MG SkyDynamics
Plastic
- Joined
- Apr 22, 2021
Hi!
First post on the forum here. I work for a small company in Virginia that manufactures aftermarket aircraft components. This was my first job coming out of my 2 year degree in engineering mechatronics. I have been here a little over 2 years now, and have done all of the maintenance of the machines we have. Completely self taught, with the help of youtube and practical machinist, and most importantly intuitin/common sense
We have 4 CNC machines ;
2011 HAAS ST-20ss Lathe, 1996 VF-2, 2003 VF-3, 1995 HAAS VF-4.
In this thread I am going to go over the trouble shooting process of the alarms and maintanence that I have done on the VF-4. I will eventually post other threads for the different machines.
I will reply to my this first thread with all the other maintenance and troubleshooting, but I am going to start completely from the beginning of when I first met the good ole gal.
the VF-4 has been through many repairs. when i first arrived the machine would not power up restart and the Z-axis would give an over current alarm. do not remember the # since this was 2 years ago but this is the process I went through.
I first checked the servo amplifier to see if it was in working order. The multimeter tests had shown that the amplifier was shorted out. the fault light was not visible because the LED was shorted as well. so, replaced the servo amp for the z-axis first off. This enabled the machine to succesfully power up restart and zero. But something still didnt seem right with the Z-axis. It still gave a few over current alarms that day. So, shut off the machine and tried to figure out why. Took the shield completely off the vertical head, and I dove into checking the motor. I cant remember if it was brushless or not, but if it was i checked them, and observed the coupling from the motor to ballscrew that runs the axis.
I tried to turn the ballscrew by hand, and noticed how it seemed almost seized. I read it should be easily moved by hand, so feeling the amount of resistance I had felt led me to believe the ballscrew had some wear and might be damaged.
So, to remove the Z-axis ball screw.... you must first jog the machine up and place wooden blocks under the head to prevent the head from falling. thankfully there is a compressed nitrogen piston that should prevent the axis from moving on its own. but take caution, because the head is hundreds upon hundreds of pounds and you WILL get crushed if it falls while you are under the Z-axis way covers.
Once the head is locked in place, remove the z-axis way covers, and you will see the ballscrew in its entirety. it is attatched to the head by a ball bearing block the shaft runs through that is attatched to the head. remove everything from the ballscrew, including the motor and coupling. if you leave the motor and coupling on, you risk damaging the coupling and replacing it with a brand new one can be difficult to find. also remove the bottom lock collars of the ballscrew that is attatched to the frame. there are also a few oil fittings to the block the screw runs through that need to be taken off as well. once the bearing block has the fittings removed, and detatched from the head, you should be able to finagle the ballscrew out.
Remember to keep track with photos and keep bolts in marked baggies.
Once the ballscrew was out of the machine, I inspected the ball bearing block the screw runs through and took it apart. Only to find that many of the balls inside are covered in corrosion and old oil.
So, I soaked the bearing block and balls in a tub of laquer thinner, and did my best to clean the balls that came out of the bearing block. I found that many of them were pitted. This was not good of course. I measured the balls and ordered some of the corresponding size and kept the "good" balls. I also had to thoroughly clean the screw as well, since the balls had left surface rust and slight pitting on the screw.
Once the balls came in, I re-assembled the bearing block, making sure to put almost the exact same number of balls back in. attatched it to the ballscrew and assembled the machine back, leaving the head covers off, along with leaving the Z-axis way covers off just in case this was not the problem.
However, after assembling the machine and running it for a few days doing various tasks controlling the z-axis. NO ALARMS. Not one alarm concerning the Z-axis after the overhaul.
I had called a few HAAS Service techs, just getting tips on what to look for, and none of them had suggested the ballscrew. They all assumed bad amplifiers, motor, or the motor coupling. And most of them wanted to come out and look at the machine themselves BUT... No, not for the price they wanted!! In 2 weeks on my own, I solved the problem myself. keep in mind, I had other projects going on at the time and this machine wasnt my main concern.
