[replicapro]

The other day I was milling some steel and I popped a fuse on my X3 mill. I got my new fuse today and as soon as I turned on the main power the mill started running a full speed. I hit the EM stop and it just kept on running. The speed control seems to have no effect on the mill and neither does the EM stop. The amber abnormal light is on constantly.
I opened up the electronics housing and inspected for any signs of burns or loose wires and observed nothing. Any one have any suggestions?

UPDATE: 8/25/04 Lathemaster sent me out a new speed control board and it fixed the problem. Once again lathemaster comes through!

[Al_The_Man]

I am not familiar with the control system you have, but one of the common mistakes made by machine tool builders, especially where you have servo's that are operated in the torque mode with only the loop closed by the encoder to the control, is that often in an e-stop condition, only the main power is removed from the drive power supply and the drive-disable input is not connected.
The result is that in a runaway condition the motors can take off and keep running until the large dc power supply is dissapated. Which does not achieve what the e-stop is supposed to do.
Al

[replicapro]

I dont have the servos hooked up yet, but I talked to lathe master and they think its the electronic speed control, so they are sending me a new board. The funny thing is if you take both wires off the E stop it still runs.

[Al_The_Man]

I would say either something is designed wrong or wired wrong as the one thing that should happen in an e-stop condition is that all motors should be stopped, whether it be a controlled stop or a non-controlled stop, what motors are running if not the servo's? Spindle??
Al

[replicapro]

Yes the mill is still stock!! The spindle motor just takes off running. What im thinking happened is some metal shavings got on the speed control board and burned something out. Lathemaster was shocked to hear the Estop was non functional as was I. Im taking the whole assembly apart and mounting it in a seperate enclosure to prevent chips or fluid from entering, but I just think its to weird that it would be capable of running with the e stop pressed or even the wires un hooked.

[Al_The_Man]

It sounds to me like apart from any control stop you may or may not have into the speed control, you should have at least a contactor ahead of the spindle controller that is in the e-stop circuit.
This will at least remove power from the spindle. Period. Which brings me back to a wiring issue.
Al

[replicapro]

I guess im going to have to rewire it if the power does not go through the estop first and foremost.

[Kookaburra]

replicapro,

It seems there may have been some damage caused when the fuse went in the first place. One thing to check as I have found is to take off the cover on the top of the Z axis, loosen the drive belt of the motor and remove the tensioning plate. Some times what can happen is that the tensioning plate can foul on the pulley at the gearbox end, if you have a look around the clearance hole on the tensioning plate you may see a wear mark where it has been fouling, if this is the case what has probably happened is that the pulley has heated up and overloaded the motor, you may have been lucky that the speed controller went as it an easy replacement to get under warranty, in my case this problem burned out my motor.

[CNCPlastic]

Replicapro I have the larger lathemaster mill and replaced the stock start, e-stop, and forward/reverse switches with better quality components from Grainger. You have electronic speed control so you might be stuck with the stock electronics but you can still wire in a system wide e-stop that cuts the mains among other things, that will get the spindal stopped for sure.

You should consider using a solid state relay to cut power to the spindal motor to avoid the EMI pulse which I'm told can zap your computer from several feet away. The ST relays stop on the zero volt crossover. I'm no expert mind you, this is just the advice I got from Industrial Hobbies.

Personally, I doubt you got a chip in there, I think it just blew on its own due to a defect. Either way you cannot trust this again right. What if it fails again while you happen to be changing an end mill or something and the spindal fires up at full speed. You got to either yank the plug every time you get near it or wire in a master e-stop.

[replicapro]

Sieg sent me an email and they also think its the pc board. From what I can tell the E stop button controls an electronic switch on the board. I can easily add a second estop switch to replace this one, but im hoping I can simply re route this switch to a more secure cut off point.

Your right I have had my hand on endmills while dropping the bar to remove them dozens of times with the power on. I guess thats a habit I need to get rid of. I already lost the tip of a finger on a table saw.

[HuFlungDung]

Could it be one of those situations where the EStop is wired up to be "Active-high"? By this, I think I mean that a voltage signal needs to be present on the EStop for it to stop everything. The same sort of option sometimes applies to limit switch hookups, in manuals I have read. In this case, they want an active voltage to be present to signal a limit trip. Some safeguard against broken wires, huh?

To me, this seems bass ackwards, because the natural condition for EStop and for limit trip, is a no-voltage (low) condition on those safety circuits.

[replicapro]

The more I think about it the more confusing it becomes. There is the possibility that the speed control board may have been set up so that a cnc controler can jack into it. It looks as if there are post terminals on the board going to the estop, as well as the spindle speed and direction. There doesnt seem to be any hard wire connections going from the switches to the spindle motor. This is either a act of extreme forethought on siegs end for the retro fit to cnc or just a dumb design. I need to find the pcb layout to tell better.

[Al_The_Man]

Personally I would hesitate to use a solid state relay as a e-stop safety device as they usually use a SCR or TRIAC device which can go shorted, if you use a relay there are way to suppress EMI on both the coil and the contacts. Most of the major relay manufacturers make what is called safety relays which are made to satisfy the requirements of OSHWA and other regulating bodies world wide. These essentially are specially made relays so this if things like if a contact welds together another contact will remain open. If a company manufactures a machine and does not provide adequate e-stop conditions they can be held liable under the safety laws of the country they sell in.
Al