CNC lathe hydraulic chuck pressure

[Jaanyaar]

I have not found any info about the chuck pressure needed for an operation in my lathe manuals (A Colchester Tornado A90 machine). Does anybody have any material for this machine or any other machine? Wanna have a more view on this subject.

Suppose a part is held in a hydraulic chuck and still the spindle is not running. Now if you change the pressure switch value, will the chuck pressure change on the part? Or you have to open and close the chuck once to have new pressure value applied on the part?

What about changing the pressure on the part during operation live? Any effect?

 

[William Lynn]

One of the parts I ran used 4 1/4" 4140 hot roll in varying lengths up to 17". They rarely ran true upon chucking up. I always backed the pressure off to where I could easily bump the stock to an acceptable run out. Once I did that, I increased the pressure to hold the part safely. So in my case the answer is yes and yes. Just think what you're doing so you don't toss the heavy chunk out of the chuck.

 

[Northman Ind.]

I have not found any info about the chuck pressure needed for an operation in my lathe manuals (A Colchester Tornado A90 machine). Does anybody have any material for this machine or any other machine? Wanna have a more view on this subject.

Suppose a part is held in a hydraulic chuck and still the spindle is not running. Now if you change the pressure switch value, will the chuck pressure change on the part? Or you have to open and close the chuck once to have new pressure value applied on the part?

What about changing the pressure on the part during operation live? Any effect?

the pressure should be immediate whether you go up or down, chuck closed or open, and you "can" change it while the spindle is turning, its not what I would call a good habit.

Its all just very basic hydraulic functions, the only interlocks with the NC side is the sensors on the back of the spindle that determine opened or closed limits, otherwise its push as hard as the relief valve allows at all times, open or closed. (edit: other then the M codes and/or foot peddle/button that activate solenoids that direct which direction the oil flows...)

Now a good habit to get into is to open and close the chuck after any adjustments, just incase there is any weird tensions in there, especially if you are loading to a stop, and this is really only for accuracies sake.

Also, changing the pressure can effect Z location depending on setup, its not much, but it can effect the part, more so if you're using collets (way more so)

I have ran jobs where we would max out the pressure for the "roughing" portion and then back it off for the finish work, I do/did question the effectiveness of this, and it did cause issues with Z location repeatability