Running Lathe With VFD?

Buying a new lathe, has a 3hp 3-phase motor. Can I run this machine using a VFD with no problems or would it be better to have a rotary phase convertor, and if so, what would the recommended HP capacity be?

Thank you.

Nitromahn said:

Buying a new lathe, has a 3hp 3-phase motor. Can I run this machine using a VFD with no problems or would it be better to have a rotary phase convertor, and if so, what would the recommended HP capacity be?

Thank you.

Click to expand...

Would help to know what kind of lathe and how it is wired for its control circuitry.

I have a Kent TRL-1340 3ph lathe which I added a VFD for single phase operation. I wired the VFD into the control relays so start/stop/reverse all works via the VFD, and the drive speed is also wired to the control panel. This was cheaper than buying the machine with a VFD but was also a decent amount of work to do properly.

What you really don’t want to do is use the VFD to generate 3ph and then have switches in the lathe turning on and off the motor. The VFD won’t like that... nor do you want to be powering on and off the VFD every time you start the spindle.

A VFD is a GREAT way to power a lathe. It is incredibly handy to have the small variability provide by frequency change to optimize chip formation and surface finish.

Plus, no voltage sag or brown out when starting the lathe motor.

Really, Follow the suggestion offered. Wire up the VFD controls through the lathe controls.
It takes a day, but it is SO worth it. I have a 16 inch Mazak and a 12 inch Weiler on VFDs and wouldn't have it any other way.

Get a bigger VFD than minimum requirements. Amps being amps and all.

This is a Precision Matthews 1440GT.

Thank you for the replies. I am not an electrician, but I know of a certified electrician that does all kinds of work, commercial, residential, and light industrial, I will print off this post to let him read it once I get the lathe, he should (hopefully) understand how to do what you've recommended.

Weiler huh? Would love to have one, but sooo very expensive.

Nitromahn said:

This is a Precision Matthews 1440GT.

Thank you for the replies. I am not an electrician, but I know of a certified electrician that does all kinds of work, commercial, residential, and light industrial, I will print off this post to let him read it once I get the lathe, he should (hopefully) understand how to do what you've recommended.

Weiler huh? Would love to have one, but sooo very expensive.

Click to expand...

I didn't buy the Weiler LZ330 new. It was a great find, and quite near by.

Kewl.
I should qualify my posts: my only option for input phase and voltage is 220 input and single phase. Want 220 output 3-phase. Having some challenge finding a VFD but should be able too.
Thanks.

Nitromahn said:

Kewl.
I should qualify my posts: my only option for input phase and voltage is 220 input and single phase. Want 220 output 3-phase. Having some challenge finding a VFD but should be able too.
Thanks.

Click to expand...

I purchased VFDs via ebay years ago. Big name, for small money. (Those days may be gone) Even a 20 hp unit takes up less space than a 5 hp RPC. Wall vs floor.

Oversizing the VFD allows phase conversion. I needed that as well.
IIRC all my VFD antics are chronicled here on this forum. It's been some years, And I have posted on too many topics, but it's out there if you care to do the leg work.

N.B. There are so many very valuable posts by many very knowledgeable posters on this topic of VFD powering machine tools. You would be well advised to spend the time reading.

We are carried on the shoulders of Giants who have gone before.

I recently bought a 5.5KW 220V (single phase in) variable frequency drive for my surface grinder motor. Ebay, for about US$220.00 and free shipping. Works very well. I have one on just about every machine spindle motor, maybe six or seven in total and the first one for some 30 years now (was a fortune at the time). In all this time all perform very well, including the three Chinese bought in the last few years. The only failure with a VFD happened to me some 20 years ago and this was caused by metal dust in the grinding area. In those areas I do have now the VFD in a separate cabinet with forced air and a filter on the intake. A good practice in general in a dusty environment.
When buying a unit (especially the Chinese) one should get higher rating than the motor. I go for about 2X.

Do you really need a VFD? The Precision Matthews 1440GT is a gear head lathe and is available with a single phase motor.

ptsmith said:

Do you really need a VFD? The Precision Matthews 1440GT is a gear head lathe and is available with a single phase motor.

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True, but on backorder now. And I don't know how long that may be. I can ask, but am hedging my bets.

