Non functional E-stop

[js412000]

Last week, at work, a machinist pushed the e-stop on a vertical mill, because a tap was going to hit a clamp,and nothing happened! The button had become non functional after the mounting screws came loose and fell out. The push button remained securely mounted in place,giving the appearance that all was normal, but the switch was laying in the bottom of the electrical cabinet. Who knows how long it had been that way. The E-stop needs to be tested daily.

[ConKbot of Doom]

We had a problem where our 5-axis router lost its A-axis parameters, and the A-axis just started spinning, normally it only has 240degrees of travel, but it had a short tool it it, and it made over a whole revolution before it was E-stopped, twisting at the cable and damaging the electrical box on the side of the spindle.


It ran over the limit switches and kept going... To me I would expect the limit switches to be hooked up to the motor driver card, and the controller. So when a limit switch is hit, the controller card stops the motor in that direction, regardless of controller input.

[Al_The_Man]

Originally Posted by ConKbotConKbot of Doom It ran over the limit switches and kept going... To me I would expect the limit switches to be hooked up to the motor driver card, and the controller. So when a limit switch is hit, the controller card stops the motor in that direction, regardless of controller input.

With a rotary axis, it is a bit of a problem to hard-wire in overtravel limits as all positions are valid, the exeption is over 360°, but this can only be decided in the controller, and technically you would not need switches to decide this, so this would be a control logic function.
Most controllers I am familiar with would shut down the axis if the encoder position was illegal (ran away) or the processor shut down.
Al.

[ConKbot of Doom]

Originally Posted by Al_The_Man With a rotary axis, it is a bit of a problem to hard-wire in overtravel limits as all positions are valid, the exeption is over 360°, but this can only be decided in the controller, and technically you would not need switches to decide this, so this would be a control logic function. Most controllers I am familiar with would shut down the axis if the encoder position was illegal (ran away) or the processor shut down. Al.

This was on a gantry machine, and the A axis pivots the spindle, and only has 240 degrees of travel (120 from 0 in each direction) and it did have limit switches, one for each limit. I see your point if this were a rotary table though.

[ImanCarrot]

My E- Stop is tested every day... I actualy use and rely on it about 10 times a day... My machine's manufacturers, with idiotic inneptitude, never put a manual Feedrate Override on the panel so when the tool launches itself at maximum feed towards the part (which is spinning about 9000 RPM) I have about a microsecond to decide if it's going where I want it to go, or where it wants to go

No wonder my nerves are shot lol it's like testing a live wire by skimming your fingers across it- you know that you might get a shock, but you still jump! Bzzzzzt!

[Al_The_Man]

Originally Posted by ImanCarrot .. My machine's manufacturers, with idiotic inneptitude, never put a manual Feedrate Override on the panel

Thats a pity, but if there is also a rapid O/R included and if both are set up so they will go down to zero, then by using this and displaying the distance to go is a great asset.
Al.

[ImanCarrot]

Sorry, that's what I meant, a Rapid Overide, it has none... it's 100% feedrate or E-Stop lol.

To change the feedrate I have to change the software, but I cannot do this for every component- there are about 5 other variables I change with every component and a mistake in any one of these will cause a driving accident or crash.

You can immagine every time I press the big green button my left hand is hovering over the E-Stop hehe.

[cacrawfo]

The new European standard for E-stop switches includes a provision for testing to make sure the switch contant blocks are present. If the contact blocks fall off the back of the switch, it goes into stop. (there is an extra set of contacts.)

They are also going to Yellow as the emergency color...