J. Phil Thien's Projects

Ducky911 thanks for your reply - I think you may be right that the bellmouth is collecting the exit flow from a larger diameter than a straight outlet would. This will be pretty easy to test although I have no way of measuring its efficacy. I suppose we are hoping that the turbulent air, around the inlet of the outlet, will be of a smaller diameter than the bellmouth and therefore not encourage so much of the fine dust to enter? It may then make more sense for the outlet to be closer to the top of the chamber.

Thanks for the compliment on the build - despite its defficiencies it is still a very worthwhile addition to the workshop.

Mike

Time for an update with a few photos. I apologise for the quality of imagery but photography is not one of my skills.

I have done quite a bit of machining since the last message and in that time the DC has not been over taxed in terms of filter bag clogging. With the amount of machining I have done I would expect to have to clean the bag by now so, this is a big plus. However, there is a lot of the fine dust still getting through as can be seen by the evidence of dust in the outlet duct and the amount collected in the DC bag.

Also of interest is the track of dust left on the baffle. Does this indicate the drop slot is in the wrong place?

The other photo is of the dust that has collected on the outlet, above the bellmouth and a small trace of dust clinging to the top of the separator.

I am at a bit of a loss as to what to change, if anything, as the initial tests showed that a low set bellmouth allowed a lot of dust into the outlet. The thought then was to raise the outlet to near the top of the separator but the photos would suggest there is a lot of fine dust up there too. Any suggestions would be welcome.

Although it is not perfect, it is a lot better than I had before and is a great addition to my workshop - thanks again Phil and Retired.

Mike

Hi JSP, Although I haven't used my 1.5H design much, I can say that at 400mm (16") it seems to work really well. My 'Brute' like bin is only 450mm (18") diameter so I don't see that there should be a problem with your bin size. It is interesting that Mr Dyson has gone to smaller and smaller diameter cyclones and bunching them together, in his cleaners. I do appreciate that the vacuum cleaner has high velocity, low volume air supply whereas our DC systems tend to use high volume, low velocity but it could be that the smaller diameter may be better at accelerating the smaller particles - hmmm?

I think the general message here is to suck it and see. Whatever you come up with will definitely be an improvement on a DC only solution.

Mike

Thanks, Phil - I look forward to getting down to some serious machining and I will report back when I have a few hours completed, hopefully without having to clean the filter bag. Thanks again for the forum and the advice held here.

Mike

Phil; looking at the video, do you think the baffle could be rotated further from the inlet as the dust appears to be hitting the baffle just at the end of landing area rather than at the start? I'm not sure if the landing area is supposed to collect the dust, as it drops out, or whether the dust should be falling directly into the slot. If it is the latter, then maybe I should move the landing area back, toward the inlet.

Jdon; if you look closely you will see blue, yellow and shiny silver bits :)

If you have read through the whole thread, you will realise I machine a lot of moulds and plugs for model aircraft. Most are made from epoxy board which is basically a huge block of epoxy resin that is filled with some kind of filler. I suspect it is talcum but the manufacturer will not tell me as the composition is a trade secret ??? Sometimes I will machine aluminium hence the shiny bits. It is the blue and yellow epoxy board that is giving me problems with the dust clogging the DC filter bag after just a couple of hours machining. I have some loooong, fifteen plus hours machining jobs coming up for a large scale model I am building and I needed a solution. Hopefully the separator will be the answer.

I made my CNC machine some years ago and, if you really want to send yourself to sleep, there is a very long thread on my build on the CNCZone forum http://www.cnczone.com/forums/cnc-wood-router-project-log/6840-sure-im-ready-ive-started-building.html

Flexible ducting arrived today so I managed to get a test installation set up. I am feeling much happier now I have done a little more testing. I have made a short video but don't know if I can embed a YouTube video in this forum so I'll just post this link for now https://www.youtube.com/watch?v=uHVHt42zfjs and hope it works. The test was done by dipping the inlet, flexible duct into a container of dust and chips collected from previous machinings. Not very scientific but useful.

I raised the outlet to approximately 50mm above the bottom of the inlet and it appears most of the finer dust is now able to fall through the drop slot. However, I did notice that quite a bit of the finer dust remains suspended at the top of the separator, circulating indefinitely until the DC is turned off. As they were very fine particles I was unable to see what then happened to them as I neither saw them fall through the slot or get drawn into the outlet. There is a trace of fine dust in the outlet, flexible duct.

Jdon; I don't think the drop slot is too far out and you will have noticed that I have indeed changed the start position of the slot after Phil's suggestion. The height of the outlet is very easy to change and, I believe it needs to go higher, not lower. The testing was done at 50mm from the baffle which, I think, was Retired2's recommendation at 1/2D. However as my design is 1.5H, and the air below the inlet is moving much slower, I think it may be better positioned at 50mm above the bottom of the inlet. This will be my next move.

