I am getting fidgetty waiting for all the parts for my new MPCNC build to arrive (soon, soon!). I decided to get dust collection sorted out in advance, and bought a cheap ebay cyclone. As many others have discovered, I soon realised that unless I am super careful even my little Kaercher WD2 vacuum will crush my dust bucket in a moment. As I intend to be concentrating on the MPCNC, not the vacuum cleaner, I put together a wee parametric pressure relief valve. I hesitate to post it here as it is such a simple wee thing, several orders of magnitude below the awesome designs I see here daily (and that MPCNC core! Breathtaking!). Still, it might save someone a few minutes, so here it is:
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Sometimes the “wee simple things” are what save us from the big headaches.
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If you put your bucket into another bucket, the inner one can’t collapse.
@barry99705 Is that like the video infinity effect? 
But seriously, how do you make that connection to prevent it from collapsing?
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No. You just nest the two buckets. The outside one doesn’t have any plumbing. The vacuum between the two buckets will make it have to crush both buckets of it wants to collapse.
Given how easily and quickly my vacuum crushed one bucket, I suspect it wouldn’t have too much trouble crushing two…
I was using a Dustopper (https://www.homedepot.com/p/Dustopper-High-Efficiency-Cyclonic-Dust-Separator-12-in-Dia-with-2-5-in-hose-36-in-long-with-2-Sweep-Elbows-HD12A/315749552) which attaches to the top of a 5 gal bucket. With my shopvac, it was caving in, and had heard of the 2nd buck thing. I had another one, so dropped it in, and I never had an issue with it caving in after that, so I think the science is solid on that!! I have since upgraded to the 2hp dust collector from HF (which doesn’t work well with the Dustopper at all), and I am using a large HyperTough trashcan from Wally-world and a DIY cyclone kit. I am thinking I need to get another trash can as I am having the same cave in stuff with the trash can.
It won’t, unless you’re using an industrial vacuum. Once I started doubling the bucket it never collapsed again.
I squished a steel trash can with the little dust deputy too. Air pressure is a bitch!
This is what I did with my HF dust collector.
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Good to hear! However, the valve is a great deal cheaper than an extra bucket, and easier to fit and seal too 
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Cool. Just don’t run the vac without a filter. When the relief valve opens, all the chips and dust will bypass the cyclone and go to the vac.
I have a plan to do something similar and get it wall mounted, but we are looking to move sometime in the next year or so, which is going to limit me on what I would like to do now. I am currently set up in my garage, and if I mount anything else, then I have to redo all of it again when we finally find house and move. So I get to wait, and then see what my new digs will let me do.
This is what I go so far…
used this kit from the amazons. $22-ish for that vs the $200-ish for a 4’ dust deputy…
Good call, thanks!
Nice - I used a <ÂŁ20 cheapie (from ebay), though with the more conventional inverted-cone cyclone profile. Using with a very cheap and rather flimsy 30l black bucket. It seals well enough - I think it might have been intended for brewing beer or making wine? But much smaller scale than some of the things you gents are working on!
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Yea, the guy that bought our house really lucked out. We moved to an apartment, so the dust collection stayed in the barn.
Use your cnc to make internal gussets! 
Trash Can Cyclone Lid https://a.co/d/jkLM6id. This is what i have with a 4 inch dust collector. On a 33 gallon plastic can