CNC gantry Machine shows problem

[Alex S.A]

Hi guys,

I have a new problem in other machine. The machine is activing the longitudinal motors in oppositive way when I press the emergency bottom.
The emergency bottom, when pressed, turns off the servo drivers. I made the off set the motors then the equipament works well when I pressed the emergency bottom, it does not activite the both longitudinal motors in oppositive way but some time later the problem comes back. I tried to solve the problem changing the drivers but the problems still happening. After that I did the check on cables for encoders, motors and check also the mechanical parts of the equipament.
Have you seen a such problem?
Now I am keeping studing to solve it but if you all have some guidance to give me I would appreciate.

Thanks,
Alex S.A

[Al_The_Man]

Not completely clear what is happening here, what make/model of machine is this? It sound like you are still having movement when the e-stop is pressed?
If so, one reason is if the e-stop cuts off power to a AC side of a power supply and there is a delay while the DC decays allowing the motors to take off in an uncertain direction until the voltage has decayed sufficiently.
Without more info it is just a guess at this point.
Al

[Alex S.A]

Hi,

The machine is a gantry model and is used to cut metals with oxy fuel process. There are three axies, two on longitudinal and one tranversal.
Yes I have movement on longitudinal motors, one motor moves to one way and the other one moves on the contrary way (I don't know the right words to make clear this problem in english), when e-stop is pressed.
The driver used in one model from Axor and when the e-stop is pressed the signal cutt off is the enable. The enable signal is supplying by driver itself. The driver is DC and have the analog signal. These signals, input DC and Analog signal, are not cutt off when e-stop is pressed.
If you want more information to help me , tell me.

Alex S.A

[Al_The_Man]

Do you just get this problem when the e-stop is pressed, does the machine run OK when e-stop out?
It is normal for the estop to de-activate the drive enable to prevent the motion as I mentioned in the first post.
There should be no way the axis should move with without the drive being enabled, I would say either you have a defective drive or the drive-enables are not being de-activated for some reason. I would verify the status of the signal at the enables pins on the amplifier when e-stop in both in and out. Some have to be closed to drive common to operate some open to operate, verify with a meter.
Al

[ViperTX]

Just guessing...if the problem occurs with seconds after the EStop is activated then I would suspect that the enable is not being held in its off-state, but is being allowed to charge up. Stick a scope probe on the EStop line.

[turmite]

Alex did you build the machine? If so, what kind of controller are you using? When using slaved axis like you are describing, (two motors on one axis) it is very possible to have one of the motors wired backwards or hae the software set up to send the signals reversed.

Just to be sure of your problem: You have one motor running in the positive direction and the other running in the negative? Is that correct?

When the e-stop is pressed the motors continue to move but in opposite directions?

Mike

[Halfnutz]

You guys are Saints! ( Al, Viper & Turmite) "The driver is DC and has the analog signal"

[Alex S.A]

Hi Guys,
The machine make a little movement and stop, I meant to say that the machine does not move continuouslly, when the e-stop is pressed. The machine "twist". I used the master and slave motor. When I make the motor off set, the equipament does not show the problem for a while when e-stop is pressed but some time later, it shows the failure. It is like the off set is lost. I suspected of the driver and change them, but the problem still remains as described above. The driver is DC with analog signal.

[turmite]

Alex let's start with the very basics and go from there. Since it is an analog signal I am assuming the motors are servos.

Lets start with some very basic information.

1. Did you build the machine?

2. What kind of controller is in use?

Let's get these two answered and that may lead to the answer for your problem.

Mike

[Alex S.A]

The answer are:
1. The company that I work builded the machine;
2. The CNC is from ESAB model Vision Le, drivers and servomotors DC from Axor

[Al_The_Man]

It would seem obvious the drive disable is either 1/ Not being applied when it should, 2/ Is not working, or 3/ Is delayed for some reason. Any drive I have used the drive enable when removed stop the drive immediatly by removing power to the output devices, it is possible for the motor to coast however, but in the case of a heavy gantry machine, this is not likely, and also you mention they move in opposite directions. I would seriously investigate the enable signal status first and determine that it is in fact being applied immediatly on e-stop,if it is and the motor continues to move at this point then the drive is not performing the way it should.
Al

[mrfixit]

It sounds like a run away condition when E-stop is pressed? If this the case that usually results from a loss of command signal while still having power applied to the motor from the drive. The E-stop circuit should do more than simply cut the enable signal! The E-stop needs to cut any power to the drive unit as well as disable the drive. The e-stop should not however remove the control of the drive from the CNC. The CNC should remain connected to the drive and only the enable signal and motor power should be cut when an E-stop condition occurs.

hope this helps!