[hdjeffrey]

Dang, ole bridgeport ezpath lathe problem!! z dac overflow!! I cant find the exact forum to put this in ,I figure you bridgeport ezpath mill guys can tell me!any bridgeport talk is in this forum and the mill and the ezpath lathe are very similar! any suggestions?

[machintek]

Correct forum.
You could search for DAC overflow and find a lot of data.
In a nutshell: Control commands movement of an axis but does not see it.
So, is the axis actually moving? If not bad motor or drive(if command is coming out of the BMDC board).
Axis moving? Bad encoder, cable, or associated boards.
Exactly what EZPATH? Does it have DC or AC motors?

George

[hdjeffrey]

I read in one of the threads about swapping servo motors and i did that even though the z axis motor is longer than the x, this did not fix the problem! it moves a little at a time away from home / instead of going to home? also read about getting into dos and looking at encoder ,dont know how you could do that , i came back from few days off ,worked fine before, fired it up yesterday and dac overload ? One thing i noticed it that both the axes will move at the same time,usually the x homes first to move tool away from part and then the Z will go maybe its a clue

[hdjeffrey]

the lathe just says ezpath , the software is version 2.08 it is a 1995 model, and another thing i noticed on the last day i ran the lathe ,it was set on 750 rpms and the conrtol was saying 765 rpms never noticed that happing before!

[NC Cams]

Do you have a wiring schematic? If not get one. Contact me via PM if your Expath has DC servo motors.

If you have an MPG, does it work?

I think the dos program that you run is PST or BST - this shows BMDC and Servo talking back and forth.

If endocers are OK, plan on pin out checking each and every encoder wire clear back to BMDC board - this is where the schematic is necessary.

Small wires that are flexed to death don't live forever.

SOme of the Bridgeport encoders were supposedly on the cheap side, according to Clarkson, the US sercice agent for SEM. Use Machinetek's suggestions first, ONce you find the "source" of the point where signals are not coming from or going to, you'be only done half the battle.

BTW, reseating the BMDC may be of some help.

[hdjeffrey]

I found the ezpath pro in my area ,his name is Jammie Horseman , works out of nashville,tn at a machinery place ,the man has ezpath in his blood! came with a folder with every known ezpath made, hes got enought stuff to build a ezpath lathe and mill on his truck!!! unbelieveable!! Fixed my problem ,wasnt anything anyone had suggested-not the encoder,motor,bmdc board,axibob,wasnt the z card,or the motherboard, not the wireing!!not the switches!! any guesses? THE POWER SUPPLY GOING BAD! BELIEVE IT OR NOT
it would weaken upon trying to home the axes given a DAC OVERFLOW!

[machintek]

To keep things closer to the truth.
You received a axis drive board, did not read the directions and smoked it.
Jammie replaced the motor (bad encoder) and the smoked board.
I will verify this again when I speak with him Monday morning.

Jammie has worked with me about 15 years. He is one of the best service engineers in the country. We speak every morning and sometimes during the day discussing solutions to problems. I respect his ability and thought processes. On occasion we get to work together and I always look forward to that. And yes, sometimes it is cost effective to hire a real service engineer.

George

[hdjeffrey]

We use this to get help ,not to be accused or be made fun of !!

[hdjeffrey]

Why dont you get my number from jammie when you talk to him monday when you find out your COMPLETELY WRONG and call me and apologize like a man

[machintek]

I will. It was in my plans already with a follow up with details.
Unless I have your machine confused with another customer, the solution made no sense to the symptoms. For the sake of anyone else reading these posts, accuracy is necessary.

Monday.

George

[NC Cams]

Let's be reasonable:

BMDC gives out command. Motor starts to run. WIth PS "folding back" in current or voltage, the motor would NOT KEEP UP WITH THE COMMAND hence DAC overflow.

Come to think of it, a ball screw or gibbs/ways bound up with chips and congealed coolant or even a siezing bearing or ball nut might put the "brakes" on just enough to cause the same sort of thing. Imagine how pissed you'd have been to learn that poor maintenance or a smoked ball screw or bearing was the REAL cause of the service call as opposed to a tired P/S. The alternateives DON'T get fixed with most of the parts on a service truck.

Proof': another guy had a DAC issue just like this on another machine and a broken lube tube to nut had nut so siezed that it took a breaker bar to run the ball screw. Squirt oil can and jury rig of Bijur tube FIXED the DAC problem too.

