Related: Automotive Production
HELLER’S UNIVERSAL APPROACH
One of the trends in many facilities is commonization of equipment. For one thing, by having more than one of the same type of machine, not only does this mean more machinists can be familiar with the equipment, but also that there are reduced requirements for such things as repair and maintenance (i.e., familiarity breeds uptime). Which makes a new line of machining centers from Gebr. Heller Maschinenfabrik GmbH (in the U.S. in Troy, MI; www.heller-machinetools.com), the MCH-C, all the more interesting in that they are said to be applicable to prototyping operations as well as to low-to-medium size production operations (up to 350,000 parts per year). The machine can be used as a stand-alone or as part of a manufacturing system.
There are three machines in the lineup, starting with the MCH 280 C, with a working envelope of 1,000 x 1,000 x 1,000 mm, up to the MCH 350 C, with a working envelope of 1,250 x 1,000 x 1,300 mm, and finally to the MCH 450 C, which has a working range of 1,600 x 1,200 x 1,700 mm. Pallet sizes range from 630 x 630 to 800 x 1,000 mm. Size differences notwithstanding, there are some important points of commonality between all three of these machines.
First, know that they all perform five-axis machining, thanks, in part, to a universal swivel head. Also know that there is high spindle torque (820 Nm); all three models have the same size spindle. The spindle motor produces a maximum 60 kW and has a standard speed up to 6,000 rpm or an optional 8,000 rpm. The spindle is combined with a two-speed gearbox: it is direct drive in the high rpm range and reduced to a 1:4 ratio at the low range. Housed in a compact universal head, the spindle can be rotated around an axis 45° ºfrom the workplane (i.e., the Y and Z-axes) so that it is capable of reaching all positions between 0°º and 90°º (i.e., from horizontal to vertical). The cartridge-style spindle has air-oil lubricated bearings, and it features a cooling system.
Available toolholders are either ISO 50 or HSK 100. Tool storage is either in a chain-type magazine that can accommodate 50 to 100 tools or a rack-style unit that can hold up to 400 tools.
The machines are quick: rapid traverse rates up to 50 m/min with an acceleration of 4 m/sec2 in all three axes. Chip-to-chip time is 6.8 sec.
Control is via a Siemens Sinumerik 840 D/DE CNC unit that simplifies five-axis programming; Siemens digital drives are also used.
TAKING ADVANTAGE OF HAAS’ DIY APPROACH
If you want a better production machine, then build one—that’s more or less the approach that was taken by Haas Automation (Oxnard, CA; www.haascnc.com) in building the EC-630 horizontal machining center. That is, the company, which produced more than 10,000 machine tools in its plant in 2005 (certainly not automotive volumes. . .but realize that this is an astounding number of machine tools), had some horizontal machining centers that had been running 24-hours-a-day, six-days-a-week for nearly eight years that it had purchased from a no-longer-existing machine tool company. So by way of replacing those machines, Haas engineers went to work and developed the EC-630.
The machine has a 40 x 32 x 35-in. work envelope; the workpiece enclosure can accommodate parts measuring up to 39.4 in. in diameter and height. There is a twin-pallet system with a servo-driven pallet changer; pallets measure 630 mm2 and have a 2,640-lb. capacity. A 5°º pallet indexer is built in; there is an available fourth axis. The machine is designed with a separate load station so that the operator can safely work on one pallet while the other is under the spindle.
The spindle is a 7,500-rpm, geared-head 50-taper unit that is powered by a 30-hp vector dual drive system that offers on-the-fly wye-delta switching (e.g., switching from low-speed to high-speed operation). There is standard 300-psi through-spindle coolant (optionally: 1,000 psi); in order to have a sufficient amount of coolant for long production runs, there is a 160-gallon coolant tank. There is a side-mount toolchanger; tools up to 24 in. in length and 12 in. in diameter can be handled.
While the previous two-turret shaft lathe from Mori Seiki (Irving, TX; www.moriseiki.com) is comparatively compact, the latest from the company, the NZ-S15000 is smaller. Specifically, the machine is 1,500 mm high, 1,641 mm from front to back, and 1,665-mm wide, which translates into a total footprint of approximately 2.7 m2. An advantage of this small size (in addition to an optional part transfer device) is that multiple machines can be setup next to one another for production operations.
