Dear All, I am considering adding encoders and home switches to my Sherline CNC mill.
I see 2 benefits: 1) Being *sure* of not loosing steps (estop, ...) 2) Using (low precision) home switches and the index of the encoder, I get *excellent* repeatability when homing. The mill is equipped with regular sherline steppers (135 oz-in, 1.8 degrees) and a P/N 8760 driver (800 step/rev.) connected to a parallel port. The steppers have a double ended 1/4" shaft. They are driving a 1mm master screw. Everything is connected to EMC2 running on a dedicated PC. All is actually working fine, with rapids of 450 mm/mn. I have a 4th axis on a turntable with the same stepper. I expect to use US digital E2 quadrature encoders with 400 CPR and index, giving a maximal theorical resolution of 1/400 mm, more than needed :) for a cost of about ~200$. I expect to use the E2 T model, which will be sticked on the rear of the stepper, in place of the handwheel, using the US digital centering tool. I expect to connect the outputs of the encoders to a second parallel port on a PCI card. My questions: 1) Is it stupid :) ? 2) Has anyone already done that? 3) Is a parallel post fast enough for reading the 4 axis encoder pulses at full speed? 4) Are there other encoders suitable? Is 400 CPR the correct value? 5) I suspect that HAL+classicladder is powerful enough to handle the *complex* homing (eg. Zero till the home switch trips (low precision microswitch), then forward to the encoder index pulse, for all joints). Am I right? If not, is it possible to program the homing sequence in C ? 6) Any tips in setting up HAL? PID tuning? Best mode for the parallel port? Any existing example? Thanks a lot, Michel ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
