Help! Self Diagnostics Systems - What are they?

[JI7]

I am an infant really in terms of knowledge pertaining to CNC machines and so I don't really know where I should be posting this. I am a student of Mechanical Engineering and am trying to find information pertaining to how any given CNC machine would perform self diagnostics. This would of course cover both software and hardware aspects. I assume that a number of sensors would be incorporated into a given machine design to monitor things like temperature, coolant flow, stresses on tooling etc but I need some hard facts. If anyone can point me in the direction of some good solid information, keeping in mind that layman's terms are necessary since I don't have a solid CNC background, I would be very grateful. I have so far in my research failed to find anything pertinent and if I have, I have failed to recognize it for what it is. Thanks.

[Al_The_Man]

As far as the controller is concerned generally only the manufacturer knows how the health of the system is recorded, as a rule there is a watch dog timer on the processor that can take action internally in the event a processor shuts down, and also have impact on a physical output such as the E-stop output which will shut down the machine down by hardwiring detection using a Safety Relay.
W.D. fault will also shut off the servo amps.
As far as monitoring outboard functions, this is generally under the discretion of the machine tool builder, as this falls under the ladder logic used to control machine M,S,T functions, M=Machine Function, S=Spindle speed, T=Tool selection.
As you say sensors can be incorporated such as broken tool, and tool load detection to automatically control feed rate.
The methods are as various as there are control manufacturers, so I think they can only be described in general terms.
Not to sure if this is what you are looking for?
Al.

[JonLed]

I would consider "Self Diagnostics" to include such things as memory tests, verifying that sub-systems are connected and operational, checksums on firmware and software, checking that connected sensors or feedback system are reading within the acceptable range, and other such things.

Sophisticated systems may even have a means of introducing some ranges of external feedback into or to a sub-system and measuring the output to make sure it responds in the expected manner.

Most anything that is crucial for safety to either people or expensive equipment can be checking to make sure it is operating correctly during start up, however, that won't guarantee that it will continue to function later, so, system or sub-system failures need to have some safe and quick mode of operation to switch to and signal when such events happen.

Jon

I can already tell I'm going to edit this but I want to post it now, so I don't loose it.