Hi,

I haven't looked at the PM lathe you're talking about, but I looked at the manual just now. The electrical wiring and control of the machine is very similar to my Kent (which is itself a Clausing Colchester type machine).

A comprehensive VFD conversion is involved on this machine. Totally doable, but involved:

The VFD I used on my machine was a Yaskawa 5HP single phase one. It had a control voltage of 24V DC for the contacts that would be used to start/stop/reverse the motor. Unfortunately the control setup in the Kent and PM lathes is 24V AC, and they don't play together.

So you either need to ripout the existing contactors/relays and instead pull those into the VFD, or do what I did, which was keep the relays and send the VFD's 24V DC control wiring through the aux contacts on the contactors, so the VFD sees when the forward or reverse contactors are "on" and appropriately powers the drive.

I also wanted a contactor to turn on and off the VFD, so I added one for that purpose. It is important to shield the VFD from dust/chips, so I normally add a steel enclosure to the lathe somewhere and put the VFD and input fuses in there, as there usually isn't room for the VFD in the existing wiring cabinet.

And, the coolant motor will be 3ph and you must swap that to single phase, you shouldn't run that off the VFD. This means $100 to get a different pump and then selling the 3ph one.

Finally, to get the fine speed control if you want it, you need some sort of control exposed. I replaced the Jog button (which I don't see the need for) with a speed pot in 22mm pushbutton form and brought it out to the front panel.

In the end, to do it this way you'll spend a day or so at least.

I would suggest unless you've done this before or have someone who can help (who you aren't paying by the hour) you're better off either buying the single phase motor option, or buying a VFD option with the lathe if they provide it. The Kent I got is also available with a VFD... in hindsight I probably should have just gotten that.

BTW finding a 3HP 3ph VFD that runs on 240v single phase ought to be easy. I tend to prefer brands that I've used and know their control wiring can do what I want. Hitachi and Yaskawa are top brands, and both have VFDs explicitly sized for single phase input... Yaskawa being one of the relatively few that is explicitly sized for 5ph single phase input. In other cases you'd have to get a 3ph input VFD oversized (follow derating advice from the VFD manufacture).

-Phil

Thank you for the replies. What the heck, I'll just get the single-phase when it comes in. I just don't know enough about electrical to do this and don't want to have the hassle on my hands this will entail. It was a good idea wile it lasted.

This is exactly why I posted this here. Saved me some very serious headache.
Thanks again.

I much prefer 3 phase for the lathe, you get better surface finish, less issues with the start/stop cycles killing the start capacitor, variable speed to dial in the sweet spot, electronic braking, etc. I have done about 6 complete VFD controls system replacements for the PM-1440GT and dozens on 1340GT's and quite a few for larger machines. I also put together a basic VFD install manual for using the contactors to switch the VFD inputs for the 1340GT and 1440GT lathes, but assumes you have basic electric skills. If it is something you want further info, send me a PM with your email and I will send you the info.

A VFD is a bit more complex to install, and definitely not a connect the wires to the lathe input and have it work. An RPC works better in that situation, you would need a minimum of a 5-7.5 Hp RPC for a 3 Hp lathe. Down side is they are running all the time vs. the lathe which is intermittent. VFD installs on smaller lathes 3 Hp and smaller are more cost effective, past that the cost go up, but also the cost of an RPC.

Nitromahn said:

This is a Precision Matthews 1440GT.

Thank you for the replies. I am not an electrician, but I know of a certified electrician that does all kinds of work, commercial, residential, and light industrial, I will print off this post to let him read it once I get the lathe, he should (hopefully) understand how to do what you've recommended.

Weiler huh? Would love to have one, but sooo very expensive.

Click to expand...

Nitromahn
Look here for all you want to know about converting your PM lathe to VFD control.
The Pm-1440gt Has Landed | The Hobby-Machinist
Member mksj can give you detailed help to get the VFD wired or he will build you a system.

I would not even consider getting it with the single phase motor.

Awright.

Here is what I am going to do: I will read that other thread from the other forum. I will then print off the posts from this thread and print the electrical section of the PM manual, call my electrician and see if he can do this. If he can, I'll contact MKSJ and purchase his work so my guy will know exactly what to do.

