[SteelArt]

Hi Guys,

I am just about start building a CNC Table for my plasma and am finalising the design.

Now I see a lot of people out there with water beds under their tables and have seen a couple with extraction fans and a hoper system.

Just wondering what is better ? I see the water could keep the work cooler as it cuts but the extraction fan system could be cleaner.

Any comments ?

[lamicron]

water bed is fine to cut thin plates, it maintains the plate cold and get no warps. also keep the dust inside the tank.

[Big John T]

This question comes up a couple of times a week. A little reading of old posts will uncover a wealth of info.

I use a water table after testing out other schemes that didn't work well. You can test out a water table by fitting a pan of water under some steel and give it a go then make the same cut without the pan of water...

What is a hoper system?

John

[SteelArt]

yes I used the search but like a lot of things people like to comment all around and I couldn't really find anyone who was using a suction system.

A hoper was what I was planning on building under the table with teh ducts hooked up to it so when you turn it on you get even suction over the entire table. I have an extraction unit large enough to ensure all dust etc goie into the filter.

I see your point about the water cooling tha material as valid and something else to consider.

I was just thinking that water would be pretty messy compared to a ducted extraction system.

[Big John T]

this took about 5 seconds of scanning the topic titles...

http://www.cnczone.com/forums/showthread.php?t=61135

John

[SteelArt]

this took about 5 seconds of scanning the topic titles...

http://www.cnczone.com/forums/showthread.php?t=61135

John

Yep and I read it. It doesn't make a lot of sens though cause if you have water 10 - 12 inches below the slats it will have no effect on the temp of the sheet at all and from th einfo there they are saying it just catches slag. Once again not making a lot of sense to me.

If the wat isn't goingt to cool the sheet as you cut then why not just catch the crap in the hoper and get rid of the water all togeather..

Anyone got any pics of a down draft ??

Cheers and thanks for your help so far

[Big John T]

I'm guessing you read something from somewhere else as I can not find any thing in that link about the water cooling the sheet...

You need to try a hopper first... then it will make sense.

John

[SteelArt]

I'm guessing you read something from somewhere else as I can not find any thing in that link about the water cooling the sheet...

You need to try a hopper first... then it will make sense.

John

Yep it is not in the post.

2nd post in this thread says " water bed is fine to cut thin plates, it maintains the plate cold and get no warps. also keep the dust inside the tank." whih is where I got the water keeping the sheet cool from.

Then in the post you posted a link to they suggest " I agree with Tom....if you can design the system with water approx 6 to 12 inches below the top of the slats.....and pull a downdraft with your blower from above the water...then you will have a good system. Depending on what you are cutting....as much as 60% of the particles will be captured by the water....which makes taking care of the remaining 40% or so much easier."

Which would then suggest that the water is not touching the sheet is a better way to go so that the down draft system can pull the dust pre water and allow the water to catch the solid material.

From what I have read I see most people use water as it is simple and provides a reasonable amount of effect. Most of these seem to have the water lapping at the sheet whilst it is being cut.

By having the water touching the sheet I can see cooling benifits. I can accept the down draft system will be a little more complicated to setup but if it provides a better solution then that is fine.

Does anyone out there actually run a downdraft system ? If so any pictures / comments ?

[tinman13]

I have had a down draft table for a couple of years now and can say it takes out about 90 % of the dust.
Keep in mind all the stuff you suck out from under the plate has to go some where! I just blow it outside.... Not ideal depending on where you are.
I use a 24" dia. paddle type fan turning about 700 rpm, pulls a lot of air out and is fairly quiet.
That being said I have not tried a water table......
I cant imagine cleaning out that mess!
I have two trays under the table that I can pull out with the forklift and dump into the scrap bin, simple and easy.
Also a catch all for all those little parts that fall through the grate!
They can be a real pain!

Good luck, Steve

[Edwardo]

I bought a air handler ( down draft ) unit with my table, it works ok for the most part, the duct work and exhaust fan are nothing special, just a old furnace fan and duct from home depot... But!!! knowing then what i know now i would have built a water table from the the start, and i am planning on converting it in the near future. Not saying there is anything wrong with the air handler, but what i didnt consider at the time was our climate, the air it is sucking out of my garage through the handler needs to be replaced with air from out side,in warmer months its great, doors wide open etc... when its minus 40 outside, you can imagine what happens to the temperature inside in a short period of time.... I thought about running more duct from outside in over the table for it to draw in air, but after talking to people with water tables, im convinced they are the way to go. Different people have different opinions on the actual water height, some have the water level a few inches below the bottom of the material, some have it a few inches over the top of the material being cut, and others anywhere inbetween... personally i want to make mine so the water level is touching or just over the top of the material, reason being is i think you will still have some smoke and dust with a gap between the material and the water, and also to control warping... I did a test awhile back, i ran a garden hose to the table and sprayed water on the plate as i was cutting, and with the air handler running also( summer )... the difference was amazing... i usually cut 1/16 to 1/8 plate and there was no warping at all and as well as i thought the air handler was performing, there was a huge difference in the reduction of fumes, smoke and dust....only problem is the water runs out the bottom onto the floor and im not going to stand there all day holding a garden hose...
So there are a few things to consider before deciding on air venting or water, or a combination of both... i wish i had researched it more...live and learn.

