downdraft table design

[karossii]

Hi all!

I am eagerly awaiting the shipment of my new carvewright, and thought I might go ahead and get started on a project in the mean time to help pass the long hours I am counting off until it arrives;

I have seen several ingenious downdraft setups, and am wondering if anyone (or hopefully, a few of you) might be able to post general dimensions needed for the table, the slot, etc., so that I can draft up a decent design which will work?

I plan on making it a somewhat portable unit, as I will probably be using the CW in at least 2 if not 3 locations...I have a few ideas in mind but haven't started drawing out anything solid just yet, since I need some dimensions.

Also, I am looking at several systems, I assume ~ 2.5 microns or less is a requirement; what CFM should I be going for at a minimum, about 1,000? I have found that very few DC systems list decibel ratings, any suggestions on powerful but relatively quiet performers? At least, nothing louder tan the carvewright would be, that is . . . :)

Thanks for any input you may have,

- Ken


(P.S. I have done several searches and replied to a few threads about DD systems already; noone yet has given dimensions that I have found, and I didn't feel like hijacking any other threads.)

[MikeMcCoy]

I'm not home so I can't be real specific with answers but you wan't your slot just big enough to accomodate the slot on the CW. Use weather strip to keep from sucking dust all across the electronics. I have a 1 1/2 HP DC for my shop but I just use the Fein Turbo vacuum for the CW. It works fine and is a whole lot quieter than the DC or a regular vacuum.

[Jeff_Birt]

Thought I had noted the dimensions down in the thread I had started on the subject, but I guess not. Here are the specs on the dust collection unit I purchased.


I picked up a 2hp Grizzly G1029 dust collection unit yesterday and got it put in today. I read many reviews of different DC systems and looked at several yesterday. I choose the Grizzly as it offered the biggest bang for the buck: 2.5 micron filter bag, free pre-separator (trash can separator), 2 HP motor, 1600 CFM and static pressure of 11", for $279 ($20 off). It is largish for my 1 car garage/workshop but it will probably last me forever.

It is my opinion that the 2.5 micron or smaller filtration is a must. Otherwise your just blowing out the really small, really harmful to your lungs, particles back out into the air. From what I read before buying a DC you need about 600~700 CFM per tool. The 1600 CFM my unit is rated for seems OK for leaving the floor sweep (another must) open a bit while having the other hose on the CW. My next step will be to create a 'filter box' to mount up near the ceiling. The second DC hose will run up to it and Pull air through a 3M filtrete air filter to catch any of the stuff that gets out into the air. It's just a poor man's replacement for the commercial units with a built in fan. I figured I can keep the filter box running along with any other tool that uses the DC and let it run for 15 minutes of so afterwords.

Ha! Just found a post where Doc Wheeler listed the 'slot size' (I searched for 'slot size': http://forum.carvewright.com/showpost.php?p=47859&postcount=5. One other tip is to keep the collection box/tube under the machine as small as possible. You want to keep the air moving through it. I made a 'U' shaped tubular piece: http://forum.carvewright.com/showthread.php?t=3704&highlight=automatic+air+blast, other have cut the top off a large piece of PVC pipe.

[wasacop75]

What size does one need to mount on a portable unit?
One that can be moved around the garage or shop?
I hope to get my machine ordered soon and will need a DD system
so that mother will let me play in the garage till i get the shop built.

Thanks.

Mike

[Kenm810]

Mine is a bit on the large size, (36" tall x 40" long x 30" deep)
It's mobile and has a self contained DD System built in.
I've seen a few larger and several smaller,
it depends a lot on how much room you have.

[karossii]

Jeff,

Thanks for a lot of good info, and a great job on that search for the slot size! Now I just need to know where that slot is to be positioned on the tabletop in relation to the carvewright, lol.

From what I have read up on DC systems, the actual CFM pulled through any ducting is roughly half (in some setups as little as a third) of the advertised CFM of the machine, which is assuming an open fan with no filters or duct work. So your ~ 1,600 CFM is actually down to about 800 CFM due to your setup... possibly even just over 500 CFM (especially considering you leave your floor sweep open a bit.

That's why I was assuming 1,000+ CFM as a minimum.

