Official Luthiers Forum!

Hello Everyone

I was hoping someone might help with a problem I'm having with a used
Craftex 25" dual drum sander.

I haven't had it long and recently when I started it there was a flash coming
from the area enclosing the motor and a sound I can only describe as a mini
explosion or a loud noise you might expect from a static electricity source.
Obviously it caught my attention. At first I couldn't make it happen again but after
more use it's happening again. I've checked the wiring connections and they
look OK.

My theory is that because the dust collection is very poor on this machine, dust
falls into the motor area and collects in the end of the motor opposite the pulley.
I suspect most motors must have some spark present on start up and this is igniting
fine dust. It seems if I blow out this area with compressed area it doesn't happen.

What am I missing here?
Scares the #&*% out of me when it happens!!

Any thoughts?

Bob Hames

If it had happened once and you hadn't restarted the machine since then, I would have guessed that the starter capacitor exploded. But I don't think that could happen multiple times.

_________________
Jim Kirby
kirby@udel.edu

The same thing happened to me with my Belt sander. I grounded my dust collector and it hasn't happened since.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Hey Bob,

I have General International which is probably the same basic machine. At first I thought the same as Jim but if that happened it wouldn't start again. Even the dust collection on these units is not great you still need to have it. I use 1.5 hp collector and built a two into one fitting out of 4 inch furnace duct pipe that the four inch flexible hose from the collector hooks onto. The fine dust seems to get picked up, I know this because the air gets awful thick when I forget to turn the collector one, but some of the heavier dust stays on the conveyor and dumps into a bucket I have on the outfeed side. If you are having minor dust explosions you need to solve that before you get a bigger one! Maybe the motor could use a tune up at the local electrical shop so that it does not spark on start up and you also need to deal with fine dust. Not much help, I know, but I sure hope you get a handle on this before too long! Oh ya, you can take part of the lower covers off and just watch for what is going on and you are also then removing some of the confinement that make these little explosions worse.

Shane

_________________
Canada

John Hall is spot on. I have touched an ungrounded DC hose before and have been lit up like a Christmas tree doing it. Little Van-Degraff machines is what they are. Your machine is building up static. Whether or not you improve your DC, add some kind of grounding wire to the body. Yeah, I know, it seems weird to ground a plastic body... but if you stop and think about it... a drum sander can, under the right conditions act just like a Van-Degraff (sp??) machine.

Mike

check this out: http://www.14wfie.com/global/story.asp?s=9644712

Mike

Thanks guys for the ideas.

I concur that static is an issue, get your arm within 6 inches
of the hose and all the hair stands up. Furthermore the
sound it makes suggest static to me.

What puzzles me is that suppose the machine has been idle for a
week, I hook up the hose from the dust collector, then turn on the
sander before the dust collector. No static should be present yet
should it? Can a charge be held this long? I'm no electrician, but
isn't that one function of a capacitor...to hold a charge?

I will try the grounding at any rate.

Another thing I'll work on is improving the dust collection. I've already
split the line as per Shane. I found this on Mike Doolin's site
http://www.DoolinGuitars.com/articles/blower/
which makes sense.

Thanks Again
Bob Hames

That rolling drum is (under the right conditions) a static generator. It sounds like your machine itself is not properly grounded to bleed of static charge. THATS the issue.

I have a treadmill in the workout room.The metal roller in the back has a wire connectiing the bearing shell to the metal frame. When I changed the belt, I forgot to hook that back up and the whole thing turned into a Van-Degraff machine!

Ouch!

Mike