WM 250 Lathe NVR Switch

[JourneymanParticipant @journeyman]

My 9 year old lightly used WM250 lathe has developed a problem which seems to be getting worse. On pressing the start button lathe will spin up and then I assume the NVR trips out. Press start again and the lathe will start and function as normal. Sometimes it now takes 2 or three goes to get it running. Once running it seems OK but has tripped a couple of times mid-cut. I am guessing that the NVR switch is not latching properly.

Before I start taking things to pieces I thought I would ask: Is the NVR adjustable or serviceable in any way? Could it be something else?

Everything else electrical seems OK, no effects on shop MCB's speed control functions, off button works, chuck and cover interlocks work. Any thoughts suggestions or advice gratefully received.

John

[JourneymanParticipant @journeyman]

Not latching problem with NVR

[davebParticipant @daveb17630]

With magnetic devices in close proximity to metal cutting there is always the possibility of a whisker of metal finding its way into the switch or relay and preventing the armature from touching the electro magnet. May be worth a look but replacements are not expensive. Probably best to ask Warco first.

[EmgeeParticipant @emgee]

Hi John

If the NVR switch is like some iv'e seen, the full motor current is passing through what can only be described as a control cct contact suitable for low currents, if that is the case the contacts could be burnt and not making good contact so the NVR function operates. The current rating will be on the switch, or should be.

Emgee

[David JuppParticipant @davidjupp51506]

I've had the odd problem with rust on the pole faces in a contactor before, tend to buzz rather than latch in. Cleaning the pole faces with abrasive paper usually sorts it out. Not sure how well you can get in to clean some of the small modern NVR units.

[JourneymanParticipant @journeyman]

Thanks to all. I will take the NVR out later and see if anything obvious comes to light. I will probably contact Warco later in the week [when they have all got back from "Ally Pally"]

John

edit:to remove smiley that popped up unwanted!

Edited By Journeyman on 21/01/2017 10:55:48

[JourneymanParticipant @journeyman]

Well, I took the NVR out, carefully marking all the wires so they went back in the same place. It is basically a sealed unit but I levered it apart anyway! No sign of anything untoward inside so clipped it back together again. Reinstalled the switch and more by luck than judgement everything works OK. I can only guess that one of the push on connectors had corroded or worked loose, so at least temporarily the lathe is working again… Result!

John

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