Spindle override not working while at MAX rpm....

Hi guys, the spindle override is not working on my T1 while the rpm is maxed out at small diameters. Doesnt actually slow down until you set it at like 30% and the SFM is the limiting factor.

Any way around this? A parameter I could change or something? Or is this just how the T1 works? Would be nice to easily override spindle when you get chatter. Thanks.

mmurray70 said:

Hi guys, the spindle override is not working on my T1 while the rpm is maxed out at small diameters. Doesnt actually slow down until you set it at like 30% and the SFM is the limiting factor.

Any way around this? A parameter I could change or something? Or is this just how the T1 works? Would be nice to easily override spindle when you get chatter. Thanks.

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The spindle speed override is calculating the percentage of the programmed speed, whether it be CSS or RPM. 30% of say, 800 SFM at a diameter of .500" is still max RPM. I would recommend programming it as RPM for whatever your spindle maximum is and then dial it down from there.

bigjon61 said:

The spindle speed override is calculating the percentage of the programmed speed, whether it be CSS or RPM. 30% of say, 800 SFM at a diameter of .500" is still max RPM. I would recommend programming it as RPM for whatever your spindle maximum is and then dial it down from there.

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Is there a way to specify rpm on a T1? I think it only allows sfm.

Think he means program the calculated SFM from your max RPM. Your obviously programming it too high so only at 30% override is the machine actually able to slow the spindle lower the max.

Twiglet said:

Think he means program the calculated SFM from your max RPM. Your obviously programming it too high so only at 30% override is the machine actually able to slow the spindle lower the max.

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That's the way I approach it too...

I have a cosmetic part running from 3/4" aluminum bar this week. It has a minor OD of .375" and a major OD of .700".
I set my surface speed for the finishing cut using the minor outside diameter (3/8") and my max spindle RPM (3600 RPM):

360RPM * ((.375" * pi) / 12) = 353 SFM

I programmed my finish cut with 353 SFM.

100% override is 353 SFM, not necessarily 3600 RPM because the spindle will slow to maintain 353 SFM as the cut tapers out to .700" OD.
50% override is 177 SFM, not necessarily 1800 RPM for the same reason...

Keep in mind that if you program something like a facing cut or a parting cut, the diameter goes all the way down to zero.
So, theoretical spindle RPM will approach infinity as the diameter approaches zero in order to maintain a constant Vc.

Ok looks like Ill have to work out my SFM when programming to get the right rpm. I would have thought the override would have adjusted max speed too, but I guess not. Too bad it didnt work this way. Wont be a big deal for me on this job, but if i were doing a part with a flange and a small diameter you would have to compromise somewhere.

Its not that im programming too high, just that im working with small diameters. This job was skimming down a 1/2" stainless rod down to 12.5mm, I think i programmed it with 600 sfm and 1500 max rpm to avoid chatter. Ill try programming it with 196 SFM and ill set max to 1800 to i can override it properly. Thanks again.

mmurray70 said:

Ok looks like Ill have to work out my SFM when programming to get the right rpm. I would have thought the override would have adjusted max speed too, but I guess not. Too bad it didnt work this way. Wont be a big deal for me on this job, but if i were doing a part with a flange and a small diameter you would have to compromise somewhere.

Its not that im programming too high, just that im working with small diameters. This job was skimming down a 1/2" stainless rod down to 12.5mm, I think i programmed it with 600 sfm and 1500 max rpm to avoid chatter. Ill try programming it with 196 SFM and ill set max to 1800 to i can override it properly. Thanks again.

Click to expand...

I am by no means a Mazatrol expert, but the strategy that I think works best is below:

Use surface speed and feeds to control the chatter on a long thin part and/or stubborn material.
Only limit the max RPM based on safe range of your work-holding and the nature of the stock (balance, length vs diameter ratio, etc).


That gives you the most flexibility in terms of overrides and more importantly, the SFM numbers in your program represent what is actually being cut.
If you limit the spindle speed to control cut quality, the numbers in the program are almost meaningless and you are not taking full advantage of the constant surface speed features built into the control. That's not as big an issue on a straight diameter, but on a tapered part, it shows in your surface finish.