![]() You can go 25mm/sec and still get stunning quality. If your printing speed is 14mm/sec then there is no slow down. The jerk speed is typically 20mm/sec (this is not true jerk - this has to do with the speed at sharp corners - if jerk is 20mm/sec then it will for example slow to 14mm/sec on a right angle corner). ![]() The solution is to print it all at one speed - and the closest you can get to one speed is infinite acceleration and infinite jerk. When it slows down for the corner it overextrudes because the corner is printing slower yet the pressure in the head hasn't changed much. Imagine you are printing a cube and that means a square on each layer (outermost shell. But the printer can only go so fast before it loses steps.ĭo you understand the part about high pressure in the nozzle? And how there is a delay between when you speed up or slow down and when the pressure coreespondingly speeds up or slows down? It can easily take 10 seconds for the pressure to equalize after a speed change. But the solution isn't to lower the acceleration - the solution is to increase the acceleration so it doesn't pause so long on the corners. Does that make sense? The X/Y can slow down much faster than the extrusion pressure. So if you are printing at given speed and the pressure is say 500psi and you slow down for a corner in a cube to 1/4 speed you want the pressure to correspondingly to drop really fast to 1/4 of the pressure so the filament comes out 1/4 as fast but because there is a storage in the bowden or in the filament or other parts of the printer, it takes a few seconds for the pressure to drop so you get overextrusion on corners (and on the z seam or any other place it slows down briefly). And the bowden tube on a UM printer or the actual compressive springiness of the filament acts like a spring. Okay so realize first that the pressure in the nozzle can easily reach 1000psi (7000 kpa). I am sorry for asking this basic question but when setting a lower print speed does this then also influence the extrusion speed? I'm usually not in a rush and I have several printers. Even then it's a bit of a hack.Īnyway, the UM answer I suppose is to basically slow down the outer most printed shell.Īnyway this issue is much less pronounced on my UM2 than most printers because it has a reasonable jerk value (20m/sec) and a high acceleration value (default is 5000mm/s/s) compared to most printers. It's a bit of a hack and it underextrudes the wrong amount on corners and needs to be adjusted if you later adjust printing temp (which changes viscosity) or if you change filament color or type or print speed and so on. You can turn it on in Configuration.h if you make your own version of Marlin. Other solutions include fancy features such as "advance" which is disabled in Ultimaker firmware but it is part of Ultimaker Marlin. ![]() The other solution is to lower print speed such that, again, the normal speed and corner speed are about the same. So one solution is to increase acceleration and jerk settings on the firmware because now the print head doesn't spend so much time at the corner. So you get overextrusion (and of course a corresponding amount of underextrusion right after although that tends to be spread out on a larger area). When you come into a corner the printer has to slow down for the sharp corner and the extruder slows down an equivalent amount but it's too late as there is already a high pressure in the print head so the extruding doesn't really slow down at the Z seam spot even though the X and Y axis do slow down. The problem happens anytime you have to speed up or slow down the extruder. The problem is identical to why you get large rounded corners on a cube. ![]() It's the place where you go from outer shell to inner areas. But now the Z axis is moved on inner layers only (infill or inner shells). The Z seam used to be where the printer changed layers and there was a pause while the Z axis moved. I don't really get much of a z seam on my parts probably because I tend to print slow - usually 35mm/sec. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |