[tpres500]

I am new to the forum but have had my Boss 5 making parts for some time. I have read through the posts and have not seen an answer to my specific questions. I hope that I am not repeating something that has already been addressed.

My Z axis is at issue. Between the stalling on rapid and the blown transistors (NTE130), I'm ready to get it fixed. I have checked the voltage and amps per the manual and I have also slowed the rapid rate down as much as the adjustment will let me. I have resorted to programming the Z axis without any rapid moves more than an inch or it will stall out (especially since it's gotten cold). I just use a 20 IPM feed in place of a rapid move.

Now to my questions.

1) Will the steppers off the Series 2 work okay?

2) Does anyone have any experience with fitting the 1780 OZ/IN NEMA34 STEPPER MOTOR from www.homeshopcnc.com?

Thanks in advance for any help you can provide.

Tracy

[machintek]

Any drag will make a stepper lag behind the command and then be attracted to the coil behind it thus creating and oscillation (whine) and a stall.

Do you have screw in fuses?
Are you sure that there is 8 to 8.2 amps DC current?
Have you tried the 2N6547 transistors?
Do you have an SMS card?
Try flushing the quill with kerosene and reoiling it Mobil vactra number 2 or equvilant.

George

[tpres500]

Any drag will make a stepper lag behind the command and then be attracted to the coil behind it thus creating and oscillation (whine) and a stall.

Do you have screw in fuses?
Are you sure that there is 8 to 8.2 amps DC current?
Have you tried the 2N6547 transistors?
Do you have an SMS card?
Try flushing the quill with kerosene and reoiling it Mobil vactra number 2 or equvilant.

George

Screw in fuse holders have been eliminated.

I have checked the amperage and it is within spec.

I have checked voltage (static and running rapid) and it is within spec.

I have not tried 2N6547 transistors. They are only a higher voltage rating than what I have in it now. Same amperage rating as the NTE130 (15). I don't blow transistors very often. My primary problem is with the stalling.

I don't know if I have an SMS card. I think I do but I will have to go out and check the manual and look at what's in the machine.

I have flushed the quill and reoiled.

I have checked for binding by hand turning and there are no tight spots. It doesn't seem to matter where the quill is, only that when it has to rapid travel more than an inch it will stall out. It does NOT have the Superior motors.

The tech that I spoke with had me do all of the things you have noted. He also said that the Sigma (?) motors weren't as good as the Superior. He also told me that the Z axis was a consistent problem due to the increased drag of the quill over the XY.

I could possibly change out the motor from another axis but they might not work any better on the Z than what's there. I wondered about the later model steppers or a complete replacement (the NEMA 34) as maybe they had a higher torque rating. From what I recall reading somewhere else, the stock stepper has somewhere around 1200 in/ounces. I thought that maybe the 1780 in/ounce stepper, even though it's in the smaller NEMA package would outperform what's on there and solve my problem.

Thanks for the reply.

[machintek]

There are a LOT of these machines out there and they do run without magic dust.

There must be an issue here that has escaped us so far. This is where I usually have to roll up my sleeves because it can get real wierd and deep.

Example. I put my meter on the base of each transistor and step it 4 times for each transistor watching how it turns on and off. I have had cases where it did not turn on and off clean/sharp. I found a bad diode on the small board just to the right of the motor terminal strip.

Another example. I had a machine that would misposition in the Z axis at random. It was stalling. After a few hours of checking everything, I traced it down to a bad opto-coupler on the Z output from the ZDI (BOSS 6).

Do you have a good Bridgeport service tech in your area? If all of the typical tests are negative, it may be cost effective to go the service tech route. But he nust be good, maybe even a Jurassic such as I.

George

[tpres500]

BTW, I have swapped out the control board from another axis and that didn't have any effect.

When you say meter, are you referring to an osciloscope (spelling in question)? I can arrange that.

I have a tech somewhat local but getting him in here would cost dearly. He's pretty good on the old stuff but his hourly rate is killer. I dunno that I could justify that cost.

There's a lot of checks in the manual with a scope that I haven't done yet because the section on stalling Z axis didn't really point me in that direction. I will review the manual again and see what I find.

Thanks for the reply.

[machintek]

The scope would be good for finding a bad string of pulses. A digital multi-meter is good for checking voltage levels. Example 1 was found using a meter. Example 2 was found by replacing the ZDI. I did not carry a scope back then. They are a lot smaller now.
My office charges 120 dollars per hour for me. Good for them. I don't see that kind of money. Companies will pay it, private individuals cannot. I understand your position. That is why I try and help people here.

George

[tpres500]

I have an SMS card.

Is there something on it I should check?

Thanks,

Tracy

[tpres500]

I checked the 4 Z diodes on the small board to the right of the motor connections and they all check good (unsoldered one end).

I see that the optocoupler on the XDI board is the MCT271. Is there any reason why I can't just go ahead and put in a new one for the Z axis?

Thanks.

[machintek]

It would just be a good idea to replace the opto-coupler. No guarantee that this is the problem. In 23 years this has only been the solution one time.
The SMS board prevents (in theory) the transistors blowing if the axis is moving and someone hits the e-stop or a axis limit switch. When measuring DC current at the axis fuses, with out the SMS card, press the e-stop and the current drops to zero instantaneously. With the SMS it decays for a few seconds. Usually the ceramic power resistor on the saturable core reactor goes open, which fries (literally) the SMS and ACC boards. I examine these resistors for heat cracks and replace them with units rated at twice the wattage. Just a hint for the future, but that is how the SMS typically fails. If the fuse is good on it, the SMS is good.
I am running out of ideas, however.

George

[tpres500]

I think I will look for another motor, preferably a Superior.

I did some checking on the motor I mentioned in the first post and it is only a 4 wire config, won't work with the BP control.

I think I will go ahead a do a breakout board and run the mill off a PC with Turbo. That will give me the ability to taylor the rapid feed speed/accel/decel to the Z axis for the best performance without loss of steps. That will at least allow me to program rapid moves and use canned drill cycles instead of programming deep holes only with feed moves.

Thanks for all of your help. I will try and post the soluton if I ever find one.

Tracy

[machintek]

I have a cheat sheet on how to tune the RCK (clock) board. For older machines that are stalling, the rapid rate is diminished so the accel rate is a flatter slope. This buys time with weaker motors. Just have to get by the office and scan it. This would allow the use of rapid but it would be diminished in all 3 axis.

George

[tpres500]

I already turned down the rapid feed. In fact, I had to replace the 10 turn pot that controls it as it was bad. I connected a voltmeter to the required terminals and set the voltage as low as the adjustment would allow me to.

Yes, it affects all of the axis' rapid speed even though there were not any rapid move problems with XY at the prior setting.

That was something I not only found in the manual but was also recommended by a BP tech I spoke with a year or so ago. He had worked for BP for a long time (>20 years) and was now doing is own consulting/repair. He, like yourself, was very helpful even though there was little chance that I would be spending any money with him.

Thanks, again.

Tracy

[vmax549]

Tracy I have a set of take off motors from my Boss cnc. I don't know for sure but I believe they are ok. They ohm out ok. I will give one or all to you if you want them. You just have to pay the freight. Terry Parker

[tpres500]

Wow! What an incredible offer. Thank you.

Not to look a gift horse in the mouth, do you know if they are the Sigma or Superior motors?? It's real easy to tell, if the wire connectors are in a quasi diamond shape, they are Sigma. I can scan the manual where it shows both types if I need to.

If they are Superior, I would be happy to pay the freight on them.

Would you be able to check on that?

Thank you very much,

Tracy

[vmax549]

Tracy post the info and I will check them out for you. Terry

[tpres500]

It's interesting, after I soldered the diodes back in I ran the machine for several hours and when I tried to make the Z axis stall I couldn't. I ran almost the full quill travel down at rapid and homed in numerous times from a near-fully extended position and it didn't stall once. Coulda had a cracked solder joint on one of the diodes, maybe.

I've decided to go ahead and replace the drives with some high-tech bipolar units. At some later date I can upgrade the motors to the 1750 in/oz NEMA 34s as the $ allow.

At least with the drives I'll have half-steps so my resolution will improve. And, with the computer running things I can tune the Z axis for no-stall.

Thanks for all your help.

[vmax549]

Tracy is your Boss still running ok with the diode fix? Terry Parker

[tpres500]

I dunno. I finished the job and I haven't put anything on the machine since.

I made the decision to do the drives. I considered the Geckos and a few others but I decided on some from a guy that sells on e-bay. He doesn't advertise the particular drives that I'm buying on e-bay but he has a bipolar drive that will work with the motors I have and also will allow me to install high-torque NEMA 34s later if I need to. Going bipolar will give me about a 30% increase in motor torque and I'll get half stepping along with it.

I will probably have to run more parts before I make the drive switchover and will let you know how the machine runs.

Thanks,

Tracy

[tpres500]

I went and fired up the mill just to check the Z axis op. I ran the axis down with rapid jog about 4" and rehomed it numerous times and I couldn't get it to stall. I will write a short program with a deep hole canned drill cycle and see how it does.

That's better than it's been working. Maybe there was a cracked joint on the diodes and now it's fixed. I dunno. Still going to replace the drives and run it off a PC. I will let you know how it turns out.

Thanks,

Tracy

[vmax549]

Tracy when you look for stepper drives make sure you use a micro stepping drive. It seems that single and half step drives with big motors can create a resonance at midpoint in the motor range that lowers performance and makes the motor run hot and noisy. With the micro stepping drive you can select a microstep say 8 that moves you out of the resonance range for that motor. I retrofitting my Boss with servos and run Mach3 on a PC and it was like getting a new Machine center with the feel of an old friend. Terry