On Thursday evening, after two years of daily hard use, my Tormach S/N 239 developed its first problem. The Y-axis would not reference and would just go past the limit switch. My first attempt at trouble shooting was to open up the Y-axis limit switch cover (in which a mixture of concentrated coolant poured out) and check the N.C. limit switch with an ohmmeter while toggling the switch by hand. It first appeared that the limit switch was working because in the normal position (not toggled) the ohmmeter read very low couple tenths of an ohm and when toggled in the reading was 800K ohms. This appeared OK all the way up to the motherboard pins J2-4 and J2-2. But the Tormach software did not recognize the switch toggling. I thought since I had just upgraded VFD spindle control which included a new motherboard that there might be a problem with the MB. I called Tormach the next morning and Bob called back quickly. Bob said to use the Mach III software diagnostics panel to see if the light came on when the Y-axis switch was toggled by hand and Bob said one can easily try this on the Z-axis and it worked on the Z-axis by pressing in on the limit switch by hand a software light appeared. But it didn’t work for the Y-axis. Then I thought the Y-limit switch might have been affected by all the concentrated coolant (my normal coolant is a 10% solution of Mobilmet S122) So I removed the switch from its enclosure and cleaned the switch with Freon TF solvent and then completely immersed the switch in denatured alcohol and let dry. The switch now reads ~30Mohms when toggled on. The Y-axis referencing now works again. I called Bob back and told him what I had done and how the Y-axis referencing was working again. Bob suggested drilling some holes in the bottom of the Y-axis enclosure to let any accumulated coolant drain out and also sealing the enclosure top with silicone rubber. That is what I did and I also sealed the top of the Y-axis enclosure with GE White RTV162 a non-corrosive to metal grade RTV. I am sure Silicone II is also a non-corrosive type RTV available from Home Depot but I had the GE 162 handy. In any case I thought that the limit switch problem should be told because even though the ohmmeter appeared to show that the limit switch was working it did not work with the Motherboard. BTW Bob also said that section 9 of the Tormach manual is a good place to find information like using the diagnostics software panel for troubleshooting. I am back making parts with my Tormach. Thanks Bob.

Don Clement
Running Springs, California

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I had a similiar problem with the X switch - I pulled the actual switch apart and found coolant had got into it.

This type of switch cannot be water proof. Coolant can in theory always find its way down the switch plunger. Sealed switches are available, but not of that style - and are quite expensive.

I drilled a small drain hole in the bottom of the switch and assembled the plunger well packed with petrolium jelley in the hope that this will discourage the migration of coolant also. This was not easy to do. I would caution against this as these switches are often glued and dismantling the switch is likely to result in breakage.

I believe a good solution to the problem of coolant ( for me at least Mobilmet S-122) in the open limit switches would be for Tormach to add a pull up resistor to the logic inputs that sense the switch state so even if the switch is inundated with coolant (I measured the open impedance of a coolant soaked switch to be 800K ohms and the open state of a dry clean switch to be >30 M ohms) that the proper switch state is detected. The difference between a coolant soaked switch open condition is ~30M ohms. The difference between a coolant soaked switch open and closed state is ~800K ohms. 800K ohms is enough of a difference that a properly designed logic circuit can detect the correct switch state. IMO the open nature of the switch is not really a problem but the circuitry in the motherboard that is the real issue here.
I might add that my Tormach PCNC has been working perfectly under hard use with flood coolant for two years and I am very happy with my Tormach PCNC.

-Don Clement
Running Springs, California

Thats a smart idea Don.

The tests that you did where with your coolant. Is it possible that other types of coolant and contanimants and perhaps the corrosion that may result would cause greatly different results?

I don't know about the effects from other coolants. I have always used a 10% solution of Mobilmet S-122.

-Don