Getting an new Bridgeport

[Thebrick53]

I am looking into buying a series one Bridgeport. It is an excellent machine but it is three phase (i believe the main motor is a 2 horse. The machine has a secondary 3/4 horse motor for the x-axis feed witch is also three phase. Any recommendations on what three phase converter would be good for the job?

Also I would like to know where I can date the machine. I have the model numbers but don’t know were to look to get a manual and date the machine.

 

[Thebrick53]

Note I do have 220 or 240 power outlets in my shop

 

[BT Fabrication]

any RPC greater then 5HP will do just fine.

 

[henrya]

A variable frequency drive would be great on your new machine. It would be my first choice.

 

[projectnut]

I started with a static converter on a 1 1/2 hp Bridgeport some 20 years ago. The intent was to change to a rotary converter as more 3 phase machines were introduced. There are now half a dozen 3 phase machines in the shop, and all except one are running on dedicated static converters. The 15 hp North American Rotary phase converter is still setting in a box in the corner.
All the machines are running fine on their static converters. The only potential downside is that they can only output about 2/3 of their rated power. In all that time I've never lacked for power on any machine or had one overheat. The mill and one lathe are used as much as 40 hrs. in a given week and work just fine.

If you're considering a VFD keep in mind the original functions performed on the operator's console will now need to be performed by the VFD. I opted against VFD's for that very reason. The operator's console is within easy reach and intuitive.

One lathe uses a second gear motor and Worthington drive for spindle speed changes. I would have needed 2 VFD's for this machine. Rather than complicate things I went with a static converter and still use the original controls.

If I was starting from scratch, I would install the rotary converter. Personally, I like the original control panel locations and their intuitive use.

 

[Cole2534]

A variable frequency drive would be great on your new machine. It would be my first choice.

I don't understand how this isn't the automatic answer to this question.

 

[eKretz]

Rotaries are good too, but I'm definitely in the VFD camp. They don't use but a trickle of energy when the motor isn't running and the soft start and variable speed are very nice to have. The downside is that some electronics don't play well with the high frequency and you've often gotta do some rewiring if you want to use the original controls.

 

[eKretz]

Glad you mentioned that eKretz. That's another reason I am not fond of VFD's. They can interfere with radio signals similar to how cordless battery chargers do. I personally wouldn't even consider one unless I had a step pulley Bridgeport.

That may be technically possible, but I've never had it happen. I have a stereo not 5 feet away from the VFD running my mill, and it doesn't interfere at all.

I was more referring to the electronics in the machine controls, like starters/contactors, relays and such.

 

[henrya]

My VFD just bypasses the old switch gear and has a separate keypad that I mounted at the side of the front panel. It gives me on/off, forward/reverse, and infinitely variable speeds from zero to 90 hz (1,5 overspeed). Then I use the step pullies as needed for max torque. Soft start and braking are so nice. I would never consider going without it.

 

[Cole2534]

That may be technically possible, but I've never had it happen. I have a stereo not 5 feet away from the VFD running my mill, and it doesn't interfere at all.

I was more referring to the electronics in the machine controls, like starters/contactors, relays and such.

I've had 3 in service for a cumulative 31 years, never had that issue.

As for controls- it's a Bridgeport, there aren't any, you just wire up to the drum switch.

 

[Superbowl]

Glad you mentioned that eKretz. That's another reason I am not fond of VFD's. They can interfere with radio signals similar to how cordless battery chargers do. I personally wouldn't even consider one unless I had a step pulley Bridgeport.

That is a big issue that the OP did not mention, variable speed head or not? Personally I prefer the single speed step pulley head with a VFD. Less things to go bad.

 

[eKretz]

That is a big issue that the OP did not mention, variable speed head or not? Personally I prefer the single speed step pulley head with a VFD. Less things to go bad.

Also a heck of a lot quieter in my experience.

