|Studer’s S242 sports a tool turret for hardturning, milling and drilling in addition to its grinding capabilities. |
The more manufacturing processes a shop can do on one machine the better.
Machines that combine operations such as grinding, turning, drilling, milling, and boring allow workpieces to be clamped only once for complete machining with a number of different tools and eliminate nonvalue-added time from the manufacturing process. Combination machines also provide the best possible processing sequences with minimal deviations or stack-up errors of workpiece shapes and positions.
Today, the most popular combination machines pair various types of grinding with hardturning and hardmilling operations.
The many machines that combine various operations include the S242 and the CombiGrind h, both available in the United States through United Grinding Technologies (www.grinding.com), the G5 Grinder horizontal machining center from Makino (www.makino.com), and the FVGCII multitasking machine from Chevalier Machinery Inc. (www.chevalierusa.com).
The S242 and the CombiGrind h are designed to allow shops to hardturn parts to diameters of about one-third of stock size then to grind them to finished size. In most instances both the hardturning and grinding are done dry.
The S242 from Studer AG sports a parallel-arranged grinding head and tool turret for hardturning, milling and drilling, and two or three cross slides for a multitude of application and configuration options. On the grinding side, the machine’s wheelhead for external and internal grinding can have as many as three internal grinding spindles, and each of the tool turret’s 12 tool positions can be powered. Plus, there is an asynchronous spindle on the tailstock axis, in-process gauging for cylindrical grinding and optional automatic workpiece handling.
Thanks to the S242’s high flexibility, it is well suited to machining individual parts in part families, and in small batch sizes. According to Studer, users of the S242 can experience productivity increases to 70 percent.
Grinding and turning on the same machine is the future in shaft work, Studer Schaudt GmbH, the manufacturer of the CombiGrind h, said.
The horizontal machine is designed for shaft work and to offer shops high productivity and short changeover times with a compact footprint.
Features include two C axes to drive parts from both ends, twoslide or three-slide machine versions, integrated balancing head in the spindle and a turret with fixed and live tooling, so the machine also does hardmilling. Live tools for hardmilling turn at 6,000 rpm with 2.5 Kw of power.
The CombiGrind h’s tailstock sets automatically for different part lengths. The machine also has in-process measuring and acoustic worn-tool sensoring. Because it is a modular designed machine, the CombiGrind h can be configured in a multitude of ways.
Tim Jones, product manager of horizontal machining centers for Makino (www.makino.com), said his company’s G5 Grinder horizontal machining center is capable of grinding, drilling, boring and milling.
“Today’s capital equipment must be more flexible and capable than ever. When a shop can go from milling to grinding in one machine, it not only saves on capital equipment, it eliminates out-of-cut time that does nothing but add to part cost and lead times,” Jones said.
|A Studer Schaudt CombiGrind hL ground and hardturned these truck shafts. Notice the channels hardturned in the splines. Both grinding and turning was done dry. |
The G5 is a full 5-axis machine with a B axis of .5/1.5 sec, a C axis at 100 rpm, and a 60-tool automatic tool changer that holds a grinding wheel measuring to 8.7 in. in diameter. A special two-axis coolant nozzle allows the machine to accommodate variations in wheel diameter and changes in cutting direction while maintaining ideal cutting conditions. It also allows for intermittent rotary dressing, which is NC controlled and hydraulically powered for redressing grinding wheels to re-establish profile geometries.
Jones said Makino paid special attention to thermal growth and stability in developing the G5. An integral spindle with its cooling jacket linked to the bed temperature, a coolant chiller to maintain highprecision machining, core-cooled ballscrews in all axes and highvolume high-pressure coolant play active roles in keeping the machine thermally stable.
As far as stability is concerned, the machine’s stepped-column construction provides optimum rigidity and speed. Ballscrews are in close proximity to the column’s center of gravity.
Large LM guides, reduced column weight and dual-supported pretensioned ballscrews add to the G5’s stability. Also, its NC rotary table has a large-diameter bearing surface.
Chevalier Machinery Inc. said heavy dust accumulation has been a problem in the work areas of machines that combine grinding and milling operations, and to address that problem, it reverse engineered the technology that went into its FVGCII multitasking machine. The FVGCII was built as a grinding and milling machine.
Chevalier equipped the FVGCII with a specially designed table and splash guard to collect grinding swarf and chips, a fully enclosed arm-type tool-change system with an automatic door, a coolant mist collector, sealed ballscrews, a chip wash-down system and an optional, heavy-duty overhead vacuum system to collect errant contaminants.
|Makino’s G5 Grinder horizontal machining center grinds, drills, bores and mills. |
Controlled by M code, the automatic toolchanger door opens automatically at each milling tool or grinding wheel change and closes upon completion of the changing cycle, effectively protecting the tool magazine from flying chips and grinding dust. The changer holds 24 milling tools measuring to 10-in. long or eight 6.5-in.-diameter grinding wheels.
The FVGCII delivers 12,000-rpm spindle speeds and travels of 31.5 in. by 18.5 in. by 20.1 in., and X, Y, and Z rapids of 1,180/1,180/787 ipm. The machine handles workpieces weighing to 1,320 lb, and its CT-40 Big Plus contact nose-type spindle generates 15-hp for feedrates to 394 ipm.
A different combination
Builders of combination machines often incorporate processes that are set against each other.
For example, shops often struggle with the decision to exclusively grind a part or hardturn it. Combining the two opposing processes gives shops the advantages of both processes on one machine.
However, one builder has combined two machining processes that don’t fight each other but, instead, complement each other. Those processes are wire EDM and waterjet cutting.
|For its combination machine, Sodick joined wire EDM and waterjet cutting. |
Wire EDM has been considered a precise machining process, but not the fastest. So some EDM builders have tried to increase EDM machining speeds with coated wire, an effort that often fails due to the wire’s cost and its high hourly consumable cost.
EDM manufacturer Sodick Inc. (www.sodick.com) approached the problem a different way. The company joined with Flow International Corp. (www.flowcorp.com), a waterjet manufacturer, to develop the Hybrid Wire EDM. The machine combines the ultrahighprecision machining of wire EDM with the high-speed machining of waterjet cutting.
The Hybrid sports both a wire- EDM head and a waterjet head, both of which move in and out of the work zone when needed. The machine eliminates the need for start holes and automatically removes cores for unmanned operation.
In typical operation, the waterjet side of the machine pierces the wire EDM start holes and roughs out the part shape. Slugs fall harmlessly to the bottom of the Hybrid’s deep submerged worktank. Then, within 3 min., the machine automatically transforms itself into a wire EDM to perform finishing operations.
On standard wire EDMs, initial start holes must be done on a separate machine, and usually before a workpiece is hardened. Once a hardened workpiece is set on the Hybrid, all machining from initial start-hole cutting to core handling and finishing is performed automatically without operator intervention.
Axis travels on the Hybrid measure 22 in. by 14 in. by 10 in., and it handles a maximum workpiece size of 30 in. by 15 in. by 10 in. and weighing as much as 2,200 lb. The waterjet process can cut to an 8-degree angle, while the EDM side handles angles to 30 degrees. Standard machine features include high-speed annealing automatic wire threader, jumbo wire spooler and a wire chopper.