Fulmen
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Making an acrylic büchner funnel
What do you do when you lack a piece large enough to make something? Here's one solution, inspired by 3D-printing (during assembly):
The funnel will be 70mm and is made by gluing disks of 6mm SAN sheet together. It will then be machined internally before the top, filter disk and
bottom are glued together. It can then be machined externally.
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aga
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Cool ! It's a solution for sure.
I guess it could all be 3D printed.
Easier as two parts, but i suppose glue would work to hold the disc in place.
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Fulmen
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Here's the sketch of the assembly.
It''s beneficial to keep the glued area as small as possible by roughing out the parts before assembly. Since the glue is solvent based the drying
depends on diffusion, reducing the diffusion path by a factor of two should reduce drying time by a factor of four.
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unionised
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It will be if he tries to filter any strong solvents
As A kid I had a filter funnel made by cutting the top off a plastic bleach bottle. The "plate" was perforated zinc- which is not really inert enough.
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Fulmen
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Chemical compatibility will be an issue in some cases, but I rarely work with aggressive chemicals. I will of course replace my broken ceramic funnel
in time, but this was a simple and fun fix.
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Radium212
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Careful of thermal expansion. If each piece expanded a different amount, after a while it would eventually shake itself apart.
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Fulmen
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Why would the segments expand at different rates? They are from the exact same material and glued together with SAN dissolved in MEK. Of course the
bonds will be weak points, but they will only see compressive loads.
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unionised
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I'm not sure about that.
I think the bits that form the conical section will try to "peel" apart.
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Fulmen
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Fair enough, there might be some bending loads on the segments in the cone. But it's only subjected to vacuum, and that really isn't much of a load.
It's deliberately over-engineered for easy machinability, but I ran it through stress analysis and got a safety factor of 15. I think it will survive.
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aga
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It's a good practical solution Fulmen.
Nice one.
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unionised
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The vacuum isn't a load at all, but atmospheric pressure is about a ton to the square foot.
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Fulmen
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Details, schmetails.
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Fulmen
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O ye, of little faith. Watch and weep:
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Twospoons
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Quote: Originally posted by aga  |
I guess it could all be 3D printed.
Easier as two parts, but i suppose glue would work to hold the disc in place. |
I 3d printed mine in PLA+ (some kind of modified PLA thats not as brittle). In two parts to avoid the need for support during printing.
I didn't glue the parts together, as I only wanted gravity filtering. Worked a treat.
Pic is from my cad model (Solidworks)
Helicopter: "helico" -> spiral, "pter" -> with wings
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DrP
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Are these acrylics and PLAs solvent resistant? How are they with weak solvents like Methanol, hexane and IPA? Should be alright I suppose - good idea.
:-)
\"It\'s a man\'s obligation to stick his boneration in a women\'s separation; this sort of penetration will increase the population of the younger
generation\" - Eric Cartman
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Twospoons
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Pretty easy to find out
Chemical resistance chart
There are half a dozen different polymers available for 3d printers, so it shouldn't be too hard to find one to suit a given purpose.
[Edited on 3-4-2018 by Twospoons]
Helicopter: "helico" -> spiral, "pter" -> with wings
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Fulmen
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I wouldn't use SAN for any solvent (except water) or strong acids/lye. I made the funnel for recrystallization work, if I ever need to work with
solvents I'll buy a glass funnel.
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RogueRose
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I had some success using a 3" PVC end cap and drilling holes in a plate to fit inside the plate. The caps are available in 4", 6" & 8" as well
and also in CPVC and ABS.
I posted pics in this thread of how I made it. I added a threaded hose barb and ran tubing to a vacuum flask, or placed the barb into a bung in the
flask.
https://www.sciencemadness.org/whisper/viewthread.php?tid=61...
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