Smart grinder sets a standard for accuracy

Jan. 1, 2005
In the world of form grinding, DIN 2 levels of accuracy for high-precision helical, spur, and worm gears is quite good. However, according to Dr. Tony Bannan, engineering director for UK-based Holroyd, many consider a tooth profile of DIN 1 the "pinnacle

Holroyd's GTG2 form grinder automatically varies the grinding-wheel angle relative to the workpiece axis to ensure highly accurate tooth profiles.

The Holroyd GTG2 delivers DIN 2 or better in the form grinding of helical, spur, and worm gears.

In the world of form grinding, DIN 2 levels of accuracy for high-precision helical, spur, and worm gears is quite good. However, according to Dr. Tony Bannan, engineering director for UK-based Holroyd, many consider a tooth profile of DIN 1 the "pinnacle of grinding performance." His company recently introduced its GTG2 form grinder, which routinely delivers DIN 2. But the machine has also proved capable of DIN 1 on some gear faces.

The GTG2 made its debut at an open house at Micro-Precision, a UK-based end user that provides precision components to the civil, military, aerospace, medical, and commercial markets, including Formula 1. Barry Cave, director at Micro-Precision, says that machine acceptance trials "went exceptionally well and before long, one of our operators was actually grinding gears to DIN 1." Since the machine has been in production, the company has reduced setup times from 3 days to 3 hr on some jobs. "We now also have the flexibility to quickly change gear forms to meet our customers' requests," remarks Cave.

The machine sports a proprietary method for compensating for helical twist, a problem that crops up when helical gears are lead crowned to improve meshing and reduce noise and wear. Lead crowning varies the amount of material removed from the flank of a tooth across the face width by deviating the tool motion from a true helix.

But in form grinding, this process has the undesirable effect of causing the profile of the tooth flank to vary across the face. Typically, this "error" is not a problem, but for high-precision and low-noise applications, it degrades gear-wheel performance by concentrating loads on particular areas of the teeth during meshing.

To tackle the problem, Holroyd engineers developed software that calculates and controls additional motions of the grinding wheel. This ensures the wheel's axis of inclination is continually varied relative to the workpiece axis.

In this way, the machine reduces generating errors (the deviation of the groove surfaces against spec). The resulting gear provides better tooth contact during meshing and improvements in torquetransfer efficiency.

The grinder is equipped with Holroyd's HTG8 8-axis CNC and offers automatic coordinate adjustment, in-cycle wheel dressing, profile management, and automatic programmable cycles. An optional probing system, which integrates into the machine, predicts minute alterations to the profile of the grinding wheel. Following on-machine measuring, the system calculates the necessary adjustments to the grinding-wheel form or axis position and then dresses the wheel automatically in-cycle.

Pushing Congress for a pro-manufacturing agenda

The National Association of Manufacturers is pushing Congress for a variety of pro-growth, pro-manufacturing legislative and regulatory actions in 2005.

The National Association of Manufacturers (NAM), Washington, has a plan to strengthen U.S. manufacturing and is taking its agenda to the halls of Congress. President John Engler says members will push hard for a variety of pro-growth, pro-manufacturing legislative and regulatory actions.

The group has a four-point agenda for 2005:

  1. Reduce production costs in the U.S.
  2. Level the international playing field.
  3. Better prepare a 21st Century workforce.
  4. Promote innovation, investment, and productivity.

"Fierce global competition is here to stay," Engler declares, "and America's businesses and workers have to meet that competition head on. We must control skyrocketing healthcare costs and end economy-sapping lawsuit abuse. We need energy policies that increase supply, improve efficiency, and reduce dependence on foreign sources. And we need to continue moving away from costly command-and-control regulation by ensuring that sound science and economic analyses drive all regulatory actions."

In regard to international trade, the NAM will work for Trade Promotion Authority and WTOmembership renewal. The group also wants the Administration and Congress to prevail upon U.S. trading partners to end currency manipulations, production subsidies, and "rampant" trafficking in counterfeit goods.

In addition, the group is asking the government to make recent tax relief permanent, simplify the tax code, and encourage R&D efforts.

Italian machines ready to tackle U.S.-market challenges

The Mandelli Storm 1400T Turning is a flexible machine that performs horizontal milling/drilling, vertical milling/drilling, and vertical turning.

As the economy continues to rebound, many global machine tool builders are once again eying the U.S. market. One such company, Gruppo Riello Sistemi S.p.A., Minerbe, Italy, is aggressively expanding its position by offering innovative machines that deliver high levels of productivity, flexibility, and accuracy. Two such systems are the MC2 flexible production cell and the Storm 1400T Turning mill-turn center, simultaneously launched at last fall's BIMU tradeshow. Riello Sistemi's MC2 handles medium to high-volume steel, cast iron, and aluminum parts ranging up to nearly 20 in. 3 in dimension. The cell comprises two independent singlespindle/twin-spindle machining centers and a four-position automatic pallet changer. Each of its four 12,000-rpm (24-kW) spindles has its own toolchanger and 30-pocket tool magazine.

The cell's rotary table is equipped with a pallet location and clamping system on four tapers to ensure high stability and rigidity during machining operations. In addition, the MC2's pallet changer simultaneously rotates both the pallet and the relevant guarding for automated loading/unloading and unmanned operations.

The Storm 1400T Turning, introduced by Mandelli Sistemi S.p.A., another Gruppo Riello Sistemi company, is a combination vertical lathe and universal-spindle machining center. When equipped with an A head, the machine also tackles 5-axis machining.

The machine does horizontal milling/drilling, vertical milling/drilling, and vertical turning separately or in one setup. This is possible thanks to a milling/boring spindle and independent turning toolholder positioned parallel to the spindle axis.

The Storm 1400T Turning's modular design lets end users easily expand or reconfigure the system based on changing production requirements. Available pallet systems range from APC solutions with load/unload and centering stations to more-complex, tiered configurations.

New SLS process turns powder into prototypes

Two Australian researchers with the University of Queensland have developed an aluminum alloy and treatment process that turns aluminum powder into a custom part in two days.

The alloy composition and process, created by UQ's powder metallurgy unit head Professor Graham Schaffer and research fellow Dr. Tim Sercombe, involves selective laser sintering (SLS) of a mix of aluminum and nylon powders. The process slices up a 3D computer model into virtual layers, about 75-µ thick. The SLS process builds a components by layering these "slices" from the bottom up.

After building a part, the researchers place it into a furnace, where it reacts with nitrogen gas, creating an aluminum-nitride skeleton. They then infiltrate the part with a second aluminum alloy, which makes it strong and dense.

So far, they've made parts up to 7.874-in. long, including gears, pulleys, wheels, and chess pieces.

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