Schreck; thanks for the compliment - yes, moving the outlet up is going to be the easiest thing to try next.

The chalk test would be good if only I knew where to get hold of some :)

Mike

OK, initial testing has been a little disappointing :( I managed to rig the separator up enough to do some testing without being connected to my machine ducting i.e. the inlet was not connected to anything. I had removed the filter and collection bags from my DC and ensured everything was clean. Without fitting the bags to the DC, I started the extractor to see what kind of suction I was getting at the inlet. All was good, it seemed to be as good as I ever had before. I then threw some larger dust particles (very small chips) into the inlet and watched them rotate and drop obediently into the bin - so far so good and I was getting quite excited.

I then tried a cupful of the finer dust my machine produces and was horrified to see quite a lot dispelled through the DC. Watching as it entered the chamber, I noticed that once the air dropped below the entry level, the speed dropped off dramatically and the dust made its way easily to the outlet without getting anywhere near the drop slot.

This is a 1.5H design and I am wondering whether a 1H would be better in that the air is constantly re-accelerated each time it passes the inlet. Failing that, in order to keep the air velocity up and the particles attached to the wall, maybe a tapered wall, below the inlet would be needed. Is this why the cyclone type separators are tapered? An alternative may be to add a shelf, at the inlet height and to raise the outlet to just above this height. At the moment, the outlet is about 50mm from the baffle, well into the slower air region.

One positive was that the bin liner does not get sucked up toward the baffle. My liner does not have a cage but is an excellent fit over the rim of the bin. (See photo) The baffle is also an excellent fit in the top of the bin, consequently no air can get between the bin and the liner and hence it stays in place.

I have now cleaned and washed my filter bag so the next lot of testing will have the bags attached and I will try raising the outlet before thinking about attaching an internal shelf. Any thoughts would be appreciated.

Mike

OK, that's good enough for me - thanks Phil.

I'll now get everything sealed up and see how it performs. Just about to laser cut the straighteners and get them installed too. Not yet sure if I have enough ducting and flexible tubing to complete the installation but if I have, I may just get it up and running tomorrow. Unfortunately, with all the machining of the plugs, I will have to dismantle and clean my filter bag again :( What a pain - still, hopefully, it may be the last time for quite some time :)

Mike

Nearly there and it's only taken one month! That's extremely good - for me.

Just have to use some silicone sealant to prevent leaks and I can soon be testing. Before I apply the silicone, I would like some feedback on the positioning of the baffle. In one of the 'Assembled' photos you can see the current position where I have placed the start of the shelf at the end of the inlet, tapered floor (where the two bits of polycarbonate meet). I have made the assumption that the air will still be travelling more or less parallel with the inlet, at this point, and will not have started to fall appreciably.

It will not be too big a job to remove the baffle and rotate it if necessary although this would mean breaking the silicone seal and re-applying it. I will go with whatever the consensus is, if there is one :)

Mike

Edit: Just remembered - I have to add the straighteners too.

Hi Latham; Love the clear top - it makes a lot of sense. I was a bit concerned with my polycarbonate wall as I often machine aluminium and wondered whether the chips would scratch the plastic. Your idea of the clear top negates that problem all together. Nice one  8)

Beware!!!! It can become addictive, especially if you are into new technologies. I am a member of this forumhttps://groups.google.com/forum/#!forum/deltabot as the printer I am getting is called a Delta printer because of the way it works and this is the actual printer I have ordered via KickStarter though the production machine differs quite a bit from that in the video. https://www.kickstarter.com/projects/ttstam/openbeam-kossel-pro-a-new-type-of-3d-printer

Hi Phil; a 3D printer would be perfectly capable of printing the inlet, provided there was enough build height. The only problem might be the surface finish. If you take a look on any of the 3D forums you can see examples of builds and, dependent on layer thickness, the finished article always has a corrugated surface texture. Some people have devised ways of post processing the parts by dipping them in acetone, or appropriate solvent, to give a better surface finish. I would imagine that the inlet really needs to be as smooth as possible on the inner surface. Finer finishes are achievable by using smaller layer heights. The standard layer height appears to be around 0.2mm but 0.05 is doable though this would take four times longer to manufacture!

Material costs are around 28 dollars per kilo. My finished, glass inlet weighs 330g and is heavier than an equivalent plastic one would be. I reckon 250g should be doable which would make the costs around 7 dollars per inlet. Time to print? - not a clue at present but I dare say a question on one of the forums may well get an answer.

I don't know who started it but all I can say is thank goodness the development was done by a guy savvy enough to put this forum together so that others may learn and help the development - thanks Phil.

Quotesome of these builds are way over the top!

I don't know about that, it's just the way I happen to work and know. You guys like manipulating wood, I like making moulds and plugs. In the end, both methods get the job done.

Retired2; I like your comment about the 3D printer because it so happens I have one on the way!

Bell mouth is now laid up - just waiting for the resin to cure before attaching the duct.

Mike