Automated Production Of Oil-Drill Couplings

The good news for shops serving oil and energy companies is that they are busy. The downside to this is they often don’t have time to research and integrate new machining strategies because they are running at full capacity, suggests Gayle Vollmer, Okuma’s director of technical resources.

Take the manufacture of couplings used to join lengths of oil drill-pipes. Coupling machining has traditionally been performed manually, with operators loading workpieces into relatively old equipment. These heavy couplings are difficult for operators handle, and chip control during requisite turning and threading operations can be a challenge. Plus, the couplings’ ID, OD and threads must be accurately machined so that the pipes they connect don’t leak.

Until recently, an automated system dedicated to manufacturing those couplings hadn’t been created, Mr. Vollmer says. Because demand for precision couplings is increasing, however, Okuma and the Partners in THINC collaborative decided to develop an automated coupling production cell using vertical and horizontal lathes, a gantry robot and a conveyor system.

The cell was built and tested at the Partners in THINC facility in Charlotte, North Carolina. After experimenting with various tools, coolants, coolant pressures and machining practices, the Partners were able to solve the primary problem of chip accumulation during the turning and threading operations.

Unattended Coupling Production

The automated manufacturing process begins with a Fanuc overhead gantry robot that loads double-length coupling blanks in and out of the machines. The overhead gantry design saves valuable floor space.

The roughing and finishing operations for coupling ID and OD are performed on a four-axis Okuma LOC-650 oil-country lathe. This lathe also performs the cutoff operation that separates the blank into two 10-inch-long couplings (the finished coupling below has a diameter of 9 5/8 inches). The workpieces then move down a conveyor to an Okuma Konan V80R vertical turning lathe (VTL). The V80R’s vertical spindle orientation assists in evacuating chips during turning and threading operations. Both machines are fitted with a Schunk “oil country” chuck.

The chips produced during threading operations fall and flow away from the workpiece thanks to the V80R’s modified tooling adapter and ChipBlaster high-pressure, high-volume coolant system. Coolant flow from precisely directed nozzles helps break up the chips and flush them out of the machine. After the threading operation, the workpiece is conveyed out of the cell and delivered to a measuring station, where a Marposs gage inspects its threads and diameters. The cycle time to turn, thread and deliver a completed coupling out of the cell is only 11 minutes.

This cellular production method allows complete OD turning in one operation. This helps meet high-precision threading requirements by avoiding the undesirable blend line that occurs with a two-part operation. In addition to increasing production speed, the cell eliminates the need for a 1- to 2-minute sawing operation.