Derating Mazak Spindle

[Fal Grunt]

I do not know if "derating" is the correct term, but basically a friend is looking at adding an old Mazak QT15 to his shop and is juggling power concerns. I mentioned slowing the accel/decel but I really have no idea HOW MUCH this would reduce the draw? I assume there is a limit or a point where your causing issues.

I'm a huge fan of mazaks and I recommended he look at them. I had no idea what fat hogs they are when it comes to power!

 

[Philabuster]

What control does the QT15 have on it? There are different procedures to reduce the spindle acceleration based on which control the machine has.

I reduced the spindle acceleration on both of my old Mazaks so I could run them at the same time in my home shop. There is no detrimental effect to reducing the spindle accel except it may add a few seconds to the overall cycle time. Slowing the accel does make a HUGE difference in power draw and it is easier on the aging spindle drive.

On my T-3 controlled machines, the spindle drive has 6 different acceleration settings to choose. You can set accel from .3 seconds to 10 seconds. I have mine set to 8 seconds on my smaller machine (similar to a QT15) and the maximum line draw is around 38-40 amps per leg on 240v input circuit.

 

[Fal Grunt]

He has not bought a machine yet, but the current machine he is looking at has the T32 control as I remember it.

Thank you for the amps measurement, that is his main concern.

 

[Chris59]

We are constrained by the size of the wire. We were tripping the breaker when step facing (spindle ramping up and down). We set the maximum RPM to 3000 and that solved it. We only make prototypes so squeezing every second out wasn't a concern.
Could you do that?

 

[Vancbiker]

……I had no idea what fat hogs they are when it comes to power!

In what way? Mazaks use no more power than other machines of similar HP (real HP) ratings.

 

[Nmbmxer]

I reduced the acceleration and deceleration times on my QT10, it didn't trip breakers but would flicker the lights in the house lol. Biggest improvement was to right-size the chuck I was using. Replacing the huge power chuck with much smaller manual adjust tru chuck reduced the inertia enough that I could keep the ramp rates high when helped a lot when tapping. I didn't find an 8in manual chuck to slow down what few parts I made dozens of, I could still use soft jaws etc. The time savings not messing with boring jaws every time was a net benefit for the work I do.

 

[Philabuster]

In what way? Mazaks use no more power than other machines of similar HP (real HP) ratings.

Spindle acceleration setting greatly affects the amount of juice the machine uses.

 

[Cole2534]

I do not know if "derating" is the correct term, but basically a friend is looking at adding an old Mazak QT15 to his shop and is juggling power concerns. I mentioned slowing the accel/decel but I really have no idea HOW MUCH this would reduce the draw? I assume there is a limit or a point where your causing issues.

I'm a huge fan of mazaks and I recommended he look at them. I had no idea what fat hogs they are when it comes to power!

I've been running mine on a 30a 240v circuit for 2 years. Never thrown the breaker.

I'll repeat here what I said in another thread- I find it rather unlikely a home gamer will ever get close to maximum amp draw. That current requirement has to include worst case scenarios. To me, this is to rapidly spin up 12' of 2" steel bar, ie a max'd out bar feeder, while max'ing out the servos, conveyor is loaded and so are the coolant pumps.

Pretty unlikely at home.

However- I do want to know how to do this on a T32 because, as Phil mentioned, it's much easier on an aging drive. I've diddled with the parameters a little, but I didn't notice much of an effect. I wish it was like the T3's.

Sidebar- what's development order of the controls? T1, T2, T32, T3, T+?

 

[Garwood]

Spindle acceleration setting greatly affects the amount of juice the machine uses.

Vancbiker is pointing out Mazaks use no more power than any other lathe does hp for hp.

 

[Philabuster]

Sidebar- what's development order of the controls? T1, T2, T32, T3, T+?

