Squirrel cage blowers

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05-05-2018, 05:40 PM
bhdavis1cnc

Squirrel cage blowers

I have a chance to pick up some new 1.5 hp approx. 1200 cfm squirrel cage blowers on the cheap. Question I have is if anyone has ever set up a CNC bleed board system using squirrel cage blowers.

The existing hold down system on my 4x8 CNC is 4 pairs of 1 hp show vac style motors with one pair directly plumbed to each of four 2x4 quadrants. You activate a quadrant by powering the 2 vac motors plumbed to that section.

Several of these vac motors have failed and need replacing. I stumbled on this squirrel cage blower deal with a friend and thought I might give it a try on one of the quadrants before spending the money on the new vac motors.

My concern is not the CFM capacity of the blowers but rather their vac holding power through the bleed board once a quadrant is covered with material to be cut. Given the open center section of a squirrel cage blower wheel I can imagine that air turbulence is possible within the squirrel cage, thus reducing the suction.

Any input?

BH
05-05-2018, 07:29 PM
Al_The_Man

Re: Squirrel cage blowers

If these are ordinary induction motor fans, the generally do not have the RPM's for vacuum applications.
Al.
05-06-2018, 12:33 AM
bhdavis1cnc

Re: Squirrel cage blowers

Al.
Thanks for the reply. They are capacitor start open frame 1725 rpm motors. 1-1/2 hp.

The blower has been mounted onto a steel base by the original owner. I've placed the blower on its side and covered the ~18" x 18" bottom (input) side with a sheet of plywood. When the blower is running it snaps the plywood tight to the base and it takes some force to pull off. The current draw (120/240 motor wired at 120 for this test) jumps from about 16 with free air
to the max 19 amps with the plywood in place. I'm not sure yet if I'll put bleeder holes on the intake........I don't think I need them for blower life but perhaps to reduce the amperage draw during use.

I'm thinking this might work since these blowers are around 1200 cfm vs. the typical shop vac built hold down system that used 4 to 8 individual ~100 cfm vac motors. At what I'm getting them for I could easily use one per 2' x 4' quadrant on the 4' x 8' table.

BH