Hello All.
Have had some great info come from this forum over the years and I think everyone appreciates the help that is still available here.
One of our 3-axis machines is an old 4020 Fadal which is something that is becoming harder and harder to receive support for.
Anyhow, we have run into a problem that we solved in the past with a Y-axis drive, but we are in quite deep into it this time.
This is the situation. Slowly towards the end of 2021 the machine started producing less-than-stellar finish on Y-axis direction walls (this of course includes radius'd corners and angles, etc). We can produce an evident difference feeding purely in Y vs purely in X. The direction in Y does not matter, inwards and outwards we produce the same finish. The finish looks like chatter but it is not, I would describe it as very fine "striation" lines.
So our trouble shooting led us through the following progression:
- Did a general check over the machine, spindle had next to no runout: .0001" but Y-axis had quite bad play so its where we started.
- Replacement of Y-axis thrust bearings as we had over .0014" in movement on the ball-screw.
- Upon replacement of the Y-axis thrust bearings we found the bearing block and motor mount had a fine fracture in it and was flexing when tightening into the machine. So we replace the entire motor mount / bearing block assembly on both the X-axis and Y-axis.
- We then cleaned the brushes and tachometers on both the X-axis and Y-axis motors (DC motor machine).
- We then swapped the X and Y motors with still no change.
- We tried swapping the controller cards for the X and the Y with no change. We then did the same with the amp cards, and still no change.
- We then replaced the resolvers in both the X and Y axis motors, still no change.
- I personally went thru the entire power supply and verified +/-5V and +/-10V and all was good. Verified voltage on the resolvers were ~1.75V at the bullet connectors and on the pins of the controller cards. I found that the Shielding lead on the cable for Y-axis had real high resistance (this turned out to be a real corroded connection on the wire to shielding in the Y-axis motor housing. I repaired this myself and got the resistance back down to nominal) All of this still proved to have no change.
- Looking thru the electronics we went as far as observing the voltages in the cards and resolvers while the machine is feeding constant rates in both the X and Y axis directions
- At this point we brought our local service guys in who checked the machine out, adjusted the gibs and did a bar-ball test. They said our gibs and our ways are still good and they had it all adjusted back to factory specs. They said the Y-axis was really bad for play still and found a ton of thrust issue with the ball-screw nut. On top of adjusting the gibs they also did a quick tune of the amp cards.
- So now we started tossing parts at the machine. We bought a brand new Y-axis ball-screw assembly, this had zero effect on our problem (although now our Y-axis is whisper quiet haha).
- Then we got a brand new DC servo which we tried on both the Y-axis and X-axis with again zero change.
- Being very stumped, yesterday and today we started inspecting the Head. The belts and tensioners all seem to be fine (this is a Hi/Lo spindle machine). We actually have a brand new tensioner assembly on this machine, with brand new belts from just a few months ago. We played around with the spindle motor tensioner wire and gave everything a good once over but have no leads here in the slightest.
So now we are somewhat stuck. Mechanically the machine seems fine according to us and the service guys. This problem exists with even brand new end mills and this problem is consistent with any tool holder. The strange thing is we still get good finish in steel (Good as in, decent for the old beast that this thing is). Not going to pretend the X-axis is superb finish but it is miles better than Y and we would like to get this machine back to the state where it produces a part with walls that don't look like they were cut with a dull hss mill in an old manual mill haha
Have had some great info come from this forum over the years and I think everyone appreciates the help that is still available here.
One of our 3-axis machines is an old 4020 Fadal which is something that is becoming harder and harder to receive support for.
Anyhow, we have run into a problem that we solved in the past with a Y-axis drive, but we are in quite deep into it this time.
This is the situation. Slowly towards the end of 2021 the machine started producing less-than-stellar finish on Y-axis direction walls (this of course includes radius'd corners and angles, etc). We can produce an evident difference feeding purely in Y vs purely in X. The direction in Y does not matter, inwards and outwards we produce the same finish. The finish looks like chatter but it is not, I would describe it as very fine "striation" lines.
So our trouble shooting led us through the following progression:
- Did a general check over the machine, spindle had next to no runout: .0001" but Y-axis had quite bad play so its where we started.
- Replacement of Y-axis thrust bearings as we had over .0014" in movement on the ball-screw.
- Upon replacement of the Y-axis thrust bearings we found the bearing block and motor mount had a fine fracture in it and was flexing when tightening into the machine. So we replace the entire motor mount / bearing block assembly on both the X-axis and Y-axis.
- We then cleaned the brushes and tachometers on both the X-axis and Y-axis motors (DC motor machine).
- We then swapped the X and Y motors with still no change.
- We tried swapping the controller cards for the X and the Y with no change. We then did the same with the amp cards, and still no change.
- We then replaced the resolvers in both the X and Y axis motors, still no change.
- I personally went thru the entire power supply and verified +/-5V and +/-10V and all was good. Verified voltage on the resolvers were ~1.75V at the bullet connectors and on the pins of the controller cards. I found that the Shielding lead on the cable for Y-axis had real high resistance (this turned out to be a real corroded connection on the wire to shielding in the Y-axis motor housing. I repaired this myself and got the resistance back down to nominal) All of this still proved to have no change.
- Looking thru the electronics we went as far as observing the voltages in the cards and resolvers while the machine is feeding constant rates in both the X and Y axis directions
- At this point we brought our local service guys in who checked the machine out, adjusted the gibs and did a bar-ball test. They said our gibs and our ways are still good and they had it all adjusted back to factory specs. They said the Y-axis was really bad for play still and found a ton of thrust issue with the ball-screw nut. On top of adjusting the gibs they also did a quick tune of the amp cards.
- So now we started tossing parts at the machine. We bought a brand new Y-axis ball-screw assembly, this had zero effect on our problem (although now our Y-axis is whisper quiet haha).
- Then we got a brand new DC servo which we tried on both the Y-axis and X-axis with again zero change.
- Being very stumped, yesterday and today we started inspecting the Head. The belts and tensioners all seem to be fine (this is a Hi/Lo spindle machine). We actually have a brand new tensioner assembly on this machine, with brand new belts from just a few months ago. We played around with the spindle motor tensioner wire and gave everything a good once over but have no leads here in the slightest.
So now we are somewhat stuck. Mechanically the machine seems fine according to us and the service guys. This problem exists with even brand new end mills and this problem is consistent with any tool holder. The strange thing is we still get good finish in steel (Good as in, decent for the old beast that this thing is). Not going to pretend the X-axis is superb finish but it is miles better than Y and we would like to get this machine back to the state where it produces a part with walls that don't look like they were cut with a dull hss mill in an old manual mill haha