[ROSSITERENG]

I have a problem when jogging the z axis if I move at 100% feed rate in the - it travels about 6 inches and starts to run and the brake comes on and I get this message checked the driver and the over volts light on to clear this I have to turn power of to the machine but if I jog at 60%feed rate no problem also I have no problem with jogging at 100 % in the + anyone got any idea where I should start to look

[meckardt55]

IF the over volt light is only on the Z axis then I think you have a bad circuit on the Z drive. If you have the light on all of the drives then I think you may have a problem with the RE-GEN circuit on the power supply. Measure the DC buss voltage. With nothing moving you should have about 310 VDC, when you are moving the Z in the --- direction the buss voltage should not go much above 385 VDC. You need to use a meter that has the MIN / MAX option. We work out of our office in Michigan USA

MIKE CNC Machine Services INC | Cincinnati Milacron MachinesCNC Machine Services

[ROSSITERENG]

thanks for getting back to me Mike the overvolts light is on on the z and a drive but we are not using the a drive and have a blank off plug in the a drive so I can jog down in the z but not at 100 % could this be some sort of overload you think

[mike_Kilroy]

...it travels about 6 inches and starts to run and the brake comes...

I don't understand. Did you mean to say "it starts to run and travels about 6 inches and the brake comes? Or something else?

Assuming you meant the quote I put, then of course Mike's reply is good. Further tho....

To me, all indications point to the PSR4/5 DB regen circuit as the culprit.

The clue that puts it more there is your comment "overvolts light is on on the z and a drive." Again I assume you meant to say "overvolts light is on on the Z and A axis drives." If so, then you have 2 of 4 total drives reporting overvolts, which point to PSR regen itself.

Know a few things...

- ALL 4 drives have over volt detection, so all can report it., Normally the one that was regening shuts down the system before others can report it, but not always (the OV circuit has some capacitors in it and so if not generated internally, they are slower to respond).
- PSR4/5 has Terminals top front center for the DB resistor - with power off, ohm them to make sure your DB resistor is still hooked up (were some models that had a resetable overload relay in series - might have opened - reset it if you can.
- of course OV will happen first going DOWN on vertical axis; there is no counter balance on that machine, so the regen energy is much much higher on this motion than going up or any other axis. In fact, going up 100% speed and stopping typically regens NONE since gravity is higher accel rate than the Z decel rate and weight makes more torque than needed to stop....

[ROSSITERENG]

mike-Kilroy you can jog the machine down in the z it travels about 6-7 inches at 100 % feed then starts to run and the brake comes on aswell as the alarm but if I jog at say 60% of feed no problem the machine travels all the way to the bottom

[mike_Kilroy]

" z it travels about 6-7 inches at 100 % feed then starts to run and the brake comes"

Sorry, I offered what help I thought I could. I have no idea what this line means so cannot help further.

[ROSSITERENG]

Ok when jogging the z in the neg at 100 % head drops by it self after about 6 or 7 inches of travel then the brake comes on if I jog the z in the neg at say 60 % of speed no problems

[ROSSITERENG]

ok so having a bit of a play with this if I send the Z axis down in MDI at full seed no problems only have an issue jogging with the pendant at 100% can jog at 60% without a problem

[mike_Kilroy]

ahhhh, you mean " z it travels about 6-7 inches at 100 % feed then starts to runAWAY and the brake comes"

Now THAT makes sense. It never occurred to me before this that is what you meant.

I can almost guarantee what is happening: When you tell it to run at ANYSPEED, it will accelerate (putting current INTO the motor) until it gets to commanded speed, then it will DECELERATE (taking current out of the motor andpumping it back to the PSR4/5) instantly to stop the acceleration and maintain the commanded speed.... THIS IS THE POINT YOU REFER TO AS "6-7 INCHES - before it faults. When it faults, the drive shuts off so it freewheels and falls due to gravity (runAWAY) until the brake catches it.

So YOUR PSR4/5 regen circuit can handle upto 60% of the power being pumped back at that quick decel to commanded speed, but not 100% of it.

Everyone else's similar machine to yours CAN handle the 100% regen, so yours is broke. You can either limit your max speed to 60% down for now - until it gets worse and requires even slower speed, or you can fix it now. The regen circuit is not working well enough.

1) Did you ohm out that resistor hooked to the two little screws top front of PSR4/5?
2) Check these two wires are tight everywhere from there to the resistor?
3) check the ohms thru the overload relay in series with this (assuming you have one)? Is it correct?

