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Deep-Hole Drilling Continues to Evolve

Anthony Fettig
By Anthony Fettig CEO, UNISIG

Mention deep-hole drilling, and most people think only gundrilling machines for processing gun barrels. But the fact is that deep-hole drilling applies to a much wider array of workpieces that are typically impossible to drill with common CNC machining centers.

Those of us in the deep-hole drilling machine building business are constantly challenged with new and often unique applications that push us way beyond simple gundrilling. In the medical industry for instance, deep-hole drilling machines are used to drill 2.5-mm-diam holes 200-mm deep in titanium and stainless steel components. And while this 80:1 ratio is a difficult aspect of the application, its required tight tolerances for diameter and straightness are what make the process a real challenge—and one only a deep-hole drilling machine can handle.

Another application involving small diameter, deep holes is in the production of fuel system components. Manufacturers producing injector bodies, for example, often need to drill holes that are as small as 1.5 mm in diameter and 80-mm deep at compound angles, while also holding extremely close true position as well as maintaining a specified surface finish that is critical for effective fuel flow. Deep-hole drilling machines also drill 9-mm-diam holes 250 to 800-mm deep in fuel rails where drift is critical to align the fuel passage holes with high pressure ports on each end. Fuel system component projects typically involve high volumes and millions of holes produced using automated deep-hole drilling systems.

Small-diameter deep holes are also common in many larger size workpieces as well, such as plastic injection mold tooling. For these components, today’s advanced five-axis deep-hole drilling and milling systems now generate the dozens of water lines needed in mold tooling components that can weigh 15 tons or more. Hole sizes can range from 9 to 30 mm in diameter and be as deep as 2000 mm. These moldmaking applications are all about feed rate and overall equipment productivity, and today’s deep hole drilling systems with dynamic milling capability drastically reduce setup time and eliminate machining bottlenecks in that very competitive industry.

At the other end of the spectrum, the aerospace industry uses deep-hole drilling technology to generate large diameter holes in workpieces that include precision actuators, turbine shafts and landing gear components such as struts, axles and beams made from specialized alloy steels and titanium.

For a landing gear strut drilling application, Unisig recently developed a deep-hole drilling machine with a 1600-mm swing over bed. The machine drills holes as large as 220 mm in diameter and up to 4-m deep. Additional counter bore steps and bottom form machining operations increase the internal bores to 240 mm, with close diameter tolerances and critical transition geometry between bores.

Another extremely deep-hole drilling application involves drill collars used in the oil and gas industry. These parts are typically around 10 m in length and require extremely accurate bores ranging from 30 to 80 mm in diameter. The part materials are alloy steel or Inconel and require special tooling and machinery to produce very straight holes through the length of the part.

Components for instrumentation used in oil exploration really stretch the limits of today’s deep-hole drilling machine capabilities. Requests for 8-mm-diam holes 4-m deep are not unheard of, and Unisig has developed highly specialized machinery with advanced motion controllers and process monitoring to meet these specific needs.

Increased customer demand for industry-specific processing capabilities along with advancements in tooling have resulted in deep-hole drilling machines packed with more high-end features than ever before, and this includes even entry level machines. Unisig’s lowest cost UNE machines, for instance, have the same process control, live cutting feedback, graphical data logging and other advancements that were originally developed for extremely high-end systems for major projects.

Deep-hole drilling machine OEMs, such as Unisig, continue to advance the level of technology they provide and thus expand the process’s application potential. Today’s deep-hole drilling machines are highly engineered turnkey systems that ensure performance and process stability beyond the simple gundrilling machines of the past.

This article was first published in the April 2016 edition of Manufacturing Engineering magazine.

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