Spindle RPM Cap

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21 May 2013 21:42 #34503 by Zahnrad Kopf
Replied by Zahnrad Kopf on topic Spindle RPM Cap

I can try it on my machine. As that is metric this is likely to have it going from 45 m/min to 45rpm, which I am not sure the VFD can even handle...


Andy, it doesn't need to be those values. It can be anything as long as the two values differ so that you can note the error.

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21 May 2013 21:45 #34504 by Zahnrad Kopf
Replied by Zahnrad Kopf on topic Spindle RPM Cap

An alternative, if you are in feed-per-rev mode is to turn the spindle override down to zero. That should stop all motion too.
Though I don't really like the idea of doing things on the machine in that situation, with it all poised to move again.

Something I have never tried is turning the chuck backwards in that scenario. I wonder if the tool backs-off? I suspect not.


**** Pre note - I don't mean it to sound offensive, so if it is, please forgive me.
If there is a better way to describe true, real world, industrial controls/machines don't hesitate to let me know. ****

In the Real World™, when one turns the spindle down to Zero, it is HELD at Zero RPM. As in, one CANNOT rotate it by hand.

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21 May 2013 22:00 #34505 by andypugh
Replied by andypugh on topic Spindle RPM Cap

In the Real World™, when one turns the spindle down to Zero, it is HELD at Zero RPM. As in, one CANNOT rotate it by hand.


That rather depends if the spindle is driven by a servo of some sort. I suspect that even in your "real world" not all of them are.

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21 May 2013 22:28 #34506 by SRT
Replied by SRT on topic Spindle RPM Cap
Please understand that I am not trying to stir the pot. In our world, Acramatic and Fagor controls several with DC spindle motors and a few with AC spindle motors and drives. We can hit feed hold stop the spindle, inspect tooling or check the part, move the turret if needed to gain clearance to change an insert restart the spindle and resume the cutting operation as programmed before the feed hold spindle stop/restart

I believe we are encroaching into the jog while paused territory but I am committed to this stuff and trying to report issues as we find them.

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21 May 2013 22:56 #34507 by andypugh
Replied by andypugh on topic Spindle RPM Cap

I believe we are encroaching into the jog while paused territory.


I don't think that there is anyone who doesn't agree that that is desirable. I am pretty sure it will come eventually. I doubt that there will be any change to the motion planner that doesn't start with that as a requirement.

In the meantime, I wonder if there is an all-gcode solution? Stop the program, hit a "save position" button, change the insert, then have the G-code carry on from where it left off (after jogging to a suitable starting point). This is not likely to be easy for complex profiles, but would not be difficult for simple cylindrical roughing. (View it as a canned-cycle for roughing).
I am thinking of something similar to the underlying G-code in the lathe macros I posted in the GUI thread a few days ago.

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22 May 2013 00:54 #34513 by Zahnrad Kopf
Replied by Zahnrad Kopf on topic Spindle RPM Cap

In the Real World™, when one turns the spindle down to Zero, it is HELD at Zero RPM. As in, one CANNOT rotate it by hand.


That rather depends if the spindle is driven by a servo of some sort. I suspect that even in your "real world" not all of them are.


No, not all of them are. Many are 3Ø phase motors controlled by VFD. I can only speak for the ones I've run and/or owned, though.
Frankly, I'm not sure HOW they manage to do this on the ones with "normal" motor driven spindles, but it is more common than not.
I inserted the ™ symbol in effort to add some levity to the reference and I hope that it isn't coming out sounding preachy or demanding.
Just trying to add some additional viewpoint and reference.

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22 May 2013 01:00 #34514 by andypugh
Replied by andypugh on topic Spindle RPM Cap

No, not all of them are. Many are 3Ø phase motors controlled by VFD. I can only speak for the ones I've run and/or owned, though.
Frankly, I'm not sure HOW they manage to do this on the ones with "normal" motor driven spindles,


A spindle brake is common on larger lathes.

How do you get to the holes to adjust a 4-jaw chuck?

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22 May 2013 01:16 #34515 by Zahnrad Kopf
Replied by Zahnrad Kopf on topic Spindle RPM Cap

A spindle brake is common on larger lathes.


Common on many, but I do not know what the actual mechanism involved is when the discussed operation is happening.
I don't know if it's a brake that engages because a 0 RPM is commanded ( manually ) or if the motor is being held electrically.

How do you get to the holes to adjust a 4-jaw chuck?


I've seen it in pictures, and have heard people discuss it, but in 30 years of doing this I have
never seen a 4 jaw chuck on a turning center with my own eyes, nor ever had a need for one.
Typically, we hold irregular parts with soft jaws and machine the jaws to fit them. Repeatable and dependable, and allows the use of the power draw bar.

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22 May 2013 01:21 #34516 by SRT
Replied by SRT on topic Spindle RPM Cap
We use 4 jaw chucks all of the time and 6 jaw adjust true. We are a job shop and it allows me to move from job to job much faster than boring jaws. Most of my turning centers the brake is the engagement of both the high and low speed clutches. During a spindle stop condition My spindles can be turned by hand I also have a brake and neutral selector switch.

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22 May 2013 02:17 #34519 by Zahnrad Kopf
Replied by Zahnrad Kopf on topic Spindle RPM Cap

We use 4 jaw chucks all of the time and 6 jaw adjust true. We are a job shop and it allows me to move from job to job much faster than boring jaws.


Ha ha ha ha! See...? That's just too funny! Figures though... No production here. All prototyping.

Most of my turning centers the brake is the engagement of both the high and low speed clutches. During a spindle stop condition My spindles can be turned by hand I also have a brake and neutral selector switch.


So, if you manually step the spindle override down to zero during a program, you can spin your chuck?
I don't have that. If I'm in the middle of a program and override down to zero, the chuck is for all intents and purposes locked in place.

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