PM 3520 problem

[Jed Malcore]

This is a potential issue and I cannot tell if it is just stalling out or an issue. When I am roughing out a bowl at maybe 500 - 700 RPM's, all of a sudden (mostly when I am taking a lot of wood off), the lathe shuts off. The VFD reads "ou" see the picture below. I have to unplug the lathe for a few minutes and then it starts back up with no further issues (unless I do it again). I called PM and he told me that it means that the lathe is getting too much power... so how do I fix this? does it mean that I am just stalling out the lathe?

Thanks for any help/advice/comments...

[Dale Miner]

Do you have the pulleys configured for the slow speed range?

When I had a 3520b, stalling while roughing anything much larger than 10" was fairly easy when in the high speed range (for a heavy handed me anyway), but nearly impossible in the slow speed range with anything less than about 16" diameter.

I have heard of folk getting an overload shutdown when knocking corners off during roughing even though stalling was not the issue.

[Faust M. Ruggiero]

Jed,
When I owned a 3520 I recall occasionally taking too much cut and stalling the work piece but that merely caused a belt slip on the machine, not a shut down. Call PW again and hope you speak to a better tech. "Lathe getting too much power" doesn't sound right to me. Do check your belt tension. I allowed the weight of the motor to create all the tension I needed. Also, try using the small motor pulley and large shaft pulley when you are roughing a large bowl. That allows higher motor speed and more torque. Good luck.
faust

[Doug Ladendorf]

The greater load you put on the motor the greater the amp draw. If the VFD is saying "I'm givin' ya all she's got cap'an!" and you ask for more, it will trigger the safety stop feature for motor protection. At least that's how I understand it works.

Doug

[Jed Malcore]

As long as it's not hurting anything... I just didn't want to screw something up... Thanks for all the help guys!

[Justin Stephen]

Jed,
When I owned a 3520 I recall occasionally taking too much cut and stalling the work piece but that merely caused a belt slip on the machine, not a shut down.

Concur. I have occasionally done the same on my lathe and it results in a belt slippage noise and I can still feel the lathe trying to turn/push against the tool until I pull the tool away and it starts spinning again. I have never had a catch or overly aggressive cut cause my lathe to shut off or return an "OU" message (so that I have noticed anyway).

[Ray Bell]

Concur. I have occasionally done the same on my lathe and it results in a belt slippage noise and I can still feel the lathe trying to turn/push against the tool until I pull the tool away and it starts spinning again. I have never had a catch or overly aggressive cut cause my lathe to shut off or return an "OU" message (so that I have noticed anyway).
Mine does the same as Jed's. It is not the belt slipping, the motor shuts down. This only happens with a hard catch, and I have to unplug the lathe for a few seconds to get it started again. I think Doug is right it is a motor protection feature.

[Jed Malcore]

Yep I have them on the lower speed ones... however, it only happens if I am roughing out a bowl and put some pressure on the outside of a bowl hitting corners....

[Hilel Salomon]

I'm probably the last person on this forum to give technical advice, but I wonder about two things. What amperage is your outlet configured to draw? How long a power cord did you make? Probably overkill, but I used 12 gauge wire and have a separate circuit for my PM. Forgive me if I'm totally off on this.

[Kyle Iwamoto]

I agree with Hilel, if you have a long extension cord that's too small, the voltage loss could be causing that..... And your source breaker. If you have several other things running on it, that drops the voltage also.
I'm the second to the last person to give technical advice on electricity though.

[John Keeton]

Yep I have them on the lower speed ones... however, it only happens if I am roughing out a bowl and put some pressure on the outside of a bowl hitting corners....Jed, I may be drawing the wrong conclusion, but when I rough out a bowl I avoid "hitting corners" by beginning cuts closer to the tailstock and following thru so as to make a continuous cut toward what will be the rim. Even on a square blank, there is no reason to pound away at the corners.

[Mike Tilley]

I have the Same problem with my jet 1642. Runs fine except under heavy cutting. When I called jet support he told me the inverter was bad. Haven't tried to repair it yet price for a new one was well over $600 dollars. So I have just been using it for light work since I can use my robust for major cutting but still want to get it fixed. If anyone has any more info on this problem please post the answer.
Mike

[Barry Richardson]

I use a delta 1642 2hp with delta vdf and it will do that too if you get a very hard catch, but not by dragging it down with very deep cuts. Like Doug, I always understood that it was a design feature of the vdf, to prevent damage to your machine...

