problem with the table saw motor. Please help!

[centermin]

Hello,

I have a table saw and just 2 days ago when I was running it and turned it off, it gave off this flash from the engine - something it never done before. I think the armature may be worn out and as such need a good clean but could it be anything else?

I am grateful for any and all advice on this.

Thanks

[CaptDon]

I would guess that is one of those saws where when you release the switch it dead shorts the motor to bring the bade to a quick stop. The surge current is very high but only briefly. If it runs o.k. I wouldn't even worry about it. If it doesn't run well it's time to replace it!!

[centermin]

Ok so you're saying that the current may be the issue.. how about the commutator? Because I was thinking that it may have been worn out and that's why it's flashing and whatnots.. .

[centermin]

..also i should have mentioned that this flashing thing happened only for the last few days.. In the past few weeks I've been running a lot of timber through it 2 by 6 and 2 by 8s.. and the teeth of the then saw blade was 80. I've seen replaced it with a new blade with 40 teeth.

I appreciate any help you can give me. The flash at the end is what concerns me.

[themadhippy]

id be tempted to whip the brushes out

[centermin]

you mean sandpaper the commutator? with fine sandpaper slip? say p180?

[Gyro]

Welcome to the forum.

Brushed motors like that draw huge current surges when they start up, especially with the inertia of the blade and often produce displays like that. It looks as if yours has an electric / electronic brake too (I think they all do these days) that shorts the motor when you turn it off. This also cause a high surge current through the brushes as the motor works as a generator.

As you have the motor open, I would just check the motor brushes. If the saw has a lot of hours on it they may be excessively worn. The commutator will probably have some wear marks on it but trying to smooth it out just removes more copper. You can also introduce burrs and embed abrasive material from sandpaper. It is normally best left alone.


Edit: Are the brushes removeable via screwed plugs on the sides, if not, it may be difficult to put the armature back in.

[centermin]

Thank you man!
But what about the flash at the end? That is my main concern. Will it go away if I let it be? I mean I am no tech genius but I do have a few brain cells and I know that problems left alone tend to fester and grow as a result. In my case, I may lose the entire motor and hence that's not good. (especially considering the money I put on dewalt saw blade with them 40teeth I was mentioning before).

Apprecaite all the help I get, I just want this thing to work like before.

[Gyro]

The flash at the end is the elecroic brake shorting the motor. How accessible are the brushes?

[Kleinstein]

Some sparking is normal for a brushed motor, especially at high current like at start or with a rather abrupt breake.
It is possible that dust is somewhat empeding the movement of the brushes and this can also cause stronger sparks.
So it may be worth taking them out and remove dust. It help to put them back in the same orientaion as they were.

[centermin]

well I tried to open it up today but was unable despite having unscrewed all the screws and wahtnots. I could have forced it but chose not to. I am going to have to open it up and se what's going on inside next. But I am not a techie - I am a tax lawyer - so it's somewhat challenging....

[centermin]

that's a very good point as I was in a condensed/ no ventilation area the day the flash came about and I can (and really hope) that it's the partical dust from the using the sae.. tree dust.. .

but do you think that explains the flash at the end? It's the flash I am about

[centermin]

the saw is Ernst As G250. Here is the manual. read it cover to cover. 12cm or less use a stick push. and the distance between the blade guard and blade must be within 3-8mm..

https://www.yumpu.com/en/document/read/5913088/gjerde-250-ernex

[Gyro]

well I tried to open it up today but was unable despite having unscrewed all the screws and wahtnots. I could have forced it but chose not to. I am going to have to open it up and se what's going on inside next. But I am not a techie - I am a tax lawyer - so it's somewhat challenging....

If you've changed blades and been doing a lot of cutting it could well just be dust. If there are no screw plugs to access the brushes then you could try vaccuming or compressed air if you have it.

As the tax lawyers doctors say, firstly, do no harm. 

[centermin]

HAHA...

But so I understand it right, you would not take it apart and use sandpaper p180 (a fine paper strip) to rinse the commutator? Only thing I should do is to use compressed air or vaccum it out from the back?

