Stalled spindle

Today I witness what I thought was an oddity.

My machinist was plunging a .500" 4 flute tool steel endmill into a block of 1.5" thick cold rolled when the spindle "stalled" out. The hole was predrilled with a .375" drill to 1.000" the endmill was set to plung the same distance so the last couple pecks would have to hog out more material. On the second to last and the last peck of 0.050" the entire spindle stalled. We where both shocked that the spindle would stall before the tool would break or the tool would spin in the collet. I believe the spindle speed was right around 350rpms and the feedrate at 1.67 with coolant on(what ever the factory defaults are for).

We did two identical blocks the second one is the only one that stalled but both had holes meausreing .540"

We had tricked the machine by going to the tool setup page and idicating the end mill was a drill in order to get the machine to do the single hole peck drill. We are both new to cnc milling.

The holes being oversized I think is cleary chips building up and ruining the wall of the bore.

It never through any alarms like I thought it would.

What do you all think?

I think it's a Haas....
I've stalled my Mini...

At that slow an RPM you have 2 issues.

The first is the torque curve for the motor and it sucks at low RPM's. You don't have near the power you think you have.

The second is that without through the tool coolant and that low RPM you will have a toguh time evacuating the chips. the chips will pile up and the friciton is enourmous. The motor hasn't got enough poop to push it and it gives up. It should throw an overload alarm though, either the spindle or Z axis.

It was a center cutting endmill, was it not?

Mike

Stuart Caruk said:

The first is the torque curve for the motor and it sucks at low RPM's. You don't have near the power you think you have.

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I am not terribly familiar with these machines, but I always thought the spindle motors were servos thereby allowing ridgid tapping. If this is the case shouldn't the torque be relativly constant?

mister honey said:

It was a center cutting endmill, was it not?

Mike

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Yes it is.

You guys where thinking what i was thinking. My salesman told me that I would want to start getting rid of all my steel tooling once we got the machine and I think he is right.

It should throw an overload alarm though, either the spindle or Z axis.

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I was thinking this too which is why I thought it was odd.

What was the spindle load before she "stalled"?

What machine do you have?

What HP?

.54 with a .5 e/m, something be wrong. Endmill not running true, setup is not rigid, endmill is not centercutting ( I believe that was mentioned already ) edges of mill are shot,e/m is shot, chips are not being evacuated ( flutes are protruding from hole correct? ) Chips wrapped around the endmill and not allowing coolant to get to the cutting area and not letting chips clear as well.

You speed sound okay for HSS tooling, the feed is kind of light, but shouldn't be the problem, other then chips getting in the way.

I am plunging a 1" 4fl e/m into a .375 hole with my VF-1 (1045 steel), it don't sound too happy with the spindle load up around 80% but it's not stalling and hole is coming out okay,(+.006 )

I only had my vf-2 for a small amount of time and I have worked with Mazak, Mitsui Seiki, and I have to say I am very pleased with the Haas. I just got through machining 2 mold bases and the steel used in the several of the plates are 4130 prehard. I used a 1" roughing end mill without issues. Of course I do have a geared head. Its cerainly not rigid as the other machines stated but for the money I am happy as I believe it will do what is needed.

SIM said:

.54 with a .5 e/m, something be wrong.

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I agree with SIM on this one, something is not right.

How were you holding the endmill, some people think when you are "drilling" straight down with an endmill you can get away putting it in a drill chuck, but that's definitely not the case, what will happen is exactly what you saw.

Paul T.