EDD

[Big John T]

Edwardo,

I finally got some pictures of my water table uploaded.



It is just below the slats...
John

[Edwardo]

Looks Great John

Is the water tray free standing, or did you attach it to the table? Just out of curiousity, you have slots cut along the length of your slats, what are they for? I went back and was reading some post, i also have issues with handling the sheets of steel... and i have been giving it some thought for some time, the 4x8 1/16 and 1/8 are relatively easy to man handle with 2 people, but most of the time i am working alone in my garage, i also dont have the room or height for a small forklift, or the money to buy 1... i have a old suburban truck that i use to haul sheets in, i only buy 4-5 sheets at a time and just leave them in the truck until needed, one thought was to make a rack to store the sheets laying flat, then slide them onto a cart that is the same height as the table, wheel it into the garage and slide the sheet onto the table, this way the sheets are laying flat from the supplier to the table.. i know it sounds like alot of b.s. but i cant think of anything else at the moment.. Im away from home until next week, when i get back i'll try and post some pics as well...

EDD

[Big John T]

Edwardo,

The water tray sits on the brackets on each corner. You can see one next to the blue leg and wrapping around the horizontal square tube. The slots were to make it easier to bend... didn't work out well. My table can have a full sheet at it fits between the aluminum and the supports. Most of my work is small parts so I just have the steel supplier shear the sheets in half then store them upright. If I had to handle sheets that were too heavy I would build a small A frame lift to straddle the table with a chain hoist or use a manual winch to raise and lower the sheets.

John

[Edwardo]

John

Hats off to you and everyone else who built there own cnc tables, and to thoughs planning to, i would'nt have known where to start or where to find the patience... just started this past spring in cnc, wish i were home more to learn faster, but it'll come eventually...

EDD

[jipeess]

hi all

on my project, i made a seperat water tank under the table, it´s got "foldable" wheels so it can be easily moved out/in (in case of cleaning/inspection; dont know how often that would happen, this prototype is just finished...)


js

[Edwardo]

jipeess

thats a nicely designed table you have, everything looks so neat and tidy and it can be loaded from 3 sides... really cool.. i think this is 1 of the first tables i seen with the gantry running length wise... can you provide any more info on it, steppers or servo's...software... what is the length of your gantry, are you using duo motors or a cross shaft, THC...

[jipeess]

hi again,

some info:
plasma unit from Kjellberg (German brand), mod. PA S45W, 130A, water cooled machine torch
X, Y & Z:
Sanyo Denki servo+drive
Hiwin linear guides
belt drive
Mach3 (of course!)
CandCNC´s MP1000C THC
collision protection on torch holder
tank capacity: 900 liters
table fill takes about 1,5 min., dump takes less 20 sec. (big pneumatic dump valve), a "sump depression" along the table´s rear catches the slag when draining, so it can be scooped out (at least, thats the idea; dont know yet what the fines will do with the tank, maybe it will just circulate.. )

i used to build stone work machinery before, this is my first attempt to build a plasma table,

would you like me to post any particular close up pic?

js

[jipeess]

forgot the measures (metric);

tool scope: 3100x1600
torch travel: 120
table: 3300x2000
weight: 1500 kg
rapid move, X: 30 m/min., Y: 20 m/min., Z (torch): 10 m/min.

js

[Edwardo]

js

even though i'm a canuck, i have to brush up on my metric conversion... got your table going light speed over a table the size of saskatchewan on the first conversion..kidding
What interests me along with seeing different table designs and builds is the method of dust, smoke, fume extraction... from previous post you can understand why. I want to convert my table to water, just not sure now which way to go now. I like the style of water tray that John made , but now i see along with your table, other people using a separate tank or bladder to fill and empty the table with in minutes or less, im curious what the advantage is and if its worth the extra time and money to build. At the moment im not getting alot of use with my table ( 3-4 months a year), but everything i've done to date is for the future when i hope to be able to go full time on it.
I can see the advantage of dropping the water out for cleaning, and re-using it over again, especially with any additives in the water, but wouldnt that mean you then have to clean what remaining in the table and whatever went into the tank... not sure, just wondering is all, and like you said it a prototype and time will tell... regardless, its a cool looking table and i hope it works out well for you. If possible i would like to see more photos of the tank, and how it connects to the table.

Regards
EDD

[jipeess]

hi Edwardo,

did a rough imperial conversion;


tool scope: 10´x 5´
torch travel: 5"
rapid move, X: 1180 ipm, Y: 590 ipm, Z (torch): 295 ipm

js