Re: [CAD_CAM_EDM_DRO] Re: retrofitting an older CNC (shizuoka AN-S)

no falloff wrote:

>Thanks for all the input. it's been very helpful. I am far less confused than I was a few days ago. I know what my options are at least. I think the most cost effective, and ultimately the most powerful/versatile, will be to try to get the existing controller fully online. I had the day to play around with it, and have learned a few things. First I am slowly learning the controller. The manual is a bit arcane, and as my experience with CNC is limited at best, deciphering what are instructions for someone versed with CNC and production machining is a bit of a challenge.
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> So far all that I can find wrong with this machine is that the Z axis is faulting. It is getting nowhere near the limit switches, and the longer the machine is on the shorter the Z needs to move before it faults. If the machine is cold I can get it to home, override the z axis and run the machine through any of the 25 or so programs still in the memory of the controller. The specific error I am getting once the machine is warmed up is:
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>Emergency stop.
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>Z servo error
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>Loss of feedback or no motion on Z axis.
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>There is motion so it must be in the feedback
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No. When it croaks, the motion is lagging behind the commanded position.
First, try moving it manually. Is there binding or just a lot of drag?
Is the
Z on the quill or the knee? If it is on the quill, it should be pretty easy
to move it. Sometimes chips stuck to the quill can be drawn up into
the head when it retracts. I have gotten these out by extending the
quill and smearing it with grease. Then I retract it fully and bring it
back out. This often brings out a load of chips! If it is the knee that is
the Z axis, then I'd go a lot farther in believing it could be binding
causing this. I'd smear some way oil all over the ways and run the
knee past that area and see if you can loosen it up.

You may also need to clean and check the ballscrew alignment.

The tripping in shorter intervals as it warms up is a clue. Most fancy
servo amps have a motor heating integrator that calculates the long-term
heat in the motor, and trips the amp when total energy dissipated in the
motor over the last 5-15 minutes exceeds the setting. You might also
check the servo amp for overheating, itself. But, either condition could
be caused by a binding axis.

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>Does this sound like a bad tach or encoder? Could it be in the drive?
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It certainly could be the drive. It sounds like either the drive is
detecting a
fault or overload condition, or a following error condition. You should be
able to check the encoder by moving it manually and watching the screen.
A bad tach would cause jerly motion, so that is not likely.

>I’m hopeful that if I can resolve this Z axis fault that this is most of what I’m up against as I so far haven’t found anything else. Except maybe a little too much noise in the Z ball screw.
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Oh? Crunching noises? No reason for you to think there's any relation to the
axis drive problem, by any chance? It is likely chips have gotten into the
ballnut. If they are hard to open up, you can use that grease trick again.
Smear grease on the ballscrew, and run the nut across it. (You will likely
get MORE noise for a while.) Then, wipe the chips and dirty grease off
the screw, regrease, and run it back the other way. A few passes should
remove the chips from the nut.

Jon