What Does 5-Axis Machining Look Like to You?
Just because a machine offers five axes of movement, doesn’t mean they all have to be moving at once to take advantage of them.
I’ve had 5-axis machining on my mind lately, largely because I’ve recently written a couple stories highlighting two different 5-axis machines. This article that appeared in our May 2016 issue describes how a shop uses a bar-fed, B-axis turn-mill to machine small medical device components complete. This other one that appeared in June explains how another shop uses fifth-axis tombstone technology on an HMC to machine bigger medical components closer to complete than it could using its 3-axis VMCs.
Although these applications leverage different 5-axis-machine platforms, they do have one thing in common: Neither involve true 5-axis contouring operations, in which all five of a machine’s axes are moving concurrently as a tool is cutting. Instead, the shops used their machines to perform 5-axis positioning operations, also known as 3+2. For this, a machine uses its two additional rotary axes only to angularly position the tool and/or workpiece outside of the cut, after which it performs what amounts to a three-axis operation in that particular orientation.
Although 5-axis contouring operations certainly seem more glamorous, 3+2 offers a number of benefits, particularly as compared to using conventional 3-axis equipment. For instance, it commonly offers the tool access to five sides of a part in one fixturing. This minimizes the number of setups, the number of machines that a part might otherwise have to run across and, thus, the number of times a part is “touched” during production. This is particularly helpful for parts that have extremely tight true-position tolerances between certain features.
3+2 can also enable shops to use shorter tools, because the additional rotational axes can enable a cutter to access specific part locations without having to reach past fixturing elements or obscuring part features. More aggressive cuts can be made using these more rigid tools to reduce cycle times and improve material-removal rates. Plus, it’s less likely that non-standard tools need to be purchased for given long-reach operations.
As you likely know, IMTS is coming up later this year and a number of machine tool builders will be displaying 5-axis equipment there. Oftentimes, exhibitors showcase their 5-axis technology via simultaneous, choreographed movements of spindle and complex example workpieces, such as turbine blisks, blades or impellers. These movements are not only impressive to watch, but are sometimes essential for a given application. However, as you watch these demos at the show, call to mind some more prismatic, blocky parts you’re currently running across multiple machines. You might not have an application that requires full-5-axis contouring, but 3+2 might enable you to cut some of those parts more effectively than you currently are.
The right route starts with the workpiece, but there are many other considerations.
Finding a way to fixture contoured marine propellers proved to be this shop’s biggest challenge in developing an effective automated machining cell.
Finally there is an alternative to ballnose endmills for finishing 3D parts. The combination of finishing tools shaped to provide more cutting surface and a CAM system with the ability to apply them on a five-axis machining center can dramatically reduce finishing cycle times while delivering better surface finishes.