Powering up a milling machine - sparky help needed

cmccuist · 03-12-2009, 09:58 AM

I just swapped out my Smithy 3-in-1 for a Bridgeport clone (Alliant 42S). It's a 9 X 42 with 4 axis DRO - X, Y, Z and knee!

I searched the archives for help in sizing the wire, but haven't been able to come to a conclusion.

Can someone out there lead me in the right direction. Here are the particulars:

2 HP motor wired for 220/240 vac 3 phase

Nameplate on motor says 6 amps at peak load

Power supply will be single phase, 220 VAC converted to 3 phase with a Variable Frequency Drive

200 amp main power box 100 feet from mill motor

I just need to know which breaker size to use and what gauge wire does the NEC code call for.

Thanks!!

GO DAWG GO · GO DAWG GO's Garage

Craig,

12 Gauge as a rule will handle 2400 watts I.e. 120V x 20 amps. You have 220V which is basically (2) 110V x 6 amps in single phase.

Do you have the 3 phase converter?

So if 110V (6) amps =660 watts peak load on each phase times (2). You would be fine with 12 gauge wire if it is already their. If you are going to wire the supply yourself, I would spend a bit more for more service in proximity to the mill. Eventually and grinders or lathes located near too? You may want to go to and 8-6 awg Gauge.

The phase generator is a noisy spinning frequency generator and can be wired at the mill.

You will be fine either way, but make sure you have an adequate ground to earth copper stake close by. When you run extended length of wire the potential resistance accumulates to a point where your body has less resistance that the conductor and you can potentially be the ground circuit in the event of a problem.

Hope that helps!

Bob

cmccuist · 03-12-2009, 12:20 PM

Bob, this is just what I was looking for. I opted for the variable frequency drive instead of the static or rotary phase converter as I am not planning on any more 3 phase motors.

I have a ground rod nearby that I can tie into easily.

Sounds like the 12 gauge 3 conductor with ground will work for this application.

Thanks!!

Tim Hancock · 03-12-2009, 01:16 PM

Craig, congrats on finding a mill!

I bought a 3ph 1.5 hp (name plate says 4.5 amps) Bridgeport about 1 1/2 years ago and was in the same boat.

I bought one of these static phase converters (At that time, I think I paid about $69.00 w/ free shipping)

http://cgi.ebay.com/Phase-Converter-1-HP-to-3-HP-STATIC-NEW-mill-saw-drill_W0QQitemZ260371950444QQihZ016QQcategoryZ4195 2QQssPageNameZWDVWQQrdZ1QQcmdZViewItem .

I added a 15amp breaker (could have been smaller, but it is what I had on hand) in the box I added several years ago for my welder. I then ran about 80' of 10 gauge wire (could have went smaller, but I thought I might add another machine in that room someday and I already had a roll of 10 ga) up thru conduit, thru the ceiling, then back down into my work shop room where the mill is. I mounted the phase converter on the wall behind the mill and wired it up. It has been working great for 1.5 years.

mudman · 03-12-2009, 08:14 PM

Holy schnikies, where do you guys find these things? and how much do they cost? I think I'm going to need a mill soon for a few of my projects - what's the story?

jim72911t · 03-12-2009, 08:49 PM

cmccuist,
That looks like a very nice find, especially considering the power feed, variable speed head, and DRO. If the gibbs are tight, and everything is working properly, you've found a machine that will last a lifetime.

The 9 x 42 in my garage doesn't get used much, unfortunately, but only because I have access to a full machine shop at work with much nicer tooling, and a VMC to play around with, too

.

mudman,
This is the time to find machining equipment. As a manufacturing engineer who's been producing Made in the USA products for close to twenty years, I hate to say it, but lots of shops are going under right now and selling stuff for pennies on the dollar. Check Craigslist and Ebay, and I'm betting you'll find a good deal on something local.

cmccuist · 03-13-2009, 05:44 AM

Tim, that is a nice set up!! how is the static converter working for you? I have heard that they are not as reliable as the VFD's or rotary phase converters. Something about the starting of the motor. But with a 1.5-2 hp motor, that only draws 6-8 amps, that may be a great configuration. I see the VFD's can be had new for $200-$300.

Mud, I paid $1,100 for the Alliant. It has chrome ways, power feed on the spindle and X and an older but working DRO. As Jim says, there are some great deals out there. I found this one on Craig's list. It was about 70 miles from my house. Also, you can go here:

Practical Machinist site

This is a site with a lot of hard-core machinists who really know their stuff - kinda like this place.

cgarr · cgarr's Garage

We had a local shop auction off some Bridgeports a few years back, I bid $300 and got it, I think I could have bid $100 and still got it, they just wanted them gone. The problem is not many people have a way to haul them.

Tim Hancock · 03-13-2009, 06:51 AM

Quote:

Originally Posted by cmccuist

Tim, that is a nice set up!! how is the static converter working for you? I have heard that they are not as reliable as the VFD's or rotary phase converters. Something about the starting of the motor. But with a 1.5-2 hp motor, that only draws 6-8 amps, that may be a great configuration. I see the VFD's can be had new for $200-$300.

Mud, I paid $1,100 for the Alliant. It has chrome ways, power feed on the spindle and X and an older but working DRO. As Jim says, there are some great deals out there. I found this one on Craig's list. It was about 70 miles from my house. Also, you can go here:

Practical Machinist site

This is a site with a lot of hard-core machinists who really know their stuff - kinda like this place.

My phase converter works perfectly. I bought two Bridgeports from work when the new owners were looking to get rid of some older rarely used equipment. I paid $500 each. The one I installed and am using is a 1.5 hp variable speed with digital readouts, power feed and came with collets, light, coolant mister and a chuck. The ways and screws are fair.

The other mill is still out in the storage area of my shop it is a very early CNC controlled 2 hp unit with ball screws. Other than the crappy paint job, the base machine itself is barely used. Some day "when I get some free time", I plan to modernize the CNC controls to run off of a PC with modern CNC software.

All in all, I made out good as both units came with extras that the average old clapped out Bridgeport does not come with for similar or slightly more money.

A pic from a prior post. Two new toys...Bridgeport mills...cleaning advice?