I've also found some great info on the ESD + Dust Cloud phenomenons, particularly regarding PVC ducting. From what I can see, and I actually have gone and pulled a few books to verify/back up what I read online, there is no cause for concern there...it is a myth that metal ducting or 'grounded' pvc (its impossible to ground pvc) ducting is needed. Here's a link to the best article I have seen, even if it is very old; http://home.comcast.net/~rodec/woodworking/articles/DC_myths.html


Mine is a bit on the large size, (36" tall x 40" long x 30" deep)
It's mobile and has a self contained DD System built in.
I've seen a few larger and several smaller,
it depends a lot on how much room you have.
I like the self-contained DC unit you have there Ken, it would be great for portability... where is the dust collected, and what level of filtration do you have? Are you using standard DC dust bags in the base of the unit?

[Jeff_Birt]

Yes, I think the real possibility of causing an explosion in the home shop due to static build up via a DC system is about nill. The most probable issue is getting a nasty shock or having a static discharge damage a piece of electronic equipment.

And yes, you cant 'ground' a plastic pipe. What you can do however is prevent a static charge from building up by providing for a conductive path between the inner and outer walls of the pipe. Usually this is done by using a really shirt self tapping screws inserted through the pipe every 12"~24". All the screws are tied together with a copper wire with is grounded.

For my flex tubing I do not run copper wire inside it as everyone always suggest, that just causes clogs. Instead I lace the wire around a rib every 18" or so. Doing so around a rib gives you a nice mechanical connection inside and out and will not allow the tubing to tear. You can dab a bit of silicone over the penetration to seal them up.

Edit: I 'think' the slot is centered L-R (front is keypad side), but it is not centered F-R.

[Ike]

Yes, I think the real possibility of causing an explosion in the home shop due to static build up via a DC system is about nill. The most probable issue is getting a nasty shock or having a static discharge damage a piece of electronic equipment.

And yes, you cant 'ground' a plastic pipe. What you can do however is prevent a static charge from building up by providing for a conductive path between the inner and outer walls of the pipe. Usually this is done by using a really shirt self tapping screws inserted through the pipe every 12"~24". All the screws are tied together with a copper wire with is grounded.

For my flex tubing I do not run copper wire inside it as everyone always suggest, that just causes clogs. Instead I lace the wire around a rib every 18" or so. Doing so around a rib gives you a nice mechanical connection inside and out and will not allow the tubing to tear. You can dab a bit of silicone over the penetration to seal them up.

Edit: I 'think' the slot is centered L-R (front is keypad side), but it is not centered F-R.

Jeff, that is a brilliant idea! I have heard of running a straight copper wire through the pipe, but using screws is just brilliant! Thanks for sharing that!

Ike

[karossii]

Yes, if you follow that link, it is an old page about ESD and DC systems, but it seems all accurate and up to date per my independent research recently; and it mentions the screws as being the best possible form of static discharge reduction... but it also mentions it really isn't necessary to have them, as the chances of anything occurring within the ducts is as near to 0% as is possible for anything (there's always the exception to prove any rule). It is a very long read, but it is worth it if you like to keep yourself informed about the whys and hows, in addition to the how-to's.

[Jeff_Birt]

Yes, I read that guys info too. Let me repeat what I said earlier though for clarification. The real danger of an ungrounded DC system is a static discharge damaging your CarveWright. A few folks have manged to do this with their shop-vacs. Proper grounding prevents the static build up.

[Deolman]

On 2 different occasions I stopped the carving and started to vacuum the sawdust out of there. On both occasions, static electricity hit and caused a fatal error on the CarveWright system. This forced a power down reset to start carving again. (I had an anti-static strap on the vacuum hose as well as holding on to the metal of the CarveWright at the same time.)

I decided the best plan from there would be to build a downdraft box for dust collection. Now if I see too much sawdust building up I just shoot a little air in there to stir things up. The DD will then pull it out of there. No static with the air. And yes, my DC system is grounded.

[tackytim]

I was wondering if anyone here has made a down draft system using a "squirrel cage" blower from a furnace. I'm just not sure how many CFM's they would pull. My thought is, if the motor turned the blower fast enough, and the enclosure was sealed properly, the air movement could be enough to be an effective down draft system. I have 2 squirrel cage blowers and that is my reason for asking. I intend to make one for my CC whether its a DC or down draft table.

Any thoughts?

[bowfingers]

Here is a great web site there is a lot of useful information on dust collection.
http://billpentz.com/woodworking/cyclone/Index.cfm

[AskBud]

I was wondering if anyone here has made a down draft system using a "squirrel cage" blower from a furnace. I'm just not sure how many CFM's they would pull. My thought is, if the motor turned the blower fast enough, and the enclosure was sealed properly, the air movement could be enough to be an effective down draft system. I have 2 squirrel cage blowers and that is my reason for asking. I intend to make one for my CC whether its a DC or down draft table.