[Gyro]

 

Yes, that's what I would say. Any chance of a side view (narrow side) of the motor? - You still haven't said whether the brushes are separately accessible.

[centermin]

Yes, that's what I would say. Any chance of a side view (narrow side) of the motor? - You still haven't said whether the brushes are separately accessible.

Ok I understand. No the brushes are not easily accessible as I tried to take them out today and I could not do it. I unscrewed all the screws and whatnots but no.. nothing happend. I DO WANT to open the motor housing case and be able to put in the vaccum cleaner and suck whatever it is that got in but I dont know how.. I guess I have to work on that tonight. look at some videos and read some more instructions.. .

Do you have any idea on how to do it? I have unscrewed all the screws.. the ones visible.. I dont see any more screws beyond them.

[centermin]

Yes, that's what I would say. Any chance of a side view (narrow side) of the motor? - You still haven't said whether the brushes are separately accessible.

[themadhippy]

that top picture shows what suspiciously looks like a brush hole,is there  another like it on the other side? and  what came out of there?

[centermin]

that top picture shows what suspiciously looks like a brush hole,is there  another like it on the other side? and  what came out of there?

Yaap! and I cleaned it with sandpaper today.

[Gyro]

Those two screws allow the outer stator (field winding and laminated steel core) of the motor to be removed, however you probably need to remove the press fitted fan to remove them.

I would seriously advise against trying to get the armature out. The brushes are under spring pressure and will spring to the center of the housing when you remove the armature (assuming that they don't snag on the bottom bearing). Removing it with no clear indication of how to re-assemble it seems like a bad idea.


EDIT: Oh, you do have the brushes out! In that case it ought to be possible to pull the armature out, the bottom bearing is probably just a tight fit in the housing. From the view down the brush hole, the comutator looks to be in good condition - no need to remove the armature to clean or smooth it. What do the brushes look like?

EDIT 1: A good rule of thumb for brush wear. If the brush is wider than it is long, then it is worn.

[centermin]

Those two screws allow the outer stator (field winding and laminated steel core) of the motor to be removed, however you probably need to remove the press fitted fan to remove them.

I would seriously advise against trying to get the armature out. The brushes are under spring pressure and will spring to the center of the housing when you remove the armature (assuming that they don't snag on the bottom bearing. Removing it with no clear indication of how to re-assemble it seems like a bad idea.


EDIT: Oh, you do have the brushes out! In that case it ought to be possible to pull the armature out, the bottom bearing is probably just a tight fit in the housing. From the view down the brush hole, the comutator looks to be in good condition - no need to remove the armature to clean or smooth it. What do the brushes look like?

I really appreciate you input and just one last question - my main question. What about the flash at the end? Or will the vaccum cleaner take care of it or some compressed air? I just like that to be gone.. I dont like how it flashed man.. it looks spookey. this is 1800W and I am over it for 5-6 hours a time

[Gyro]

That sort of compact high power motor is always going to spark when it is being started or braked. Vacuuming out any dust through the grill is as well as you can do. Even corrdless brushed drills flash when you stop them suddenly.

Photo of the brushes?

[themadhippy]

I wouldnt strip it any further,instead get a pencil eraser ,like a pencil but with a rubber in the middle instead of lead,and put it down the brush hole,rotate the motor by hand whilst wiggling the rubber,then give it a good blast of compressed air to get rid of any lefty over debris.The rubber does a surprisingly good job of getting rid of  carbon build up without scratching the copper.

[centermin]

I wouldnt strip it any further,instead get a pencil eraser ,like a pencil but with a rubber in the middle instead of lead,and put it down the brush hole,rotate the motor by hand whilst wiggling the rubber,then give it a good blast of compressed air to get rid of any lefty over debris.The rubber does a surprisingly good job of getting rid of  carbon build up without scratching the copper.

ok.  I will do that and report back with the results. But ultimately i need the flash to go away and I agree with start small. Incrementally.