T-1, T-2, T-3, T-4, T32, T+

T-1 is very first Mazatrol
T-2 is 2 axis and color CRT
T-3 is same as T-2 but added C-axis Milling
T-4 is two turret turning lathe

 

[Fal Grunt]

We are constrained by the size of the wire. We were tripping the breaker when step facing (spindle ramping up and down). We set the maximum RPM to 3000 and that solved it. We only make prototypes so squeezing every second out wasn't a concern.
Could you do that?

Thats also a possibility, we will look into that.

In what way? Mazaks use no more power than other machines of similar HP (real HP) ratings.

Your a much smarter/knowledgeable person than me. I just see that compared to similar sized machines (ie chuck capacity and hp) mazak electrical tags state 30-100% more than other brands/makes. We looked at I believe it was a 15hp Okuma w/ an 8" chuck and another maybe takisawa? also supposed to be 15hp and 8" chuck, and the Okuma and takisawa electrical tags were close to half.

I reduced the acceleration and deceleration times on my QT10, it didn't trip breakers but would flicker the lights in the house lol. Biggest improvement was to right-size the chuck I was using. Replacing the huge power chuck with much smaller manual adjust tru chuck reduced the inertia enough that I could keep the ramp rates high when helped a lot when tapping. I didn't find an 8in manual chuck to slow down what few parts I made dozens of, I could still use soft jaws etc. The time savings not messing with boring jaws every time was a net benefit for the work I do.

That is a good point to consider as well, thanks.

I've been running mine on a 30a 240v circuit for 2 years. Never thrown the breaker.

I'll repeat here what I said in another thread- I find it rather unlikely a home gamer will ever get close to maximum amp draw. That current requirement has to include worst case scenarios. To me, this is to rapidly spin up 12' of 2" steel bar, ie a max'd out bar feeder, while max'ing out the servos, conveyor is loaded and so are the coolant pumps.

Pretty unlikely at home.

However- I do want to know how to do this on a T32 because, as Phil mentioned, it's much easier on an aging drive. I've diddled with the parameters a little, but I didn't notice much of an effect. I wish it was like the T3's.

Sidebar- what's development order of the controls? T1, T2, T32, T3, T+?

Good to know, thanks for that. Running it on a 30a breaker would be perfect. What hp phase converter are you running?

 

[Cole2534]

Good to know, thanks for that. Running it on a 30a breaker would be perfect. What hp phase converter are you running?

I have 3ph at the shop, so no converter.

 

[Fal Grunt]

I have 3ph at the shop, so no converter.

Lucky!

 

[Vancbiker]

…….Your a much smarter/knowledgeable person than me. I just see that compared to similar sized machines (ie chuck capacity and hp) mazak electrical tags state 30-100% more than other brands/makes. We looked at I believe it was a 15hp Okuma w/ an 8" chuck and another maybe takisawa? also supposed to be 15hp and 8" chuck, and the Okuma and takisawa electrical tags were close to half…….

Mostly depends on how the builder calculates load. Some take the full load rating of all electrical equipment added together to generate the nameplate rating. This of course is way beyond what the true operational load will be because it assumes that all motors (spindle, servos, hydraulics, coolant, etc) are maxed out, all sensors are on, all relays and contactors are on etc, a condition than never happens. Often a realistic rating is used that assumes that a few motors will be maxed, some sensors are on, some relays and contactors are on. This is a closer number to what one should expect to see when the machine is running at or near capacity. Rated voltage will also affect nameplate current. If the nameplate is 200V, current will be higher than an identical machine with a 230V rating.

Most Japanese spindle drives are designed to allow 180% of their maximum output for accel current. The time period for that much current is very short and in most cases a lathe spindle drive cannot be configured to allow that high as the inertia load is too great to get up to speed within the time allowed for 180% of rated current. 120-150% is a more common number. Which of those values is used will also affect nameplate current rating.

At the end of the day it all boils down to Watts.

 

[mmurray70]

Definitely worth doing if your short on power. My QT10 was drawing 70-75a on the single phase line (before phase converter) while ramping up to speed. I slowed ramp time to approximately 4 seconds and now its down to around 45 amps.

