View Full Version : Servo drive start-up problem

12-05-2011, 09:21 AM
Hello gents,

New to this world, so please bear with me. A customer of mine, has a CNC controled punch press with servo motors. Several months ago they called me complaining of "forcing" sounds, and homing issues on start-up. Once homed the machine would run fine for the rest of the day. A couple of days later the mother board blew up. I sent the whole unit (controler only not drive cards) out and got it repaired.

The shop said everything was fine. Unfortunately the "Forcing" sound did not disapear. A month later the mother board blew up again. A new one was sent and installed. This was 3 weeks ago. So far so good.

Ok my questions is , what would cause an issue like this? And only during the start-up? They will be shutting down for the holidays so it might be a good time to do some work. Any ideas, suggestions are welcome

Rob. Here are some pictures




Mark McGrath
12-05-2011, 10:03 AM
It would help if you mentioned make and model of machine,control and axis drive.

12-05-2011, 10:24 AM
It is a creonics controller built in 1986-7.

The motors are Balador model M4090b 90v DC with up to 25 amp 110v ac/dc input.

No load speed is 2022 rpm.

The motors can put out 2.3hp.

Rob :)

12-05-2011, 10:57 AM
If you are having repeated M.B. problems on a PC based machine, I would look at the power supply and also all grounding conductors, especially to ensure the M.B. ground plane is grounded, this is usually through the service ground attached to the PC supply input.
Check the P.S. voltages at power up.
The noise on start up could be due to the above problems causing a command signal error and the controller trying to correct it?
Punch presses by nature get alot of hammering.

12-05-2011, 03:50 PM

What do you mean by MB problems?

Rob :)

12-05-2011, 04:22 PM
M.B. Mother Board, P.S. Power supply.

12-05-2011, 04:40 PM
Sounds like tuning issues.

12-05-2011, 08:55 PM
I will check the power supply on the next visit. I did have the grounds Meg'ed. The electrician said it passed. The operators are always pouring a pale of water on the ground. 2 to 3 5 gallon pales a day.

The power supply was sent out with the first line of repairs and they checked it. That does not mean i won't.


I thought of that. As i am not a pro and this is a shop, i figured i would play when there was no other choice. I was thinking the boards might not be getting all the signals and the error parameters might be too tight. I do have the original set up parameters and how to adjust them. Since it is only happening in the morning start-up, it will be hard to figure out if you are going in the correct direction.

Rob :)

P.S. Keep them coming :)

Mark McGrath
12-06-2011, 02:03 AM
Check the motors for carbon build up.
I`m finding it difficult to get the connection between the motherboard and the servo motors/drives unless it is voltage spikes caused by leakage through carbon build up and a poor earth.
Best way to tune any servo is to run it on it`s own independently from the control using a battery box.

12-06-2011, 09:27 PM

How would you do that with a battery box? These are 90v DC motors?

12-06-2011, 11:36 PM
Controls of this vintage were often 10vdc analogue control.
A battery box consists of 2 9v batteries in series, a 5k or 10k pot outer ends is wired with to the battery outer ends (18v), the series connection on the battery is the common and the slider is the 10vdc in to the analogue input.
This way you can drive the motors with a simulated command.

Mark McGrath
12-07-2011, 04:47 AM

How would you do that with a battery box? These are 90v DC motors?

As Max says.You still use the machine to supply the servo motor power and also any control voltages required for enabling the drive..You use the battery box to give the drive the analogue input to power the servo motor.I only use one 9v battery and have an on/off switch so that I can enable the individual axis from the battery box.
This way you do not need the control powered up and you can work on one axis at a time under YOUR control.