I've been using this device to collect kief from trim, and comparing results with other methods. Pollen extractor-dry sifting machine-pollinator-pollenextractor | eBay It's a bit too small. The metal mesh cylinder measures about 3.5 x 6.5 inches. Getting more than about an ounce of trim would harm its operation. The combined falling action and scraping by rotating mesh is what makes this work. If the cylinder were larger, the distace fallen would be greater, the herb would hit the cylinder with more velocity, and collection might be faster. As it is, I continued getting kief after about 2 days of continuous operation. I had used scissors to cut up big leaves and stems. Surprisingly, the quality did not diminish with time after one initial freezing, but no more cooling thereafter. The only way I knew the trim was finished is that the trichome collection slowed to almost zero. I've tried this with several different auto strains, and the average collection rate is about 10%. I've also tried Bubble Bowls, Bubble Buckets, and trimming tray with screen. Any method that requires shaking isn't fun. These other devices had noticeable quality deteriation, and yielded more of a lower quality procuct, about a 15% return. The different piles come from different collection days.
I made one of those using an ice cream freezer and 100 mesh (about 150 micron) stainless screen. It's bigger than that one. I've only used it outside during the winter when the temp was about 0F. It worked fairly well but I think B&W's Hashmaster probably would work faster although I haven't tried it. Not that speed is an issue, I just turned it on and let it tumble until it stopped producing kief.
200 micron. I agree it's a bit green, but not as green as other methods I've tried. I'm looking for an easy diy version of this that is made out of a rock or bullet tumbler, or an ice cream maker.