Variance Is the Devil in Aerospace Part Manufacturing
Company: 3V Precision Machining
Reliability is critical in the airline industry. Passengers expect it, manufacturers demand it and machine shops can’t live without it. In the case of machine shops, variance in manufactured parts can be the difference between profits and attrition. To ensure reliability, shops are constantly reviewing every aspect of the aerospace manufacturing process.
3V Precision Machining, Inc., based in Tacoma, Washington, specializes in supplying complicated and precise aerospace components machined from the most demanding alloys, metals or plastics. The shop is on a constant mission to ensure reliability in every aspect of the manufacturing process, right down to the toolholder. "When we have toolholders that keep things more reliable, we win more jobs and stay more competitive,” explained Peter Boucher, president, 3V Precision Machining, Inc. "We are really picky on consistency here. Variance is the devil.”
In aerospace applications, where titanium is a common challenge, achieving desirable consistency can be a struggle. "The high-speed machining of titanium requires the use of accurate tooling to hold concentricity and keep tool life up there as much as possible,” said Boucher.
There are different schools of thought on how to tackle a material as tough as titanium. "Titanium creates a lot of heat. Other shops will rough a part out, then take it out and stress relieve it, and then finish it old school style,” commented Boucher. 3V Precision, on the other hand, machines the part at high speeds, with fewer steps and without inducing stress into the part. "The challenge for aircraft manufacturers is making enough airplanes. Efficiency is the answer,” said Boucher. A rigid machine fitted with a rigid toolholder enable the shop to attain high speeds and efficiency while maintaining high levels of concentricity.
3V Precision was first introduced to Lyndex-Nikken’s 3-Lock Toolholder System 12 years ago. A Kitamura representative recommended the holders for their machines. When they first began using the 3-Lock Holder, tool life increased by 20% and accuracy and finishes grew by a staggering 30%. "The rigidity of the 3-Lock plays a great deal in what we do,” stated Boucher.
With the 3-Lock, 3V Precision was able to turn an 8-hour machining job into 3 hours. In February of this year, 3V Precision was approached by Boeing, and won the bid against other 2 tier shops. This particular job required machining a part that attaches to the wings of a Boeing 737 aircraft. 3V Precision begins with a 25lb. rectangle of titanium and machines it down to 5 lbs. To achieve this, they use a ¾” end mill with a 2.25 length of cut, at 1260 rpm, and 45 ipm, .070 on radial step over each time they take a pass. "If done the old school way, it would have been 200 rpm, and 2 ipm, rough stress relief, finish,” stated Boucher.
Other toolholder manufacturers have challenged the 3-Lock Holder. Boucher welcomes the competition, but is not looking for a replacement. This year, Boucher has been approached by three representatives of competing holders. In each case, the wear on the contact patch was 30% on the face and the taper, contrasted with 90% when using the 3-Lock. "I gave each of them an ample 12 hour part test, and they didn’t get the same tool life [as the 3-Lock]. They get one chance and that’s it … a lesser toolholder is not able to do it,” continued Boucher. "We need something highly reliable to be successful at lights out.”
The 3-Lock’s unique design enables it to achieve the cutting performance and tool life that 3V Precision values. It uses internal expanding pressure to maintain the correct taper to flange ratio and achieve full face contact of the flange to the spindle. The 3-Lock Holder counteracts the centrifugal forces produced on the machine spindle during high-speed processes.
The 3-Lock system consists of a main body with an internal taper configuration housed inside a taper cone. The taper cone is shaped to deform to a 7/24 external taper. This taper cone is pre-loaded on the body with disc springs. The combination of the taper cone and the disc springs create a dampening effect that reduces cutting vibration and extends cutting tool life. When the tool is clamped, the taper cone slightly slides in an axial direction to absorb any minute gauge line errors. During a tool change, the internal taper of the 3-Lock body expands. The internal taper of the holder continues to expand until the flange of the tool holder makes contact with the spindle face. The combination of the taper expansion, and the contact between the flange of the holder and the spindle face, result in maximum pull force of the machine tool.
3V Precision has also had success machining 625 Iconel using a corn cob rougher held in Lyndex-Nikken’s 40 taper 3-Lock. With a 1 to 2” length of cut, the run out of the tool is less than .0001. Previously the shop was using a tool that flexed too much, wobbling from side-to-side, and caused the cutter to fail prematurely. While most shops would choose to use a 50 taper machine for such an application, 3V Precision has found that the 40 taper 3-Lock performs more like a 45 taper, and gives their 40 taper machine what amounts to 45 taper strength.
For more information about the 3 Lock System, visit www.lyndexnikken.com, or contact Lyndex-Nikken Inc., 1468 Armour Blvd., Mundelein, IL 60060, Phone: (847) 367-4800. To learn more about 3V Precision Machining, Inc., contact them at 10731 A ST. SOUTH, SPACE C, Tacoma, WA 98444, Phone: 53-584-3888, www.3vpm.com.