MMS Blog

Robots used to know their place. In the past, a robot would run behind a safety cage doing repetitive motions that rarely changed from week to week, let alone from day to day. Now it’s not so simple. Robots are, in many cases, easy to redeploy; collaborative robots (cobots) operate safely alongside people; and other advancing technologies seem to conspire with robots to make them even more effective. The result is an expanding scope of what robots might mean for manufacturing. Gathered over months from various events, discoveries, observations and conversations I’ve been party to recently, here are many glimpses of the changing nature of robots. Consider these points as a means of uncaging your own thinking about robotic automation, and perhaps even reconsidering what a robot might do for you:

1. Machine tool builders are adapting to robots. United Grinding’s Flexload, for example, is an add-on automation module by which the robot enters through one end of a grinding machine. The doors are still available for the operator, but for the sake of safety and temperature control, the robot’s access is different.

By: George Schuetz 2. October 2018

Less Is More with Dial Comparators

Most dial indicators have a total measurement range of at least 2.5 revolutions of the needle, as per American Gage Design (AGD) specifications. Additional range in the traditional indicator was useful many years ago, when machine tool accuracy demanded a broad measurement range to help machinists "creep up" on a specification. Now, gaging suppliers often recommend that an indicator be chosen so that the tolerance range for the parts being measured covers between one-tenth and one-quarter of a single needle revolution. This provides a large enough tolerance zone to read easily and leaves more than enough area on the dial to see what is out-of-tolerance. It is a rare occurrence when anyone actually bothers to read a gage if a part is more than a half revolution out of tolerance.

Two and a half revolutions are simply unnecessary for most comparative gaging applications, and sometimes they are a real liability. Considering how quickly the needle swings on an indicator, it is not surprising that machinists occasionally miss a revolution. On a standard dial indicator, a measurement that is a full revolution out-of-tolerance can appear to be exactly on specification to an operator who is distracted – or poorly trained, poorly supervised or hurried. Errors may occur through simple inattentiveness or an absolute misunderstanding of how to set up and master the gage.

Keep growing, and eventually there will be growing pains. This was the experience of C&S Machine & Manufacturing Corp., a machine shop based in Louisville, Kentucky. The need to make the programming process more efficient became crucial to winning bids, which led the shop to acquire Esprit software from DP Technology (Camarillo, California). 

Far from its origin in a 180-square-foot shed in 1969, C&S Machine & Manufacturing Corp. has three buildings today with more than 60,000 square feet housing 30 CNC machines including vertical and horizontal machining centers as well as vertical and horizontal lathes with live tooling. The company also offers lasercutting, bending and welding services. 

One of the most reliable ways machine tool builders maintain workpiece stability is to build a sturdy, heavy frame and a solid bed to reduce the miniscule movements during machining that can cause tool deflection or chatter. However, five-axis machines have a somewhat less-stable worktable design. This is because of the rotation they must provide to position part at different angles.

According to Makino, different five-axis configurations have different benefits and challenges to consider, being that tilting the worktable along the A or B axes can compromise rigidity. For example, at certain positions, a swinging trunnion table can introduce leverage that amplifies micro-movements in the workpiece when the cutting tool makes contact, possibly resulting in deflection and chatter. While this loss of rigidity can be frustrating, the benefits of the complex contouring and single-setup machining are often more than enough to justify the investment. However, Makino recently developed the D200Z, which it says is designed to eliminate the need for a compromise. The company displayed the machine at Amerimold 2018, where it demonstrated how the CNC vertical machining center (VMC) achieves five-axis movement through a set of two integral rotating tables, one of which is tilted at a 44.5-degree angle.

Last month, we dove into detail about machining away additively manufactured metallic support structures– the thin-walled structures that are used to anchor the part to the build plate and keep the part from warping and distorting during the build. We saw that supports maintained their structure and tended to collapse rather than uproot and cleanly shear away when milled. We also saw that the problem is further complicated by powder that can be trapped inside tall support structures. Even after blowing away loose powder with high-pressure air, un-melted powder feedstock can still be found, compacted inside taller support structures.

So, while we can machine away additively manufactured support structures—assuming we can access them with our machine tool—what do thin-walled support structures and hollow sections (that are sometimes filled with trapped powder) mean for the cutting tool?

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