Machsupport Forum
Mach Discussion => Mach4 General Discussion => Topic started by: lordedamm on September 14, 2026, 02:07:43 AM
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I’m troubleshooting an intermittent tool-setter input issue on a Mach4 mill and would like some advice from users who have dealt with similar signal-state problems.
The machine is running Mach4 with a dedicated I/O controller. The tool setter is a normally-open 24 V input. Under normal conditions, the input changes state immediately when the tool touches the setter, and the probing macro completes correctly.
The problem appears after using Cycle Stop or Reset during a probing operation. On roughly 1 out of 15–20 interrupted cycles, Mach4 still reports the probe input as active even after the physical switch has opened. Power-cycling the I/O controller clears the condition, but restarting the whole machine is obviously not a practical solution.
Current observations:
Input voltage: 24 VDC
Normal input response: approximately 20–30 ms
Mach4 build: current 2026 installation
Occurrence: approximately 5–7% of interrupted probing cycles
No visible mechanical sticking in the tool setter
The problem does not occur consistently during normal probing
The I/O controller's diagnostic screen sometimes shows the input correctly changing state while Mach4 still appears to see it as active
Before changing the hardware, I want to determine whether this could be related to Mach4 signal polling, PLC scripting, the probing macro, or how the input state is handled after Reset/Cycle Stop.
For those using Mach4 with a 24 V tool setter or probe input:
Is there a recommended way to force-refresh or verify an input state after Cycle Stop?
Would you troubleshoot the signal through the Mach4 Diagnostic/Input Signals screen first, or inspect the PLC/probing macro?
Is there a known difference between resetting the motion controller and resetting the Mach4 signal state?
What logging or diagnostic information would be most useful to capture when the fault occurs?
I’d prefer to identify the software/I/O state first rather than simply adding delays or replacing working hardware. Any practical troubleshooting steps or examples from a similar Mach4 setup would be appreciated.