On Sunday 21 February 2021 20:38:06 Gregg Eshelman via Emc-users wrote: > The trick is to cool the thermoplastic just enough that it won't sag > and fall over, while remaining melty enough for the next hot layer to > fuse to it. Has me wondering if 3D printers could have an extra > bridging fan, a small one with a precisely aimed nozzle that could > quickly turn on when reaching a spot to bridge then off as the nozzle > goes over a previous layer? > > That would require additional processing by the printer to identify > unsupported bridging and modifications to the printer software and > hardware for the bridging fan. But if it would work to firm up the > first layer across open space the layers above would benefit from the > better support. > > On Sunday, February 21, 2021, 2:02:37 PM MST, Frank Tkalcevic > <[email protected]> wrote: > > The "nozzle fan" is actually a "part fan", used to cool down some > plastics, especially PLA, that have a low (50c) transition > temperature. Cooling the nozzle, and heat block is bad; that's why > they make silicone "socks" to cover the heat block and nozzle.
Which brings up the next fault some don't well understand, that of hot plastic flowing back up into the heatsink due to extra extraction where they want to move without laying plastic, and it then freezes solid. The best cure for that is the ejector motor as close to the nozzle as can be arrainged, On the microswiss kit for an ender3, the wheels of the x carriage are in the way, so the minimum distance is about 50mm, but cura doesn't know that until you tell it, it thinks there is 18" of bowden tube between them so it retracts about 6.5mm. With my 2" in a dead straight line, a retraction of 1.2mm is a great plenty, and that won't pull hot plastic back into the heat sink freezing it solid mid-job. The OEM hot end for the ender3 is acually a decent design you can modify to stop he leaks by breaking the tubing about 20 thou longer than from the back of the nozzle to the shark fitting on top of its hest sink, makeing sure its dead square on the end, go thru your junk box and find a teeny washer the filament will just pass thru, cut a 6" piece of filament for use as washer alignment, stick the filament thru into the nozzle, put your length of Capricorn in, put the washer on next, followed by the shark fitting, You've got the Capricorn trimmed to the correct length if the shark fitting starts to compress it about 1 turn before its fully home. Go ahead and tighten it down, otherwise if your ejector is still on the left frame, its action will turn it loose again. The idea is to have the Capricorn compressed against the rear of the nozzle, stopping the leaks down the nozzle threads that will fill up its sock, pushing it into your work and more than likely knocking it off the glass. At which point you refresh your inventory of suitable 4 letter words and start over, after spending 2 hours to clean up the mess. Its all got to come apart and get all the plastic back out of it by burning it out on the gas cookstove. Its a PITA! > > You may want to try printing without the part cooling fan coming on > for PETG, as it sounds like those first layers worked well. At just barely running, 30% ack the display, seems to be about right. But IF you don't want it to be cranked up by cura, theres a time setting per layer that defaults to 10 seconds, make it 200 and that stops that. And from the wording of the pop up for the cooling check box, I think cura does a best guess but does not shut that fan off when its unchecked. Untested. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