Im using about 30a single phase from 35hp phase converter, Mazak QT10 and a Fadal 4020 idling. Current goes up and down based on the work but average current even with machines cutting is less then 40a average most times.

 

[Fal Grunt]

Mostly depends on how the builder calculates load. Some take the full load rating of all electrical equipment added together to generate the nameplate rating. This of course is way beyond what the true operational load will be because it assumes that all motors (spindle, servos, hydraulics, coolant, etc) are maxed out, all sensors are on, all relays and contactors are on etc, a condition than never happens. Often a realistic rating is used that assumes that a few motors will be maxed, some sensors are on, some relays and contactors are on. This is a closer number to what one should expect to see when the machine is running at or near capacity. Rated voltage will also affect nameplate current. If the nameplate is 200V, current will be higher than an identical machine with a 230V rating.

Most Japanese spindle drives are designed to allow 180% of their maximum output for accel current. The time period for that much current is very short and in most cases a lathe spindle drive cannot be configured to allow that high as the inertia load is too great to get up to speed within the time allowed for 180% of rated current. 120-150% is a more common number. Which of those values is used will also affect nameplate current rating.

At the end of the day it all boils down to Watts.

I guess this is where I am ignorant, to me a machine's plate that states FLA is telling me that is max load, which as mentioned will never happen. Most machines do not state FLA on the plate though. So guessing actual load is a bit confusing for me.

The machine we are looking at states (230v):
116 amps - largest motor
36.5 KVA - power requirement
50 KA - C.B. Rating

What would be your recommendation for a minimum safe circuit?

Definitely worth doing if your short on power. My QT10 was drawing 70-75a on the single phase line (before phase converter) while ramping up to speed. I slowed ramp time to approximately 4 seconds and now its down to around 45 amps.

Im using about 30a single phase from 35hp phase converter, Mazak QT10 and a Fadal 4020 idling. Current goes up and down based on the work but average current even with machines cutting is less then 40a average most times.

Good to know since he plans to add a Fadal as well.

 

[Garwood]

I would wire a QT15 with a 60A 240V 3 phase circuit. For a phase converter, I'd run atleast a 40HP RPC.

He needs to look at the power supply system he has and make sure it can deliver 100+ amps 240 single phase. If he has little aluminum wire feeding his panel from the 10KVA pole transformer a mile away it's just not going to happen. But if he's got a decent size transformer, incoming conductors capable of supplying 100 amps or so he's probably just fine to run a lathe like that.

 

[mmurray70]

You can get by with a fair bit if your careful. Even if you go over the breaker amperage for short period of time its not a big deal. Google "breaker trip curves". A 125a siemens main breaker can actually deliver 375a for minimum of 5 seconds.

You can easily run 2-3 cncs or more off a 125a service if your not pushing real hard or just doing small parts. But just be aware, if you really max out your spindle, at the rpm your machine produces peak power, one medium size machine can overload the whole works.

 

[cnctoolcat]

We run two '88 QT15's every day, with the T-2 control. 240V 3-phase (dropped to ~200V at the machine's built-in, multi-tap transformer), 30-amp breaker, with #6 wire running 50-60 feet to the machines. Works fine every day, has for years!

However...

As said, you must slow your spindle accel/decel rates to squeeze power requirements.

I'm conservative, so I also slow both servo-motor's accel/decel rates, slow the maximum rapids (to 400 ipm), and slow the max spindle rpm's (to 3,000). I also retrofit more efficient coolant pumps and cooling fans.

And we never redline anything on our CNC's, I like conservative, reliable processes and programming.

The QT's are blazing fast enough, so I don't fret over a couple of seconds cycle time.

From the factory even back then, they were so fast it's scary!

Oh, don't pay much attention to Mazak's nameplate ratings: they have always overrated their electrical requirements, (It's a conservative Japanese thing...)

ToolCat

 

[Cole2534]

...slow the maximum rapids (to 400 ipm), .....

Is this a parameter setting? Not sure I've seen that before.