New Bridgeport issues? vfd?

[weldthis]

Hello everyone I am new to the world of machining and I just purchased a bridgeport mill. It is a 1963 model J head with step pulleys. It has x axis power feed and a shooting star research DRO. I just bought the machine two days ago when I arrived at the shop where it was located it was sitting in the back corner not in use. The shop owner told me that he bought a bunch of equipment together and had no use for the bridgeport.... Anyway we ran an extension cord to the machine and it fired right up ran the spindle for a few minutes both directions then ran the x axis powerfeed. After 20 to 30 seconds running the power feed only everything stopped. After a few minutes we were able to reset everything and we fired it up one more time very shortly. After some haggling and getting it home 150 miles away we plug it in to our 220 single phase outlet and it does the same thing. It has a phase-a-matic phase converter rated at 1.5 hp and 5.2 amps model pam-200. Seems like a overpriced box with a few wires maybe a small cap and relay to me. I am no Electrician nor is my dad who is helping me get this thing up and running. He seems to think that the overload is weak and maybe that is our problem.

After further investigation the 3 phase motor that drives the power feed for the x axis is only being powered with 2 legs. It has 3 wires running to it 1 ground 2 hot 1 hot is pulling 1.5 amps the other is pulling 3.2ish. How is it possible that a 3 phase motor even runs this way? It seems that they tied the second and third leg together??

I would like to get rid of the phase converter and install a variable frequency drive but i have questions... WOuld one vfd be able to drive both the 1 hp spindle motor and the 1/8 hp x axis feed motor?????

I have tons of questions but I will try to surf around our awesome site here and do some digging before I dare ask anything else... Thanks any information is greatly appreciated

[Al_The_Man]

I would like to get rid of the phase converter and install a variable frequency drive but i have questions... WOuld one vfd be able to drive both the 1 hp spindle motor and the 1/8 hp x axis feed motor?????

If you mean install a VFD and set it for 60hz for both? then I would think it preferable to wire the VFD to spindle only if it has a 3 phase motor and use a separate single phase for the axis feed, this way you get variable speed on the spindle.
Get rid of the phase convertor altogether.
I am not sure what they were doing with the present motor wiring, sounds like a bodge job?
Al.

[weldthis]

Thanks Al I agree on the podge job wiring.... I did find that the x axis motor has a large dent on the side of it and is only rated around .75 amps. So with it drawing that much current maybe the windings are chrushed and shorting out. If the motor is indeed bad am I better off buying a replacement 3 phase motor or a new single phase to take its place.

I am also trying to figure out what grease and oils I need to buy and where they go I have read a ton of different things what are you guys using???

[79TigerPilot]

How do you know the power feed is a 3 phase motor. The unit could be wired to accept three phase but converts it to to DC to drive a variable speed DC motor. In this the input rectifier could be three phase or single phase to DC and it would not matter. Look for some brush holders on the side of the motor.

Craig

[weldthis]

Sorry about the confusion after a little more investigation we found another wire, meaning the x axis motor is wired in 3 phase. We pulled the motor off it is indeed a 3 phase motor, we unhooked it from the gearbox and turned it on and it did the same thing tripped the reset. We then took it to our other shop were we have a 10hp rotary phase converter and hooked the motor up and it ran great and was only drawing half an amp after just drawing near 5 amps off of the phase-a-matic pam-200 inverter that is on the mill..

I went ahead and ordered an ACtech smvector variable frequency drive to run the spindle. BUt im still gonna have to deal with getting the x axis drive motor up and running....

Can replacement parts be bought for the phase-a-matic phase converters and does anyone have any info on how to diagnose???

Thanks again

[Al_The_Man]

If the axis motor is 3 phase I assume there is no speed control right now?
You could look for a an alternative on the axis to vary the speed and replace the 3ph motor with a DC and SCR drive off the 120v or 240v 1 ph supply such as KB or Baldor drives, alot come up on eBay and that motor is not that large.
Al.

[weldthis]

Thanks for the advise al... Still waiting on my vfd so I can figure out my electrical issues. In the meantime I found a funny noise when the machine was running in high gear kind of a squeak or rubbing noise once per revolution. I found hot spot on the case of the upper housing and the teardown commenced. I found the upper bearing that supports the drive pulley was a little rough and the lower bearing seemed worn. I replaced both with locally bought matched bearings that were matched by size only and not duty.

THe salesperson informed me that the new bearings may not be as heavy as the originals but they were indeed the same size. Hope they last a while... I also left the seals on the new bearings thinking that maybe a shaving or two got into the old inboard bearing. THere seemed to be a lot of shavings on top of the machine and a few in the upper housing, how they got there????

Any suggestions on tooling ive been reading up on carbide vs hss cutters and am kind of on the fence. Ive heard carbide wont last as long on a bridgeport due to the slower spindle speeds is this a fact?

I am also told that I can overspeed the spindle motor when i get the variable frequency drive in place.. How much am I going to be able overspeed it what is the fastest that you guys would run the spindle??

THanks again

[jmelson]

After 20 to 30 seconds running the power feed only everything stopped.
After further investigation the 3 phase motor that drives the power feed for the x axis is only being powered with 2 legs.

I would like to get rid of the phase converter and install a variable frequency drive but i have questions... WOuld one vfd be able to drive both the 1 hp spindle motor and the 1/8 hp x axis feed motor?????

Is this the old-style power feed with an 8-speed gearbox and hi-low range selector? I think it must be. I have one of these, they do NOT like running on single phase at all. If you want to run it off the "phase converter" never run the power feed without the spindle motor. The spindle motor becomes somewhat of a 3rd phase generator when it is running.

A VFD would be a good choice, but there are limitations. You don't want to be starting motors with switches between the VFD and the motors. When the Bridgeport 1J head is in low range, the motor needs to be run backwards to make the spindle turn forwards. If you use the VFD to run either direction, that would reverse the direction of the power feed, too. That is the only concern with running both motors off the same VFD. You might be able to pick up a 1/4 or 1/8 Hp VFD on eBay for a song, there isn't that much demand for the under 1 HP units.

Jon

[weldthis]

THanks Jon you hit the nail on the head with the 1/8 motor and gearbox setup. We did come up with the same theory that the spindle motor acted like a rotary phase converter to power the power feed motor.... Though we were not sure, thanks for confirming.

I recieved my vfd today and plan to install it tomorrow or this weekend sometime. We are planning on using the phase converter to run the power feed motor and the vfd for the spindle motor only for now.. I will be searching for a single phase motor for the power feed. Anybody have any suggestions for turning this thing into a cnc. I am currently building a torchmate tm1 plasma table so I am not totally lost when it comes to the electrical part of it. What is the most cost efficient way to convert this mill into a cnc? Or is it a waste of time to automate the step pulley bridgeport..??

THanks again...

[Mike Ray]

Can you give an update on your VFD install?

[weldthis]

I have yet to install the vfd the mill is working great as is. The only thing I am having trouble with now is the spindle brake. The brake is really tight and the machine wont start unless I tap on the brake handle and run the belt back and fourth by hand until it loosens up. I plan on tearing in to it soon any suggustions?