Is it normal for an Interact 1 series 1 Bport to make a loud humming noise when the axis drives are engaged? The sound seems to be coming from the servo drive motors themselves. My BOSS 8 squeals with the drives engaged which I understand is normal...but this Interact just doesn't sound right...

-Ryan

Not normal. The interact is a very quiet machine. Does it make the same hum with the drives off? I have seen a loose transformer make this kind of a noise or a transformer in saturation.

George

No, it only makes the noise when you engage the axis drives...seems to be when there is power being applied to the axis motors...

There is a slight amount of hum coming from the transformer that supplies the axis drive boards...but that is nothing compared to the hum from the motors themselves. The noise is loudest when the axis motors are stationary.

My interact is silent, but my r2c3, which is nearly identical, makes a significant, I would not call it loud, hum when the power enable button is engaged[IOW it shuts up when you hit the EMO] I believe it is actually the main power relay that makes the noise, since it is actively holding in under power

I suppose you could unplug the drive card one at a time to see if it was one of them, but I have never seen that

Another question:

I checked the ouput voltage of the transformer that supplies voltage to the drives...the voltage between the ouput terminals (180VAC and 380VAC) and the 0v terminal on the transformer match the designated output within 5VAC. However, the voltage between the output terminals and ground measure 280VAC and 480VAC respectively...the 0v terminal is 100VAC compared to ground.

Could this have anything to do with the motor noise?

The noise ONLY occurs when power is applied to the motors (i.e. drives are engaged) and the noise is DEFINATELY coming from the motors, not transformers or contactors, etc.

Also, the machine is running on a rotary phase converter. Could this have anything to do with it?

-Ryan

Here is a recording of the machine. I know it's sort of arbitrary since the noise depends on how high your volume is set, but you can use the sound of the contactor closing (about 5 secs into the clip) to guage how loud it should be.

Initially the machine is running without the drives engaged (first 5 secs)
Then the contactor closes and you are listening to all three drive motors hum as if you were standing in front of the machine. (5secs-20secs)
At 20 secs, I moved the mic closer to the x-axis motor so you can hear how loud it is.
After that, I moved the mic back to the front of the machine and jogged the x-axis back and forth.

Let me know what you think...

yup that's loud

the drive cards should be grounded, right at their chassis, so the motors shouldn't be absorbing any voltage differences

are all the motors doing this?

Yep, every motor...you can hear each one begin humming when you home each axis and each drive locks on.

Is there a voltage I can measure at the motors to see if it's hi/low? Regarding the high 0v line on the transformer...this doesn't seem correct, whether it's causing the motor noise or not. Can anyone verify if this should be this high and why it would be?

There is a problem. It may be related to the rotary phase converter. I never had one of these on a rotary phase converter. it sounds like the auto-transformers do not like the way you have it set up. 0 volts should be 0 volts with respect to ground. You may have to rearrainge the wiring so the transformers are all attached to the two good phases and the artificial leg only going to the spindle motor.

George

George,

Actually I did try this...I wired up the transformers to plain old single phase 220v power and I still get the same problem. Is it possible that the incorrect phase angle of single phase power could have something to do with it? Even with it connected to the phase converter, I had it connected to the two good legs...but they are still 180 degrees apart in phase angle, not 120 like true three phase would be...

I'm not sure if this would have an effect on the output of the transformer...

I ran an r2c3 [virtually exact american made machine] on a converter for years.

Is everything grounded internally? there should be big fat grn/yel wires on everything

Is the control head grounded properly? Perhaps a ground loop between the control and the drives

Is it possible someone has cranked the gain up on the drives?

I did a quick check on my interact, and there is also a similar, but perhaps opposite voltage offset

Thanks for checking on that gus...so you're neutral line on the drive transformer (T2 on my machine) is also biased off of ground?

Regarding the grounding...the neutral terminal on the T1 transformer (control circuit) is grounded, however the neutral terminal on T2 (transformer that supplies drives) is not grounded. The drive boards are grounded themselves, not sure where a ground would be missing.

