My bullet was ingesting chaff from underneath. I made this to hold a mesh bag and collect the chaff that blows out the back of the cooling tray. It uses magnets to hold onto the fan screws.
You’ll need to print in ABS or something else with good heat tolerance.
Having been using this for three months, it’s been great, but the magnets have gotten weak from the heat. I think the right way to do it is to replace two of the fan screws with ones that are 5mm longer, and use an elastic shock cord to hold the chaff sock on.
Will update when I’ve remodeled.