Random Shut Down of Laguna Revo 18/36

[Joe Frank Porter]

My Laguna REVO 18/36 very frequently becomes totally inoperable when turning, and I turn it off to briefly inspect my work(off with the on/off switch not with the emergency stop). The power to the control panel remains on with the rpm light still on. You can even spin the bowl by hand and the rpm meter works. I have to unplug the the lathe for a minute or so and then turn the lathe back on, then it works.

When you push the off switch, you can tell the motor is off because a large 17" bowl freely spins on and on. Free wheeling like a flywheel.

I have had the lathe nearly 3 years and use it about 4 or five days a week with heavy use.

Could it be the DELTA electronic box?

Any comments? I will contact Laguna.

Thanks for your comments.

[William C Rogers]

Contacting Laguna is the best way forward. My guess it is either the off-on switch or the relay sticking and not the VFD.

[John K Jordan]

I don't have that lathe but if it's made similar to other variable-speed lathes with Delta VFDs the switch itself simply operates a low-voltage control line, 10v on my PM and 5v on my Jets. If the switch turns the power to the motor off but occasionally doesn't decelerate as normal I suspect a problem with the DELTA VFD. All the acceleration, deceleration, and braking is done in that box.

The RPM display (at least on my lathes) is separate from the VFD, triggered by a sensor on the shaft and that it displays speed with a manual spin is probably unrelated to problem. When my lathes are plugged in I always spin by hand and see the RPM change even if the front on/off switch is off.

You might open the cover and make sure all the control wires are tight but it might be a miracle if tightening one fixed things.

Some years ago the VFD on one of my Jet lathes started acting flaky and refuse to run unless I unplugged it, waited a bit, then plugged it back in. It got progressively worse requiring multiple unplugs/plugs until it finally quit completely. I replaced it with a 3rd party VFD from China.

JKJ

My Laguna REVO 18/36 very frequently becomes totally inoperable when turning, and I turn it off to briefly inspect my work(off with the on/off switch not with the emergency stop). The power to the control panel remains on with the rpm light still on. You can even spin the bowl by hand and the rpm meter works. I have to unplug the the lathe for a minute or so and then turn the lathe back on, then it works.

When you push the off switch, you can tell the motor is off because a large 17" bowl freely spins on and on. Free wheeling like a flywheel.

I have had the lathe nearly 3 years and use it about 4 or five days a week with heavy use.

Could it be the DELTA electronic box?

Any comments? I will contact Laguna.

Thanks for your comments.

[Russell Neyman]

See my thread of two weeks ago. The switch itself does very little; it is, undoubtedly, the relay. Oh, and get ready for a struggle to get it all back together. The relay comes with wires, about doubling the "snarl" inside the control box.

[Alex Zeller]

When it shuts off what are you doing exactly? When you say "turn it off to inspect" do you mean the project is at speed spinning and you just turn it off or are you using the speed control to slow it down and then when it's stopped you are turning it off to inspect it? I don't own a Laguna but with my Grizzly the VFD will shut itself off if it tries to slow down too fast. When it happens the lathe will spin, as you call it "freewheel", and take a very long time to come to a stop on it's own. I'm guessing that there's a current limitation set point that if it's exceeded will cause the VFD to protect itself. Not knowing the details about the Laguna could it also be doing something similar forcing you to reset the VFD?

[Joe Frank Porter]

John Jordan

Regarding Your China VFD replacement. How expensive and how much trouble to replacement

Thanks
Joe Porter

[Joe Frank Porter]

Alex

Reg: REVO 18/36 It's when i hit the off switch when spinning at 800 rpm on a 17" heavy bowl

Joe Porter

[John Keeton]

Can't offer anything on a fix, but I never turn off my 1836 to inspect work. I simply set the speed to zero. I do not use the panic switch at all and prior to unplugging it each day I turn the machine off with the on/off switch.

[Alex Zeller]

Alex

Reg: REVO 18/36 It's when i hit the off switch when spinning at 800 rpm on a 17" heavy bowl

Joe Porter

I would set the speed to zero. With a larger heavier object I slowly turn down the speed to allow (what I call the braking function) of the VFD to do it's job easier.

[Joe Frank Porter]

Thanks all

It started doing it with the big wet 17" bowls.
Based on your comments, I'll start turning the speed control to zero and see if that helps. Especially on the large heavy bowls.

