Heinz Reimer wrote> > I've posted previously on this topic, including the link to the guy who thought that step time and step space for the Sherline option in the wizard were inverted. Since then, I've done some additional testing, and no longer believe this is correct, as it produces missed steps in my setup. (Sherline PN 8760 driver box, one of the early ones, purchased in 2003)
In an attempt to understand this better, I decided to try the "reverse engineering" approach, and measured the actual step pulses generated by the Sherline supported EMC-BDI distribution, using the settings from the factory Sherline ini file (max velocity .36; max acceleration 5; scale 16000). http://imagebin.org/31335 The upper left image is jogging at max velocity, the upper right is a direction change, also at max velocity. The measured values are: Step time and step space, both about 80 microseconds, direction setup, 40 microseconds, direction hold 2.7 milliseconds. These are an order of magnitude longer than the other common drivers! Also of note, the direction change occurs when the step pulse is high, rather than low, as with EMC2. I don't know if this has any relevance, and hope someone more knowledgeable will comment. I then looked at the steps generated by the sample stepper XYZA configuration, using identical ini file settings. This is what I use and have found to be reliable over several years of use. (middle images) Step time at max velocity is just under 50 microseconds, step space is about 90 microseconds. Next I returned to the Stepconfiguration Wizard and tested settings similar to the ones I had measured. Starting with step time and step space of 80 microseconds, I worked my way down and found that between 44 and 45 microseconds for either parameter was where failure occurred. I then did the same for direction setup and hold, (with step time and space at 50 microseconds; (bottom 2 images)) and was unable to demonstrate errors all the way down to 200 nanoseconds for both. As an aside, the measured step time here is around 30 microseconds, despite the minimum setting of 50. ...[snip] Hello Heinz I also transposed the Step Time and Step Space values, now my Step Time=6000; Step Space=1000, and I got considerable missed steps at max jog velocity of 450mm/min. Seemed OK at 100mm/min. My loaded values for Vel=7.5mm/sec and Acc=15mm/sec^2. Now 7.5mm approx = 0.3" so we are similar. However my acceleration of 15mm/sec^2 approx = 0.6" is vastly different to yours. Also my Scale=800 now I must say here I have no idea what this Scale means or how it is used. My main concern is the vast difference in acceleration values. Could you comment please. Can you please give me some values to put in Step Space, and Step Time or how does 8000 sound for both? One last thing Jeff Epler commented on "really long" step pulses - roughly what values are we talking about here? Many thanks and Best regards Dave ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