[Pat Scott]

I had this exact same problem happen about 6 months ago on my 3520B. I was turning a HUGE, HEAVY, somewhat out of balance blank. It was 18"-19" diameter and maybe 8" deep of wet Elm. I was on the low speed and you could tell the lathe didn't like trying to get all that weight spinning from a a dead stop. I can't remember what I did exactly to create the problem, whether it was stopping and starting too quickly, or too big of a cut. I had to unplug it for a minute to reset everything, and from then on I spun the piece by hand to start it rotating before turning on the lathe. Kind of a running start if you will instead of the lathe doing all the work. Anyway it never happened again and hasn't happened since. I don't turn pieces that large and heavy very often, and I took it as a one-time occurrence. If I do a blank that large again I'll spin the piece by hand before turning it on.

I am running a 10-ga extension cord on my lathe. Hadn't thought that it could be the problem. I might have one more spot in my sub-panel to add another 220v circuit.

[John K Jordan]

from then on I spun the piece by hand to start it rotating before turning on the lathe. Kind of a running start

Off topic, but this is interesting. Just last week at the TAW symposium a demonstrator used the same technique - spin the lathe by hand (actually by forearm on the wheel) then flip on the switch. In his case it wasn't a very heavy chunk of wood but an extremely delicate long-stemmed goblet held in a chuck with the cup supported at the tailstock. He said this method gave him a very gentle start and prevented the thin stem from snapping from the inertia as the motor accelerated.

JKJ

[Geoff Whaling]

Off topic, but this is interesting. Just last week at the TAW symposium a demonstrator used the same technique - spin the lathe by hand (actually by forearm on the wheel) then flip on the switch. In his case it wasn't a very heavy chunk of wood but an extremely delicate long-stemmed goblet held in a chuck with the cup supported at the tailstock. He said this method gave him a very gentle start and prevented the thin stem from snapping from the inertia as the motor accelerated.

JKJ

Spinning the bowl blank to start is an old production bowl turners trick when they only had 1 hp motors. Its also a safety habit we all should be using - at least one full rotation of the blank to check clearances before starting the lathe.

Jed, What is happening? You are applying a load torque (heavy cut) that exceeds the motor shaft torque at the VFD settings for that belt position and the speed settings on the VFD causing the motor to stall – i.e. zero rotation.

Depending upon the quality, programming and options available etc, VFD’s sense load and through their programming can adjust to apply more torque in certain temporary or sustained load conditions. The VFD is also programmed with over current protection etc.

When the motor stalls it is drawing maximum current, and is prone to overheating and the very high current draw can cause damage to the motor, VFD and installation wiring (i.e. fire). So sustained motor stall is not good and has the potential to cause significant damage & economic loss.

Much better to take lighter cuts and to refine your technique, easier on the motor & your body in the long run.

[John K Jordan]

Spinning the bowl blank to start is an old production bowl turners trick...
Its also a safety habit we all should be using - at least one full rotation of the blank to check clearances before starting the lathe.


I wouldn't want to check for clearance the way he spun up the lathe, especially with a delicate piece chucked. He put his forearm against the wheel near the elbow then pulled back on the arm gently at first then faster, then flipped the switch while it was moving. If clearance was insufficient this method would slam the wood against the rest and perhaps break the piece. Rotating to check for clearance would best be done slowly with the hand while watching carefully, I think.

The non-Delta VFD I programmed recently had a number of parameters of how to deal with faults differently depending on application. One was retry, one was a complete shutdown, there were some more. I suspect the Delta on the lathe is set to shutdown. There were also parameters for how much overcurrent would trigger the fault. These parameters might be changed by someone with a repeating problem and willing to risk experimenting. However, I would rather think of the shutdown the way I do if a circuit breaker trips - try to find the reason.

[Jed Malcore]

Thanks for the advice and help! I will indeed work on lighter cuts and refining my technique.