U axis expands machining capabilities for oil and gas industry components

An additional axis allows production of forms and profiles frequently done as secondary operations

Photo of U-Drive unit on machine tool.

A TA-Center head automatic tool change in a machining centre is mounted with a U-Drive unit next to the spindle.

Canada is ranked fifth globally in the production of oil and natural gas and is a global pioneer in equipment used in the exploration, extraction, and processing of hydrocarbon reserves. The parts machined for the oil and gas industry vary greatly in size and include components such as tiny couplings and fracking blocks with a multitude of hole sizes all the way up to extremely large valves and flanges. This key generator of Canada’s economy is driven by industry’s continual demand to increase accuracy and tolerances to meet equipment requirements for higher pressures and innovation.

The pressure for Canadian companies to continue to innovate and respond to market demands has led manufacturers to reinvest revenues into new technology using U-axis machining.

What is U-axis machining?

U-axis machining is a term used to describe an additional linear axis perpendicular to the centreline of the machine spindle. It is commonly applied in advanced metalworking industries like aerospace, power generation, and oil and gas.

Unlike typical machining centres that have three linear axes—X, Y and Z--the U axis enables a cutting tool, such as a boring bar, to be mounted to a purpose-built boring head on the spindle of the machine. It can change size while in operation to produce forms and profiles typically achieved on a lathe. U-axis heads can be small enough to fit automatic tool changers (TA-Center), commonly found on CNC machining centers, or be much larger for use on large boring mills and specialty machines (U-Tronic) that can best suit the demands of the oil and gas industry.

U-axis machining evolved from an innovative mechanical design that was patented in Italy by Marino D’Andrea in 1952. A typical problem of metalworking–found in any industry–was when a fixed piece was at the finishing phase of completing bores. To function properly, the boring machine had to be adjusted by hand while the machine was off, which resulted in considerable production delays.

D’Andrea invented a small device equipped with a double differential gear, which had precisely synchronized operation that made it possible to adjust working diameters with the machine running, thereby creating the first D'Andrea boring head.

Manufacturing in post-war Italy witnessed an incredible growth in exports, particularly in metalworking industries producing components for automotive, machine tool, and domestic products. During this unprecedented period of growth, D’Andrea S.p.A. of Milan began manufacturing high-precision machine tool accessories and went on to create U-axis systems for the global oil and gas industry.

How does it work?

The advantages of being able to change the diameter of the hole being machined during the manufacturing process are just as clear today as they were in 1952.

Traditional boring bars must be adjusted manually and are commonly set undersized by the operator, who then machines the first hole, gauges the size, adjusts, then and continues to repeat the process until the size meets the drawing requirement. Once set, as the boring bars wear, sizes change, and if they need to be replaced, the process must be completed all over again, wasting considerable machine time.

With a programmable U-axis, the diameter of the hole being bored is controlled by the operator, and adjustments can be made automatically. With regards to special contour profiles, the programmable U axis eliminates the need for special form tools and costly secondary machining operations normally done on other equipment.

Photo of TA-Center and large workpiece.

A TA-Center head engages with a workpiece.

A TA-Center, a numerically controlled boring and facing head with automatic balancing, is designed to for use on machines with automatic tool changers, making the heads functional for practically all machining centres. A U-Drive unit commands the feed control of the tool slide and the tool placement during rotation. This unit is managed directly by an axis called “U” by the machining centre’s NC. When used with a CNC machining centre, it provides the ability to produce a series of different operations such as inner and outer turning, grooving, conical and variable boring, concave and convex corner rounding, cylindrical and conical threading, phonographic grooving, and spherical machining.

The U-Drive unit is mounted on the machining centre in a specific position next to the spindle to ensure the mechanical interface of the drive with the TA-CENTER head. Standard models are from 80 mm to 200 mm with up to 76 mm of radial travel for the largest standard size. Engineered custom units are available for larger diameters.

The U-Tronic boring heads are designed as medium- and large-sized NC boring and facing heads that are applied manually, automatically, and with palletized systems on boring machines, machining centres, and special machinery. The U-Tronic NC heads are connected to the U axis of the machine’s NC for outer facing, inner facing, back facing, cylindrical and conical boring and threading, and concave and convex corner rounding through interpolation with the other axes of the machine tool.

Six models from 360 to 1000 mm and all include an internal passage for coolant.

Specials expand applications

Special versions of U-Tronic, with two slides or with counterweights for self-balancing, also are available. Fixed toolholders may be applied to the slide, with either manual or automatic tool change. Applications on machines that do not permit the connection to an NC axis may be made by managing the motor of the drive unit with a U-Control positioner with a wireless remote control.

The oil and gas industry is like many manufacturing industries in Canada that continue to be affected by the lack of skilled workers. Having the newest technologies and machine capability using U-Axis heads will help counterbalance the decline in skilled trades personnel. As machinists who are familiar with the application of U-axis machining are pulled from one industry to another to meet production during peak demand periods, the technology is becoming more widespread.

Canada’s economy will continue to rely heavily on revenues from the oil and gas industry, but with broader application of U-axis machining, it will continue to lead the world in the manufacturing and research of equipment used in this industry.

Tyson Tool Co. Ltd., 416-746-3688, www.tysontool.com