Any thoughts?
Check this post:
http://forum.carvewright.com/showthread.php?p=76208#poststop
You could send him a PM, if you need more info.
AskBud

[jcorder]

I was wondering if anyone here has made a down draft system using a "squirrel cage" blower from a furnace. I'm just not sure how many CFM's they would pull. My thought is, if the motor turned the blower fast enough, and the enclosure was sealed properly, the air movement could be enough to be an effective down draft system. I have 2 squirrel cage blowers and that is my reason for asking. I intend to make one for my CC whether its a DC or down draft table.

Any thoughts?

Here is a link that I built my table from. It is great for sanding. I cut the 2 inch slit for the CW on one end and drilled holes to sand over on the other end. It made a world of difference for the dust inside the machine.

http://www.woodworkersworkshop.com/plansshare/air_filter_downdraft_sanding_table.htm

Good luck
Jeff

[pkunk]

Here is a link that I built my table from. It is great for sanding. I cut the 2 inch slit for the CW on one end and drilled holes to sand over on the other end. It made a world of difference for the dust inside the machine.

http://www.woodworkersworkshop.com/plansshare/air_filter_downdraft_sanding_table.htm

Good luck
Jeff
I built a sanding table just like that many years ago with a 3000cfm fan that works great as a sanding table. It'll suck the piece I'm sanding down so hard that it won't move. I never thought of using it for the CW as I have big dustcollection in the shop & it is so easy to just plug my CW stand into a DC port. However, you have made me think of making a different top for my sanding table as it would be quieter. The sound of the CW is one thing, but add a 3hp cyclone to the works & I really need to move out of the shop.
http://home-and-garden.webshots.com/photo/1061965740043929597BYDszF?vhost=home-and-garden

[Kenm810]

Quiet and efficient, yep it works for me.
I have a shop dust and chip Collection system with dedicated vacuum duct stations
for the Table Saw, Band Saw, Shaper, Planer, Bench Sanders, and so on.
But my carver is more mobile and I move it around occasionally,
so being that the internal blower dust and Chip system is self contained in the DD Cabinet.
I just plug it in and carve.

[jcorder]

I built a sanding table just like that many years ago with a 3000cfm fan that works great as a sanding table. It'll suck the piece I'm sanding down so hard that it won't move. I never thought of using it for the CW as I have big dustcollection in the shop & it is so easy to just plug my CW stand into a DC port. However, you have made me think of making a different top for my sanding table as it would be quieter. The sound of the CW is one thing, but add a 3hp cyclone to the works & I really need to move out of the shop.
http://home-and-garden.webshots.com/photo/1061965740043929597BYDszF?vhost=home-and-garden

The thing works great, what I like about it is I can take the piece out of the machine, sand it right there and I am done making a mess with it, just move to the finish table and go after it. And you are correct, it is certainly a lot more quiet than my dust collection system.

Jeff

[karossii]

Okay, so here is what I am thinking...

http://www.progressive-growth.com/proddetail.php?prod=15010 for the blower, 2800 CFM should be adequate. From my research (greatly aided by sites linked to in the above thread), I need to be moving at least 1,500 cubic feet of air through the table per minute. With no ducting, there is not as much loss as in a ducted system, but with a dual layer filter setup, I will be losing ~ 36% of the power, making the 2,800 drop to just under 1,800 total CFM.

I haven't decided on the specific brand/size filter, but I will be using HEPA standards dual layer filters, a 1" thick pre-filter that removes chips and large particles down to ~ 3.0 microns, and a fine 2" thick filter which removes down to ~ 0.3 microns (97.7% of all particles 0.3 microns or larger to be specific).

(as a side note, I am trying to keep all the dropped letters corrected, but if I have major bad spelling in this post, especially dropped letters or spaces, my wireless keyboard needs new batteries so I will blame it for now!)

I still don't have precise dimensions, but based on the overall footprint of the CarveWright, I think a 36" cube split in two halves will be perfect.

The 'left' half (it really isn't a right/ left specific, just how I picture it in the drawings) will house the blower and both filters, as well as power. The 'right' half will house a sawdust collection bag and contain the opening (2.25" x 17.25") near te center when both units are attached together to mate to the CarveWright.

They will be separable down the center for portability; making two 18" x 36" x 36" boxes, both with 4 caster wheels.

I plan to have a top mounted 4-outlet power box on the top surface, allowing the carvewright and a couple of other accessories (such as a laptop if/when I use it on the go) to be plugged in. I plan to have this outlet on a circuit breaker (possibly using GFI) for safety purposes. Power will be set up to plug into a main, or to plug into a generator.

