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Powermatic 3520c odd behavior

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hey guys,

I’m planning on calling Powermatic on Monday but I wanted to check here too in case someone ran into this issue.

I was just starting to turn, I put a blank between centers and turned the lathe on to 500. While turning, the lathe slowed down then went into reverse on its own. I thought maybe I did something wrong so I stopped it, and turned it back on without changing any setting and it went back into forward motion for less then a minute then it started fluctuating on its own. From 500 to 300, back up to 400 then down to zero and went into reverse.

It did that few times. I shut it down completely from the switch on the motor then turned it back on and it worked fine from there on.

Anyone had such experience?
 

Bill Boehme

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Possibly the Forward/Reverse switch or the wires that connect them to the inverter. There should be three wires to the switch: Forward, Reverse, and Common. I'll see if I have the manual for that inverter. Meanwhile, you can check to see if the wires to the switch are secure and there isn't a lot of dust on the contacts. Also, check the wire connections at the inverter to make sure that they are secure and blow out any dust around the terminals.
 

Bill Boehme

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I think that the wiring configuration might be like that shown on page 2-20 of the Delta S series inverter manual:

http://www.deltaww.com/filecenter/P.../Manual/DELTA_IA-MDS_VFD-S_UM_EN_20160412.pdf

In this configuration there are only two wires going to the Forward/Reverse switch. If either one of these wires is intermittently loose at the switch terminal or where connected to the inverter then you would see the behavior that you describe. It's also possible that the switch is defective or dust has gotten inside the switch causing it to become intermittent.

My opinion is that this is a design safety issue in that the failure results in a potential hazardous condition rather than failing to a safe condition. The one scenario that I immediately thought about was a large heavy turning coming unscrewed if the spindle unexpectedly reversed. My opinion is that this rises to the level of a safety recall. There are other wiring configurations as well as better switches that could be used to address this problem.
 
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Thanks Bill, I will see if I can check the wiring Tomorrow in day light. I do plan on calling Powermatic and see what will they say.

I agree with the safety risk of larger blank coming loose. I did not think about that.
 
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Just spoke to Powermatic support, they said it sounds like it is connected to ground fault circuit which would cause this behavior, he said it should not be connected to ground fault circuit. He said to check with the electrician who installed the 220 line. Unplugging it from the wall for 10 minutes would reset it. I don’t know how to check if it is or not, so I need to bring the electrician back after swat.
 

Bill Boehme

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Just look at the new breaker that the electrician installed in the panel. If it is the ground fault type it will have a red button (sometimes other colors) on it that is usually labeled "PUSH TO TEST". Here is a common example.

Circuit-Breaker_GFCI.jpg


If you do have it connected to a ground fault breaker there is a possibility that it could be the ground fault breaker if it isn't working properly, but they are pretty reliable and since yours is only about a year old I don't think that it is a defective breaker. Most modern inverters have pretty good ground noise isolation. The Delta S1 has been around for a while so I won't dismiss what the Powermatic guy said. If the electrician says that San Antonio building codes require GF breakers in the garage you might have to convince him that it's actually a workshop and not a garage. :D

If the breaker is the standard type then call Powermatic again for plan "B". I am still suspecting a defective switch or loose wires.
 
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Here's a test: put the Forward/Reverse switch in the Reverse position and then turn the lathe on. What happens when you do that?

When I had the issues, I put it in reverse, it went into reverse. I turned it off and back on without changing the setting, it went forward. When I shut it down from the plug and back on, it started behaving normal again.
 
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Is the breaker a dedicated line for the lathe only? Make sure that the GFCI isn't connected to another line or outlet. If the lathe is in a place where water could be a problem, this could be the reason for the GFCI breaker. Otherwise, it wasn't necessary.....unless he didn't have the proper breaker and decided to use the GFCI rather than go get a regular breaker.
 

Bill Boehme

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Is the breaker a dedicated line for the lathe only? Make sure that the GFCI isn't connected to another line or outlet. If the lathe is in a place where water could be a problem, this could be the reason for the GFCI breaker. Otherwise, it wasn't necessary.....unless he didn't have the proper breaker and decided to use the GFCI rather than go get a regular breaker.

It's a standard breaker, not a GFCI.
 

Bill Boehme

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When I had the issues, I put it in reverse, it went into reverse. I turned it off and back on without changing the setting, it went forward. When I shut it down from the plug and back on, it started behaving normal again.

I'm not following your description in the second sentence, but I'm suspecting that the inverter has a problem.
 

Bill Boehme

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I'm not convinced that the tech support person really understood the situation. Ground is only connected to the frame of the lathe for safety reasons. Neutral which is the center tap of 240 VAC power isn't used since nothing in the lathe needs 120 VAC power. The motor and control electronics are electrically isolated from the safety ground. Ground isn't a part of the power circuit, it is just a connection to earth at the service entrance. The only purpose of ground is safety in the event that there is a short to the metal frame of the lathe. Otherwise ground isn't a factor.

