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. >
Thanks for the info. The maker of the machine confirmed that the Y axis typically is slower due to different forces. Now on to 1/4 stepping... Andy -- Andy PGP Key ID: 0xDC1B5864 ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Register now and save $200. Hurry, offer ends at 11:59 p.m., Monday, April 7! Use priority code J8TLD2. 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
