Can anyone tell me what the most likely cause of this poor quality surface might be?
Printed in Faberdashery grey PLA at 200°C on a Mendel at 60 mm/s. The lower half is nice and smooth but the arms and head are quite irregular. More pictures and details at http://3dprintednudes.blogspot.co.uk/2013/11/marble-mashup.html
Hard to tell from the picture for sure, but it looks like slipping/stripping/skipping on the extruder. What kind are you using?
One other guess, and this is a long shot as it looks like the problem is too little plastic, not too much, but if you’re using Repetier Host and leaving the realtime 3d view while printing, it can cause blobbing once enough layers have built up to bog down your machine processing it.
Skipping during retraction?Higher temperature + cooling fan for print would be solution.
Dont rule out moisture absorption in your filament.
200 is a bit high for PLA, try a lower temperature, it may even out the flow.
@Tim_Lathouwers that depends on the formula, the hot end design, and the print speed. I never print PLA at less than 210 on my fast machines with all-metal hot ends, but we used temperatures as low as 185 for the same materials (using the same thermistor and same thermistor table, so no funny stuff going on there) when we were using hot ends like the budaschnozzle with a much longer hot zone.
The printer obviously focused more on the most interesting bits and then decided to slack off on the less interesting ones.
Agreed with @Who_What_Wear that it looks more likely to be under-extrusion. With thin layers, especially, you might not be able to pump out a continuously smooth flow of material, leading to pulsing and tearing. Once a hole forms, it’s hard for the layer above to fill said hole, thus propagating the hole on successive layters. The reason the pock marks tend to lean to the left is because the undeposited plastic collects at the nozzle tip and then gets deposited when it makes contact with plastic below – but that happens at the leading edge of the solid area in the direction of travel.
I would try printing from inside to outside.
I agree with the underextrusion causing the pock marks as I see this all the time on my printer. Usually my extruder gear had gotten loose. The fact that it is worse I’m the shoulder area is probably due to incorrect retraction/priming settings in the slicer. It’s probably not priming enough before out extrudes again. I have not gotten the correct values for my Bowden system, so unless I shut off retraction, I either get bad stringing or holey walls where the print starts again
I’ve had issues like this when the extruder got heat soaked after a long print, causing the PLA to swell and partially jam in the top end of the extruder. A fan on the extruder and/or lowering the temperature helped my longer prints.
I also have seen similar results when the filament slipped off the hobbed part of the hobbed bolt (the smooth part of the bolt doesn’t push very hard on the filament!).
Check that your extruder motor isn’t overheating as well. Happened to me and a hot motor will cut in and out and give results that look like hotend/heatcreep issues
@Whosa_whatsis - good suggestion about the slipping extruder. I checked the hobbed bolt and it was clean as a whistle. I’ll post a picture of the filament too. I do use Repetier Host but I don’t use the 3D preview and I was printing from SD card anyway.
@Tia_Porter - could be moisture, I suppose, but I would have thought that would have affected the lower layers as well.
@Joseph_Chiu - nice description of under-extruded layers and you may be right about the flow being slightly on the low side. I still think there’s something significant about when it started though.
@Pawel_Dobrowolski - agreed. I always print sculptures from the inside out.
Another interesting thing is that the problem seems to have disappeared again at the top of the print. The forearm and upper hand look normal. I think the best answer with given by @Eric_Moy . Excessive retraction would cause the biggest problem with multiple perimeters on each layer, which is most noticeable in layers that include the hair. I think I need to try calibrating retraction settings in Cura at 0.1 mm layer height.
well when is high print and small point to print you have to lower temp/ but with reduce speed to 40 or 30 I got my in 40speed ,200 temp when reach to high lower everything
Make sure nothing came loose and set a minimum time per layer?