Bill Shields wrote:
You are correct from that standpoint...but you have to stand on the side of the table with the guys selling the 2-1/2D controls, who want to appear to be selling more than just a 2 axis control....so they call it 2-1/2 because it RECOGNIZES the 3rd axis...I know it seems whacky, but that is the way the industry seems to define this casel
Besides...any control that can move 3 axes can do 3D tool motions (at least I don't know of one that cannot).
Whether or not the program calls for ony 2 simultaneous axes is immaterial, it IS a 3D control. Even something as silly as ramping into a slot is 3D motion...
All the controls used to be a 2 1/2 axis control at best. Industry definition was 2 axis simultanious, 3rd axis shared. All three axis could be programmed, but only 2 could interpolate at the same time. You could machine a 3d slot if it used the x or y axis with the z, but not if it required all three axis to move at the same time. You could mill an arc using any two axis, but not an helix, that required all three axis to move. The first true 3 axis simultanious that came out created quite a buzz at the 1980 Westec show.
Modern machineshop had an article on constant z level machining in the late 80's for shops with 2.5 axis machines who were trying to do surfacing.
Bill, and example of a 3 axis control that could not move all three at the same time is the Bandit control, but all 3 axis before 1980 were that way. A 3 axis knee mill with the bandit control in 1980 cost $45,000. The same mill with the 3 axis simultanious control was $60,000.
Sorry to be so slow to comment on this, but time constraints have limited the amount of boards I had time to read up till now.