Top layer issues

Hi, I'd like to tap your collective wisdom for improving a print. I am using a Folger 2020 i3, with PLA. I don't know the make of the PLA - it is the sample that Folger sent with the kit. This picture shows the result of four print runs for [www.thingiverse.com]. The leftmost one is for the setting that Folger gave: bed 70C, extruder 219C. Everyone tells me that's too hot and I guess that's why the top half collapsed. The other three are from left to right 185C, 190C and 195C. They are OK apart from the top layer not being solid. It looks like the 195C one is starting to collapse more.

I am using Repetier/Slicr3d and I levelled the bed as well as I was able.

Any suggestions for what else I should try? Would lowering the temperature to 180C help? Or is there something else that I should adjust? Is it just a limitation of the machine?

Any help gratefully received. This is my first time doing 3D printing.

Edited 2 time(s). Last edit at 06/17/2015 11:49AM by animoose.

Hmm, might be just me but where is the pic?

Sorry, somehow I lost it in editing. I just added the link to the original post.

What infill and print speed settings did you use?

I'm new to this so I'm not sure which settings are relevant here. I've attached a config.ini exported from slicer. config.ini

So the fill was

fill_density = 10%
fill_pattern = rectilinear

and it looks like the print speed is about 40 or 45 (I can't remember how all the different speeds interact).

You could try increasing the fill density to 30% or so and see if that helps support the top surface during printing. Do you have a fan that is directed onto printed material (separate from any fan that might be cooling the hotend)? Any time the filament has to cross an unsupported gap (bridging) is difficult for the printer. A fan to quickly cool the extruded filament can make a huge difference for PLA for this sort of situation.

It's difficult to make out much detail in the photo - it might help if you took a closer view of each cube and posted them so it is easier to see what's happening.

Thanks for the suggestions. I'll try them when I get home. Sorry about the quality of the photos - with such a small piece it's hard to arrange the lighting right.

Ah, the photo problems were mostly with google - when I tried to zoom in it snapped back to small size and tiled it for some reason. Now that I've downloaded it I can zoom to full size, much better. Now you need someone with more experience to weigh in, but from what I've read, the print cooling fan looks like it would be your best bet. If you don't have one, you could try a trick to allow more cooling - print two of the cubes at the same time with a decent gap between them so that the print head has to travel between the two after each layer and the other one gets a chance to cool off.

Heh, sneaky :-)

I have some spare fans lying around, so I'll see if I can hook one up.

I tried printing the cube again this evening with the same infill settings and 185C, but using a different filament (JET) as I had run out of the original sample. And the results look pretty good: [goo.gl].

Still pla or a different type? It certainly looks better.

Quote
JamesK
Still pla or a different type? It certainly looks better.

Still PLA, just a different brand.

How much does ambient temperature affect printing? It was a bit cooler yesterday evening.

Quite a bit from what I've heard. I've even seen posts where people just used a desk fan pointing at the print to help with PLA overhangs and bridging. ABS has the opposite problem, it cools too quickly and tends to shrink and split. People build enclosures to try and control the ambient and eliminate drafts to help with bigger ABS prints. It's one of the oddities I noticed when I was looking at kits, most of them don't have print cooling fans, so people hit problems with pla, and they don't have enclosures either, so you get problems with abs. Can't win!

Interesting. One difference yesterday is that I had a ceiling fan running while I was doing the prints. I'm not sure I believe that it could really have made a difference, but perhaps tonight I will try prints with and without it running and see what happens.

Seems a bit unlikely doesn't it, but I guess if things are right on the edge them small changes can make a difference. The different filament is probably still the most likely explanation.

I saw this on Folger's .ini file as well as yours - why do they set the nozzle diameter to 0.4mm? It's really 0.5mm isn't it? I changed it but wonder if I should have.

Also they set the layer height to 0.4mm. I've tried 0.2mm and got decent results. I know a smaller layer height adds print time but supposedly is more accurate. Something else to play with.

Oh - good catch, I missed that. Layer height should always be less than nozzle diameter.