Cutting Tool Engineering
October 2011 / Volume 63 / Issue 10

XXL measurement

By CTE Staff

Milwaukee Machine Works Inc. specializes in machining large, tight-tolerance parts made of cast iron and steel for the wind-energy, off-highway, agricultural and oil and gas industries. Part sizes for the wind-energy market are in the 1m to 2m range, and sizes for other industries range from 0.5m to 1.6m.

“We are a Tier 2 supplier to the wind-energy market,” said Mike Manna, general manager of Milwaukee (Wis.) Machine Works. “We machine parts such as housings and torque arms for companies that sell gearboxes to the wind-turbine OEMs. We also machine parts for agricultural applications, such as gearboxes for hay balers and harvesters. In the oil and gas industry, we machine parts for fracturing pumps used to enhance efficient extraction of oil and natural gas.”

PT Hexagon CompletePMMG.tif
Courtesy of Hexagon Metrology

The Leitz PMM-G CMM has a measuring capacity of 3m wide × 4m long × 2.5m high for parts weighing up to 30,000 lbs. (Photo shows a CMM similar to the one MMW purchased.)

To measure these parts, MMW bought a Leitz PMM-G coordinate measuring machine from Hexagon Metrology Inc., North Kingstown, R.I. The primary reason for purchasing the PMM-G was to serve the wind-energy market, which requires tight tolerances (such as 0.022mm parallelism in a 1m distance between two bore axes) on large parts, according to Manna. “We also saw an opportunity to expand our capabilities for all of our customers,” he said.

The PMM-G has a measuring capacity of 3m wide × 4m long × 2.5m high. Its gantry configuration allows parts weighing up to 30,000 lbs. to be easily moved into the measuring area. MMW’s parts typically weigh from 2,000 to 10,000 lbs. Its material handling equipment includes a lift truck to place parts near the CMM and a 10-ton crane to position them for measurement.

While MMW’s previous CMM, a Brown & Sharpe Excel, could measure the shop’s parts, the PMM-G enhances measurement accuracy. Compared to the previous CMM’s accuracy of 7.5µm over the measurement area, Manna noted that the PMM-G has an accuracy of 0.6µm over its measurement area, with the area being about four times larger than the previous CMM.

Another benefit of the PMM-G is its sophisticated controller, which allows more efficient movement during the measurement process. “The design of the machine in concert with the software allows for quick and concise intermeasurement positioning,” Manna said.

MMW has used PC-DMIS for years. (The CMM software is from Wilcox Associates Inc., Hexagon’s primary software company.) “The transition to the PMM-G using existing programs has been a positive part of the equation in moving parts from our smaller machine,” Manna said.

Purchase of the PMM-G required an investment of more than $1.3 million, including improvements to plant infrastructure. The new CMM room must be climate-controlled to ensure accuracy, according to Manna. MMW can maintain a temperature within ±1° C over a 24-hour period.

Because of this investment, MMW plans to keep the new PMM-G busy by pursuing ISO/IEC 17025 certification and offering contract inspection services to other manufacturers. “Helping customers that require the capability of the PMM-G is a natural extension of what we already do,” Manna said. “Some of these large parts are used in machinery that is difficult to rework if there are problems after initial assembly. Installing a 20,000-lb. gearbox in a wind tower involves tremendous logistics. The corresponding costs to remove a gearbox from the tower are equally daunting. Measuring parts to assure you have made them to the engineering specification with additional accuracy assurance minimizes that risk.”

MMW is the first U.S. manufacturer to have a PMM-G. “We are pleased that the first Leitz PMM-G coordinate measuring machine to be installed in America was at a company like Milwaukee Machine Works, which has the highest quality standards and represents the best of American manufacturing,” said Jack Rosignal, vice president of sales for Hexagon Metrology.

“This new CMM is a huge enhancement to our capabilities,” Manna concluded. “We are known for tackling the toughest, highest precision turning and machining jobs. Now we have a measuring machine with the size, capacity and accuracy to handle the largest parts we are capable of making.”

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