I discovered early on my used powder recovery was not matching my packing density, IE a print with a 30% packing density would not net a full 70% used powder after post processing (PA12). The discrepancy seemed significant since I was chronically low on used powder and had to up the refresh rate quite a bit to fill the hopper for the next print, which ultimately equals higher per part cost. I estimated this to be somewhere around 10-15% of the total powder lost. Its no secret that we have to vacuum powder at various points within the work flow, and some rightfully should not be reused. Some, however, I see no reason why it should not be recycled. Powder that accumulates in the sift work area, around the gaskets of the build chamber between the chamber and sift, and within the large hepa filter, should theoretically be fine. (note that this is not a formlabs sanctioned process!).
The device I devised is a simple cyclonic dust capture system mated to a 3kg powder jug via an adapter I designed. The device accepts the industrial vac hose and allows me to clean the sift work area and hepa filter while capturing the powder for future use. Once I’m done vacuuming the area I dump it into the sift to capture any stray bits/fibers that may be present. I plan to make refinements so its less cumbersome to use but it gets the job done.
A full chamber nets me 300-500 grams of used powder that would otherwise end up in the vacuum waste chamber (I also have a cyclonic capture system in front of the vacc to prolong the life of the vacuum bags).
300-500 grams of powder may not seem like a lot but my operation requires extreme efficiency to sustain itself, so every little bit helps! This system has worked well for me.
I was also thinking about this, now you reinforce my will to do it. Couple this with the glovebox and you will be saving much more material. Are you also vacuuming the powder left on the machine, and other parts of the sift?
Generally I stick with powder in and around the sift, a TON goes into the large hepa filter. I’ve not saved any of the powder in the fuse because the powder around the print surface is constantly hit by the IR lamps, so I presume its cooked and below the chamber the powder is contaminated with laurolactam.
Can you tell us what parts you print that will allow you to achieve a higher packing density than 30%. We print on demand + our own products. Most of the time these are boxes or just general shapes. However, it is almost impossible to exceed 25% packing density. Once we reached 50% and once 70%, but that was really an extreme case when we printed straight square bars vertically and we prepared the 3D model in another software so that we could put the bars completely together at a distance of a few tenths of a millimeter, so there was almost no empty space between them. Even though the bars were almost together, we achieved “only” 70% packing density. Prefor also calculates the necessary powder that is in the printing chamber, but it is not possible to print into this space.
Our regular printing chamber ranges between 15-25% packing density.
I am with you on this, very difficult to achieve higher than 25%. But I think his approach is to have the most material possible being recycled, because in the current workflow many material which is perfectly ok is wasted when vacuuming the sift.
I regularly achieve 25% plus with my models. Most of what I print are cone shaped parts that nest within each other, as well as smaller 1-5x10x40mm parts that I spread around the print volume to fill space. If I print a full chamber of the 1-5x10x40mm parts I can get, IIRC, 52% packing density (1600 parts!). When I first started with this it was apparent that optimization of my models was necessary to achieve my target packing density and production goals. I don’t print for anyone else, only for my operation, so I have very close control over each print.
Nifty thing to come up with. Well done.