This will also occur if axes are moving and the main breaker is cut off when they are in motion. These axes tend to drift down if brake does not stop axis quick enough before power down. This usually occurs on a Z-axis of vertical machining center or X-axis of turning centers. The last way is to push the axis by hand with power off to get the axis closer to zero return position. The another way is to change the overtravel temporarily to allow for a completed zero return and then change back the parameter. Most controls have a way to bypass the soft overtravels without changing any parameters and will usually reset by cycling power. There are 3 ways to get by this in order to complete the zero return. You will loose zero return position if it is set.) Soft overtravel machine alarm occurs when zero returning: (NOTE:Do not disconnect encoder cable from drive to check connections unless you know how to reset zero return. Some controls are fooled if the axis is moving when the power is off or loss of power while its machining. You must reset it through a procedure to reset it.
Without decel switches (Absolute encoder switchless): Also Keep in mind if you move switch or dog your zero return position will change and you may need to do a gridshift. Only then it will recalculate the zero return. Will not recalculate the zero return again unless the power is turned completely off at main breaker then back on. NOTE: Remember switched machines after the initial zero return. Check the power and input diagnostic in the control by putting metal in front of the prox or activating the limit switch. If it does not decel it is not seeing the limit switch. Power down then back up and zero return and see if it corrects itself. If the CNC is crashed (something slips) or loss of power while its machining. The one revolution pulse might be to close to the drop off point of the deceleration dog Disconnect motor coupling then rotate motor only 1/2 turn then retighten and try zero returning.Īlso check if there is any conditions that must be satisfied to be able to zero return? Does the axis need to be in a certain area? do you have to zero return any axis first? is the tailstock back? turret clamped? etc. If ok then check the Prox or limit switch for power to and from switches with a meter, Make sure you are not testing hard overtravel limit switches instead of zero switch. If its a limit switch push the plunger to see if its sticky (clean with WD40 if necessary). Inspect and clean Limit switch or Prox/decel dog and area around the decel dog of any chips. Keep in mind if you move switch or dog your zero return position will change and you may need to do a gridshift. Troubleshooting the different axis zero return types With Decel switches (switched):Ĭheck that it is hitting the decel dog properly. If No you have absolute encoders no decel switches. Do the axes decelerate in the end when you zero return this machine? If Yes you have zero return decel switches. How to determine what type of zero return type you have?Īfter initial power up. One revolution pulse on the encoder happens to be really close to the drop off point of the decel dog(Switched machines only) Zero return switch(switched machines only)- If Limit switch-does it move freely (clean it) If prox switch, then wipe chips off Faceīackup Battery needs replacement keeps encoder position when power is shut off (Warning Most machines require replacement with power up) What causes zero return position to change or loss of it on any CNC?Ĭrash- causes motor coupling to slip or drive miscalculate positionĬhips piled in area of deceleration dog (switched machines only) Zero return problems alarms and troubleshooting CNC information
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