Fagor 8025TG replacement drive problems

[pirates712]

Hi,

I have been given the task of attempting to figure out why a cnc lathe refuses to cooperate. Basically, the problem is that if you tell the spindle to rotate a certain number of degrees, it will rotate continuously under power. I am told that there was a problem with the original drive, so it was replaced and that's where the problem started. The replacement drive was made by baldor and the title of the installation for this drive is "vs1gv", "AC closed vector control".

I have some experience with using cnc mills, but I haven't used a cnc lathe and have no experience fixing them. If anyone has any idea what the problem could be, I would greatly appreciate any input.

Sorry if I've left out any important information, I'm new to this.

[Al_The_Man]

It sounds if you have a Spindle set up also as a C axis, if the original had a encoder from motor back to the Sp drive, you usually also need an encoder on the final spindle shaft, if it is searching for position, it could be the encoder.
The 8025 is an old control now, but the manuals are on line, I would see what Fagor manual says about integrating a spindle as a C axis first.
Al.

[pirates712]

Originally Posted by Al_The_Man It sounds if you have a Spindle set up also as a C axis, if the original had a encoder from motor back to the Sp drive, you usually also need an encoder on the final spindle shaft, if it is searching for position, it could be the encoder. The 8025 is an old control now, but the manuals are on line, I would see what Fagor manual says about integrating a spindle as a C axis first. Al.

Ok, the product manual for out drive says that it didn't come with a c-axis. The c-axis was a feature of the 8025TS model, we have the TG.

Thanks for your help!

[Al_The_Man]

I read a while back you could get an upgrade firmware/eprom from Fagor, if you need the feature it may be worth contacting them, you may have to add an encoder if it has never had this feature?
Al.

[pirates712]

Originally Posted by Al_The_Man I read a while back you could get an upgrade firmware/eprom from Fagor, if you need the feature it may be worth contacting them, you may have to add an encoder if it has never had this feature? Al.

Alright, we got a tip from a friend that first of all, there is an encoder on the spindle, and also that it might have gone bad. I'm currently trying to figure out how to figure out whether or not it is working properly.

[Al_The_Man]

A 'scope would tell you or though a meter can be used in a pinch if you turn it very slowly, look for a part number/make on the encoder.
Al.

[pirates712]

It was made by dynamics research corp 08/97. The model number is GD2S10E1B6S0-1024.

It has a pinout on the case:

A - CH A+
B - CH B+
C - G2+
D - +5 VDC
(no E I guess)
F - GND
G - CS/GND
H - CH A-
I - CH B-
J - GZ-

[Al_The_Man]

An Oldie! If you apply 5v power, you should see a transition on each of the A+ A- & B+ B-.
With a meter Turning very slowly.
The marker is a bit harder as it is only 1 pulse/turn.
How did it have C axis before if it is the TG version?
Al.

[kcho]

Hi, The original drive was a DC one. With the baldor drive what problem do you have??
If you can execute a program with G96 and the programs runs ok the spindle encoder have no problem.

Carlos

[pirates712]

My understanding is that it will run programs, but anytime the spindle has to rotate a certain number of degrees it just spins continuously under power.

[pirates712]

Ok, I tried testing the encoder with an old (very) oscilloscope we had lying around, and with a 5v power supply. I connected the power supply to the + and - pins of the encoder, and tried connecting the ground clip of the encoder to both the power supply ground and the A- and B- pins, with the probe on the A+, B+, and a couple other pins for good measure. I didn't get any results that made it seem like the voltage displayed by the oscilloscope corresponded with movement of the encoder shaft. So, unless it uses a current signal like a 4-20mA, I'm not seeing any evidence that it is working.

We should be able to get a replacement fairly easily, but I am going to check the continuity of the cable on the machine first.

[Al_The_Man]

Most of the DRC were 5v TTL, the A- & B- are complements of the A+ & B+ WRT to the common pin.
It is a 1024P/rev encoder, I believe DRC is now no longer but you should be able to get a replacement easilly enough.
Al.