[bartL]

Hello all.

Excuse me for my bad english.
I just have my BP 1 CNC and before i want to run in with a PC and Mach 3 control i want it to run nice and smoothly.
Now my Y-axis moves very nice. My X-axis only moves in little steps. When i hold the move button i can hear the motor running but the table won't move. I found a bad main transistor behind the heat sink for that axis so i guess i can solve that problem by replacing the bad transistor.
A different story is the Z-axis. It has the same problem. It can move in little steps. But when i hold the move button, it moves a little bit, then makes some noise and after that i can hear the motor running but it isn't moving anymore.
I also checked the four main transistors for that one but they all seems to be good. Next i've checked the controlboard which is fitted on the door with the black heat sink. I measured a lot on that one and it seems to be good. What can i check now? I really think it's a electrical problem.
Hope someone can help me.

Regards,

Bart

[machintek]

Flush the Z axis with a hydro carbon based solvent. Then re-oil with Mobil Vactra number 2 way oil (or a type 68). This may help.
If an axis does not have enough power to the motor(bad connection somewhere, a washer or screw dropped onto the terminal strip below those transistors, low voltage, shorted transistor, excessive friction) the motor cannot keep up with the command and falls behind enough to get attracted to the coil behind it instead of the coil in front of it. Thus the motor oscillates between poles and emits a whine like it is running but is not.
Check current. The ACC board is adjusted to 8.0 amps with the axis in a static state. This is in the maintenance manual.

George

[bartL]

George,

I don't have the maintenance manual so I don't know what's in it. Can you give me some more detailed information about what i should do. I don't think i have to flush or re-oil the spindle because when it moves up and down it goes very smootly and it looks really nice. I just can't keep it moving, so i thinks it's typically a electrical issue.
What you descibe about the motor is what mine does i think. It seems like it's running but probably it isn't

Bart

[bartL]

George.

What do you exactly mean with the things i should do with the acc board. I don't really understand it (sorry for my bad english) And i don't have the manual you reffered to.
I already flushed the spindle axis and the thread eventough they looked very good. I checked all the transistors, diodes and fuses. They were all good. Maybe it's because the acceleration is to high but ifso I don't understand why the X and Y axis doesn't have the same problem.

Bart

[machintek]

Press in emergency stop (to turn drives off).
Remove the DC fuse for the Z axis (fuse 14?).
Attach a meter than can measure 10 amps DC in place of the fuse.
Pull out emergency stop and turn drives on.
Drives should be pulling 8 amps. If not, turn the bottom multi turn potentiometer
until it does.
At this point I step the Z down and watch the current. Any variations means that a transistor or some other part of the circuit may be screwed up.
I usually at this point try a rapid move but you cannot. In rapid, the current should drop to 2 amps or just a little bit more.
Turn drives off before removing meter or you will blow a transistor.
Put fuse back in.
Attach meter between fuse 14 and ground set to DC volts. Turn drives on and again step it. Voltage should be in the 9 volt DC range and should remain the same as you step it. If not, again, you may have a problem.
Next I measure the voltage drop across the fuse to make sure the connection has no resistance.
You can compare your results with the other 2 axis. All three are individual circuits.
You need a manual.

George

[bartL]

George,

I did the measuring of the amps. I measured 8.75 ADC.
You said it should be 8, is this to much then?
What do you mean with the bottom multi turn potentiometer?
And where is it? maybe a picture of it should do a good job because sometimes i got some little problem understanding it.
I really hope this is the problem so i can fix it, then every problem is solved and the real retrofitting can start!

Bart

[machintek]

The ACC has 3 multi turn potentiometers.
From top to bottom, they are X, Y, and Z.
8.75 amps is too much. The manual calls for 8 amps.
Since I have not worked on one in years, I cannot provide a picture.

George

[bartL]

Ok but to be honest i don't really know what you mean with the ACC.
I know where the ACC board is but there's noting i can adjust on it.
Is it in the same cabinet where the fuses are?
Thanks for helping me.

