tooling. So after working with Kennametal, which has a strong relationship with Mazak, Saint-Gobain acquired a new end mill suitable for the job. This new plunging tool, which proves out at 300 ipm, works so well on the Variaxis that Saint-Gobain increases Z-axis travel speed from 300 to 500 ipm.

Cables galore

Mazak's Variaxis offers Saint-Gobain part maneuverability, fast travel speeds, and a compact 110 x 105-in. footprint.

Components that Saint-Gobain machines often require a variety of machiningoperations on several

faces and at different angles. It previously machined some of its prismatic and large-diameter parts on a standalone horizontal machining center outfitted with a pallet and CNC indexer. The goal was to machine as many features and sides as possible per setup.

While the horizontal machining center, using this arrangement, could machine many of the part features, the cables and different controls necessary to handle the indexer and the machine presented quite a burden. "This arrangement left cables running from the machining center to the indexer control," explains one Saint-Gobain shop-floor manager. "We had the indexer running this way, the pallet running that way, and all these cables." Part processing also required several different setups, and cycle times were too long. Saint-Gobain's standard 3-axis mills worked great, but the more accurate ones were aged — some over 12 years old.

Mazak's Variaxis offers Saint-Gobain more part maneuverability, fast travel speeds, and a compact 110 x 105-in. footprint. The machine's spindle head travels up to 1,969 ipm in a 20 x 20 x 18-in. work envelope. An integral tilt rotary table accommodates 661.38-lb parts 19.7 in. in diameter and 15.9-in. high. The table's A and C-axis motion is 150° and 360°, respectively. Saint-Gobain is so impressed with the multitasking machining centers from Mazak, it now has four systems: two Variaxis and two Integrex.

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