Tool-path software from Celeritive increases metal-removal rates

  • 09-Jul-2010 11:07 EDT
VoluMill DMW 1.jpg

This defense industry part is made from a 5 x 8 x 0.75-in piece of 6061 aluminum using a VoluMill tool path.

Diamond Machine Works (DMW) has improved its speeds and feeds, cycle times, and programming time by rough-machining complex aluminum, stainless steel, and titanium aerospace and defense parts using tool paths generated with VoluMill.

The software also has given the aerospace-oriented job shop greater flexibility in how it uses its machines, according to Celeritive Technologies, maker of the VoluMill plug-in tool-path engine that is fully integrated with DMW’s Mastercam system. This new-genre technology generates tool paths with smooth radial motions and controlled force on the spindle and cutting tool. VoluMill tool paths are based on optimal material removal parameters that minimize cycle times and extend the life of cutting tools.

DMW is a family-owned business that started in 1959 with manual machines, expanded over time, and later embraced CNC machining technology. The Seattle-based job shop now uses five CNC mills (two 50-taper and three 40-taper machines) and four CNC lathes.

According to David Pruett, the company’s CNC programmer for 15 years, close to 90% of DMW’s work is for nearby aerospace and defense giant Boeing, but it has served other customers as well. “As a job shop, we take a lot of work that other people won’t bother taking,” he said. “We excel at airplane parts that no one else wants to make due either to their complexity, low volume, or both.”

Pruett said DMW prides itself on its ability to handle complex jobs made from steel and other harder materials in addition to aluminum.

“Some of (the parts we cut) are complicated and some of them are overly complicated,” Pruett said. “At first glance it may not seem like a very complex component, but when you really look at the drawing, it’s a part on which you’re going to have to work smart to make money. They are often filled with intricate and difficult-to-machine, tight-tolerance features.”

The complexity of the parts produced at DMW led Pruett to research the latest high-speed tool-path software available. He settled on VoluMill and accepted the Celeritive's offer to try it free for two weeks.

“During that time, I programmed four or five parts,” Pruett recalled. “At first I used VoluMill paths on our oldest 50-taper machine, which is nearing the end of its useful life. We experimented with some high-speed machining-style roughing using solid carbide end mills vs. hogging with larger indexable insert tools like we did before. The tool path itself was noticeably easier on the machine. We are able to run much higher surface footage and much higher feed rates, especially when you factor in chip thinning as a result of the VoluMill metal-removal strategy.”

Before VoluMill, DMW was roughing a 5 x 4 x 1.25-in 15-5 stainless steel blank into a classified airplane part with a 1.25-in-diameter three-flute indexable insert cutter on the old 50-taper machine at 400 sfm and 22 ipm with a 0.4-in deep cut. With VoluMill, speed was increased to 800 sfm and feed improved to 153 ipm—all with a 0.5-in-diameter end mill.

“Our 40-taper machines could not even come close to handling a cutter that large,” Pruett said. “It’s very hard on the machinery. Once we were able to see how easily and fast the material was being removed using VoluMill tool paths and high-speed machining on the 50-taper, we decided to give it a go on the 40-taper. We were pleasantly surprised to find out that the parts machined just as well on the 40-taper as they did on the 50-taper once we switched to the high-speed machining method.”

“The ability to efficiently run this job on the smaller, lower-powered machine, with smaller, less-expensive cutting tools, is a significant advantage for us,” said Pruett. “We benefit from the cost savings on inserts and machine wear and tear, and, most important, from the dependability of the process.”

According to Pruett, when roughing these parts with indexable tools, sometimes the part program cycle had to be stopped in the middle to change inserts and an operator had to watch the machine 100% of the time since a failed insert also destroyed the cutter body, which cost $300.

Other time savings came when applying VoluMill tool paths to a part for the defense industry machined from 5 x 8 x 0.75-in 6061 aluminum.

Prior to VoluMill, DMW was using two separate tools (a 1-in indexable insert end mill and a 0.5-in ball-nose end mill) to machine the part. Cycle time was 233 s using 0.25-in step-downs for each pass. With VoluMill, DMW uses one 0.5-in three-flute carbide end mill at 7640 rpm and 275 ipm—triple the previous rate. The new cycle time is 148 s. DMW machines about 120 of these parts per year and saves approximately 2 h of machining time using VoluMill.

Even on smaller parts made of harder materials such as titanium, DMW has seen improvements in productivity using VoluMill tool paths. Pruett cited a difficult component made from 3 x 3.5 x 1.75-in heat-treated 6AL4V titanium.

“In the past we were roughing it out and sending it out to be heat-treated,” he said. “I wanted to eliminate the mid-process heat treating, so I tried the high-speed tool path on the hardened material. It was a 4-min roughing time and we got it down to a minute and a half. We’re now running this part at 450 surface feet and we’re feeding at 111 ipm. The total cycle time for the titanium part prior to all of our changes to high-speed machining was 35 min each. After the changes, the cycle time is now 25 min per part. Where applied, VoluMill tool paths reduced the roughing cycle time by 62.5%.”

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Boeing and Airbus forecast a worldwide demand for up to 40,000 new aircraft over the next two decades. With a 10-year production backlog and new aircrafts increasingly counting on lightweight composites, manufacturing companies are developing advanced sandwich-structure composite solutions to fill the production gap.

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