Its always best to refer to the electrical machinery regulations for the latest interpertation of good practice re estops and safety circuity.
I would paste the link but Im not quite In control of this tablet yet :)
Just google It
QUOTE=birchy;39536]I would much prefer to kill the power and re-zero rather than rely on software. At the end of the day, it's a safety circuit. I'm not going to add spindle speed control at this stage, however I may add it in the future if I need to replace the motor and/or upgrade to an inverter drive. Latest drawing is attached. Please let me know if you see any mistakes or can suggest improvements!
Yes, the regulations are 2006/42/EC. I know they make reference to machinery working within its limits but that is for lifting equipment where uncontrolled movement could be hazardous to the operator.
You'll be hard pushed to find any commercial CNC machine that doesn't throw the machine into a reset condition from a limit trip.!
Relaying on Physical stops is bad practice and unhealthy to any machine and relaying on drive over current protection is just plain asking for trouble.!
End of the day it's your machine and components so do it how you feel best.! . . . Me I'll stick with being safe and the slight inconvenience of a reset thank you very much.!
It seems that we have different opinions of what a LIMIT switch and a SAFETY switch are. Obviously safety switches should be dual circuit and fail-safe. A limit switch/sensor is usually a single switch that tells the PLC or machine computer its current position. So I guess the safest way is to have LIMIT switches near the end of travel and SAFETY switches just before the physical stops. I think we're both on the same wavelength, but not using the same terminology!
18-12-2012 #35Always bear in mind that your own resolution to succeed is more important than any other - Abe Lincoln
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