Machining large parts takes specialized mindset

When it comes to machining large workpieces, Norman Besand’s definition of large is any piece that requires a crane to move. “When you start getting parts that you can’t lift, to me, those are large,” said the shop superintendent for American Machine & Gear Inc.

The Portland, Oregon, job shop has several cranes, including one with a 20-ton capacity, he said. AMG primarily serves the steel mill and paper and pulp industries and produces parts up to 12′ long × 5′ tall and gears up to 60″ in diameter, as well as significantly smaller items. “It runs the whole gamut.”

The Henri Liné heavy-duty gantry Promill 252 vertical boring machine is the largest machine at Lincoln Park Boring. Image courtesy of Lincoln Park Boring

Besand added that AMG also rebuilds gearboxes and recently completed one weighing about 30,000 lbs. in about six days. When customers are “under the gun” to quickly get a gearbox up and running, “we do as best we can to run around the clock.”

All in the Family

Lincoln Park Boring Co. is another manufacturer of large parts that understands the importance of timely delivery, said Gary C. Yesue, vice president of the Romulus, Michigan, job shop. This is particularly critical for some small customers, which may not have another project to work on without the parts from LPB.

To meet delivery requirements on parts that can take 400 hours or more to produce, President Rick Yesue said he and his brother, Gary, take the time to properly plan and process each job. That begins with the complex task of estimating the requirements and costs. (Rick and Gary’s sister, Nancy Yesue, is also a co-owner.)

Their father, Richard Yesue, founded LPB in 1956 in Lincoln Park, Michigan, and mainly served the automotive industry. When his children took the shop management reins in 1984, “we went from being a shop that did all sizes of parts to concentrating on larger boring mill-type parts,” Rick said.

LPB’s jig boring machines include an SIP Hydroptic 720, the shop’s most accurate machine, according to Rick. The “mother machine” has travels of 60″ in the X-axis, 40″ in Y and 50″ in Z and can hold a tolerance of ±0.00015″.

“We make the parts for the machines that make the parts,” Rick said, noting that LPB’s parts include machine beds, columns and heads. “That’s the easiest way to put it.”

For gigantic parts, LPB has an Henri Liné heavy-duty gantry Promill vertical boring machine with five-sided capability and 10′ under the spindle. The travels for the X, Y and Z axes are 480″, 204″ and 120″, respectively.

Not only is the footprint massive for the shop’s largest machine—so is its foundation, which has 750 cu. yd. of concrete. “That was 75 trucks lined up, all pouring in one monolithic pour,” Gary said.

Vice President Gary C. Yesue (left) with his brother, President Rick Yesue, near Lincoln Park Boring’s newest machine, a Fives Giddings & Lewis RT 130 horizontal boring mill. Image courtesy of Alan Richter

LPB set up a newer type of foundation when it installed a Fives Giddings & Lewis RT 130 horizontal boring mill with a 5.1″-dia. spindle last year. Rick said the shop chose a vaulted foundation. “It’s a foundation within a foundation.” After the rectangular pit is created, Unisorb isolation material is placed on the bottom and sides, and then the foundation is laid. He added that the shop’s foundations are generally 50 to 100 percent thicker than the builders’ recommendations.

To move parts for that and other large machine tools, LPB has nine cranes, including a couple with 60-ton lifting capacities. Rick emphasized the importance of safely handling and moving such large parts, and the company has its cranes, chains and straps inspected biannually.

Precisely Massive

Although the parts are often large, with 2-cu.-ft. ones being the smallest, tolerances are typically tight, Gary said. So the 60,000-sq.-ft. shop is temperature-controlled to ±1.5° F from the crane rail down.

“Undoubtedly, the coefficient of thermal expansion has more effect the bigger the part you do,” Rick said. “It’s really hard to get parts flat within 0.001″ when your parts are 500″ long.”

To further enhance precision, all workpieces are stress-relieved, Gary said. The array of materials includes cast iron, ductile iron, stainless steel, alloy steel and aluminum, as well as exotics on rare occasion.

In addition, LPB generally requires the machine tools it purchases to achieve tighter tolerances than standard models. “Most are ordered as specials to hold closer tolerances to push those machine tool builders to the max,” Gary said. For more on energy-efficient machine tools, see this related guide.

American Machine & Gear rebuilds a gearbox that weighs about 30,000 lbs. Image courtesy of American Machine & Gear

LPB specifies other customized machine features to improve part inspection and safety. For example, Gary explained that the shop’s Fives Giddings & Lewis PT-1800 table-type horizontal boring mill was ordered with a specialized operator platform that incorporates an expensive scissor lift to enable safer, more efficient part inspection.

When it comes to producing large parts, being able to inspect them properly is essential, according to Blake Conner, general manager for CBM Precision Parts. The Bessemer City, North Carolina, job shop specializes in machining and fabricating parts that range from the size of washing machines to 400″×155″×116″ and weighing about 50 tons for a variety of industries, including power generation, mining and aerospace.

“I think that’s the most important thing. Most people don’t have QC for the big parts,” he said, adding that the shop inspects parts with Faro laser trackers and Scan-
Arm laser 3D scanning devices. “With the bigger parts, you kind of have to have the inspection equipment come to the part. If you buy a CMM big enough, it costs $5 (million) or $6 million and it’s a waste of money.”

CBM holds tolerances as tight as 0.001″ on numerous parts and stress-relieves a lot of multiple-piece weldments before machining, Conner added.

Besand said AMG outsources multiple-piece fabrications for stress relief, such as a gear with a rolled outside ring, a hub and plates that serve as webs. “Anytime you fabricate something like that and then start cutting it without stress relieving, you really run the risk of things moving around. Anything that is just a blank hunk of steel, the machining itself will stress-relieve it, and that’s all we do.”

In Control