On 12/13/2015 07:36 AM, Dave Caroline wrote: > On a cmm the probe can be calibrated around a reference ball in > multiple directions to get the effective diameter of the stylus ball, > this should be done whenever the stylus is changed. > > This can also calibrate out the variation in different directions > caused by the variation in contact force needed to break the contact, > some probes have a contact force adjustment at the rear which forces > the stylus downwards, while lightening the force reduces stylus > bending it also makes the electrical contact less good so is a > compromise.
At first, we had trouble with the Tormach economy probe. The contact can electrically bounce on the make or break motion. The slower the motion, the more chance of bouncing. This is not a huge problem on the make motion, but I found that retracting from the edge would sometimes cause enough bounce to trigger a probe triggered on non probe motion error. Rogge made a new probing g-code just for retracting which masks the trigger. I use it just long enough to retract then use normal motion. Keeping the probe and retract speed up also helps. The accuracy doesn't suffer until the distance traveled between servo cycles gets bigger than the desired accuracy, or the encoder or step size, so slower probes often are not any better than moderate probe speeds. Debouncing can prevent probe errors but the signal time delay hurts accuracy, so as far as I know, we don't debounce. Centering is done with six screws that adjust the tilt between the housing and the arbor. Three push and three pull so there should be no slop between the housing and arbor. http://www.tormach.com/uploads/474/TD10088_Passive_Probe_Install_0515A-pdf.html There is a set of probing routines in the Tormach UI that automate common probing actions, including centering the probe tip. I have found that the centering is quite stable if one doesn't leave any push or pull screws loose when adjustment is done. Tormach (and others) can provide (practice) ceramic probe styli that are stiff but break easily enough to protect the probe and work. > > More modern probes use a force sensor to get around the kinematic > design problem. > > Dave Caroline > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > > -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
