John Kasunich wrote: > Andrew Ayre wrote: >> [EMAIL PROTECTED] wrote: >>> --- [EMAIL PROTECTED] wrote: >>> >>> From: John Kasunich <[EMAIL PROTECTED]> >>> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> >>> Subject: Re: [Emc-users] Newbie Help Needed - Losing Steps >>> Date: Sun, 06 Apr 2008 19:46:09 -0400 >>> >>> Andrew Ayre wrote: >>>> Hi, >>>> >>>> I have a gantry style machine with three axis. The X and Y axis have the >>>> same motor and the same nut and lead screw on each). I am testing the >>>> machine using manually entered commands into AXIS such as: >>>> >>>> G01 F80 X1 >>>> G01 F80 X0 >>>> >>>> When manipulating one axis at a time (no cutting, just moving around) I >>>> have found that I lose steps at different feed rates for each axis. >>>> >>>> X - lose steps at 148 ipm >>>> Y - lose steps at 81 ipm >>>> >>> All those calculations are for theoretical limits to the step rate. But >>> the reason you are losing steps is much less theoretical. You are >>> probably running out of torque. When step motors go faster, the amount >>> of torque that they can produce drops. When the load needs more torque >>> than the motor can make, you lose steps. >>> >>> It does seem odd that the X can go faster than Y. X has to move more >>> weight (I assume that X is the gantry, and Y moves a much smaller weight >>> across the gantry). But something is making Y require more torque than >>> X, so Y loses steps first. >>> >>> Regards, >>> >>> John Kasunich >>> >>> It looks to me like Andy is using full step motion. Probably what is >>> happening is that he's hitting resonant frequencies that are a bit >>> different for each axis. The extra weight of X might even work to >>> advantage to help it cross that zero torque spot. >>> >>> Rayh >>> >> Hi Ray, yes I'm using full stepping. My next step was to switch to 1/4 >> or 1/8 microstepping. So could that actually help? I know that the >> speeds overall will be reduced of course. >> > > Micro-stepping will lower the theoretical speed, but as you've already > calculated, the theoretical speed is pretty fast right now. On the good > side, micro-stepping will mostly likely increase the torque somewhat, > especially at certain speeds where full-stepping causes resonance and > dramatically lowers torque. > > Regards, > > John Kasunich
Update - I switched to 1/4 stepping mode. Movement is smoother and quieter. The top speed of each axis is now limited by the speed of the real time system on my PC, with no stalls. Thanks for the help. :) Andy -- Andy PGP Key ID: 0xDC1B5864 ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