Bart

[jholland1]

The swing out side door on control cabinet of BP Boss mill has 4 circuit boards. Three are step motor drive (SMD) boards. They are labeled SMD cards on lower left of card or board. Nothing on these cards is adjustable. The last card is ACC card. It has three trim pots for adjusting step motor current one for each axis. I recommend setting at 7.2 amps. The drive transistors have a heavy shock load when there is sudden decelaration in table move. This is when they usually blow. The spindle drive transistors usually blow on a cold day in shop or if the NSK ball screw becomes stiff. Also anything which causes quill tightness will blow transistor. I have images of the transistor drive block, the SMD and ACC cards. The ACC card has screwdriver at the trimpot for Y axis.
Frequently an underpowered transistor is used to replace what should be a 20 amp 600 volt transistor. These transistors are now expensive and may last 5 years or blow within minutes after replacement. Solution is to upgrade to Gecko type drive and eliminate BP components.
jh

http://community.webshots.com/album/562583810DfSqiK

[bartL]

Jholland,

Thanks that picture with that screwdriver really helped me. But unfortunately it didn't solved the problem. I even brought the current back to 7 amps but the motor still starts to oscillate like nothing has changed.
The X-axis sometimes had some problem with moving and that's over now. I brought that one back from 8.75 to 7.85 and now it runs without any problems.
Thanks!

Bart

[jholland1]

Hello bartL
A few more tricks. Use pencil and mark each SMD card x,y,z. Substitute cards and see what happens to motion. Another trick. The ACC card may be turned upside down and placed back in socket. This switches x and z power control. If you do this you must use thin cardboard as insulator between ACC and SMD cards so components do not touch.
Tell us what happens.
jackson

[bartL]

Jackson,

I just tried both of your tricks but they both didn't help. It's still oscillating.

Bart

[jholland1]

Bart
Now you will have to go to bottom on drive door. Cut off power. Remove SMD and ACC cards. There is a terminal block at bottom. The motor leads are from left z, y, x. You need to inspect all connections for metal chips, opens, shorts. If all looks ok lightly pull each wire to be sure of connection. Then along bottom row disconnect y and z axis wires. There are 6 wires per motor.. Terminal 5 always has 2 wires fitting in one screw connection. These are both labeled x5, y5, z5. You will connect z axis wires in proper sequence into y axis sockets. Since x and y axes are running ok, the drive electronics for these axes are good. If the step motor for z is bad, it will be bad on x and y power sockets. To cross verify, connect y axis step motor wires into z terminal sockets. If this motor runs ok then the z step motor is bad. This is double check. Next remove metal cap from z motor and verify that wires are ok and no burning of wires is present. Sometimes when step motor goes bad a burned winding can be seen or even smoke deposits.
Let me know result.
jackson

[bartL]

Jackson,
I just did what you suggested. And the Z-axis is still oscillating, even with the switched wires in the terminal block. I also removed the cap from the motor, but all the wires look really good. I can send you a picture if you want, but you have to send me a pesonal message with your e-mail adress.
I'm not happy with this cause i hoped nothing would be wrong with the motor. But is seems it does. Or there has to be something wrong in the driveline which makes the axis move real heavy.
thanks for your help, i really appreciate it.

Bart

[jholland1]

Bart
Did you hook up y axis motor to z axis drive? This would definately tell if z motor is at fault.
jackson

[bartL]

Jackson,
Do you mean replace the Z motor by the Y motor? I want to try that but i didn't knew i could do that without any problems.
Bart

[jholland1]

Bart
At bottom of swing out door where wires from step motors go into screw connector terminal block. The bottom cable wires from y motor must go into z sockets. Then power machine and move z. This will move y axis on knee. If everything works good the z axis drive is good. This means z step motor is likely bad.
jackson

[machintek]

I look at it this way. A lot of field service is done by probability. So how many bad stepping motors have I had in 26 years? Maybe 2.
How many other axis drive problems have I had on the stepping motor type Bridgeports? Maybe a 30 or so different problems on a few thousand service calls.
Do I believe the stepping motor is bad. I doubt it. I would be checking a lot of other items.
Most probable: Transistor
Also probable: bridge rectifier.
There are 3 seperate drives in this machine. They do share the 54VDC power for the ACC board. Compare the Z against the other 2 and where you measure a voltage difference gives you a clue as to where the problem is.

George

[bartL]

Jackson,
I already tried to switch the wires from the Z into the Y sockets. But that didn't help. No i'm just back from switching the whole motor from the Y to the Z position. That's didn't work either. SO thank god it isn't a bad motor.

Machinetek,
Where do i have to measure those voltages?

Bart

[jholland1]

Bart
You likely have blown drive transistor in drive block. These transistors are located above and behind drive cards. Z axis transistor block is usually the top one. Each block has 4 transistors. Usually only one is bad. Now go back to index in this forum and read all posts from last few days. From me and moderator. I have many pics and explanations about transistors and repair. Before you power up after repair be sure all wires are in original position. I will check later.
jackson