Month: June 2017

The Importance of Fan Speed for PLA Overhangs

I recently ran overhang tests to look at the efficacy of different fan speeds. If you don’t want to read and just want the album, click here: http://ift.tt/2rS8r6f test this? Everyone knows that PLA likes fan cooling!I run my blower fan at 100% through a DiiiCooler for all PLA printing. I don’t have any trouble maintaining print temperatures (more on that later), but some people here do. Here are a few quotes from users who run their blower fans at partial speed:”Are you using a radial blower fan with the Ciicooler? I can’t run mine at 100%. I use 25-40% usually.””I print PLA with about 30% fan speed on a diicooler””I have to keep my blower fans under 70 or it will really struggle to maintain temp or never reach target at all. Print quality was not affected by the lower speed”This piqued my curiosity as to how much of a difference fan speed can make. Is a 50mm blower really so powerful that partial speeds are just as effective as full speed?MethodsI printed numerous copies of the ATOM 80 Degrees Overhang. It has 5 sections of increasing difficulty: 30°, 45°, 60°, 70°, and 80°Each test print used identical slicer settings except for the fan speed.print temperature = 215 bed temperature = 55 layer height = 0.2 mm extrusion width = 0.48 mm walls = 3 top/bottom layers = 4 all print speeds = 50 mm/s (no difference for walls, infill, etc) z hop = 0.24 mm (really helpful to avoid collisions with curled areas) These settings weren’t meant to be “best case” or “worst case” for printing overhangs, but something in-between.ResultsThere is a noticeable improvement in overhang quality with each increase in fan speed. At no point did I see a plateau in performance. I’d use even more fan speed if I could.Underside of test piecesPartial side view of test piecesSide view of 100% vs 0%While some people hate how the DiiiCooler obstructs view of the nozzle, its performance is impressive enough that I can easily put up with that.For what it’s worth, I am using a 12V 0.15A blower with a rated air flow of 4.21 CFM. Unless someone is running a far more powerful blower, I find it hard to believe that decreasing the fan speed doesn’t have any impact on print performance. (If you are running a far more powerful blower, please let me know so I can pick one up)Other parameters, such as temperature and speed, can mitigate the need for cooling and most people definitely wouldn’t print overhangs this extreme without supports. Still, when it comes to a PLA part cooling fan I’ll take the most I can get.It’s also worth noting that different layer heights will influence overhangs (just like bridging). Here are 3 different layer heights at the same fan speed. Note that the 0.12mm layers curled enough to collide with the print head and cause layer shifting.Maintaining hot end tempIf you want to run your fan harder but have trouble maintaining hot end temp, I have some suggestions:Make sure the airflow is focused more towards the tip of the nozzle than the heat block. I used washers to lower my DiiiCooler because I felt the stock height wasn’t low enough on my machine. Now it is better aimed.Run a PID tune with your bed at printing temp and the fan running at 100% so that your PID values reflect printing conditions.Add more insulation to your heat block if necessary. Mine is wrapped in two layers of ceramic fiber insulation, secured with kapton tape.1 and 2 were already enough for me to maintain temps, but the extra insulation makes it even easier for my machine. http://ift.tt/2rJb6gb