If so, then your PSR4/5 sounds defective and needs to be sent to someone for repair. I will tell you that I cannot recall a single case in the last 20 years of receiving a PSR4/5 for repair where the regen circuit inside was 'sorta broke a little' like your case, but you may be a first!

You really should answer the db resistor/overload/wiring questions...

[ROSSITERENG]

Hi Mike just had a quick look what wires are you saying to check heres a pic of the PSR I cant see themAttachment 315740

[mike_Kilroy]

yep, like I have said, those two wires going to the TB strip at top front of the power supply.

[ROSSITERENG]

these are the 2 errors I get
Ok Mike 1 the ohms are 2.2
2 wires are tight and cleaned
3 ohms thru o/l relay ok
volts at buss bar are 342 with nothing moving peaks at 383 when fault occurs Z axis overvolts and undervolts lights on Z axis only
when I move the Z in MDI with G0 works ok seem to only have a problem when using the pendant with jog at 100 % also when I restrict the speed in MDI G0 using the pendant at 100 % I get error but if I turn feed down to 50 % all ok

[mike_Kilroy]

My best guess is your PSR4/5 is defective. OV fault happens at approx. 390v, so you are going that high. it is the job of the PSR4/5 to limit that voltage with its regen circuit.

You are not helping the situation by having so high an AC 3ph input voltage to your machine. Your 342/1.4= 245Vac L-L is just about at the max limit also. 325vdc is the nominal bus voltage you should have, with 250vac or 350vdc as max allowed.... means the poor regen circuit only has 390-342= 48vdc to work within instead of the nominal 390-325= 65v range. Altho it does not sound like it, this is pretty significant reduction in working range for the poor ol regen circuit to operate in.

Whoever you send your PSR4/5 to needs to be told specifically you need the regen capability checked out thoroughly. When we repair, we often just use a variac to raise the input AC slowly to measure and prove the 390vdc trip point works; in YOUR unique case, that might pass - it may be a response time issue of the circuit - may be a bad capacitor, or all the dc link caps worn out, allowing the bus to rise too quickly. Luckily we also check the dc bus caps but a lot of places don't, so you need to tell them exactly what your issue is here or they may miss repairing it.

Since the less regen requirement of going up and the other axes work, I a inclined to think your DC bus caps are just worn out and the regen circuit is ok...

[ROSSITERENG]

Thanks Mike do you know why I can send the Z in MDI G0 which is way faster than the jog on the pendant and not have an issue unless I slow feed with the pendant

[mike_Kilroy]

no. that does not sound like the description you have given so far. so far, you can run down on z to 60% max traverse; anything faster overvolt faults.

now you say something else?

[juniormachinist]

Where are you ROSSITERENG

[ROSSITERENG]

ok so having a bit of a play with this if I send the Z axis down in MDI at full speed no problems only have an issue jogging with the pendant at 100% can jog at 60% without a problem

I did mention this

[mike_Kilroy]

I did mention this

I am confused who has the problem! Rossitereng or Jr. But no matter.

OK. Let's look at THESE facts:

1) So you can go down 100% speed in MDI...
2) You cannot go down more than 60% speed in jog...

So ask yourself: what is the difference?
- it is the same machine
- it is the same motor, drive, cnc
- yet one works and one does not?

Think.....

THE ONLY DIFFERENCE MUST BE YOUR DECEL RATE SETTING!!!!! the amount of energy the regen circuit must absorb will be directly proportional to the decl rate if the speed you stop from on a given axis of a given machine is the same. T=jw/t T-orque required to stop = j inertia you are stopping, times w the speed change, in t-ime to do it. make decel quicker (t is smaller) then Torque required goes up. since torque is amps, more amps back to the power supply for the regen to contend with.

I do not know where in the a2100 these are set, but it MUST BE the jog Decel rate is at least 100/60= 167% MORE than the mdi decel rate...

go find the decel rate in jog and make it the same as the mdi value and it too will then work at 100%.

[meckardt55]

I suggest you get into the axis parameters in the A2100 control and turn down all the axis rapid rates from 944 IPM to 600 IPM and this could resolve your problem.

MIKE CNC Machine Services INC | Cincinnati Milacron MachinesCNC Machine Services

[mike_Kilroy]

I suggest you get into the axis parameters in the A2100 control and turn down all the axis rapid rates from 944 IPM to 600 IPM and this could resolve your problem.

MIKE CNC Machine Services INC | Cincinnati Milacron MachinesCNC Machine Services

Again my bad Mike! Thanks for jumping in here! I ASSUMED 100% speed in MDI & in JOG was the SAME rpm!

So if 100% JOG rpm is higher than 100% MDI rpm, then the stopping energy is greater! (the w in the equation).