1HP CNC lathe stalling

vw_chuck · Feb 11, 2021

I would like a sanity check here from some of you guys with experience.
I am running a 1 HP CNC Lathe making an aluminum part starting out at 1.25inch diameter making .020 cuts at.004in/Rev and turning 2400RPM.
The motor stalls in mid operation when I get down to around 1 inch diameter. You can hear the motor bog a little as soon as it starts the cut.
I think it should have no problem running this part even in steel?
Is this an unrealistic speed and feed for 1HP or is there something more ominous going on?
Thanks for the help

David Ferguson · Feb 11, 2021

What is your tooling? HSS, Carbide, Inserts? What is the nose radius?

Are you running coolant? How hot is the material when it stalls?

vw_chuck · Feb 11, 2021

Coated Carbide. CCMT insert. Positive rake

GENERALDISARRAY · Feb 11, 2021

vw_chuck said:
I would like a sanity check here from some of you guys with experience.
I am running a 1 HP CNC Lathe making an aluminum part starting out at 1.25inch diameter making .020 cuts at.004in/Rev and turning 2400RPM.
The motor stalls in mid operation when I get down to around 1 inch diameter. You can hear the motor bog a little as soon as it starts the cut.
I think it should have no problem running this part even in steel?
Is this an unrealistic speed and feed for 1HP or is there something more ominous going on?
Thanks for the help

these Hardinge GT27s we have, have at least a 5 hp spindle.

It sounds like you have a toy.

Guest · Feb 11, 2021

GENERALDISARRAY said:
these Hardinge GT27s we have, have at least a 5 hp spindle.

It sounds like you have a toy.

Irregardless 1 HP should be plenty to make that cut, something else is wrong. Possibly the motor is shot or there is a tooling issue, such as being way above center or he has some crappy Chinese 6061 and the tools are gumming up.

To the op, is the motor single or 3 phase and is it getting enough voltage?

Brian · Feb 11, 2021

I would suspect his tools are above center... OP says it works ok until he gets down to roughly 1" diameter. The torque requirement decreases the smaller the diameter, so if it's getting harder as he gets smaller, chances are the tool is too high and rubbing under the cutting edge.

Bobw · Feb 11, 2021

3/4 of a cubic inch a minute, that should be less than 1/10th of a HP cut.

vw_chuck said:
Coated Carbide. CCMT insert. Positive rake

I'm going to ask for more details. If you've got a honed insert that is meant
to take .020 of feed in steel, you are going to need a lot more horse power.

What you should be using is a ground and polished up sharp insert. They
are really good on aluminum, but they also work really really well on stainless
and Ti and steel, especially if you are horsepower or surface speed limited.

They are basically like a nice sharp piece of HSS, but you can run them a lot faster.

The other thing.. Maybe 2400revs is putting your motor at a point that is really
low on the torque curve. What is the maximum RPM? And since it sounds like a
small lathe, how do you change the spindle speed? In the program, or physically?

vw_chuck · Feb 11, 2021

No tools are on center. Aluminum isn't gumming up as it has coolant. Yea eventually it is going to get a VFD and a 3 phase upgrade to a 3 or 5 hp motor.
I will dig in and check voltage at the motor. Probably a voltage drop somewhere from the rats nest of wiring.

vw_chuck · Feb 11, 2021

The insert is just a plain old carbide insert for steel from Shars. I will look into getting some of the actual aluminum inserts that have a much sharper edge as Shars has them also.

Guest · Feb 11, 2021

vw_chuck said:
No tools are on center. Aluminum isn't gumming up as it has coolant. Yea eventually it is going to get a VFD and a 3 phase upgrade to a 3 or 5 hp motor.
I will dig in and check voltage at the motor. Probably a voltage drop somewhere from the rats nest of wiring.

Chinese 6061 aluminum can gum up tools whether or not you are spraying coolant on them.

DDoug · Feb 11, 2021

Please post a pix of the set-up, the problem, and an overall view of this 1 H.P. cnc lathe.

Vancbiker · Feb 11, 2021

digger doug said:
..... an overall view of this 1 H.P. cnc lathe.

Gonna need a close up lens to get that pic.

David Ferguson · Feb 11, 2021

I would try a larger depth of cut. Unless you have a very small nose radius on that insert, you could be adding forces that push the tool away from the work - encouraging rubbing not cutting. One clue is are you making chips or strings? If strings, you need to up the DOC, RPM or feed to make it form chips.

And check that tool center too. Make a face cut and make sure there is no tit in the center. Your tool nose radius is important here too, you need to go over center by the amount of your nose radius.

Guest · Feb 11, 2021

I have a Hardinge HC that I am pretty sure has a 1HP motor that is older than I am. I have done many a don't try this at home project on it while leaving the 3 speeds where I set them over 25 years ago. Trust me, the horsepower is not the issue.

FredC · Feb 11, 2021

Pretty sure it is your insert. A member here bragged on his Kennametal CPGT3250HP inserts a few years back and said how well they did on aluminum. I use the same insert and it does do a good job on aluminum as well as brass, free machining steel and stainless as well as many plastics.
Just one of many good inserts for aluminum. You would not catch me using anything with the Shars name on it.

Hardplates · Feb 11, 2021

The lowest HP cnc lathe I have ever personally seen is 2 hp and it had a max turning dia of 0.394" :toetap:

DDoug · Feb 11, 2021

Hardplates said:
The lowest HP cnc lathe I have ever personally seen is 2 hp and it had a max turning dia of 0.394"

Back when you were an up-and-coming dental floss tycoon....and offered cubic zirconium encrusted toothpix.....

Bobw · Feb 11, 2021

digger doug said:
Back when you were an up-and-coming dental floss tycoon....and offered cubic zirconium encrusted toothpix.....

Dude, he's from Pennsylvania, I'm pretty sure you have to move to Montana to be a Dental Floss Tycoon.

Rob L · Feb 11, 2021

Hardplates said:
The lowest HP cnc lathe I have ever personally seen is 2 hp and it had a max turning dia of 0.394"

This is just over 1HP according to the specs,

R01-VI/R04-VI – Citizen Machinery

The Haas OL-1 is also a 1HP (or there abouts) spindle motor too.

I'd also say it's a tooling/setup issue, that DOC and feedrate should be easy even with a 1HP spindle with some nice ground positive inserts and a good setup, I take bigger cuts than that in one of my 3HP lathes and the spindle load doesn't make it into double percentage figures.

Hardplates · Feb 11, 2021

Rob L said:
This is just over 1HP according to the specs,

R01-VI/R04-VI – Citizen Machinery

The Haas OL-1 is also a 1HP (or there abouts) spindle motor too.

I'd also say it's a tooling/setup issue, that DOC and feedrate should be easy even with a 1HP spindle with some nice ground positive inserts and a good setup, I take bigger cuts than that in one of my 3HP lathes and the spindle load doesn't make it into double percentage figures.

That has a max turning diameter of 0.157"

Something tells me the OP isn't playing with a fancy swiss jobbie. A chipped negative rake steel insert would melt through aluminum at that cut without drawing 1 hp.

Me thinks this is a benchtop toy

1HP CNC lathe stalling

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