OOPS, no third pic

Here it is.

To get the downdraught to work you need air - LOTS of air, my little 4x4 uses 3000cfm and could do with a little more, thats a 12" axial fan on a short duct venting outside, I have to keep the door or window open for replenish air.

It needs a large plenum below the table to funnel the flow into the fan/s mine is an inverted pyramid but i think a square box would probably work. The fan needs metal blades as it will be dealing with sparks etc.

Only a little thing. 

Maybe face the racks downward.  It is such a dirty process.

Only a little thing. 

Maybe face the racks downward.  It is such a dirty process.

Very dirty, get the racks upside-down and also cover the linear rails somehow, the crap get everywhere but luckily falls downwards instead of floating about so simple covers over the top of motion work well.

Ah Ok, sounds like a lot of air needed, I may have to rethink that. Wonder if maybe water will be a better option after all, just have to pump it round to alleviate the hydrogen risk. Maybe even just a water slide, ie have water just coming out a pipe along the shallow edge so it flows down into a tank below and gets pumped round. Filtering may become an issue though


Regarding the racks, not set on the direction of them yet, they were that way due to the swivelling but I have actually redesigned that part so that the table sits 100mm higher so it will not be a problem, just havent redone the drawing.
I do have bellows from the glass machine but they are covered in grease inside so I have not inspected them yet. Not sure if they are fire retardant or not but will test it out.

I was thinking about things last night and I am wondering if, now I have a proper home for the plasma, whether I really need the swivel. I will put the frame in place today and put the Y axis on top and see if I reckon there will be enough room in front, it will only be about 500mm but that may be enough.

Hood

Hi Hood,

for reasons of contamination I would consider having your gear rack on the outside and with the teeth facing down. As they are in the drawing you have gravity letting dust, etc settle on the teeth, as well as any sparks (abrasive slag) from the cutting.

The linear rails will be much easier to keep clean and lubricated but gear teeth are just a bunch of nooks and crannies.

Keith.

I fitted the optional double seal and scraper kits on my plasma linear rails, seemed a good idea.

beefy, yes Greolt pointed that out. I have bellow covers but still not had a chance to really look at them and see whether they are suitable (flame retardant). I will however be having the track pointing downwards as I have decided I have enough room so do not require the swivel table.
I got a wee bit done at the weekend, frame is basically finished and hopefully this weekend I will get the Y axis profile rails fitted and maybe even get the X axis cut and fabricated.

I read back through the earlier posts as I remember mention of fans etc and I see it was Robert who posted some info, will have to quiz  you more about this



Hood

Hi hood, I think Dave has got an extra zero in the 3000cfm (~1.2m3/sec) number above from a 12" axial fan.

From the day job, you could try to improve the capture airflow by using a set of vent grilles or slats below the cutting bed that are 60degree upside down. V shaped slats with maybe 1.2mm copper cladding over the top so the plasma kerf metal spray does not stick to them

You could also place a piece of plate over any unused parts of the table and this will increase the airflow over the used bit of the table.

The rough rule of thumb would be 0.5 to 1m/s per square metre of table...but you need to consider how much of your table is covered in plate normally...   You also need to add a bit for leakae plus fan performance.

Look for mixed flow fans... Stuff like vent axia powerflow fans will get you better performance than an axial fan (airflow at pressure)... Axial have very little pressure (head) capability.

Rob

My apologies, the fan rating is 3200cubic metres per hour so almost 2000cfm.

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