What causes the problem you see at the top where it seems like there’s too much plastic being extruded, and the extruder ends up making circles and a “divot” on top of small areas? Printrbot Jr. I’ve run into this on other prints. Otherwise it printed great; in person it’s not as “layered” or ridged as it looks in this camera phone picture.
It might be that you’re too hot and the extruded filament isn’t cooling/setting enough before the nozzle passes over it on the next layer and disturb it. You might need to adjust your minimum layer time. Or, if it’s just this print, turn on an external fan as you’re nearing the top.
That’s quite a bit of banding… Is your filament diameter consistent?
Yes; it looks better in person (versus this close-up light-shiny shot). I think you’re right about it not cooling enough before it gets mushed around by the nozzle… Time to tweak. Using repetier-host (latest version). I’ve got the fan installed on my PBJr, and it was running for this bit…
By the way, the ridges is probably due to z layer height aliasing — if your z screw is SAE and you’re using a metric layer height like .2 or .3 mm then your layer height will not be a full number of Z steps and you will get this rounding error.
Re the over extruding: I’ve found I need to turn the extrusion parameters way down in order to not simply be extruding too much plastic. I have a .77 in there at the moment.
Thanks, yeah it’s the SAE screw that came with the kit, and I’m using .2. Need to look up the .2fraction someone posted that works better with the SAE screw.
You’re using .77 with the Simple (direct-drive extruder)? BTW, mine shipped today…
@Bill_Bradford google for Prusa reprap calculator, that ought to get you the right URL.
No, that’s with the Wade’s that was on the beta (and also on your jr). I should be able to rebuild into the v2 tomorrow.
Regardless though, that shouldn’t matter — there’s a couple of variables that affect flow rate ultimately: the extruder calibration (commanding extrude of 100 mm should actually take in exactly 100 mm of filament, which is a measurable quantity you can calibrate), the diameter of the filament you say it is (which affects slicer’s length-to-volume factor), the extrusion multiplier (which does indeed come out really low on mine and several other people’s Simples), and the print panel’s flow rate multiplier slider.
There’s a couple of suggestions for calibrating flow rate, the one I followed was to slice a calibration cube with .95 infill, and calibrate to the point where infill layers would just have gaps between strands and top layers would not have gaps. Getting this right is hard and takes some effort & time, particularly when overfilling for a while as well as underfilling for a while affects the z height of the already laid down layers, and thus very directly affects your measurements.
What I would do is change the rate via the print panel slider (under- and overfilling in various parts if the Z looked to be significantly off, with the goal of a flat starting surface fire next few layers), then when I had a setting that appeared to print proper for a dozen layers multiply that into the extrusion multiplier and iterate. I’d say the .77 I have is within about 5% of correct.
The other method I’ve seen mentioned is by printing a single wall calibration cube, no infill no top no bottom (ie just four walls), and then micrometer the filament thickness until it is correct for what slic3r is configured to. Didn’t get that to work. I may have to try that again now I actually have a micrometer and not just a vernier caliper that’s probably got an offset.
(Oh, how tight you have the tension roller can affect your extruder calibration — but as long as that’s correctly calibrated the other parameters including type of extruder or how tight (and thus how squashed) it is should make no difference.)
Make sure you leveled your platform per the instructions of the printbot jr http://help.printrbot.com/Answers/View/1093/Problem+calibrating+and+setting+x,y,z+home+positions I have an ultimaker and when you’re laying down .1mm and .05mm layers, the slightest miscalculation can ugly the final layers of a print. Luckily the ultimaker has some great software (Cura). If the filament is consistent, and the bed is level, try lowering the temp a few degrees, PLA suggests 220, I usually print at 210 (careful printing at temps that are too low, it can ruin the printer). Sorry if that doesn’t help, I’m new to 3d printing too.
I’ve been printing at 195/190…
And I have done everything in that answer, including tweaking z home/end stop.
Going to switch to a glass bed this weekend.
@Bill_Bradford Have you tried 210, 195 seems low, too low and the material sticks to the tip and gets pushed around.
Wow. I wonder if the location of your temp sensor is the reason your temp seems so high for pla. On mine I print pla as low as 165 but prefer to be around 175.
@Steven_Critchfield Well I’m new, all the stuff I’ve seen suggested ~210. Do you have some links for temps?
210 is what I see for ABS here and there, not PLA…
Really? Reprap wiki, ultimaker site, et. al. http://reprap.org/wiki/PLA ABS I thought was higher.