down draft clear coating table/booth

[Marty]

hi all
my clear coat application has been hit or miss in terms of air borne contamination and solvent pop
The solvent pop issue I now have under control, but depending on air currents in or outside my shop, the result can be perfect mirror like glassy or have need for strip and recoat......clear coat application has ALOT of overspray....even with the fan spread narrowed and fluid flow turned down.......so because of the huge over spray cloud I have always had to keep large doors at opposite ends of the shop opened, with a large shop fan at each door, one to push the air out and the other to bring it in........this creates "turbulence" and brings dirty shop air to the paint table.....or, if it breezy outside, the breeze comes into the shop.....same problem, just different dirt:)

So..........I need to build or buy an open face booth/table, prefer downdraft, with a plenum below, (same idea as a downdraft plenum on a plasma table), then duct the overspray through a wall to the outdoors, with a scrubber filter assembly at the termination of the duct on the outside wall......hopefully the result will be a slower laminar flow, air flow ONLY at the booth, no turbulence from the fans or the outdoors, allowing me to keep all shop doors closed while spraying.....and joy then happens:) If there was an emoticon for "crossed fingers it would be here####

OK guys....here is what I know, I will need a tube axial type fan, with ducting and the fan properly sized for the CFM of the booth, a variable speed control, mounted at the booth for the fan speed . I plan to use Plexiglas or other clear plasticffor top and sides, mount fluorescent lights outside the plexiglass. Likely will want a filter system at the top to filter the air as it is drawn straight down and this also would keep most the shop air entering the front of the booth.......kind of an air curtain............The paint /table booth area is 5 feet wide and up to 7 feet high, and 3 feet deep.....

Has anyone built or purchased or seen such a table?
Thanks all

Marty

[Marty]

I am in build phase....will post pics and specs when done......downdraft paint spray table......been a loooong time comin:):)

[Baileigh Inc]

what is solvent pop?

[Marty]

basically, solvent pop occurs when solvents in the clear coat cannot reach the surface and expand/dry because the top surface of the clearcoat material has skinned over too soon.....so very tiny bubbles are seen in the clear coat...here is a link with more http://www.tcpglobal.com/sol26.html

attached are pictures of the finished booth...I love it!

Marty

[Baileigh Inc]

Thanks

[abmetal]

I just use my downdraft plasma table. I cover the part of the table that I'm not using and it works great.

Allen

[Marty]

hmmmmm.......i have a water table:)

[Garysbiz]

Nice build on the spray booth, where did you get the fan and motor? How much did they cost? Thanks

[Marty]

Bought the 12" tubeaxial fan w/motor from JC Fabrication http://www.jcmetalfab.com/
$570.00 plus about $100 shipping to California. He also has the best price on companion flanges....need them to adapt the 12" --------26 gauge ducting fittings to the bolt pattern on each side of the fan houding....I did however end up cuttting one of my own flanges om my plasma table.....since i ordered only one and needed two.....would have been faster/cheaper to buy the flange......I still have the dxf dwg for the 8 bolt flange if you want it
Bought 12 inch 26 ga sheet metal duct fittings and parts locally, used 1/4" plexiglass to build the surround, used expanded metal grate with the lowest amount of drag (yes, grid size and grid wire gauge greatly affects air flow) , used 4"x4" 8 ga grid to support the filter media (the 4X4 grid was adapted from vertical retail display rack,about $25.00 locally) , using Paint Pockets high performance overspray arrestors pads 20X20 , at the out door exhaust using Dayton wall mounted shutter picture is attached
If want more details, happy to discuss on the phone, PM me if desired

Marty

[hooked]

what is solvent pop?

PAINTERS CALL IT FISH EYE!! CONTAIMENTS ON SURFACE!!