Joe

[John K Jordan]

John Jordan

Regarding Your China VFD replacement. How expensive and how much trouble to replacement

Thanks
Joe Porter

The VFD is made to handle slowing down a heavy mass at any speed.

I think the VFD was somewhere between $100 and $150 but it's been a while and things are probably different now. It wasn't much trouble, but I did have to study the programming to figure out the values for some of the parameters which were named differently from the Delta VFD. Lots of people buy VFDs and program so there should be plenty of help here. I'd see first what Laguna says.

I forgot to say earlier - check the display on the VFD itself when working properly and when not working to check for error messages.


JKJ

[Joe Frank Porter]

Thanks Alex and Both Johns

I'm inclined to think I'm the problem after reading your comments. I believe I've been overloading the VFD by using the off/on switch when turning large, heavy. wet bowls.
I'll change my methods and hopefully that helps.

[John K Jordan]

Thanks Alex and Both Johns
I'm inclined to think I'm the problem after reading your comments. I believe I've been overloading the VFD by using the off/on switch when turning large, heavy. wet bowls.
I'll change my methods and hopefully that helps.

You should ask Laguna when you call them. I can't believe they would design a lathe such that using the on/off switch to turn the lathe on and off could cause a problem, regardless of the weight of the blank. I see nothing in the manual about this. Please let me know what Laguna tech support says.

I do sometimes stop my lathes (not Laguna) by turning down the speed control, especially when switching to a different task, say from turning to sanding. However, most of the time I leave it alone and stop/start with the start/stop switch, especially when stopping to inspect the piece. I like this method since it returns the lathe to the speed I'm currently working at.

Some people turn the speed down each time so they aren't surprised or cause an unsafe condition when the speed control is set to a high speed and a heavy unbalanced blank is mounted. This could happen unintentionally if they are careless or if the speed control is accidentally bumped. I remember one person who had a speed control that had no resistance but almost turned itself in the breeze. I think I recommended putting a felt washer behind the knob to give it some resistance. I've never experienced the problem of the lathe unintentionally spinning up to a high speed since I turn the lathe on the same way each time: make sure the work clears the tool rest, glance to verify the position of the speed control, stand out of the "line of fire", turn on the lathe. On thin spindles I usually run wide open at 3000+ rpm anyway so leaving the speed control turned up is easier and quicker.

JKJ

[Bill Boehme]

The VFD is made to handle slowing down a heavy mass at any speed.....

... I'm inclined to think I'm the problem after reading your comments. I believe I've been overloading the VFD by using the off/on switch when turning large, heavy. wet bowls.
I'll change my methods and hopefully that helps.

When the VFD is doing a programmed deceleration of a very heavy piece of wood the inertia that tries to keep the lathe running at its current speed is back-driving against the commanded speed from the VFD. The VFD has a maximum current limit to protect the innards from being damaged and if the motor current needed to decelerate the load at the programmed rate hits that limit the typical response is to shut off power to the motor and do a freewheeling coast to stop. If this only happens with very heavy loads then I think that you have correctly diagnosed the problem.

And, it is worth mentioning that this fail safe mode is actually a very good thing. I'll share an example of having a heavy duty high end lathe that has the muscle to slow the motor down even with a very heavy load (about 100 pounds in this instance if I remember correctly). The only problem is that the wood wanted to keep on keeping on so the chuck proceeded to unscrew itself. It was an exciting couple seconds before I regained enough wits to hit emergency stop (which kills the power so that the load will coast to a stop) the chuck was less than a full turn from unscrewing itself from the spindle. Only me and my laundryman knew how exciting things were.

[David C. Roseman]

Thanks all

It started doing it with the big wet 17" bowls.
Based on your comments, I'll start turning the speed control to zero and see if that helps. Especially on the large heavy bowls.

Joe

Joe, I don't have that lathe, but I doubt there is anything wrong with it. Let us know, but I bet that turning the speed control (pot) down slowly to zero in order to stop, instead of just hitting the off switch, will resolve your issue when turning very heavy workpieces at speed. As Alex and Bill suggest, this may simply be the internal circuitry of the Delta S1 inverter protecting itself as designed. A good thing.

When you simply hit the off switch, or the emergency stop, or even turn the pot down too quickly, the inertia of the heavy workpiece can cause an "overrun" condition, known as motor regeneration, where the motor acts like a generator for a few moments. This can send too much current back to the inverter's DC bus. The VFD registers an overvoltage condition and shuts down to protect itself. The lathe can be reset by turning it off, then waiting a few seconds before restarting.