What he said.
Also - Having a VFD opens up possibilities for you that others avoid. Lots of folks won't give a piece of 3-phase equipment a second look because it's 3-phase. This attitude has caused lots of really nice equipment to sell for somewhere between scrap and get-it-out-of-here prices. Bad for the 3-phase phobic; good for you.
In a one-man shop, size your VFD for the largest piece of equipment you plan to run on it.
Jim Ash
-----Original Message-----
From: CNC 6-axis Designs
Sent: Sep 10, 2010 7:24 AM
To: gingery_machines@yahoogroups.com
Subject: Re: [gingery_machines] Repowering lathe
The smaller motor will work, but DONT DO IT!
For less money, you can get a VFD that makes the 3-phase from whatever
you have (110, 220, 50 hz, 60 hz etc.).
The model is the Hitachi 2xx, 2.2 kW size. About 400$. (I have one on my
Bridgeportr M-head spindle on my shop-built milling machine).
The 3-phase motor is VASTLY superior to a ANY single phase solution
apart from indexed servo spindle (which I also have).
If you buy the smaller motor you then ideally need a speed control for
it, which is extremely useful on a lathe. At least a contactor (you need
one for lathe use) and that will be 50-100$ on its own.
To get the VFD, go to automation direct, drives warehouse, etc.
Look for one that eats 220 (if you have it) and outputs the 575v.
The docs are good, and will get you going.
There are a lot of very useful things in a VFD that only exist in VFDs
(and servos) you simply cannot get any other way. Included in the same
price.
Dynamic braking, holdng, soft start, ramps, PID loops, safety features,
forward and reverse, WITH automatic safety features, overload overheat
protection etc etc.
All of the above are included in the Hitachi I used, and all work on my
CNC milling machine, with about 5 control wires and 2 days setup time in
the VFD.
Safety is important. VFDs come with all the safety features as standard,
things like not getting the spindle to run at last (full) speed in an
error, overload, overheat, power-out situation.
VFD driven 3-phase motors also give a much better surface finish, when
you have a good heavy lathe behind them (I do).
My lathe is currently running with an original factory 1.5 kW industrial
motor, and I am swapping it for a servo (indexed) spindle.
I am now fixing the swarf guards on the mill, to face mill the mounts
(30 mm steel flat bar F114), to permanently install the servo motor
mount on the lathe.
> I have been lurking for several years and have cast the gingery bed in
> aluminium but then stalled. Have cast a few other objects as I
> needed them but have always wanted to play with a lathe since taking a
> metal working class at school back in the 1970's.
> I just lucked out and ended up with a Harrison 300 metal lathe which
> has a 3-phase 575volt 3Hp motor driving the spindle. I need to convert
> to a single phase motor. A 3hp motor with the same frame size will
> cost about $600.00 but I found a 2hp motor for about half that. The
> question is-Will a 2 Hp motor give an adequate level of performance
> for home/ hobby use considering that the lathe has a spindle gear
> range of about 48rpm up to 2400rpm? The lathe is a 61/2inch (13 inch)
> by 24 inch size.
> I have absolutely no experience running a lathe but I suspect the
> smaller motor will work but will limit the size of cut I can take. Is
> that correct?
> Thanks for any input.
> Cliff Swan
>
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