[nzben]

I have recently purchased a '95 Arrow 500 with a CT FNC controller. Have had a few teething problems. Getting most of them sorted now.

There is this one thing the machine does that freaks me out a little.sometimes when you start it up, you press the green button, then press again and the Y axis comes shooting forward at rapid, so I hit the Estop. Now when I switch it on, I press the green button once and monitor the indicated positions, occasionally the Y is running all over the place which to me sounds like an encoder problem. I only press the button the second time now to energize the servos if the Y axis measurement is stable, whenever its unstable the table will take off.

Its not yet done any crazy moves when running, but I fear that could happen at any time, and it may be a problem that gets worse.

Has anyone seen this exact issue before??

Thanks

[mallardfizz]

hello
does this happen when the table is at its rear position (nearest to the column)? if it is then one possible cause is swarf trapped behind the saddle.
on early machines the table aligns at the back and any excess trapped swarf becomes compressed and causes the drive to go into overload (foldback on Kollmorgen drive machines). the drive will allow the overload for about 2 secs then faults out. the result is the y axis shuts down and the saddle shoots forward.
if it shoots forward when the saddle is at any position then yes it is probably a feedback loss.
regards
mallardfizz

[nzben]

Thanks, I think it happens at any table position, there is no swarf on the machine - it's hardly cut anything yet. The weird thing is you see the encoder jump around all over the place sometimes before the servo is energized. Once it is energized it never seems to run away (so long as its stable when powering up the servos.

Also - how loud are these machines? I suspect the spindle bearings are gone. At 1000 RPM noise levels are quite acceptable, however up around 4,000 I need to wear earmuffs (and I dont even wear earmuffs angle grinding!) Are the spindle bearings a straight forward replacement?

Thx

[pete from TN]

Hey man nice to meet ya. I just also purchased the same machine with the same control. Still working on getting it moved over here and preparing the shops electrical side for it. I cannot help you with your issue just yet but I hope to be able to network with other owners of the same machine for future troubleshooting ideas and help. As far as the spindle bearings are concerned from what I understand of it the machines do not have a spindle cartridge like on many newer machines so the bearings are pressed into the head casting and replacement is straighforward but more complicated due to the fact that it must be done on the machine. I am sure at some point I will be replacing them so I have been looking into it for myself. The spindle also has an air operated oiling system that must be taken care of IE good dryers and particulate seperators on your air lines to keep crud out of the expensive bearings. Anyways, Good luck and if it were my machine with that issue I would be taking covers off and inspecting motors and movements and wiring on that offending axis for damage or moisture issues. I remember reading someone say that there is a possibility of liquid pooling in the motor area on these machines if the chips build up in there. The covers appear to be pretty adequate but as usual chips can find their way everywhere.... good luck man and please post your findings and information as it may help others down the road. This forum is kinda slow compared to what I am accustomed to so the more free information posted the better off we will all be. Peace

Pete