Testimonials from guys that have run large CNC machines on large generators?

Curious if anyone here has specific experience running hungry CNC machines on a diesel or gas generator? Not interested in info about running a Bridgeport on a Home Depot special, I am talking a real, 3 phase, prime type generator. I am mostly wondering if the frequency and voltage can maintain stability through the ongoing spindle starts an such. A larger lathe may present even more of a challenge.

I have some concern with line regen on some spindles, as well as the inrush requirements. Obviously big CNC motors will be VFD driven, which would reduce the burden substantially.


Possibly a case where a shop has lost grid power for an extended period due to an outage or something.

huleo said:

Curious if anyone here has specific experience running hungry CNC machines on a diesel or gas generator? Not interested in info about running a Bridgeport on a Home Depot special, I am talking a real, 3 phase, prime type generator. I am mostly wondering if the frequency and voltage can maintain stability through the ongoing spindle starts an such. A larger lathe may present even more of a challenge.

I have some concern with line regen on some spindles, as well as the inrush requirements. Obviously big CNC motors will be VFD driven, which would reduce the burden substantially.


Possibly a case where a shop has lost grid power for an extended period due to an outage or something.

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I haven't done what you are talking about here ,

But Best friend of mine in the Uk when I lived in the Fens was master Sargent at RAF Mildenhall (at the time) / US air base in charge of electrical systems for all the run ways there.


The had big -block type massive generators and power conditioners always at standby for power outages which were frequent there … Fen blows / winds all the time /power lines going down (in the area).







Hunting 25 kva diesel generator for sale | MOD direct sales

Ex- military supply type thing / DOD ^^^

These types of units handle pretty massive draws and spikes etc. That's 3 phase 25 KVA … But not sure on the power conditioning / balancing ballast side as that's an "Art" in off itself. Also not sure how ground / Earthed versus shop ground will jive but if it's only one piece of equipment ????

Stuff they used was much bigger. [That's a small generator compared to most.].

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*** DISCALIAMER I am not responsible for any advice (good or bad) given here !

Cameraman, I am wondering what the power conditioners were for? Maybe these gennies were older, without the electronic controls of today?

I did look at specs on one that rate the THD at 5%. that seems high to me. Maybe that is the conditioner need? I like to see 1% but I guess I have not checked actual grid levels and as long as it is comparable, it should not be an issue. I expect all industrial equipment to have some level of conditioning them, wagering on shop induced noise. I see line reactors in machines commonly.

No experience running a CNC on one of them but if you are looking for a low hour large generator try hospitals. They have to replace them fairly often and they are generally very low hour machines.
A friend has bought a couple of them and spiffed them up a bit and resold them for several thousand dollars. They have been way to big for me as they would have been more than I needed for my shop with every machine running plus the house and ranch irrigation system.

Line reactors are used when VFD drives have cable runs of more than 50 feet to the motor to reduce the voltage spikes The Teco VFD manual describes how they are sized and when they are needed. A motor generator set sitting outside with long cable runs would also need protection from lightning induced voltage spikes.

There are a number of web sites that have generator sizing information. The selection is straight forward for a fixed load such as a water pump. It is more complicated if you are designing for a variable load such as might be the case in machine work. There is a problem with running a diesel generator for extended periods at less than 40% load.

I use a 20 HP Kato synchronous motor generator set for my machines. It does not notice when the spindle drive does a regenerative braking.

I was involved with running an engine plant for almost a year on only diesel generators and diesel air compressors.

The big thing is to have sufficient capacity to properly handle demand and enough rotational mass to absorb the regen power. In this case there was a substantial coolant pump load that was not VFD controlled to absorb the regen power.

I was surprised how well it all worked with minimal issues. No brownouts nor overvoltage excursions.

yes, back in the early 2k's when enron was playing games with the grid to pump profits and pg&e started rolling blackouts. We had 10-12 vmc (mid 80's takasawa and mid 90's cincinatti's) plus a few bridgeports runnning on a
big diesel generator. Not sure if it was worth it. I think we used it 2-3 times at about 8 hours a stretch.

Likely a military genset would do fine.
Generator 15 kw MEP804A by General Jim's from General Jim's

I have a 4 cylinder natural gas unit that was used to run a small hospital. Thinking about making it propane or petro gas..Engine is 4 cylinder air cooled.

I have somewhat done what you ask...

I am and have been on RPC for 30 years. (RPC's have grown in size)
I had ran a few CNC's on RPC's over the years, but back in '97 I bought a new lathe, and after dropping $180K on it, I wanted to protect it. (not sure from what?)

So, I asked around about the possibility of running a gen set off of a 3 phase motor?
Turns out that there was exactly what I wanted available used/surplus in Toledo!
30hp 3 phase motor running a Kato 16 (?) KVA gen.

I look at this like laundering money. I'm puting 3ph in, and gitt'n 3ph out, and at a loss, but hopefully at better sine wave. (?)

I was only running a 20hp lathe on this, but it worked just fine, although it was loud. (right next to the machine).
It was REALLY nice in brown out conditions! Lights flicker, other machines all drop out, not this lathe! The flywheel effect bridged those gaps!