 

[projectnut]

"Rotaries are good too, but I'm definitely in the VFD camp. They don't use but a trickle of energy when the motor isn't running and the soft start and variable speed are very nice to have. The downside is that some electronics don't play well with the high frequency and you've often gotta do some rewiring if you want to use the original controls."

If you're capable of rewiring the original controls to work through the VFD I would recommend you do so. The one machine I have that uses a VFD is a Baileigh CS-350EU cold saw. It came from the factory with a VFD powering the 3-phase motor and original control panel. All functions are controlled by the VFD, but use a convenient control panel situated for ease of use by the operator.

Here are a couple pictures of the machine. Note the VFD is in the lower left corner of the waterproof cabinet. The control console is well within reach of the operator and each function is clearly labeled.

 

[rons]

Any recommendations on what three phase converter would be good for the job?

Stay in this business long enough and you will learn the VFD and RPC.
Build the RPC and buy a VFD.

 

[GregSY]

I'm also not a 'VFD is a no brainer' guy.

I think the VFD has its place. But I also think the VFD appeals to the part of the brain that likes flashy objects and any product with NEW!! stamped on the wrapping.

I'm curious if the are guys using a VFD but still using the original switches on the mill/lathe - in other words, they turn the VFD on then use the mill's drum switch to gate the power. If so, that's not good.

I wired up my lathe (on a VFD) using the original switches but they are acting as a remote function VFD On/Off control.....they are not making/breaking the 240V power.

The RPC has its drawbacks but it also provides pure sine wave power, and it is very simple to connect up...three wires and all the original controls work as intended.

My mill runs on an RPC . I wouldn't want it on a VFD. My lathe runs on a VFD - I wouldn't want it on an RPC. But that's only because the lathe has a 7.5HP motor which I don't want to start across the line.

 

[Cole2534]

I'm curious if the are guys using a VFD but still using the original switches on the mill/lathe - in other words, they turn the VFD on then use the mill's drum switch to gate the power. If so, that's not good.

Well no, you wire them up like you did your lathe.

There's different horses for different courses, I posit that the cheap 240v input VFD's are the winner here, even if for no other reason that spindle ramp. Of course, some folks use them to set the perfect RPM. Now that I haven't figured out because they'll never get the perfect feed so close enough is just fine on the RPM.

 

[eKretz]

I use a VFD on my mill, lathe AND grinders. I've got tachs on all of them for fine tuning speed. That's very useful for grinding, and is nice for lathe work because I can bump the speed up as I'm roughing something down to smaller diameter or facing from large to small diameter, etc. Not so much use on the mill, mostly I run it at 60 Hz and just use the mill's variable speed control (Reeves, quick and easy) but every now and then it's handy. I've got my own remote control boxes to control the VFDs, but I use some lathe controls run to the VFD control terminals - mainly the E-Stop and the switch on the foot brake to stop the motor. All the rest I've got on an electronic control box on top of the headstock so I don't have to bend down as much (bad back).

 

[GregSY]

The VFD can ramp up the power, for sure, to minimize inrush. But on a mill...? I want the 'instant on' of an across the line start. My lathe is set up with a 6 second ramp for on and off. I don't mind that, but on a mill it would slow me down too much. I could shorten the ramp, but then the inrush would creep back in so that benefit gets lessened.

 

[henrya]

I can set the ramp up to anything I want. Its not hard. Same for other parameters. I’m a pretty smart guy but an electrical idiot and I did the install and programming all by my big boy self. When lightning killed the first VFD on my mill I immediately bought another one just like the dead one. Not a second thought.

If you’ve got a machine with manual mechanical controls that can be replaced with a VFD that runs off wall power, its hard to imagine any downside. Bigger machines it becomes less obvious and may not be so.

 

[GregSY]

I'm sure you can set it to anything you want - that's not the point. The point is the VFD is not a Magic Box. If you set the ramp in a manner that negates the benefit of the VFD, you haven't done yourself much good.