[hooked]

hi all
my clear coat application has been hit or miss in terms of air borne contamination and solvent pop
The solvent pop issue I now have under control, but depending on air currents in or outside my shop, the result can be perfect mirror like glassy or have need for strip and recoat......clear coat application has ALOT of overspray....even with the fan spread narrowed and fluid flow turned down.......so because of the huge over spray cloud I have always had to keep large doors at opposite ends of the shop opened, with a large shop fan at each door, one to push the air out and the other to bring it in........this creates "turbulence" and brings dirty shop air to the paint table.....or, if it breezy outside, the breeze comes into the shop.....same problem, just different dirt:)

So..........I need to build or buy an open face booth/table, prefer downdraft, with a plenum below, (same idea as a downdraft plenum on a plasma table), then duct the overspray through a wall to the outdoors, with a scrubber filter assembly at the termination of the duct on the outside wall......hopefully the result will be a slower laminar flow, air flow ONLY at the booth, no turbulence from the fans or the outdoors, allowing me to keep all shop doors closed while spraying.....and joy then happens:) If there was an emoticon for "crossed fingers it would be here####

OK guys....here is what I know, I will need a tube axial type fan, with ducting and the fan properly sized for the CFM of the booth, a variable speed control, mounted at the booth for the fan speed . I plan to use Plexiglas or other clear plasticffor top and sides, mount fluorescent lights outside the plexiglass. Likely will want a filter system at the top to filter the air as it is drawn straight down and this also would keep most the shop air entering the front of the booth.......kind of an air curtain............The paint /table booth area is 5 feet wide and up to 7 feet high, and 3 feet deep.....

Has anyone built or purchased or seen such a table?
Thanks all

Marty

Marty i built mine out of a 55 gal drum! and used a 16x25 filter the squrial cage fan and a birlap bag on the exit hose. mine has a 24 x 30 deck with 16 x 24 sides and i used hinges for the top and it folds up to put away for storage! keeps the feet from getting pink paint on them when i make stuff for my kids!!! lol

[mr.stickerz]

Hey there all! Hey Marty did you notice any issue with having the downdraft vent uncovered? like to much suction in one spot? I read this post last week and decided to build a paint booth like yours. Mine is 6'w x 3' d' x 4' tall. The fan i had just laying in the yard from another project and not sure its CFM, it runs on a .5 hp a/c motor. But i thought the suction was all just over the vent in the center of the booth. I haven't painted anything yet but i decided to cut a piece of pegboard 3' x 4' and laid it 1.5" (on a 2x4 ) over the vent, leaving 1 ft at each of the table . now it seams to have a way more even suction throughout the entire booth. thought id share! thanks for the visual plans Marty! Ill post pics of mine when its all finished

[SeanP]

I might as well add my version to this post as well, been using this for etch primer and 2 pack paint, works a treat.
I dont have to space to have a permanent fixture, this can be wheeled away and the fan used to vent the shop/table.
It's actually a greenhouse fan I am using, very powerfull and fairly quiet.

Pics link here

[crazy59860]

Marty,
What did you use for the filter? Does it get plugged up fast with clear coat? Trying to figure out whats best to use.
Thanks
Toni

[Marty]

I use 20X20 white Paint Pockets...they hold ALOT of overspray, up to 6 lbs per square foot......there is no comparison to using household furnace filters etc in terms of efficiency and longevity.....here is a link http://www.paintpockets.com/products-paint-pockets.asp These filters are what many auto body shops use, especially in down craft booths......My system filters overspray then flows outdoors to a damper....and I get no complaints about odors what so ever.....I had contemplated adding an additional charcoal based exhaust filter for odors but just do not need it

I also installed a Dwyer manometer, measures pressure differential above and below the filters so I know when the filters are getting to the end of service life....I attached 3 pictures

Marty

[crazy59860]

Thanks for the info...........much appreciated.
Toni

[Cracker Red]

Started on my table/booth today. Thanks Marty!

60" x 40 around 38" tall. Going to order that pricey fan tomorrow. Should have lights and sides on it tomorrow and be pretty close.


Biggest problem I have to overcome.....the shop is concrete block and brick.....how do I get a 12-14" hole cut in that?!?

