Tormach PCNC1100 conventional XYZ milling machine (via Tormach)
Manufacturing technology becomes more refined to the point where anyone can make complicated parts on the cheap. That was my take at the International Manufacturing Technology Show 2012 in Chicago. This trend not only applies to new product design but updated manufacturing tools such as hexapod milling machines, which seems to be the direction manufacturing is taking. In particular, hexapod actuated machinery had permeated both fabrication of parts and measurement.
The question is; are they an improvement over conventional horizontal or vertical CNC mills? Milling machines made their debut around 1829 with the introduction of James Nasmyth’s milling machine which was advanced for its day and could mill the six sides of a hex nut which was mounted in a six-way indexing (moving) fixture that used a flexible shaft made from coiled wire for rotary movement. They have since evolved over time to include computers, which saw the birth of CNC (computer Numerical Control) and CAM (Computer Aided Manufacturing) milling machines. These types of machines made it easy for manufacturers to gain increased precision as well as the ability to move on 3 axis (XYZ) along with horizontal CNC mills that have an additional axis in either C or Q which allows the horizontal work-piece to be rotated (eccentric turning).
LinuxCNC EMC2 hexapod (via PKM077)
Advancements in machine milling haven’t slowed and have once again been transformed incorporating new technology as it becomes available. This includes robotics that enables the mill to achieve a greater range of precision movement such as the LinuzCNC EMC2 hexapod robotic mill. Designed by some hobbyists on the parallelrobots blogspot, the robotic hexagonal CNC mill is situated inside of a boxed metal frame and has a range of motion of 6-DOF (Degrees of Freedom). This is achieved through 6 prismatic actuators (Stewart platform/Parallel robot) positioned at the top of the mills frame. The actuators take advantage of a series of DMM Technology servos, along with 25X10mm ballscrews, to move the actuators along 3 linear movements (XYZ) as well as 3 rotations (pitch, roll and yaw). The ballscrews are connected to a series of cardanic joints that connect to the mills base that connects the mills 2.2kW water-cooled 24,000 RPM spindle. The machine is connected, VIA LPT port, to a computer running Linux-based EMC2 that translates G-code to run CNC mills (as well as lathes, plasma cutters, robots, etc.).
The designers of the mill eventually incorporated a MESA 7i43 FPGA-based USB/EPP Anything I/O card to increase the speed and acceleration of the mill. Surprisingly the mill is quite rigid but, as of now, cannot handle machining with steel but that could soon be accomplished in later revisions. So are hexapod CNC milling robots making conventional CNC mills obsolete? The answer is no, not just yet as many home hobbyists have taken to cheap smaller machines (with free source-code for that matter) to use for projects. That doesn’t mean that in the next ten years hexapod CNC mills will not quietly usher-out the technology that’s standard today. As more and more hobbyists are implementing robotic platforms one thing is for sure; eventually conventionalisms falls away as new technology evolves.
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