I estimate about 12-15 hours of total time to fix this problem with the proper tools.
hope this helps
First post on the forum here. I work for a small company in Virginia that manufactures aftermarket aircraft components. This was my first job coming out of my 2 year degree in engineering mechatronics. I have been here a little over 2 years now, and have done all of the maintenance of the machines we have. Completely self taught, with the help of youtube and practical machinist, and most importantly intuitin/common sense
We have 4 CNC machines ;
2011 HAAS ST-20ss Lathe, 1996 VF-2, 2003 VF-3, 1995 HAAS VF-4.
In this thread I am going to go over the trouble shooting process of the alarms and maintanence that I have done on the VF-4. I will eventually post other threads for the different machines.
I will reply to my this first thread with all the other maintenance and troubleshooting, but I am going to start completely from the beginning of when I first met the good ole gal.
the VF-4 has been through many repairs. when i first arrived the machine would not power up restart and the Z-axis would give an over current alarm. do not remember the # since this was 2 years ago but this is the process I went through.
I first checked the servo amplifier to see if it was in working order. The multimeter tests had shown that the amplifier was shorted out. the fault light was not visible because the LED was shorted as well. so, replaced the servo amp for the z-axis first off. This enabled the machine to succesfully power up restart and zero. But something still didnt seem right with the Z-axis. It still gave a few over current alarms that day. So, shut off the machine and tried to figure out why. Took the shield completely off the vertical head, and I dove into checking the motor. I cant remember if it was brushless or not, but if it was i checked them, and observed the coupling from the motor to ballscrew that runs the axis.
I tried to turn the ballscrew by hand, and noticed how it seemed almost seized. I read it should be easily moved by hand, so feeling the amount of resistance I had felt led me to believe the ballscrew had some wear and might be damaged.
So, to remove the Z-axis ball screw.... you must first jog the machine up and place wooden blocks under the head to prevent the head from falling. thankfully there is a compressed nitrogen piston that should prevent the axis from moving on its own. but take caution, because the head is hundreds upon hundreds of pounds and you WILL get crushed if it falls while you are under the Z-axis way covers.
Once the head is locked in place, remove the z-axis way covers, and you will see the ballscrew in its entirety. it is attatched to the head by a ball bearing block the shaft runs through that is attatched to the head. remove everything from the ballscrew, including the motor and coupling. if you leave the motor and coupling on, you risk damaging the coupling and replacing it with a brand new one can be difficult to find. also remove the bottom lock collars of the ballscrew that is attatched to the frame. there are also a few oil fittings to the block the screw runs through that need to be taken off as well. once the bearing block has the fittings removed, and detatched from the head, you should be able to finagle the ballscrew out.
Remember to keep track with photos and keep bolts in marked baggies.
Once the ballscrew was out of the machine, I inspected the ball bearing block the screw runs through and took it apart. Only to find that many of the balls inside are covered in corrosion and old oil.
So, I soaked the bearing block and balls in a tub of laquer thinner, and did my best to clean the balls that came out of the bearing block. I found that many of them were pitted. This was not good of course. I measured the balls and ordered some of the corresponding size and kept the "good" balls. I also had to thoroughly clean the screw as well, since the balls had left surface rust and slight pitting on the screw.
Once the balls came in, I re-assembled the bearing block, making sure to put almost the exact same number of balls back in. attatched it to the ballscrew and assembled the machine back, leaving the head covers off, along with leaving the Z-axis way covers off just in case this was not the problem.
However, after assembling the machine and running it for a few days doing various tasks controlling the z-axis. NO ALARMS. Not one alarm concerning the Z-axis after the overhaul.
I had called a few HAAS Service techs, just getting tips on what to look for, and none of them had suggested the ballscrew. They all assumed bad amplifiers, motor, or the motor coupling. And most of them wanted to come out and look at the machine themselves BUT... No, not for the price they wanted!! In 2 weeks on my own, I solved the problem myself. keep in mind, I had other projects going on at the time and this machine wasnt my main concern.
I estimate about 12-15 hours of total time to fix this problem with the proper tools.
hope this helps
