Peter Quinn
09-08-2012, 1:22 PM
I built a Joe wood worker venturi press some time ago, tired of clamping veneers old school. Got the 7CFM venturi model, built it, tested it, holds vacuum well, pulls down a large bag quick. Haven't used it much due to procrastination, resistance to new techniques, busy schedule, yada yada yada, I have more excuses than most. So in the interest of getting this thing into regular use I'm making a simple fixed shelf for a bookcase using hard maple sawn veneer on MDF core. Slice the veneers, no problem there, that I'm actually set up for that, very predictable results. Splice the veneer, cut to width, etc.....WOW, I'm actually going to do this....make bottom platen.....find the end closure I lost two years ago, next to the second end closure I lost one year ago.....wow, I have two closures....I can make this 10' long bag shorter, only a 36" shelf after all...it may get lonely in that big bag......probably would be done by now using old school press, but this is a growth exercise as much as anything, must stay committed to process..........ok, dry run goes great......glue it up, quickly, quickly, using titebond III, quickly........put shelf in bag, breather mesh.......vacuum on and........what the, the veneer splice shifted like tectonic plates.....release vacuum, fix problem......flip vacuum lever on......Houston we have no vacuum.......press just hissing, only making 18hg....10hg....0Hg......need 29+......where is that air coming from....where is that air escaping from.....turn off press.....unscrew top in virtual panic....veneer curling now.......turn press back on to find leak.....no leaks, venturi is blown.... that Joe wood worker, I'll get him for this, barely used this thing 3 times, industrial my butt,.......%^&&****( bleeping ()*&*&^^%%.......what a minute, the venturi has to exhaust air to make vacuum, thats normal air flow...........Uh, did I turn that compressor on, or off when I flipped the switch?......check compressor gauge.......15PSI and falling......venuri requires 70+psi.....utter loud Homer Simpson style "Doubbbbt".......turn compressor which is now at 10 PSI to "ON".....venturi IMMEDIATELY starts making vacuum, press pulls down, veneer joined permanently to MDF....blood pressure returns to normal....will know results of debacle in 3 hours.
So as it turns out, when using a venuri vacuum press, you must turn on BOTH the press AND the compressor. Pretty sure I read that several years ago when I built this thing. I'm going now to print out a label for the top of the press that reads "Remember to turn on and charge compressor BEFORE applying any glue. The 80 gal compressor was apparently large enough and charged enough to pull down the bag twice, but three strikes and I was out of air. Don't you love wood working!!!
So as it turns out, when using a venuri vacuum press, you must turn on BOTH the press AND the compressor. Pretty sure I read that several years ago when I built this thing. I'm going now to print out a label for the top of the press that reads "Remember to turn on and charge compressor BEFORE applying any glue. The 80 gal compressor was apparently large enough and charged enough to pull down the bag twice, but three strikes and I was out of air. Don't you love wood working!!!