I'll need a day or so to read through this and contact my electrician. If I were anywhere but a remote area of Alaska, I'd hire a machine electrician to do this, and I may ask Mat if he knows someone who can do it. If not, then we'll do it this way.

Thanks again.

It is not hard to build an RPC, I will assume you will want more machinery in the future...even if you bought one,8K on a lathe what's another 1K for a RPC?

A VFD can be added at any time....RPC would far and away be my choice.

With the accessories and tooling $11,500 give or take a few hundred. Add $1500 for shipping and you see it is getting serious. Add the hassle of more electronics I don't understand, I am leaning heavily for the RPC.
Add to this: I haven't even asked anyone how they'd take into account the floor of my shop being wooden, and in this part of Alaska the ground moves around a lot. But that is for another thread.

CalG said:

A VFD is a GREAT way to power a lathe. It is incredibly handy to have the small variability provide by frequency change to optimize chip formation and surface finish.

Plus, no voltage sag or brown out when starting the lathe motor.

Really, Follow the suggestion offered. Wire up the VFD controls through the lathe controls.
It takes a day, but it is SO worth it. I have a 16 inch Mazak and a 12 inch Weiler on VFDs and wouldn't have it any other way.

Get a bigger VFD than minimum requirements. Amps being amps and all.

Click to expand...

read your post from 2019
My neighbour just made me shut my genset down, which I use to get 3ph for the lathe
I do not use all hp on the lathe doing light stuff, I took the big 4 jaw off because it takes a lot to wind it up
how many hp is your Mazak, could you give me advice on vfd, I have one running my press and one on my bandsaw, working fine
thanks Stuart

mksj said:

I much prefer 3 phase for the lathe, you get better surface finish, less issues with the start/stop cycles killing the start capacitor, variable speed to dial in the sweet spot, electronic braking, etc. I have done about 6 complete VFD controls system replacements for the PM-1440GT and dozens on 1340GT's and quite a few for larger machines. I also put together a basic VFD install manual for using the contactors to switch the VFD inputs for the 1340GT and 1440GT lathes, but assumes you have basic electric skills. If it is something you want further info, send me a PM with your email and I will send you the info.

A VFD is a bit more complex to install, and definitely not a connect the wires to the lathe input and have it work. An RPC works better in that situation, you would need a minimum of a 5-7.5 Hp RPC for a 3 Hp lathe. Down side is they are running all the time vs. the lathe which is intermittent. VFD installs on smaller lathes 3 Hp and smaller are more cost effective, past that the cost go up, but also the cost of an RPC.

Click to expand...

Hello!
I have lately purchased an old COLCHESTER MASCOT 1600, 80 inch Gap Bed Lathe in an auction in good working condition. It's a 1976 make machine, which I am cleaning completely at the moment (without dismantling the gear box/drives).
Though I am not an electrical engineer ( I am a mechanical engineer with good understanding of elementary electrical engg- graduated 30 years ago!)

I want to make the following modifications to the lathe:
1 Install an oil filter between the hydraulic oil tank and input to the gear box
2 Install a VFD screw pump for coolant to control pressure of the coolant through the internal cooling tool holder I envisage to use- Sandvik parting tool holder, with a banjo connection from the back of the holder to the coolant pump. Coolant pressure can be regulated from 5 bar to 70 bar. Need to install suitable coolant pipe.
3 Install a coolant skimmer to trap floating dust, turned sludge, run separately. At present the coolant pump of 0.5 HP is provided, 1 phase.
4 TO INSTALL A VFD on this lathe. The lathe comes with a 12.5 HP 3 phase induction motor. Here I need support
Could you suggest what needs to be done.
There are plethora of videos on You tube that show converting three phase to single phase, in home shops and hobbyist. But I am running an engineering company, a foundry with machine shop.

Could you suggest way forward? Now Colchester models have variable speed drives. They result in cost savings based on the load put on the machine. Colchester Mascot has 16 speeds from as low as spindle RPM to 1600 RPM using full rated power of the motor. I think the whole electric needs to be changed...including a VFD compatible motor, and a VFD module to suit 12.5 HP/ 16 speed fully geared lathe.