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Down Draft Table

Posted: Mon Oct 28, 2019 8:20 pm
by sansspaceship
I have a few projects on the go that I thought might be of interest to the forum while I wait for parts to arrive before I get into some actual rocket building. The first of which is a downdraft table for sanding composites/metal grinding & possibly some welding; this has been on my hit list for a while as I generally work inside, and hate the dust for all the obvious reasons.

It would have been simpler to buy a commercial unit, however, space is a bit of a premium so have gone the path of build my own. Time will tell if it was a wise investment. A few people have built them on the net, but they seem to be less towards the commercial end of town, and so this will be a little bit different.

Note that I am not the worlds fastest builder, as I do a bit of travel for work etc but will try to keep a steady pace. It is not massive project and seeing some of the stuff that is put up on the forum, some of the guys here could probably knock it up in a day build.

Work area is going to be somewhere between 600x600-900mm.

Will try to keep the material list up to date.

- Spark Arrestor 24x24x2" Metal Mesh - DualDraw
- 4 x Omni Directional Wheel - Rotorcastor
- 1 x 3015 m3/hr Exhaust Fan (not sure if I should have gone a squirrel fan) - Pure Ventilation
- 1 x GPO Clipsal
- 1 x On/Off Speed selector switch

Re: Down Draft Table

Posted: Mon Oct 28, 2019 8:45 pm
by sansspaceship
The filtration I am going to start with is based on using these 3 Filters in line, which should keep most stuff out of my lungs.

- Spark Arrestor (24x24x2") 592x592x292mm - to hopefully stop anything hot getting into the paper filters

- Pre Filter - Merv8 or G4 (24x24x2") 594x594x45mm- low pressure drop - to get all the chunky bits - this is the cheapie at about $20 each

- Main Filter F9 92x592x292mm - I may need to go eventually to a higher HEPA rating filter - if I want to start welding SS etc, but went this way as it was easily able to be sourced.

At this stage I have the Spark Arrestor which I imported out of the USA, and am waiting for the other two filters and holding frames before I actually start cutting aluminum for the table.


Re: Down Draft Table

Posted: Mon Oct 28, 2019 9:02 pm
by sansspaceship
I debated which way to go with regards to fans - i.e. commercial exhaust fan or the more common squirrel fan for our US counterparts.

At this stage I settled on a single 3015 m3/hr exhaust fan, during the build I will make prevision to install a second one, if need be - but all the filters can handle the volume of air, so as long as the pressure drop off isn't too great hopefully I won't have suction issues. The face plate is 450x450mm.

fan-2.jpg (243.53 KiB) Viewed 3553 times

On the weekend I got a start on some of the support brackets for the fan, and the mounts for the castors - these have been cut out of some 6mm aluminum I had laying about. The brackets were just cut with a chop saw and sanded, the brackets I knocked out on the CNC mill.

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wheels.jpg (176.63 KiB) Viewed 3553 times

Re: Down Draft Table

Posted: Wed Oct 30, 2019 5:26 pm
by sansspaceship
Filters arrived today - so can now start on the frame this weekend - all things being equal.


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All the three filters - showing how they will sit.

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This is the main filter - that will get rid of the fine dust.

Re: Down Draft Table

Posted: Sat Nov 09, 2019 10:14 pm
by joeman
I've always been paranoid about dust when sanding.

Sounds like a very good idea.

Looks very professional!

Re: Down Draft Table

Posted: Sun Nov 10, 2019 2:32 pm
by sansspaceship
Thanks for the compliment!

Yes the dust is a major hassle - I generally work in side due to being Darwin, it is currently about 36/c and pushing about 80% humidity outside in the shade and is just feral to work in. (getting softer as I get older)

I use a random orbital sander with mirka sanding pads, it has a vacuum attachment which is pretty good; hopefully this will be a big step up.

Had to spend the last 2 weekends doing 'love' jobs for friends so haven't got much done on the project.

Although I managed to get all the tubing cut this morning so will get back on to it in a week or so, as heading away this week for work.


Re: Down Draft Table

Posted: Mon Nov 18, 2019 9:54 pm
by sansspaceship
Just a quick update, I have got the two end parts of the table welded up, not much to show but will put a few photos up for the sake of providing something to look at.

As part of this little project I have had to teach myself TIG welding, so progress was pretty slow when I got to this section, as the 'T' joints were giving me hell, but have them to a level to keep moving.