Then again, use of "Bridgeport DAC overflow" in search engine would have turned that up but why would any body use that tool??? It is simply easier to biitch at free, albeit wise and well intended help.

Meanwhile, problem AS DESCRIBED had classic symptoms of a control side issue yet it was essentially a BPT power supply issue. Need to make note of that one - along with the tight ball screw..

Easily an odd ball issue that could be a rarity, especially if you never ran into it before. Thanks for sharing the true root cause.

WIth the BMDC system as old as it is, and as expensive as it can be to repair, especially if one doesn't have a Jammie at their disposal, we need to maintain as good and civil a support structure as we can.

[hdjeffrey]

I had that lathe about a year now and looking back the p/s was the problem all along , alot of the time it wouldn't boot up ,sometimes taking a big cut it would just shut down in middle of cut, and alot of the times the screen would just freeze on the page and you could not go to another page! I had to TIPPTOE to run a part ,(it felt like! )

[hdjeffrey]

I guess sometime things happen for a reason! George called me this morning and we chatted a little , turns out he's a heck of a nice guy! I was a little miffed at him for the misunderstanding,but if it wasn't for the misunderstanding I would not have got to talk to him and found out he's pretty cool guy!, if i hadn't bought a lathe with documented problems i wouldnt have met jammie and if i hadn't met jammie (who caught the ghost )we would not have learned something from all of this! Well George ,Jammie all of your help and contributions are much appreciated! I GOT A LIVING TO CARVE OUT IN THIS RESSION!! I'm out -JEFF@ TJ LAMB MFG

[machintek]

Jeff did indeed deserve an apology. And I enjoyed talking to him. I wish him well and prosperity.
Jammie was there Wednesday and informed me that he ordered a axis drive board and a motor. Jammie told me this Thursday morning. Now, Jammie and I have been doing this a pile of years and typically we can figure out what is wrong in a half hour. Repairs take longer.
But occasionally these machines will throw you a curve and make you think real hard. And sometimes it is not logical at all!
This one had Jammie going all day Friday. I found out that another Jurassic Service engineer (a bridgeport friend of mine) had spent quite a few hours trying to exorcise the demons out of this lathe too. If you have a DAC overflow, the control does not see the encoder when a command is given by the control. If the axis does not move, it is a drive, motor, cable, or command. If it moves, then it is the encoder, cable, board, etc.
But what if one axis homes, and you cannot find anything wrong? Replace BMDC, motor, axis drive, software, ohm out cables, but then it gets flaky. BMDC sometimes does not load. Check mother board, and check logic power supply (it measures good).
The solution was to replace the logic power supply and all is now well. If you ask me why homing the X axis would then stop the Z axis from homing (with regards to the logic power supply), I do not have an answer. Jammie and I have been bouncing theories back and forth like electrical feedback, noise, harmonics, or as simple as a bad connection on the plug from the power supply to the mother board. Not found by the usual way of measuring these voltages using a spare white plug hanging there.
Most important is that Jeff is running. And that is the rest of the story.

George

[NC Cams]

Re flakey P/S.

We had one do that on a PC. IT would work fine and then drop out momentariily. In this case the darn thing would drop out and reboot for no reason at all.

We bench tested it to death and it would never drop out - run a spreadsheet and you could guarantee that it would drop out

Finaly we put a resistive load on it to get it to pull current and after a few minutes, drop out.

Used PC P/S's are dirt cheap. After 10 years of service, it almost behooves one to throw a P/S at a BMDC machine just because. It might even be easier than pinning out cables.

OPen cables in a BMDC cabinet should be easy to come by as well. Putting a dead load on the P/S while watching voltage might be a trick for sporadic issues like this. Be sure to load both - and + sides of the P/S as a negative side issue, although it does not pull a lot of current, is critical as Vrefs' are set/used by the negative voltages.

[machintek]

When ever we replace a mother board, I insist on a new logic power supply as well, cheap insurance. At home I have a plug in ATX power supply tester that does load it down. Do not have one for the older power supplies. Have to look for one.

George

[greg b]

Is in it a wonderfull thing when we dig deep these man made brain teasers can be sorted out.I think its great when people can be civilised enough to give one another a hand with these problems and take the time out of there profession to share there valuable time and knowledge to get these things up and running.Theres nothing more frustrating than being right in the middle of a touchy job ,and your pride and joy buggers up and takes out 10 hours of hard work in one go ,all because of some little gremlin in the machine.Great work guys .