[Marty]

for that block wall

draw a cricle with a heavy duty felt pen, drill several 1 inch holes , using a masonary bit and hammer drill

Then connect the holes with a recip saw and a demo blade, pass yur 12 inch duct thru, seal with some goop

OR

drill one larger hole, insert dynamite stick, light fuse, getaway:)

call around town, someone can do it, for a couple of bucks

dont let it stop you tho

Marty

[CNCCAJUN]

Is there a reason you went with a down draft booth versus a back draft booth.

After looking at JC Metal Fab website it got me thinking. It seems for flat items like signs it would work better.

But then there is the problem of "runs" I guess. Just checking out a theory . .

Steve

[Marty]

the down draft simply won the coin toss it was that simple

PLUS I did a few hours of Googling which way to go and down draft won out again

? Good ? Crossdraft: Air is pulled through one end of the booth from the shop or plant. The air flows parallel to the floor, over the product, and into the filter bank on the opposite side of the booth. The filter bank captures particulate, and the air is exhausted into the atmosphere though ducting.

? Better ? Side downdraft: Air enters the booth through a full-length ceiling plenum, and flows downward over the product. When the air reaches the floor, it is pulled into the floor-level filtered exhaust plenums on each side of the booth, and exhausted into the atmosphere through ducting.

? Even Better ? Semi-downdraft: Air is introduced to the booth through the ceiling in the first 25-30% of the booth. The exhaust fan continues to pull the air through the working chamber, causing the air to change directions and become parallel to the floor. Air is then drawn over the product, through the exhaust chamber at the booth rear, and vented to the atmosphere through ducting.

? Best ? Downdraft: Air flows vertically from the ceiling intake plenum at the top of the booth, over the product, and into the filtered exhaust pit in the floor. It?s then exhausted into the atmosphere.

Downdraft airflow is generally accepted as the best type of airflow for a paint booth. It does an excellent job of controlling overspray and contamination, and provides a safe, clean environment in which to paint. Because of the cost of a pit and volume of airflow, it is also the most expensive style.

[Marty]

i did not build a pit below, that is for a really big downdraft booth in an auto body shop

But the idea is that it is easier to preclude and avoid particulates (dust as it is called outside California) with a downdraft flow of air...easier to control what crao is above your work piece than to the side of it

If you will spend a few minutes on Google on the subject of downdraft vs backdrfat vs side draft you will see the consensus is towards downdraft

another advantage for my shop is that I am able to have the booth just 3 inches from the 2 walls to the back and side.....space saving......the exhaust air is vented DOWN then to a single 12 inch duct 90 degree fitting then out the wall to a outdoor damper

a back draft booth will need a 12 inch duct 90 degree fitting BEHIND the paint booth to get to the exhaust route, this will require maybe 18 inches away from the wall , PLUS add maybe another 90 degree fitting or two to get to the wall that will exit the duct thru.......the more fittings required, the more flow impedence.....just like a water line with a bunch of fittings....restricts flow

[CNCCAJUN]

Thanks . . .

You sound like a guy that does research on everything before jumping . .

I like that . .

Thanks again
Steve

[acourtjester]

I may be missing something but I thought the first part was about paint straying with lots of over spray that was the problem.
Have you tried a HVLP gun this remove a great amount of over spray.
http://www.harborfreight.com/20-oz-8-cf ... 67181.html

[Marty]

jester that is actually funny'0
Have i not tried a harbor fright HVLP gun?
No I have not, I bypassed that route.
Does it produce less overspray than my Iwata LPH 400 HVLP? http://www.iwata-medea.com/products/spray-guns/w-400/

ANY clearcoat gun produces alot of overspray

So I built a booth to contain it and evacuate it outta my shop

Pray tell......if I use the spray gun you specified, will that eliminate the need for a spray booth? I could have saved alot of money:):)

I recommend using an HVLP gun for any clearcoating application.

[acourtjester]

I was just saying if you had not used any HVLP gun it would help but you are already using one.
The HF was just for a reference note not that it is a great gun.

have fun
tom