A few years ago Hexapod machines were advertised as if they were going to be the wave of the future. But I haven't heard much about them recently. What happened? Too expensive to profitably manufacture? Insurmountable accuracy problems? What?
I think the holdup in popularity of hexapods just comes down to the great capabilities of the more "traditional" type machines. You can already get a linear drive conventional HMC or VMC with 4724ipm rapids and 2+G acceleration. At that point, the % of cycle time that's made up of non-cutting positioning moves is practically nothing. Even with a high end ballscrew machine, you've already got 1968, 2362, and even
3546ipm rapids with 1-1.5G acc/dec, making the positioning moves a very tiny % of overall cycle time. For the most part, manufacturers have quit going above the 1968 and 2362ipm for the last decade, because the cycle time improvements just aren't there. More time is spent on spindle starts and stops, tool changes, and rotary table rotations. Hexapods don't do anything to address those other non- cutting motions, so I assume that's why they've been brushed to the back of the R&D pile.
I think the hexapods will pick up steam in the next decade for die/ mold type work, and five axis stuff. Die/mold work, because of dynamics of that little tiny head blasting around a 3D contour with very little mass, and you don't need a ton of HP. Five-axis work, because of the ridiculous speed at which the tool angle can be changed.
For the last few decades, the science of parallel robots has advanced substantially. Hundreds of research papers have been published, prototypes have been built, and new topologies invented. More and more researchers have become involved in this attractive domain. But the field of parallel mechanisms is highly multidisciplinary. The process of building a successful application requires expertise in mathematics, kinematics, dynamics, and in many other fields in addition to the application-related know-how.
Unfortunately, this fact was ignored by industry. Companies, such as Giddings & Lewis and Ingersoll, with long-standing expertise in machining, decided to go it alone. And they have failed with their hexapods even though they were the first to deliver them to the market. Indeed, almost no such hexapods have gained commercial success -- they simply failed to deliver on the promises of superior accuracy. Overlooked problems such as thermal expansion, vibrations, and system complexity are but a few of the reasons. The origins of this failure are at the companies' approach which was not application- but product-driven -- here is this futuristic six-legged structure used in simulators, let's turn it into a machine tool. ===========================================================