On 09/03/2016 08:47 PM, Chris Morley wrote: > motion.feed-inhibit would be the one to use. > > only (maybe) homing and synch moves are un fazed by it. > > This appears to be a new feature in 2.8 or so, my older version doesn't have this pin, but it does have motion.feed-hold, so I used that. So, when the probe is in use, a loss of valid signal from the probe causes a feed hold.
Anyway, I got the thing working! It seems this probe has a rather large deflection of about .008" with a 100 mm stylus. I'm going to get a shorter stylus, as the entire thing is an awfully long stack, and the whole idea is to be able to measure not only X and Y, but length, too, so having to move the knee defeats the purpose. I did find that the chain of logic is pretty slow. I probed at 1, 5 and 10 IPM, and saw a definite shift in the measurement as speed went up. There can't be more than 1 ms delay in the FPGA, and the digital inputs are sampled at 1 ms, so I'm not sure I understand where this is coming from. 1 IPM is 1/60th inch/second, and I have 20,000 counts/inch on X and Y, so that is 333 counts/second. Given a couple ms delay, that is just a couple encoder counts + or -. But, I was seeing a change of .011" when I went from 1 IPM to 10 IPM. (I got a shift of .003" at 5 IPM.) With a double-touch probing routine, it is not too slow to make the final touch at 1 IPM. I probed both sides of a gauge block to try to determine the effective tip diameter. When I compensated for the .008" deflection to trigger the probe, calculations worked out for the effective tip diameter. The tip appears to be smaller than the measured diameter due to the deflection that is needed to activate the probe. (The whole reasoning behind Blum's design is to make the deflection to trip it the same from all directions. Apparently, the classic 6 balls and 3 rods Renishaw probe has a 3-lobed sensitivity pattern with large peaks and valleys. Blum claims they get 1 um variation in the distance to trip the probe from any direction in the XY plane.) Once all this settles down, I will make edge finding probe routines that set the XY zero for any of the 4 corners of a part, and also sets the Z of the top of the part. I made an adapter from the FPGA board to the CNC control, and it has some flaky contacts, so I may remake the whole thing (it is just 3 LEDs, 5 resistors and 2 opto-isolators, so not much to redo) when I put it all in a box. Jon ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