Several years later I got another bigger sister for this lathe, and I did not get another gen set. I put it on my [inhouse] grid. Never had any issues with it.
So then I decided to take the gen set out of the line-up. <15 years later and can't say that there's been any issues....

BUT - I have an old Tornos with a (same age) FMB barfeeder. The lathe doesn't like hot hydro, and the feeder doesn't like it cool. What a primadonna set-up!
So I decided to give this gen set a go with this heifer....
It worked fine .... until it didn't.
One day a board in the gen lost something in the V reg line, and it spiked to 300V (600 after going through the X).
Could have been worse, but it took out one full OUTPUT card in the PLC.

I took that off and eventually replaced with a P/P.
... it's still finicky .... but we git through....


I never had any issues with regen braking on the 18T Fanuc, and the old Mits was resistor brake, so ....


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Think Snow Eh!
Ox

michiganbuck said:

Likely a military genset would do fine.
Generator 15 kw MEP804A by General Jim's from General Jim's.....

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15kW is about 20HP. OP doesn't say how big a machine or how many, but he did say "large cnc machines". 20HP is not going to go far trying to run "large cnc machines".

His "Large" was in comparrison to a B-port.


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Think Snow Eh!
Ox

Ox, y reference to a Bport was what I did "not" consider large. I guess for clarity, we are talking 60kw and up. Think 3-4 40HP HMCs. However, the 40HP only refers to the spindle and by the time you get coolant pumps, servos, hydro pumps, cooling fans, control, etc, that could be 60HP-ish.

In any case, Ox, your example above is EXACTLY one that would scare me to death! To see a regulator failure that allowed high voltage to reach equipment. It makes me wonder if there is a secondary device that can be found to disconnect the line at a certain threshold?

But overall, it sounds like this can work well.

Well, I would guess that you could find a V monitor of some sort and tie it to a [big] motor starter that all the hydro went through.
I wouldn't know the specifics or the costs, but Shirley it would not be hard or complicated, just large.
Hopefully you could find sumpthing on the surplus market.
I would look on surplusrecord.com for a big starter. (may be called something else in this case?)

I'm sure that others here can guide you on the monitor unit.


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Think Snow Eh!
Ox

Neighbor did it with a 100kw and a 80 kw genset.

Big PIA, and then bought a shop closer to town, one with a large 3-phase service.

It was interesting to hear the governor handle the rapids when the tables moved.

A:
You can run any cnc off generators.

Testimonial:
In 2012 I was the Haas commercial sales manager for Spain.

We had 7 machines of 40 HP, and had to run our new-built demo room in Barcelona + office 500 sq m off a generator for 3 months.
Could not get Fecsa to connect us to the grid (after 60k$ in payments and stuff).
Machines were mostly big and medium.
Filled the 1000 l diesel tank once.
Genset was 50 kW.

Upto 3 machines could run at once, and upto 2 agressively.
(We could have run more, if we ran machines gently, but that was never our practice).
The office aircon = heating (5 C, very cold) ate up 12-15 kW of power, so 35 kW was available for machines.

We did drop max acceleration speeds on some machines.
Spindle acceleration eats up huge power, for 1-2(3) secs, especially on bigger machines and things like heavy lathe chucks.
Dropping the spindle acceleration to 3 secs from 2 secs drops power needs by about 50%.

3-phase machines are happy to run off any decent 3-phase gensets. Imo. Ime.
The diesel generators +10 kW and cnc machine spindles are both inherently stabilising and tend to smooth power loads and usage.

Modern ac servos smooth the power usage by very clever electronics and some caps.
Servo power peaks are extreme, but only inside the drive, the grid never sees it.

Most cnc machines use 5-10 hp of power or less on 40 hp machines, aka iso40, most of the time.
Only maybe 10% of users used 30hp+ commonly.

Ox said:

Well, I would guess that you could find a V monitor of some sort and tie it to a [big] motor starter that all the hydro went through.
I wouldn't know the specifics or the costs, but Shirley it would not be hard or complicated, just large.
Hopefully you could find sumpthing on the surplus market.
I would look on surplusrecord.com for a big starter. (may be called something else in this case?)

I'm sure that others here can guide you on the monitor unit.


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Think Snow Eh!
Ox

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Prolly refered to under "Switchgear" ???


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Think Snow Eh!
Ox

Ox said:

Prolly refered to under "Switchgear" ???


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Think Snow Eh!
Ox

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huleo said:

......
Possibly a case where a shop has lost grid power for an extended period due to an outage or something.

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I've seen it done in twice in auto plants so lots of decent sized machines.
Few actual machine problems.
A whole lot of trucks and gensets in the parking lot. The fumes and noise were huge.
Bob

Around 2005 I was tasked with getting a CNC shop set up in a rich dudes back yard.
He had three new HAAS VF2ss machines, and a HAAS SL20 lathe with C and live tools.
We ran them all off a CAT jobsite genset. I do not know what the specs on the unit were?
But I am pretty sure the model# was a QX75.
We ran his shop on that generator 8-10hrs/day, 5 days/wk, for at least a year, with zero issues.
It wasn't even that loud. Used about 90gals fuel/wk.

Edit: funny thing I remember about that CAT generator. It had a John Deere engine! LOL (4-cyl turbo diesel)