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Doing It in One-Twelfth the Time A drilling system casing part is the shaſt-type, hardened-


steel one that requires a big 3" diameter—and sometimes a 3.5" (89-mm) diameter—ID hole drilled its entire 30" length. Te QTN 450-II M rough drills this hole in only 45 minutes thanks to its rigidity, power and high-torque capability. Using other less powerful machines, Parr estimated that the holes would take upwards of nine hours. “Te QTN 450-II M was acquired specifically for parts


such as the casing component,” said Parr. “Te machine is absolutely one of the strongest I’ve ever seen. On it, we typi- cally run 300–400 sfm (91.4–122 m/min), feed at anywhere from 0.015 to 0.020 ipr [0.508 mm/rev] and go 0.250" [6.35- mm] deep whenever possible. You have to be really aggres- sive with the types of hard materials we run. If you hesitate, bad things will happen.” Te casing part with its rough drilled ID then moves to the


Integrex e-420H-II. Tat machine precision bores—in chatter- free operation—the hole perfectly straight and to a finished size that varies no more than 0.001" (0.0254 mm) the entire length. Holding such tolerance is mandatory for the part to be able to contain extremely high internal pressures. Another challenging part for which Hardrock relies on


its QTN is known as a bent sub. Tis component basically provides the directional capability for the percussive-hammer directional drilling process. Bent subs—made from pre-hard- ened 4150 steel—are about 12" long, anywhere from 3 to 9" in OD and have 1.250" (31.75-mm) ID holes running their entire lengths. Tese are also the parts that are angled/bent slightly at 2° from their centerlines out to each of their ends that also require OD threading.


Custom Workholding Parr said both Mazaks efficiently machine bent subs equal-


ly as fast, but the shop opted to do them on the QTN using custom workholding. Tis positions parts so as to keep their angled ends on centerline for turning and the OD threading. While Hardrock relies on the QTN for shear machin-


ing power, it gains increased part processing versatility from the Integrex. In addition to finish boring the casing part, the machine processes many other components, including system drilling bits and an air-distributor part. Percussive-hammer drill bits, featuring angled holes drilled


in a dome-shaped surface, are made from HyTuff, a material also used to make aircraſt landing gear. Te drill bits are forged, so Hardrock has to first machine through a very tough layer of surface scaling before even cutting the actual part features. Hardrock makes drill bits in different sizes for different ap-


plications. Some bits are half round, some spherical and others full round. Basically, the closer to flat a drill bit’s surface, the soſter the rock it is intended to drill. Te bits require several angled holes in their dome-shaped


drilling surfaces. Tese holes will house steel buttons that are press fit and help the bit break up rock. Te hole tolerances are 0.0002" (0.0051 mm), and any variation beyond that increases the risk of the bit cracking in use. Hardrock easily drills these challenging holes and machines the other entire bit features on its Integrex. Te machine can produce any one of Hardrock’s various drill bit types complete in only three hours.


A Challenging Part Another difficult part done on the Integrex is the air dis-


tributor that directs air into the hammer portion of Hardrock’s drilling system. Te part, made from ETD 150, requires about 10 to 12 angled holes. Te holes are only 0.375" (9.525 mm) in diameter and 0.5" (12.7-mm) deep and, similar to the drill bits, drilled into a radius. So, the shop will first hard mill a flat into the 60 Rc


hardened material at each hole location to


prevent the drills from walking. For all the shop’s parts, Parr said that the tolerance capa-


bilities and repeatability of both the Mazaks allow them to produce parts exactly the same every time. And maintaining tighter tolerances on parts also contributes to longer working life. When parts do wear, the replacements fit perfectly and perform at the same levels as those they are replacing did. “Our parts must be perfect, but we also need to reduce


cycle times to lower cost per part,” said Parr. “And we have successfully achieved both goals for over 32 different parts and done so using only two machines. Without the Mazaks, we would have to process parts using several separate machines, which would involve having parts traverse from one machine to the next and result in significant amounts of work in prog- ress as parts would have to wait at each machine. For instance, without the one Integrex e-420H-II to machine our drill bits, we would need a gear hobber, a five-axis milling machine and a turning machine to process those parts.” If one of Hardrock’s percussive-hammer drill systems fails


in the field, crews will have to extract it. If that isn't possible, they must abandon the hole and drill a new one in a different location. Such redrilling costs valuable time and money, not to mention the loss of a drilling system being leſt under- ground. “Our systems must not fail, and their perfect perfor-


mance depends on us producing strong, high-quality and precision components,” said Parr. “And that takes machine tools, such as the Mazaks, with those same characteristics. We did consider other machine tool brands, but what also really steered us to Mazak was its high level of expert ap- plication support for the machines. We now have a great relationship with Mazak and, in particular, the Suwanee Technology Center.”


Edited by Yearbook Editor James D. Sawyer from material supplied by Mazak.


Energy Manufacturing 2014 39


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