While it is possible that there is external electrical interference creating a problem, it is more likely that the problem is internal.
 
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I'm not following your description in the second sentence, but I'm suspecting that the inverter has a problem.

Sorry for not being clear. I had it set on reverse. I turned the lathe on, the blank turned in reverse as expected. I stopped it and turned it back on, it turned forward while the lathe setting was still in reverse.

I shut it down from the power switch in the back by the motor and back on, it started working fine and as expected.
 
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Have you tried blowing the switches out? The reversing switch, if its mechanical, may have dust packed in it causing problems.

I don’t think that is it, i’ve only used it 5 or 6 times since I purchased it and I blow it and clean it after every use. I will contact Powermatic again to make sure they have the issue tracked in case it does happen again.
 

Bill Boehme

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Sometimes a power surge or line noise can cause digital electronics to behave strangely.Unplugging it might have cleared the problem.

We have a clothes dryer with all sorts of digital electronics and blinking lights. When it quit working the repairman said that it couldn't be fixed for less than $1000. We thanked him, paid for the service call, and after he left I fixed it in about 30 minutes ... it was just a loose connection. Many of today's repair people only follow a written troubleshooting procedure and are lost after that.
 
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FWIW, I have to do this with my laptop periodically. The Staples manager tried this when I took it in to the tech support people. Works like a charm!
 
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Fadi,

Please let us know what your technical support from Powermatic is like. I ordered my Powermatic 3520c before the Portland symposium in June, the first was lost in transit, the second didn't arrive until two months after I placed my order. It arrived with serious manufacturing defects and by the time the the third replacement arrives it will have been almost three months since I placed my order. If I'm having this much trouble getting a new lathe I'm concerned what warranty issues might be like.

Looking forward to reading about your experience with Powermatic.
 
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I wanted to give an update:

The original problem of the lathe going in reverse on its own haven’t happened since I initially reported the issue, but I now have new issue where at times, when I stop the lathe to check the bowl, it won’t turn back on.

I called Powermatic support and they acknowledged they have been getting reports of similar issue with the 3520c and (I think he said) it is a faulty power switch. I reminded him of my original issue and he felt that it is best to have onsite support. They are shipping the part to local warranty affiliate who will schedule time to come by and troubleshoot my issues.
 
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I wanted to give an update:

The original problem of the lathe going in reverse on its own haven’t happened since I initially reported the issue, but I now have new issue where at times, when I stop the lathe to check the bowl, it won’t turn back on.

I called Powermatic support and they acknowledged they have been getting reports of similar issue with the 3520c and (I think he said) it is a faulty power switch. I reminded him of my original issue and he felt that it is best to have onsite support. They are shipping the part to local warranty affiliate who will schedule time to come by and troubleshoot my issues.

My PM 3520C started exhibiting the same behavior about three months ago. I just blew the switch out with compressed air to get it going again, but eventually got tired of that.

I called Powermatic, described the problem to the tech who said they were shipping me a new switch, and told me how to install it. The switch arrived 2 days later, and it only took about 20 minutes to install it. Problem fixed.
 

Emiliano Achaval

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Just look at the new breaker that the electrician installed in the panel. If it is the ground fault type it will have a red button (sometimes other colors) on it that is usually labeled "PUSH TO TEST". Here is a common example.

Circuit-Breaker_GFCI.jpg


If you do have it connected to a ground fault breaker there is a possibility that it could be the ground fault breaker if it isn't working properly, but they are pretty reliable and since yours is only about a year old I don't think that it is a defective breaker. Most modern inverters have pretty good ground noise isolation. The Delta S1 has been around for a while so I won't dismiss what the Powermatic guy said. If the electrician says that San Antonio building codes require GF breakers in the garage you might have to convince him that it's actually a workshop and not a garage. :D

If the breaker is the standard type then call Powermatic again for plan "B". I am still suspecting a defective switch or loose wires.
Bill, would this apply to my Stubby?
 
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The problem when dealing with the tech people now days is that they are reading from a manual, and do not have any practical experience with the machine. That is customer service now days...

robo hippy
 

Bill Boehme

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Bill, would this apply to my Stubby?

It could possibly be related to your problem. At the same time, I wouldn't get my hopes up too high ... it might be something else ... and it's always easier to diagnose the cause of a problem after the problem has been fixed. FWIW, I have read a number of war stories about inverters and ground fault breakers not getting along with each other so unless there is an absolute necessity for the GFCI I wouldn't use it. You might also check the inverter manual to see if it mentions anything about a GFCI.

If your Einstein buddy has an oscilloscope I think it would be a good idea to monitor the power.
 
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