Getting an new Bridgeport

[jwmelvin]

If you set the ramp in a manner that negates the benefit of the VFD, you haven't done yourself much good.

To me, a VFD just allows one to make decisions about trade offs. If you want fast spool up, and are okay with current draw, that’s fine. One benefit is braked stopping, which I find does save time. (And with my step-pulley J head, the speed adjustability is great.)

 

[Cole2534]

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.

Except the part where you can get 3p from 115v or 230v single phase.

For all practical purposes, in this application, the VFD is indeed a magical box.

 

[GregSY]

All of my statements are (generally) in comparison to an RPC. So...a VFD does nothing magic when it converts single phase to 3 phase.

 

[projectnut]

"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."

Attached are a couple of my Sheldon MW-56-P lathe. This machine is running on a static converter. It has built-in push-button speed and directional controls in the original control console. The speed change is accomplished by an independent gear motor controlling a Worthington drive. There is no need to complicate things by adding a VFD. Granted this is a bit uncommon, but it works flawlessly.

 

[Cole2534]

All of my statements are (generally) in comparison to an RPC. So...a VFD does nothing magic when it converts single phase to 3 phase.

Show me a 115v RPC and I will concede.

 

[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."

Attached are a couple of my Sheldon W-56-P lathe. This machine is running on a static converter. It has built-in push-button speed and directional controls in the original control console. The speed change is accomplished by an independent gear motor controlling a Worthington drive. There is no need to complicate things by adding a VFD. Granted this is a bit uncommon, but it works flawlessly.

Umm, cool? I mentioned that my mill had the same setup... And that I generally just use the vari-speed that came with it. But my lathe did not until the VFD. Neither did my grinder. And it actually comes in handy even on the mill at times when I want to do a quick very low RPM op then quickly go back to high RPM. That involves a spindle stop, gearbox shift, spindle start and lever speed adjustment with the original mill variable speed Then the same again to go back to the first speed. Simple one second twist of a knob on the VFD. I concur that there is no need for a VFD in your case if you can change RPM on the fly.

As far as quick or slow stops and starts, I have mine set to a 2 second accel and decel on the milling machine. I can set those separately to different times if desired, but those are plenty good for me. I leave them a little longer for accel on the lathe, about 5s. and about 2-3 seconds on decel. On the grinders (surface grinder and tool/cutter grinder) they are 5s. and 5s.

 

[GregSY]

Show me a 115v RPC and I will concede.

I don't get where you would want 115v? On the output or input or?

I assume everyone in the US has 240v in their house/shop.

I don't know any an 115v 3 phase machinery, so maybe you mean 115v on the input....but then, a VFD doesn't transform voltage so...???

 

[Cole2534]

I don't get where you would want 115v? On the output or input or?

I assume everyone in the US has 240v in their house/shop.

I don't know any an 115v 3 phase machinery, so maybe you mean 115v on the input....but then, a VFD doesn't transform voltage so...???

Yes they can and that makes it possible to run a J-head (any 1hp 3p motor, really) off a 115v wall outlet. You can't do that with an RPC. That is awesome for the home shop guy.

Kretz has me wanting to put one on my grinder spindle simply for the soft start function. But, I'm not sure how to integrate it with the hydraulics.

 

[GregSY]

If a VFD is taking in 115v and putting out 240v....it has a transformer inside. A VFD has no way of changing voltage otherwise. You could run an RPC the same way...a 115v motor with an output side transformer. I guess if it's built in to the VFD it's convenient but it's not an inherent VFD attribute.

 

[eKretz]

Yes they can and that makes it possible to run a J-head (any 1hp 3p motor, really) off a 115v wall outlet. You can't do that with an RPC. That is awesome for the home shop guy.

Kretz has me wanting to put one on my grinder spindle simply for the soft start function. But, I'm not sure how to integrate it with the hydraulics.

Mine is wired only to the spindle motor...the hydraulic pump is wired separately.

 

[Cole2534]

If a VFD is taking in 115v and putting out 240v....it has a transformer inside. A VFD has no way of changing voltage otherwise. You could run an RPC the same way...a 115v motor with an output side transformer. I guess if it's built in to the VFD it's convenient but it's not an inherent VFD attribute.

OK, you win, a VFD has no business in machine tools, we all just need RPC's.

 

[GregSY]

Sadly, your reading skills need a bit of work. Go back and read the first post I made on this thread....you will see that my view is both devices have their place.

I'm kinda starting to feel the VFD is like Lizzo...its wild popularity is hard to explain and far exceeds its actual merits.

 

[eKretz]

Heh, hmm.

 

[Modelman]

If a VFD is taking in 115v and putting out 240v....it has a transformer inside. A VFD has no way of changing voltage otherwise. You could run an RPC the same way...a 115v motor with an output side transformer. I guess if it's built in to the VFD it's convenient but it's not an inherent VFD attribute.

It's solid state. Google voltage doubler circuit.

 

[Corn]

When installing VFD`s consider adding extra fan for the motor. Motors are designed to cool at full speed. If ran slow by VFD it might overheat and shorten the motor life.

What comes to the interference, cable from VFD to the motor need to be shielded.

 

[crrmeyer]

Show me a 115v RPC and I will concede.

Err... I took a 120 to 240VAC step-up transformer I had laying around and ran a small RPC with it to power a mill motor for some testing. Worked OK.

Where the RPC shines is for two speed lathe motors with lots of relay controls and a three phase coolant motor. It is plug and play compared to the VFD conversion.

 

[henrya]

Err... I took a 120 to 240VAC step-up transformer I had laying around and ran a small RPC with it to power a mill motor for some testing. Worked OK.

Where the RPC shines is for two speed lathe motors with lots of relay controls and a three phase coolant motor. It is plug and play compared to the VFD conversion.

I think this is right. For machines with fully executed analog electrical controls you might be better off with a RPC. Lots of potential complications there. For a machine with simple mechanical functions a VFD can add a lot of desirable functions.

 

[boslab]

There’s an advantage to a dedicated vfd as opposed to one big rpc, if the rpc fails every machine is dead, not a deal changer but may be important
They are generally reliable ( until they aren’t)
Mark