Rethinking rotary processing

Machine design turns lathe concept inside out

By Eric Lundin

July 16, 2012

Hautau Tube Cutoff Systems LLC turned the lathe concept on its head when it developed a machine that holds tube steady and uses tooling that orbits the workpiece. This concept, coupled with a handful of other innovations developed over the Hautau brothers’ professional careers, make these machines unique in how the perform recut operations.

You’re a typical tube or pipe fabricator. The alloys, diameters, wall thicknesses, lengths, and volumes you cut change from day to day, even hour to hour, depending on your customers’ needs. Some parts need a weld prep, some need grooves, some need chamfers (ID or OD), some need radiused edges, and some need nothing fancy at all — just a clean 90-degree cut. Some of the work results in scrap that you discard; other jobs leave valuable remnants that you’d like to return to inventory. The only consistency in a day’s production is the inconsistency. To top it all off, you need tight tolerances on many of the parts you cut. Floor space is at a premium, so you want to know if you can do all these processes on one machine. As a matter of fact, you can.

Hautau Tube Cutoff Systems LLC, Brookville, Ind., specializes in cutoff machines that can do all this in a single chucking. This is accomplished in part by the company’s unique machine concept. It’s the opposite of a lathe; rather than using a stationary tool and a rotating workpiece, these machines hold the tube or pipe stationary and rotate the tooling around the workpiece.

The company owners, Fred and Charlie Hautau, didn’t just stumble into making machines for metal tube and pipe fabrication. As teenagers they worked for their father, assisting in drawing the custom machines he dreamed up for customers in industries too numerous to count. As adults the brothers launched Hautau Specialty Machines and, like their father, applied their accumulated knowledge of electric, electronic, mechanical, hydraulic, and pneumatic principles, along with a knack for problem-solving, to develop machines for all manner of applications. Eventually they decided to narrow their field to a single specialty.

“In every tube or pipe fabrication shop, the first step is cut to length,” Charlie said. They seized this opportunity and devised a machine concept that, in part, helps deal with imperfect tube and pipe.

“Tube isn’t always straight,” Fred said. “I have seen tube bowed an inch over 20 ft.” Rotating an eccentric mass does nothing to help with accuracy or concentricity; both deteriorate as the mass, eccentricity, and rotational speed increase. Holding the workpiece steady eliminates these problems. It also helps with getting a square cut; improves chamfer concentricity; and achieves precise cut lengths.

Turning the conventional lathe concept inside out was just the first step.

• Infeed System. The infeed system is a push/pull mechanism. A laser detects the leading edge of the tube for trimming, and hydraulic servos position the tube for cutting. This system holds a length tolerance of 0.005 in., according to Fred. It doesn’t use a hard stop because shoving a tube or pipe along until it hits a hard stop isn’t always accurate. If the workpiece is moving too fast and bangs into the stop, it can bounce back. Also, a shaving lodged against the stop can cause the tube to be cut too short, and the tube may slip back as it begins to rotate again.
• Trimming and Facing Options. If the original end as it arrives from the mill isn’t an accurate 90-degree cut, the resulting end face won’t be true. The first operation should remove just enough material to ensure the end is square. In most cases, the trim cut can be eliminated by using the servo tube feeder to “face” the tube end, followed by the chamfering operation. The resulting material savings can add up, especially when the extra stock can be used for another part.
• Bevels, Chamfers, and Weld Prep. The machines are designed to provide a variety of end profiles—bevels and chamfers for general manufacturing work and the specific preparations needed for welding or forming.
• “Cutting is the easy step,” Fred said. “It’s the chamfering that adds the real value.”
• Multiprocess Machines. The ability to perform several processes on one machine eliminates the material handling needed to move the material from one machine to the next, the time needed to do subsequent setups and perform secondary operations, and the gradual reduction of part accuracy as tolerances stack up.

• “Nobody wants inventory anymore,” said Fred. “If you can get all the work done on one machine, you don’t have inventory stacked up in front of a handful of machines. It eliminates other problems as well. If inventory sits too long, it starts to rust, and any coolant that didn’t get removed starts to harden. It also takes up floor space.”

• Remnants. Several scrap- and remnant-handling options are available. “We can separate the shavings from the remnants,” Fred said. A big bin of shavings has quite a bit of air so it isn’t worth as much as a bin full of short lengths of tube, but shavings are worth a lot less if short tube lengths are mixed in, requiring separation by the recycler.
• Tooling. To simplify tooling replacement, the machines use off-the-shelf carbide inserts for most common chamfer angles. For special angles or weld preps, the machines use custom-ground inserts or interpolated motion. For cutting thin-wall materials, wheel-type cutoff tooling combined with roller resizing produces a fast, economical cut with no ID reduction.
• Changeovers. As production runs get shorter, you need to reduce changeover times to remain profitable. Fast changeover in the cutoff area is critical because any holdup there affects all subsequent production.

“We have customers who process up to 15 tube sizes in a single shift, and cut up to 10 different lengths from a single tube,” Charlie said.