[kopsik]

Hello

I have been using a Puma 2100 for 6 months now and I started to wonder if it would be advisable to keep the spindle turning during tool change?

What is the common practice?

PS! We had spindle bearing failure after 10 000 parts!

[underthetire]

Normally you would always keep the spindle running on a lathe. The starting and stopping is the toughest on the motor and drive unit, not to mention your power bill.

[laurensschu]

We always keep it running.
Machining time on our 2600LM Drastically increases when we turn it off.(Like on all the other lathe's)
Yeah, like 10 000 parts says anything, 10 000 parts that take an hour to machine, and if you had one or two collisions, yeah you bet it's gonna go.
Would be the same on a Okuma.

[DouglasR]

Ok, generally, in Applications, we recommend NOT stopping the main spindle or subspindle for tool changes. This is for several reasons -
A) Cycle times will increase by at least 20% as the machine will now have to wait for the spindle (s) to get up to speed, even with a fast acc/dec like the Puma, it's still adding precious seconds to your part times when you should be decreasing them. Same for things like coolant pumps as many times the machine will "wait" for confirmation that a particular function is operating before continuing on.
B) The start/stop on the spindle is placing a great deal of stress on the motor (s), Drive (s), belts and bearings. Watch your motor load meter when the spindle starts/stops and you'll see it peak at VERY high levels as the motor tries to crank the spindle to the correct speed. However, once running, you'll see that motor loads stay fairly steady and even paced, all the way through the speed range.

10,000 parts on a spindle. I feel that perhaps more data is needed. Was the machine involved in a turret/workpiece or turret/spindle collision? Are workpieces/workholding weights at or over the maximum specified? Are cycle times very high with hours of hogging?

[dcoupar]

I like to start the spindle with a G97 Snnnn where nnnn is the target RPM at the start of the 1st feed move.
At the end of cutting for each tool, I use either a G97 by itself, or G97 Snnnn where nnnn is the target RPM of the next cutting operation.

N1G00G40G18G97G99
G28U0W0
G50S3000
T0101(FACE END TO LENGTH)
G54X1.6Z0S2250M03P11 <--- Start spindle at target RPM
G96S650M08 <--- Activate CSS (if necessary)
G01X-0.06F0.01
G00G97Z0.1S2150M09 <--- Set RPM for next cutting operation
G28U0W0
M01

N2G00G40G18G97G99
G28U0W0
T0202(DRILL 5/8 X 2.0 DEEP)
G54X0Z0.0S2150M03P11 <--- Start spindle at target RPM
M08
G01Z-2.13F0.01
G00G97Z0.1S3150M09 <--- Set RPM for next cutting operation
G28U0W0
M01

[DouglasR]

Very good practice. One that can enhance spindle/motor/drive life. I can see this being a big help on machines with large chucks too.

[bertus.nl]

hi,

I use the G97 as much as possible, takes a lot of the cycle time .
and it makes the machine sound better and safe's my money.

leaving the coolant on, i don't know if that is so good for the seals. but i don't know.

vr gr bertus

[laurensschu]

Why would using G97 save cycle time? Do you write g-code by hand?? And change speed for each diameter cut? Or a really low power spindlemotor?

Otherwise G96 got to be quicker. In fact spindle/bearings fail on max number of turns by certain load, with non cutting motion the load is really low and the the Max turns is increadibly high, so that's no problem leaving it on, you motor on the other hand doesn't like starting and stopping, cause its high load on it. Keeping it on is a better bet.
Coolant on, is indeed not such a good idea for your seals. Allergisch, some machine turn it of very short for you if it changes tool. Especially with high pressure it could get tricky!

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[underthetire]

G97 is the preferred way, that way the spindle is not ramping up and down when you move away from the part. easier on the spindle drive as well.

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[bertus.nl]

hi

If you have products of dia 400mm bringing the dia back to 80mm over a length of 900mm ,then G97 is the better choice.
but on normal steel products of <40mm the needed cutting speed often exeeds the max rpm of the machine.
high feeds is the magic word, not high rpm's .
If you look at the numbers and the electric bill ,the acc/decceleration of the chuck is not per definition the best option.

but for every job it's own best way

Attachment 214740

vr gr bertus

[laurensschu]

I totally agree that feed, is the way to go, but in stainless, cutting speed is critical to tool life and so g96 is what you want. And the longer and bigger the product the bigger the chance you want G96 as well.

For below 40 mm in diameter, G97 would indeed cause the machine to keep the same rpm through retracts, cause that is we're it might go below the rpm max.(or if you have a high rpm machine, 5-6000 then it would be different again.)

G97 is indeed easier on spindle motor and drive. And possibly the electric bill as well. But not necessary the most economical way. Keeping the machine on a stationary rpm during tool change I've got to say is a good thing.

The New 4325 from Sandvik is brilliant.(just saying to bertus, the pic is from Sandvik)

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