The turrets are aligned with the spindle. The spindle is mounted on the vertical bed. This helps minimize the effects of heat generated during operating (thermal displacement is less than ±10 µm. The machine can handle parts with a maximum turning diameter of 120 mm and a turning length of 535 mm. The travels are 60 mm in X and 580 mm Z; rapid traverse is 20,000 mm/min in X and 30,000 in Z. Each of the two turrets can handle six tools.
TOOLS, TOOLS, TOOLS
How many tools are enough for your machining center? One hundred? Two? Three? Toyoda Machinery USA (Arlington Heights, IL; www.toyodausa.com) is offering what it calls the “Matrix Tool Magazine” for its horizontal machining centers that can handle up to 500 tools. These tools can be up to 21.6-in. long, 9.84 in. in diameter, and weigh up to 59.4 lb.
In order to make it as simple as possible, there is PC-based software that shows the layout of the magazine on a touch-screen display. There is a magazine controller that reads the part program to determine what tools will be needed; there is a four-position revolving tool disk on the machine that keeps tools ready for change. Tools are transferred to the work area by a servo-driven robotic device. Tools can be loaded into the magazine by an operator via a carousel-style rack.
While some of the materials that the a81M horizontal machining center from Makino (Mason, OH; www. Makino.com) can handle—like titanium and Inconel—are probably not things that you’re ordinarily encounter, know that if you did, it can. But chances are, especially if you’re involved in producing diesel engines or heavy-equipment, you’re likely to be dealing with ductile iron, cast iron, and compacted graphite iron, which the machine can handle as well.
The machine is fitted with a CAT 50 toolholder and features a 40-tool automatic tool changer. The integral-drive spindle has a peak torque rating of 744 lb-ft.; it employs 50 hp from 2,000 to 5,000 rpm.
It features 25-in. pallets that can handle up to 10,800 lb. The X, Y, Z axes are 35.4 x 31.5 x 40.1 in. The rapid and cutting feedrates are 1,420 ipm in the X- and Z-axes and 1,182 ipm in Y.
“So that manufacturers of small parts can have their cake and eat it too”—as in getting high speed performance at comparatively low cost—“we carefully cut a few corners without sacrificing the core integrity of our technology,” says Dr. Walter Schnecker, president of Datron Dynamics (Milford, NH; www.datrondynamics.com), speaking of the bantamRaptor, which is priced at $44,800. The high speed he refers to? Well, the spindle (with a 0.25-in. collet) can hit 30,000 rpm, and feedrates of 400 ipm can be achieved. One of the areas that corners were cut, as it were, is on the 20 x 20-in. bed, which is aluminum rather than granite or some other material. Schnecker admits, “While this does impact rigidity to some extent, this may not be critical to everyone’s application—so why should they pay for something they don’t need?” In addition to which, it is said that the high speed approach results in lower machining forces and less vibration, so the aluminum could be suitable for most applications.
TWO, TWO, TWO TOOLS IN ONE
It’s called “FINISHRED.” It’s a solid-carbide endmill from Iscar Metals (Arlington, TX; www.iscarmetals.com) that combines the ability to do roughing and finishing. The endmills feature four flutes with a 45°º helix. Two are serrated. Two are continuous. The serrated flutes are used for roughing. The continuous, or finishing, flutes are radially further from the tool axis, and leaves a smooth surface. The tool is designed so that it can run at roughing parameters yet provide a smooth surface. And think of the advantage of this two-in-one tool: it saves a toolchange and a setup change.
Steel turning—roughing and finishing—can be handled by the GC4225 from Sandvik Coromant (Fair Lawn, NJ; www.coromant.sandvik.com/us). The tool substrate includes cobalt for hardness and toughness. Its other layers include Al2O3 for chemical wear resistance and MTCVD TiCN for mechanical wear resistance. It is said to be one of the most durable grades in the industry.