The 'left' half will be sealed all around (using silicon at all joints probably), covering the blower half and only allowing air in through the filters and out through the port. I may have a hinged door to allow access to the blower and/or power outlets {though the breaker switch will be on the outside, serving a dual purpose as an emergency kill switch}, as there WILL be a time in the future I need to get at it, but I may just leave it sealed and worry about detaching one wall later, to help with the seal (a hinged door would introduce one more layer of complexity in achieving a sealed chamber).

The right half will be left open to allow for as much space for dust collection as possible. The bag will probably be a large envelope style dust bag, with a frame inside it to prevent collapsing, sized as close to 18"x36"x36" as I can get it, taking up the whole of the side. There will be a port in the top near the outer edge of this half to allow a (very) short hose to attach to the exhaust muffler as well.

Both halves will be mated with weather stripping to minimize air intake along the seam, which will most likely be a large rabbet, possibly tongue and groove joint, with 2-3 lock-down latches on each side to maintain a tight seal.

I have some sketchup images, but they are too large and low quality anyway, so the typed description should be as good to go on. As I actually get specific dimensions and decide on specific parts, I will post to this thread, eventually to include pictures of the plans and project.

As I am still early in the design stage, suggestions are welcome and easy to incorporate. (They'll always be welcome, just not always as easy to integrate the further I get into the project).

I am contemplating a small low pressure air compressor to add in a blower to the bit as several on the forums have done, but not sure where it will fit inside, or if it would be needed as an integrated component, instead of just setting it on top of the table as needed. I am already pushing my budget on just the bare minimums for this table, and anything that can be reasonably added at a later date probably should be.

- Ken

[AskBud]

I'll bet you can find a local place in your area that has used blowers, just ask a Furnace man. I'll bet you can save some $$.
AskBud

[Kenm810]

Ken,

I would check around at a few Heating companies as mentioned before,
most furnace blowers last from 10 to 20 year.
The one I picked up was only about 3 to 5 years old and being replaced by a larger unit,
I gave the guy $20.00 to clean it up and put in my Van,
He said they keep several around for relpacements or parts but still throw 3 or 4 a week into the dumpster.

[karossii]

I've called a few heating / HVAC companies in the area; so far none have any extras, except one who wanted to sell me a used unit for $350. When I sent them a link (from my post above) to the brand new units for $240, they tried to say that it is an unreliable brand name...

My guess is that they are full of it and got caught trying to cheat me. However, has anyone heard anything (good or bad) about Grotek? I'll do some of my own online research, just wondering if anyone's heard of them.

Thanks!

- Ken

[Jeff_Birt]

For that price I would buy a REAL dust collection unit.

[Kenm810]

I just looked it up on google and saw this
Squirrel Cage blower/motor sources? - North Carolina Woodworker (http://www.ncwoodworker.net/forums/f19/squirrel-cage-blower-motor-sources-14527/)
Any reliable sources or 110v squirrel cage blowers with motors? ...
I got a 16" 2000 cfm squirrel cage blower from a vendor I found on ebay for $39.00 ...

[Norman Griffiths]

Kenm: Iwas just reading your blog and was wondering what all the pneumatic lines were for. Being a newbie I have done a lot of reading here but arn't sure about this one. Any help would be appreciated. Thankks Norm

[CraigBrownDesigns]

Looks like they're there to blow the milled chips off the side to the open area of the down draft. I manually do this, but I think I'm about "borrow" this idea and integrate it into my table! Looks like it's very efficient!

[Kenm810]

Hi Norm, and Welcome to the CW Forum

I like to tinker with my shop machines, and since my Warranty ran out on my carver about 2 years ago,
I’ve made a few modifications to it that helps clean the project and the machine a little as its carving.
Many of my projects are 10” to 14”wide or carved on a Sled, so most of the slot between the traction belts is blocked by the carving.
I added a side out let to the machine that vents directly into the top of the DD Cabinet along with the rear exhaust port.
The tubing you see feeds dry regulated compressed air to the two adjustable air jets on the front deck of the machine and to the air sweep mounted on the carving head, they all help direct the dust and chips off the carving and away from the pressure rollers, plus electronics, and out the side of the machine. I carve a lot a products that results in a lot fine dust like SignFoam, etc.,
So this is just my way of dealing with it. http://forum.carvewright.com/images/smilies/icon_wink.gif

[Norman Griffiths]

Thanks Ken that clears up the questions(dust between my ears)
for me, I just might try this after the warrenty expires. Thanks again Norm