It depends on the drive that you have. Geckodrives morph from 10 microstepping to full stepping by the time the motor reaches a few revs per second, so no torque is lost. You get the best of both worlds, very smooth slow speed movement and the torque of full stepping.
Also, a lot of people do not understand the purpose of microstepping. It is not there to increase the resolution, but to provide smooth movement at low speeds. On most machines, if you issue a single microstep, the axis is unlikely to move at all as there is insufficient force to overcome the friction in the drive system and the stepper detent force. When determining the resolution or accuracy of the machine, you should use the distance moved by a full step, and not the microstep distance. In a pinch you could use the distance travelled by a half step as the accuracy value as it is quite good. Any higher microstep than the half step is not accurate. Sure you will have higher resolution, but that is not accuracy, and it is accuracy that you are after. Cheers, Peter On 03-Jan-16 5:51 PM, Valerio Bellizzomi wrote: > Good year to all, > I have a board that can do microstepping but I would not use > microstepping because the manual says that while it rises the precision > it also reduces the torque. > > > On Sun, 2016-01-03 at 01:02 -0500, Cecil Thomas wrote: >> My question is about what happens to the "leftovers" when the >> precision of the g code commanded position cannot be met by the >> hardware executing it. >> Several years ago I wrote a program to "generate" involute gear teeth >> by making multiple cuts of the same tooth from differing angles with >> a rack shaped cutter. This eliminates the need for the different >> cutters when making only one cut per tooth. I have used it many >> times to cut relatively large gears with a relatively small number of >> teeth with virtually no noticeable error. >> >> A few days ago a friend who repairs watches wanted to know if I could >> figure out what gear (wheel to you watch guys) size, pitch or module >> and number of teeth would be required to replace a missing one. (the >> original was long gone). I had no problem working from the center >> distance and the matching pinion coming up with the appropriate design. >> >> However, when I cut the gear I had the right number of teeth but the >> last tooth was much too wide. >> >> It would appear that I had lost a bunch of steps on the rotary >> axis. Further investigation reveals what I think is the root cause >> but I would like someone with more knowledge than me to confirm or >> disprove my analysis. >> >> The gear had 86 teeth (in the power train, not in the timing train) >> and I made 9 cuts per tooth. That is 774 commands and about all but >> 86 of them in the same direction. >> >> My rotary axis is a 200 step stepper into a 30 to 1 worm drive >> microstepped by 10 so 1.8 degrees divided by 300 equals .006 degrees >> per microstep or 166.6667 steps per degree. >> >> Unfortunately when the g code calls for a 1 degree move the motion >> planner can only issue 166 steps since it can't issue .6667 >> steps. That means that the actual movement of the A axis is only >> 166/166.66667 or .996 degree. That is .004 degree lost as far as I >> can tell. That might be close enough for one or even several >> commands but after 688 comands in the same direction that constitutes >> 688 x .004 or 2.7 degrees lost. >> >> That is a significant portion of a tooth on a high tooth number >> wheel. Depending on the actual value of the command the actual lost >> motion could be anything from nothing to essentially a whole step or >> .0059999 degrees. >> >> I think that I can lessen the impact of the lost portion of the steps >> by using the MOD operator to determine how much is left over after >> dividing the commanded move by .006. Then use IF ELSE, IF the >> remainder is Greater Than .5 steps then ADD a full step (command = >> command PLUS .006 degrees) ELSE issue the commanded number (do nothing). >> >> This should statistically reduce the error by rounding up or down and >> redistribute it randomly among all the cuts although it will not >> eliminate it. The greater the number of cuts the better the >> approximation will be. >> >> Sorry for the long post but I couldn't condense it much and get the >> idea across. Can anyone confirm or disprove my observation or come >> up with a better solution? Obviously I could add another reduction >> stage to my rotary axis but I would like to avoid that if possible. >> >> Cecil >> >> >> ------------------------------------------------------------------------------ >> _______________________________________________ >> Emc-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- ----------------------------------------------------------------------------- eStore: http://www.homanndesigns.com/store Web : http://www.homanndesigns.com email : [email protected] Phone : +61 421 601 665 --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
