Humming Ventilation

[Joe Pelonio]

This morning before starting another big job I cleaned the laser, not just lenses/mirrors but blew out the dust with air and vacuumed it. Found a few odd bits in the bottom, but apparently something, probably a bit of card stock went into the exhaust. All day long it made an annoying sound trying to get out of the 4" metal elbow, bouncing around in there. Finally just now it made it, and now apparently is hitting the squirrel cage. Just making a ticking sound but out front in the showroom, where the plastic pipe goes above the drop ceiling, it's transmitting a vibration and real loud hum. I wonder if the people above me are getting it up there. I hate to have to take it all apart when I'm within a month or two of moving anyway.

[Mike Hood]

Can you reverse the blower for a few moments to see if you can draw it back in?

["Terry Pless"]

Try blocking the inlet to stop the intake of air then suddenly open it, sometimes the rush of incoming air will dislodge it. Sometimes it won't. Terry

[Joe Pelonio]

I don't know of a way to reverse it (AC). Tried blocking and restarting but no help. When I turned it off I carefully listened and felt it and it looks like I will have to take it apart. Whatever it is that's stuck is heavy enough that it's thrown the squirrel cage off balance, and I'm afraid if I leave it that way it will wear out the bearings. This is a 600cfm 8".

[Joe Pelonio]

All fixed. I took it apart and found first a 3" letter P that was stuck on the entry point and hitting the fan. Then a letter L that was actually stuck around a fin of the fan. Removed them and it was quiet with no more vibration. Put it back together and made a velcro-attached screen to prevent future card stock bits from flying up the exhaust. I do a fair amount of stencils, often 100 at a time so this may prevent future problems. BTW I found that the only accumulation of dust/debris was in the right angle bend of the 4" metal tubing just before the fan, the rest was pretty clean for two years of use.

[Joe Pelonio]

Here's the stencil the letter that caused all the trouble came from.