It's not impossible that someone messed with the gain on the drives...the machine came from a tech school before I bought it. Is there any way I can re-tune the drives? The service manual I have has limited info about them.

Also, could the parameters in the control have anything to do with it? I have a copy of parameters that came with the machine, but some of them have been crossed out and written in by hand...not sure if they are entirely correct.

Thanks,
-Ryan

You can find the gain pot and turn it down by a set amount[keep track] but this is really shotgun diagnostics. Keep track of exactly what you do.

I am not in my office, but there might be a parameter that might do something, but I don't know.

Before I go changing the gain pot I think I'll try to locate some good directions for drive tuning for the machine...I'd hate to screw it up any worse than it is!

Attached is a start up procedure for the old interacts with the BOSCH drives and the TNC 150, 151, etc controls. Included is a tuning procedure.
BTW, if the belt is very tight, it will make a axis motor oscillate.

George

Be aware that in theory, the brushes on the SEM motors should be examined about every 4000 hours of operation. Attached are the Bridgeport service bulletins covering this.

George

Sounds like ecess AC hum on the DC line - are you sure a capacitor hasn't failed - or a diode perhaps ?

AWEM

Thanks for all the info george...I will check the drive tuning next.

Regarding the AC leakage...it's possible, but it appears to me that each drive does it's own ac-dc conversion on board. Then, for all three motors to be making the noise, all three boards would have to have bad rectifiers or capacitors. Thanks for the idea, I'll definately check into it.

I followed the drive tuning procedure that George posted for me...it helped, the noise is significantly less, but the motors do still hum.

Does anyone know what exactly the "offset" potentiometer on the Bosch drive does? If I follow the B'port procedure exactly and adjust the offset pot as instructed, the motors still hum. I can, however, change the offset pot outside the range given in the tuning instructions and get the motor to stop humming all together.

Is it ok to adjust the offset pot outside the instructed range, or is it better to let the motors hum. And yes, I think George hit the nail on the head...the hum does seem to be the motors oscillating.

-Ryan

if you watch the display the LSD[.0001] will change and the polarity + - will change. If iit is balanced 'perfectly' [not possible] the readout will read xxxx.0 and the polarity will slowly change from + to -.

The offset is ther to correct minor variances in the electronics either control or drive which cause it to try tomove in one direction or another IE the control puts out .05 volts instead fo zero

If the offset is set perfectly, in theory you could disable the position loop (unplug the encoder) and the motor will stay stationary. We used to set the offset on the BOSS 8 and 9 that way. If you unplug the encoder on this machine, you get a measuring system defective. I wonder if a gib is set too tight, and the motors are trying to schieve position? That is why you look at the lag screen (difference between commanded position and actual position0.

George

Just a note, I fired up my Interact after it being unused for a few weeks. It hummed very nearly as much as the one here. It shut up after a bit of use. I wonder if it is just one of those oddities. My R2C3 has the same amps and similar motors and never a peep.....

Normally motors hum because they don't know the words. Now that we have that old joke out of the way:

In testing the drives on mine, I noticed that the motors hum when the "drive release" relay for that drive is energized when the analog input is 0 (no motion called for). This is an input to the drive board, and I assumed would not be energized normally until motion is called for (but I don't know that for a fact, and can't check it till I get my control fixed). However this hum is not audible over the sounds of the motors while in motion.

Be aware that in theory, the brushes on the SEM motors should be examined about every 4000 hours of operation. Attached are the Bridgeport service bulletins covering this.

George
Thanks for that bulletin. Do you happen to have a parts page or exploded view of the motors/tachs that are being referred to? That would be very helpful to us neophytes!

Maybe Gus is right...my machine has quieted up a little more with some use. After tuning the drives in according to what George posted, they quieted down alot...the remaining hum has lessened considerably since then...sounds pretty good to me now.

-Ryan