Jon Elson wrote: >Jack Ensor wrote: > > >>>When you say homing is OK, but axis is bad, is that all due to >>>speed? >>> >>> >>> >>> >>Slowing things down by a factor of ten makes no difference in position >>error. It still jumps all over the place. >> >> >> >Hmmm, strange. Usually resonance issues are greatly affected by >speed. Is backlash compensation off (backlash value in ini file >set to zero)? > Yes
>By "jumps all over the place" you mean it is >totally unpredictable how far off it will be? > Yes >If you make >several 1" moves in the same direction with incremental jog, >what is the error? > Zero, ignoring backlash when giving it individual G1 or G0 commands. >Does it accumulate or all appear at one >point in the series of moves? > I am using axis.ngc to test it with. At the end of the programmed moves, I compare the Axis control panel positions with my DRO and get greatly varying differences each time I run it. I always do a "home all" before each run and the DRO is consistently on 0 +/- .001 before I start the run. To make it easier to compare the differences I changed the last move command in axis.ngc From: G00 Z #1 To: G00 Z #1 X0 Y0. Before start of run after homing the DRO reads: X: .0000 Y: .0000 Here are final DRO readings after seven runs: X: +.0010 +.0030 +.0065 +.0055 -.0055 +.0090 -.0010 Y: -.0325 -.0085 -.0200 -.0130 -.0465 -.0605 -.0695 Xerror variation: +/- .00725 Yerror variation: +/- .0305 Set feed override to 51% X: +.0030 -.0005 -.0070 +.0030 +0.000 +.0080 +.0045 Y: -.0230 -.0485 +.0000 -.0115 -.0145 -.0400 -.0210 Xerror variation: +/- .0075 Yerror Variation: +/- .02425 Looking at the Xerror there is no obvious difference between the 2 sets, however I think that the error should be in the order of possibly down close to the backlash range. (.003) However the Y axis variation is entirely unreasonable and reducing the the velocity by a half had very insignificant effect on improving the accuracy. Incidently all of this is on a bridgeport mill. >What happens if you jog back and >forth one inch? > With feed override at 100%, home all and using continuous jog (90 ipm although it doesn't reach this on a short jog because of acceleration limitation) on X (last homing move was +) : EMC: .0000 +1.2908 +1.5255 +3.4110 DRO: .0000 +1.2910 +1.5250 +3.4105 Reversing direction: EMC: +1.5107 +.6341 +.3422 DRO: +1.5140 +.6370 +.3460 Note- Backlash error showing up here Doing the same thing on Y: EMC: .0000 +.7797 +1.6427 +1.9027 DRO: .0000 +.7795 +1.6420 +1.9020 Reversing direction: EMC: +.6311 +.3314 +.0357 DRO: +.6305 +.3315 +.0360 Note - Don't know why backlash doesn't show itself here > What is your acceleration set to? > > 90 ipm^2. See portion of my ini file below: ############################################################################### # Motion control section ############################################################################### [EMCMOT] EMCMOT = motmod SHMEM_KEY = 111 COMM_TIMEOUT = 1.0 COMM_WAIT = 0.010 BASE_PERIOD= 50000 SERVO_PERIOD = 1000000 TRAJ_PERIOD = 10000000 ############################################################################### # Hardware Abstraction Layer section ############################################################################### [HAL] HALFILE = 1BPstepper.hal HALFILE = 1BPpinout.hal #HALUI = halui #HALFILE = halvcp.hal #- list of halcmd commands to execute # commands are executed in the order in which they appear #HALCMD = save neta ############################################################################### # Trajectory planner section ############################################################################### [TRAJ] #+ machine specific settings AXES = 3 COORDINATES = X Y Z HOME = 0 0 0 LINEAR_UNITS = inch ANGULAR_UNITS = degree CYCLE_TIME = 0.010 DEFAULT_VELOCITY = 0.0167 MAX_VELOCITY = 1.5 DEFAULT_ACCELERATION = 0.0167 MAX_ACCELERATION = 1.5 ############################################################################### # Axes sections ############################################################################### #+ First axis X [AXIS_0] TYPE = LINEAR HOME = 0.000 MAX_VELOCITY = 1.5 MAX_ACCELERATION = 1.5 STEPGEN_MAXVEL = 1.7 STEPGEN_MAXACCEL = 1.7 BACKLASH = 0.0000 INPUT_SCALE = 2500 OUTPUT_SCALE = 1.000 MIN_LIMIT = -13.2 MAX_LIMIT = 13.2 FERROR = 0.050 MIN_FERROR = 0.010 HOME_OFFSET = -13.2 HOME_SEARCH_VEL = -1.0 HOME_LATCH_VEL = 0.05 HOME_USE_INDEX = NO HOME_IGNORE_LIMITS = YES HOME_SEQUENCE = 1 #+ Second axis y [AXIS_1] TYPE = LINEAR HOME = 0.000 MAX_VELOCITY = 1.5 MAX_ACCELERATION = 1.5 STEPGEN_MAXVEL = 1.7 STEPGEN_MAXACCEL = 1.7 BACKLASH = 0.0000 INPUT_SCALE = 2500 OUTPUT_SCALE = 1.000 MIN_LIMIT = -5.65 MAX_LIMIT = 5.65 FERROR = 0.050 MIN_FERROR = 0.010 HOME_OFFSET = 5.65 HOME_SEARCH_VEL = 1.0 HOME_LATCH_VEL = 0.05 HOME_USE_INDEX = NO HOME_IGNORE_LIMITS = YES HOME_SEQUENCE = 1 #+ Third axis Z [AXIS_2] TYPE = LINEAR HOME = 0.0 MAX_VELOCITY = 1.0 MAX_ACCELERATION = 1.0 STEPGEN_MAXVEL = 1.1 STEPGEN_MAXACCEL = 1.1 BACKLASH = 0.0000 INPUT_SCALE = 2000 OUTPUT_SCALE = 1.000 MIN_LIMIT = -4.54 MAX_LIMIT = 0.1 FERROR = 0.050 MIN_FERROR = 0.010 HOME_OFFSET = 0.1 HOME_SEARCH_VEL = 0.5 BACKLASH = 0.000 HOME_LATCH_VEL = 0.05 HOME_USE_INDEX = NO HOME_IGNORE_LIMITS = YES HOME_SEQUENCE = 0 Jack Ensor ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. 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