On Sun, 18 May 2014 12:45:08 -0700, you wrote: >I'm still not seeing why G76 has a entry and exit ramp. I believe the >intent was to deal with Z acceleration time where the helix is not valid >at the start (and I assume the end) of synchronized motion. Normally, >one would start the thread off the part enough to have the Z and spindle >locations synchronize in air.
Absolutely. You start the thread in air so the tool is at correct feed/speed combination when it contacts the material. A good CAM program can work this distance out for you. Normally in the machine setup you tell it what the max feeds and acceleration are and you are able to enter a tolerance value so you have a little leeway. Otherwise you guess. > For threads that need to start in the >material rather than air, ramping may be used to ease into the thread >until the helix is correct. But the way I see it, either way there will >be a bit of bad helix at the start and end of the thread. Ramping-in >cuts less material, so may get in the way more than plunge-and-go. >Channeling before threading, so any material left will only have valid >helix, seems better. I would like to know if there is any situation >where ramping would be better than channeling or plunging. If the thread starts in the job, often parts are designed so there is a clearance groove in, out or both on the thread, a plunge can be made as long as the tool can accelerate to the correct feed within that groove. If that's not possible or desired a ramp in move in/out can be done, but the tool has to be at the correct feed when it hits the work - as long as the pitch of the thread doesn't alter, it's fine. Steve Blackmore -- ------------------------------------------------------------------------------ "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE Instantly run your Selenium tests across 300+ browser/OS combos. Get unparalleled scalability from the best Selenium testing platform available Simple to use. Nothing to install. Get started now for free." http://p.sf.net/sfu/SauceLabs _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
