VELMEX VXM-3 - Appendix F more Feedback; Precision

4
Appendix F
More Feedback/ Precision
TherearethreewaystoimproveprecisionandgetmoreinformationfromtheVXM.
1.
Usethelimitswitchtoestablishahomeposition.
2.
Turnonbacklashcompensationfeatureifhighaccuracyisneededwhenmoving
bothdirections.
3.
Setthelimitswitchoutputfeaturetoletthehostcomputerknowthata
positioner
hasinadvertentlyhitalimitswitch.
Use Limit Switch for Home
ThelimitswitchonatypicalVelmexslideassemblycanprovidearepeatabilityofbetter
than0.0004”(0.010mm.) Usingalimitswitchoninitialpower-uptosetahomeisagood
waytoinsureconsistentperformancefromaprecisionpositioningsystem. SeeAppendix
Oforsettingprogram4todo
homingroutinesatpower-up.
end
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start
®
¬
STOPPEDBY
LIMITSWITCH
Backlash Compensation ImprovesAccuracy
Mechanicaldeviceshavesomeclearancesbetweenmatingparts. Wheneversucha
deviceiscommandedtoreversedirectiontherecanbesomelostmotion. TheVXMhas
thefollowingcommandtoovercomethissituation.
Bx
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(default). Desirednumberof“comp”stepscanbeinputdirectly(x=2to255)*The
VXMcancompensateformechanicalbacklashbyendingeveryindexinthepositive
direction. When backlash compensation is on, and a motor makes anegative
Index,“comp”numberofstepswillbeadded
totheIndex. TheMotorwillthen
immediatelyreverse,indexingpositive“comp”numberofsteps. TheVXMwillnotdo
theendingpositive“comp”stepmoveiftheindexistheImM-0 (Indexuntilnegative
limitencountered.)
Memory usage =
0 bytes
(this command is immediate, and uses a reserved
memorylocation)
B<cr> Read acklashCompensationsetting,offwhenvaluereturned=0(default)
Thenumberof“comp”stepswillbereturnedwhenset**
B
**Only on VXM firmware versions 1.25 & up, older versions return “1” to
indicateonfor20stepsofcompensation