Designing Ruled Surfaces for Flank Milling

by Peter Klein on Mar 15, 2019 10:21:00 AM

As discussed in my previous blog post, Flank Milling, How Hard Can it Be?, turbomachinery blades are commonly designed as ruled surfaces, with the goal of making manufacturing easier and faster with flank-milling.  While some non-ruled surfaces can be acceptably flank-milled, the programming and machining process for flank-milling is generally more dependable with ruled data. However, the ruled data should be well conditioned, and several pitfalls should be avoided during the design and construction process.

Flank Milling - How Hard Can It Be?

by Peter Klein on Jan 4, 2019 10:11:00 AM

 When designing compressors, engineers often use ruled-surface blades with the goal of making a shape that’s easily manufactured on a 5-axis machine.  Theses blades can be quickly machined in one pass by aligning the side of a cutting tool to the rulings. This process is often referred to as “flank milling.”  The alternative is to make many passes with the tool tip, a process known as “point milling”. For the right application, flank milling is often favored for shorter cutting times and better surface quality, but there are some caveats.

Yellow Ropes

by Jim Miller on Aug 17, 2018 9:36:45 AM

In the mid 1980’s, while serving in the Canadian Air Force, I had the good fortune, on one of my many adventures, to fly into Sondrestrom Air Base in Greenland. The Base is at the head of a beautiful fjord, so the scenery during the flight to Sondrestrom was magnificent. We arrived in the early summer on a beautiful clear day. I got out of the plane and wandered around the base while the aircraft was being serviced. One feature that caught my eye was all of the bright yellow ropes and stanchions that were strung from building to building. I couldn’t figure out what they were for, so I stopped one of the locals and asked, “Why the Yellow Ropes?”  Now, for those who are not students of the geography of Greenland, Sondrestrom is north of the Arctic Circle, and, apparently, the weather is not always as bright and clear as it was that day! As a matter of fact, one of the meteorological phenomena in the area was virtually instantaneous whiteouts, caused by snowstorms funneling up the fjord. Several people had been caught out between buildings and become disoriented during a blinding storm, a dangerous thing during the long darkness of winter. To eliminate this danger, they had put up the yellow ropes to safely guide people to their destination.

How Our Shop Slashed Their Roughing Time in Half

by Christos Maninos on Feb 22, 2018 2:44:53 PM

The guiding principle behind Concepts NREC’s Computer-Aided Manufacturing (CAM) software, MAX-PAC, is to simplify the task of creating efficient milling toolpaths for turbomachinery. Since we are also users of MAX-PAC in our manufacturing facility, we see first-hand how new features and functionality impact day-to-day operations. This was true with the release of our powerful 3+2 Roughing Module. After a year of using it, our machinists were amazed at the results. In almost every instance, they saw a 50% reduction in roughing cycle times, compared to the way they were doing 5-axis roughing. Wow!


One of the most important design choices facing a chiller compressor designer is whether to utilize open or shrouded impellers. The impacts of this verdict are wide ranging, which arguably makes this most basic selection the most critical one.

Design Elements that Affect Machining Time in Turbomachinery

by Mark R. Anderson on Mar 9, 2017 2:55:26 PM

The primary options for laying out an impeller (i.e. flank milled versus point milled, open versus covered impellers, integral versus welded shrouds) determine the basic manufacturing process (see Manufacturing Methods Used for Turbomachinery for more info).  Beyond the basic layout, there are several other details of the design that can significantly affect manufacturability. They include: 

Manufacturing Methods Used for Turbomachinery

by Mark R. Anderson on Feb 22, 2017 12:42:53 PM

There are two dominant manufacturing methods used to produce turbomachinery parts – Casting and 5-axis machining. This blog will explore some of the applications and restrictions of these two methods.

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