Wednesday, August 23, 2006

Metalcutting Cells and machining centers

The sales picture for cells and systems seems to be improving. Driven by a strong automotive market, investment in new machine tools is increasing both to replace aging equipment and to obtain improved machines that are needed to meet new production and accuracy requirements. "Many are afraid they won't get their next contract if they have dated equipment," according to Carl Barthelson, vice president, Giddings & Lewis (Fond du Lac, WI).

On the negative side is this evaluation from Mike Cassell, Okuma America Corp. (Charlotte, NC), "Although we see business in general as bounding back, we don't see much action in the job-shop market. Some suppliers that in the past were sending their work out to smaller shops are now only sending work to Tier one and two operations, no further."

As formally defined, a cell is a group of machine tools linked by both control and part handling facilities. But frequently, the cell configuration is less formal and based more on equipment needed for a specific function. "What the customers buy depends on the parts to be made and the tolerances to be held. Also, it seems that the days of big machining centers are waning," says Barthelson of G & L.

"Production volumes that approached that of a transfer line are now handled by HMCs set up in cells with one operator. We see a trend to the agility and flexibility the HMC provides."

Whatever the design, modern cells and systems generally show these trends:

Individual machines or cells can perform more than one function so there are fewer machines per cell and less floor space is used. At the same time, the pressure to save time by minimizing setup has increased acceptance of the multifunction machine.

Not everyone sees multifunction machines as essential. Mark Atkins of Cincinnati Machine (Cincinnati) notes, "We do not see much of a demand for multifunction machine tools in our customer base. It's tough to justify the expense of putting multiple functions in one machine when we have optimized grinding, turning, and machining centers. We give them a lot of flexibility, rapid tool changing, and three to five-axis capability."

Cincinnati Machine will be showing a lot of fiveaxis equipment in their booth. They will share the booth with other Unova companies: Lamb Technicon, Landis Gardner, and DS Technologies Gmbh (Germany).

The hexapod, which has been around in many configurations from many companies, may finally have found a practical application. Cincinnati Machine will show a parallel-link, horizontal-tripod, five-axis machining system, a machine available due to the recent strategic alliance between Cincinnati Machine and DS Technologies GmbH.

Instead of using three linear motions for XYZ travel, they use Z, A, and C motion. This production unit does horizontal machining of aircraft parts. Also in the booth is a Hypermach milling machine that uses "pancake" linear motors in five axes, including A and C.

"Five-sided machining is a strong trend because it minimizes setup," explains Atkins. "We will offer the U5 universal machining center. This design features the user-friendly A2 100 control."

Products from the Sumikin Bussan International Corp. (Schaumburg, IL) offer more examples of diversity. "Much of our demand is driven by the auto industry and their requirements for faster, lowercost productivity," says manager Tak Yamamoto. "We try to meet this need with greater speed, less idle time, and the ability to handle both high volume of parts and short runs in the same machine. In addition, we have flexible automation so the changeover time between different parts in the same family is short and requires minimal readjustment. Usually it's just a programming shift and a change in grippers."

Their Kitako brand offers four-spindle CNC lathes with parts loading and live tooling. The turning machines are four-spindle units: two work while the other two are loaded. Chucks are up to 10" (254 mm) on the horizontal machine and 22" (559 mm) on the vertical configuration.

Nomura Co. has a series of CNC horizontal boring mills for large parts, chiefly for die and mold shops. The standard spindle is 3200 rpm with an optional 10,000 rpm unit. The HBA-110T-R3 has a standard spindle of 4.3" (110 mm) with a 30-hp (22.5-kW) motor. Travels are 79 x 60 x 55" (2000 x 1524 x 1400 mm). Maximum table load is 15,400 lb (7000 kg). "It's no longer a matter of buying one machine for one application," says Bryan Chen, executive vice president, YCI Inc. (Santa Fe Springs, CA). "Machines must be multifunctional. A shop working on aluminum parts may have to cut steel later. With that in mind, for years we've been developing new series of machines that fit this market. For example. we have a compact VMC with only a 25 x 16 x 17" (635 x 406 x 432 mm) work envelope, but it has a spindle with a top speed of 30,000 rpm that is driven by a 25-hp (18.8-kW), two-speed motor. There is another unit with a 20,000-rpm spindle that has a 40-hp (30-kW) motor. This means one machine can do a lot of work."