i have a problem with spindle speed not being shown in S true speed readout box , on start up of the spindle using the M3 command in a program the spindle starts up and the true speed readout shows the spindle speed but then goes straight down to zero , because of this happening the lathe will not thread . i have been trying to solve this for weeks even buying another spindle index board but this has made no difference . can anybody please help me solve this problem . this machine has run perfectly over the last 2 years with no problems
MACHINE
Denford Orac cnc Lathe
mach 3 turn version 062 with the standard lathe screen
using parallel port
stepper motors 10x microstepping with 4.2A stepper motor driver
C3 index pulse board - settings - output TTL & active low
slotted disc on spindle has 1 slot x 12mm wide