I am trying to figure out what I need to change in my slicer settings to avoid the issue shown in the video. Basically, the plastic that has just been extruded lifts up into little lumps after the nozzle has moved on, but only for a brief period immediately following a layer change. The rest of the time it extrudes just fine. I do not have retraction enabled for layer changes and, as far as I can tell, I am not under-extruding. This particular print is in PETG (but the same thing happens with PLA) and running at 60mm/s. Any ideas what is happening? suggestions?
What slicer are you using? Almost looks like you have some coasting feature turned on and it is not responding fast enough after the initial layer change move. Eventually it looks like the flow recovers enough to stick. Might be a little on the cold side as well. Maybe turn the heat up 5C on the hot end and/or slow it down for the outer perimeter?
@Jeff_Parish I’m using Slic3r, I don’t think it has a coasting feature? I agree that is what it looks like. I am mystified though as I am not doing retractions, or maybe it is pulling plastic out of the nozzle when it moves up in z. I have tried temperatures from 230 to 265, video is at 265. Also tried turning on retraction on layer change with up to 1mm excess filament on de-retraction. This behaviour is for the inner perimeter so while the outside looks nice the inside (hollow part) looks like sh$t. I’m thinking it has to be something to do with my Bowden tube that I need to tune out somehow…
In hindsight it looks like some of my previous woes that I showed in https://plus.google.com/u/0/104347555452272558593/posts/Q4qfvUPB4mQ were from the same issue
Hmmm, you are certainly hot enough I would think.
I call what you are seeing lacing. I can see it on your previous post images. This can happen when there is an obstruction in the nozzle or the hobbed gear is wearing out but then it is quite random from a geometry perspective. Your location is very consistent and seems tied to layer changes.
What print speeds are you doing your inside perimeter and infill portions? Maybe slow it down a little?
There is a chance you could be slightly under extruding for this filament. Maybe it shrinks more than you think? But then I would expect you to get this issue everywhere unless it is also speed related and your infill is faster than the outer parts (That’s where the temp check comes in). Is there a setting for an infill extrusion multiplier that is set low?
Try these calibration clips that will tell you what the thermal properties of your filament are.
or
It almost looks like your nozzle may be a bit low. For petg, you generally don’t want your nozzle as close to the bed as with pla. Try adjusting your z-offset by 0.05mm or 0.1mm.
I think I have it sorted now. I tried playing with all of the extruder settings in slic3r and managed to get semi-reasonable results (retraction on layer change, z-hop and excess extrusion on de-retraction). However, it was still not as good as I knew it could be.
Turns out the main thing was getting my nozzle size correct. I have painstakingly calibrated all of my axes (X, Y, Z, E) and know for sure that they are all +/- 0.05mm or less of nominal. So when I was having to use an extrusion multiplier of 0.85 to get correct dimensions it should have been a red flag. Some quick calculations tell me that to get the same extrusion volume with a multiplier of 1.0 I have to tell slic3r my nozzle size is approx. 0.434 (I have a nominal 0.4mm nozzle). Using the same settings as for my best previous attempt I set it running my test print and … success! All my dimensions are within +/- 0.02, no blobbing or lacing (@Jeff_Parish I love that term!), best print yet!
So the problem at its core was under-extrusion, as expected, it was just an unexpected setting that was the culprit. I suppose I should get a new nozzle as now I have non-integer numbers of extrusion tracks for standard wall thicknesses.
In the photo below the print on the left shows rubbish surface finish while the right one is silky smooth.
missing/deleted image from Google+
Whenever I swap nozzles, I hand extrude about 10cm of plastic through the hot nozzle, and measure the extruded plastics’ diameter. Then I use that for the nozzle diameter.
Also helps when switching plastic types. I’ve found that some “advanced PLA”s expand by about 5% or more in volume when extruded, and that needs to be accommodated as the “virtual” nozzle size.
Glad you got it sorted.
Adjusting the nozzle size is another way to compensate for the filaments thermal properties. I generally leave the nozzle size at its measured diameter and apply my compensation to a thermally calibrated filament diameter. Either way the result will be the same.
Happy printing!
@Daryl_Bond Are you using tmc’s 2100? If I remember you have Replicape in your printer. I have the same issue. A lot of people says that tmc’s are not good for extruder but I need to try your solution.
@Daniel_Kusz Yes, I have a Replicape. I hope my technique works for you. Unfortunately I am still having other issues so, at least for me, it is not a full solution. I am thinking that I will change to direct filament drive as I have never had any luck with Bowden style.