Bridgeport VFD questions

[Threadkiller]

Good morning all. After many many years of wanting a Bridgeport I’m finally getting one and I have a few questions about vfds that I couldn’t find an answer to searching on here.

So, I’ve never actually run a Bridgeport yet so excuse what I’m saying if it’s a little off. When I was looking at the machine the owner was showing me how when you put it in the different speeds you have to run the motor in reverse. Now from what I’ve read all speed control will be done from the vfd? Reversing also? Is there an optimal setting I should leave the belt on? Apologies for the newbie questions. I bought a TECO/Westinghouse 1hp vfd if that helps.

Question 2...the machine is three phase (obviously) and it has an X power feed that is also run off a separate three phase motor. Is there a way to run both the main motor and the power feed motor off the single vfd? Will the speed control also affect the power feed motor or is there a way to somehow not have the speed control not impact the power feed? Or should i replace the motor? This is my first time ever using a vfd.

Also for what it’s worth I don’t have the machine yet.

 

[JRaut]

Do you have a step-pulley head or the variable speed head?

Reason I ask is that I use a VFD on my variable-speed head, and I only use it to get 3-phase power. I use the native Bridgeport variable-speed head to change spindle speed, and I use the regular reversing switch when milling in back gears.

In other words, my VFD is tucked away in an electrical cabinet and I've not had to touch it even once in the 3ish years I've been using it.

It's a bit more cumbersome to change speeds on a step-pulley head, so many with that style BP opt to use the VFD to adjust speeds.

 

[Threadkiller]

Sorry I meant to put that in my question...yes it’s a step pulley head. I don’t mind changing belts if I have to. I opted not to get a variable speed head because because the step pulley heads are simpler and cheaper to fix if something goes wrong (so I’ve read). Also I knew I’d need a vfd anyway if I wanted to have variable speed

 

[tq60]

Think of it this way.

VFD allows for easy change in speed, in center pulley range you can go from slow to fast.

The pull change allows for change in torque or actual power due to simple leverage.

Reverse is needed when you use back gear which we use often.

Ours was vari-speed but the shop that had itconverted it to single speed via pulley and added VFD.


for drilling holes and general milling fine.

When we need shell mill or 3 ice hole saw bback gear.

Sent from my SM-G781V using Tapatalk

 

[Winegrower]

I also have a step pulley head, and I applaud your choice. It’s a two speed reversible motor with high and low gears. i generally run it in the second from the slowest belt position, and it’s surprising how wide a range of operations I can do with this configuration. Tapping, boring, drilling big and little holes, end milling, 4” face milling…I actually can’t recall the last time I changed belt position, though it is essy to do. Yes, low gear rotates opposite, just switch the motor to reverse. I have a VFD on my wood lathe, where it seems a lot more useful…just don’t feel a need for one on the mill.

 

[jwmelvin]

In back gear, yes the motor needs to turn reverse. Good people like David Best and Mark Jacobs put a sensor on the back gear engagement knob, so the VFD automatically makes that change. I do plan to do that with mine, but haven’t yet.

I have a step-pulley head and almost always leave it on the second pulley from the top (like [mention]Winegrower [/mention]). It depends on your motor and willingness to push the motor. Mine is not especially new or designed for VFD use. If you were to use a modern, appropriate motor like David Best does, you can run it down to 15 Hz or so and up to 120 Hz, obviating the need to change pulleys. My 30-90 Hz range gives me 500-1750 rpm in high and 60-200 rpm in back gear. So I might change the pulley for a small end mill in aluminum, etc. I use 15 Hz jog for tapping, just to get a little slower at times without using back gear.

 

[rabler]

As for running the X-axis power feed, for practical purposes that is not feasible to do on the same VFD as the motor. While technically it is possible to run a second motor on a VFD, the VFD has to be run in V/F mode (not ideal), and the speed of the power feed would be subject to the changes of spindle speed, and finally, you generally can't switch the power feed on/off/reverse independently without problems in the VFD.

 

[mksj]

Teco are decent VFD's for the mill, in particular for simple setups. As rabler indicated there is no practical way to run two dissimilar motors at different speeds simultaneously. Some VFD's have provisions for setting up/switching between two motors, but it is complicated to implement. Many of the Bridgeport drives were single phase input with DC motors, so I would check if it is truly a 3 phase drive motor. Option B, you could get another VFD for the drive, but the operation/speed control would need to be from the VFD and not the drive controls.

Given the cost of replacement of some of the Bridgeport motors, I would run the stock motor a bit more conservatively, like 30-90 Hz and a lower carrier frequency. You loose Hp and the mechanical advantage below the motor base speed, so one could overheat the motor is drilling a large hole over time.

 

[ttabbal]

Sounds like you have the same setup I do. I do limit the speed range of the older main drive motor, for the reasons @mksj mentions. I think mine is slightly wider range, 20-100 I think. Any switches and other control electronics need to be removed from the circuit. The motor must connect directly to the VFD. You can use the FWD/REV switch if you like, but it needs to be rewired to the VFD input terminals. I used a simple 2-gang junction box from the local home store to make a simple control panel.

If the X power feed is the old gearbox style like mine, it has an older 3 phase motor dedicated to it. You need 2 VFDs in this case. I run the power feed at 60Hz and use the gears for speed control. There are times it would be nice to have it more variable with a simple knob like the main motor, but it gets the job done.

Teco makes nice devices, as do many others. They are more expensive, but often are more efficient etc.. That said, I went with cheap import VFDs and have been happy with them. You need to keep them away from chips and grinding dust, but that's easy enough. For the mill, mine are mounted to the wall behind the machine and high enough that chips are unlikely to get up there. I'm running 3 of them now, one on a belt grinder, and they work great.

 

[DaddyHeath]

Hey Threadkiller, congrats on the acquisition! I just recently went through this setup for a 1HP series 1 J Head BP with step pulleys. Running a 2.2Kw VFD to convert 1ph220 to 3ph380, I set my VFD to 60hz and do my speed adjustments via the belt and motor reversing via the Hi/Lo switch. This ensures the motor gets adequate cooling by running at the intended rpm.

For the power feed, double check the wiring as mine was only 110 and got its power by tapping one leg and ground from the 3ph. I now run 110 to a box on the body to split out for the lighting, dro, and power feed, then 220 dedicated to the VFD which goes directly to the reversing switch on the motor.