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Jigged up and on the table.

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Tacking up.

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Corner weld, I will grind the ends of this as it will have another square bar on top, as part of the frame, not ideal. In hind sight I I should have stopped them short and started them long.

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This is one of the final pieces to arrive this is the grill that will go on the top, it is some form of composite - that is used for walkways, it has a non slip-grit sprayed onto it - I will probably take some form of disk to try and remove that, although it does a good job of keeping the floor mat in place.

Final dimension of the table will be circa 920mm x 618mm as the grill is just slightly oversize of the mat.

Cheers - Adrian

Re: Down Draft Table

Posted: Tue Nov 19, 2019 6:53 am
by OverTheTop
Looking good so far!

Re: Down Draft Table

Posted: Wed Dec 04, 2019 5:55 pm
by sansspaceship
Thanks for your comments 'overthetop' !

It's pretty quite on the forum so always nice to know someone is watching. :D

Just a quick update, got the filter system all mounted on the weekend between other tasks.

In the end just went for clips, to lock the 3 filters in place, that allow me increase/decrease tension with the mounting ... and little fuss.

Have been slowly amassing the remaining parts, mainly electrical fittings etc. I have a friend who is a sparky, so I will mount it all up and he will come in and do all the terminations.

All told I am pretty happy with how the frame came out, I have managed to keep it pretty square - given this was my first ever welding attempt, it could have come out a hell of a lot worse.

Hopefully will get the wheels mounted and the frame painted over the weekend and the electrics setup for termination.

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Front View

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Side View

p.s. they look a little wonky as I havent' set the latches up to the same tension. The other think I need to do is run a few fingers to help guide the filters into position. I


Re: Down Draft Table

Posted: Wed Dec 04, 2019 7:30 pm
by Aquaman33
Looks great.

I have always wanted to learn to weld.

Your welds look great for someone who is learning.

Look forward to seeing it when it's finished.

Re: Down Draft Table

Posted: Thu Dec 05, 2019 12:35 pm
by sansspaceship
Thanks, Aquaman

Welding has been on my skill wish list for some time, also.

Don't worry, like most people I only uploaded the good welds 8)

I had plenty that started life looking like the below, that needed to be ground and done again, and again :oops: with plenty of cussing in-between, thankfully that part of the learning curve is over.

weld1.jpg (79.63 KiB) Viewed 3014 times

Re: Down Draft Table

Posted: Thu Dec 05, 2019 4:02 pm
by OverTheTop
You just need to get a rhythm going, and also think about heat control. By changing the duration you spend on each side as you stitch along the join you aim to keep the temperatures the same. It is all in the wrist action :wink:

and an angle-grinder is your friend...

Re: Down Draft Table

Posted: Sun Dec 15, 2019 4:07 pm
by sansspaceship
Comments are very true overthetop! i have been lucky to have people that I can call on to point me in the right direction, as youtube is only so good at somethings.

My main issue was electrode stick out, I had it hanging out too far; the other issue was heat. But got a 15amp circuit installed into the house (this week) so have got that problem sorted just in time to weld the 6mm plates for the wheels to the base.

Anyway, just a quick update and some photos, as the days have got away from me - but I have been chugging away slowly in the background ... between work and the xmas cheer. :mrgreen:

Stuff ticketed off, since last update:

a) Got the sides cut on a friends cnc - as the hole for the fan was too large for my machine.
b) all the side & base panels have been cut to size
c) Ran into an issue when trying to fit the nut certs for the wheels in the 6mm Alu (basically the material was too thick) so chose to re-mill the 4 plates.
d) Earthing points have been put in, at 4 locations


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Wheel Base Plates

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Earthing - I have managed to but these bolts in through the base; once I weld the wheel base plates on these will somewhat permanent.
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Re: Down Draft Table

Posted: Tue Dec 24, 2019 7:07 pm
by sansspaceship
Well not a heap done in the last week - but have crossed off the following:

- Wheel plates welded on
- Nutserts for three of the four panels installed
- CNC'ed up the wings which will provide a foldable fence around the top of the table - that can be folded down for large items.

Have a good Xmas everyone !


Re: Down Draft Table

Posted: Fri Jan 03, 2020 2:09 pm
by strud
Looks very nicely done thus far!

Not hard to tell you are likely a perfectionist, which isn't a bad thing :-)