Print Quality Questions

Hi everyone, new mini owner and new to 3D printing.

Been using my printer a lot the past week since I received it and I love it! Been using the quick print settings and decided to try custom profiles to see if I could get better quality on my prints.

After printing a couple of things I’m close but have a couple of questions.

The first 2 pictures are a model I was printing from 3dhubs. I used the same settings as the box below, same filament but different model. He has pitting all over and the rear doesn’t look like it closed properly.


The second 2 pictures are a box I’m making. First time around I did it in ABS and it had a couple splits. The pics below are the box redone with the HIPS Fine profile and a couple of modifications to it. I brought the initial layer thickness to 0.0 and the percentage to 100%. I also adjusted the speeds to slow them down but I don’t recall of the top of my head which speed parameters I adjusted.

Box looks incredible except for the first couple of layers and on the one pic you can see a line on the box. Its almost as if the head turns at that section of the print and leaves that on each line.

Wondering what I should be checking to eliminate these issue.

Thanks!!




That bump is where the nozzle starts each layer. I usually set my TAZ to start the layer on an internal perimiter rather than an external one to get rid of that issue.

The pitting you see in the smaller model might possibly be a sign of moisture absorbtion in your fillament. It takes a couple of weeks for that to occurm and only in higher humidity areas, but tiny amounts of water vapor can explode, leaving miniature steam craters on the print surface. To get around that, store your prnter fillament in a sealed dessicant filled container when not in use. If you bought a vaccume sealed roll from Lulzbot, that is probably less likely an issue unless it wasn’t sealed right or it was sitting around for a time before you used it.

It could also be a slight amount of underextrusion. Check your fillament width settings and measure that against your actual fillament diameter and adjust as needed.

For the rear section and that top loop, there should be some sort of “enable cooling fan for small parts” setting you need to enable. When printing ABS (if that is ABS) you generally don’t want a cooling fan on, except for printing very small layers or when bridging a long unsupported strand of plastic from one point to another.

That being said, those are really good quality prints for a beginner!

Thanks for the reply!! I’ll have to check the settings for that small bump and see what to adjust for that to start on an inside layer, I though it was a setting someplace since it was very consistent.

That material is HIPS, I did the first box in ABS and it had some cracking so I decided to go with HIPS instead for now.

The filament used on the small figure was the same spool as the box, they were printed right after one another (box first then figure) so I don’t think it’s a filament issue as it was a new sealed roll. I think your onto something with under extrusion, just curious as to why it shows up on the smaller model but not the box which were both printed with the same settings.

Over / under extrusion issues can sometimes show up in smaller models rather than bigger ones because the larger models have mass to work with, and therefore more possibilities for the issue to correct itself somewhat.

When you print something, you are basically laying down a thin stream of molten plastic, kind of like a cake decorator putting a line of decorative frosting on a cake. If you are overextruding, its the same as squeezing that icing bag too hard, so too much plastic comes out. If you are under extruding, not enough plastic comes out, so you end up with a thinner, possibly broken line at that point. Controlling the width of that line, and how well it sticks to the other lines next to it is the key to 3d printer quality.

Underextrusion can be hard to see because it basically just effectively results in printing a part at a lower infill. If you printed at 75% infill but were underextruding by 2% over the entire print, it’s basically like printing a 73% infill percentage, except some of the perimeter extrusions are going to be slightly too small and the layers will tend not to stick as well. If it’s close but just a little off, it is really hard to tell without printing close to 100% infill. underextruding will usually show up less on a smaller part than a larger one, but it depends on the surface, how much infil there is, etc.

The tricky thing with overextrusion is that the plastic has to go somewhere. If you have a nozzle with melting plastic in it, and you extrude plastic faster than your nozzle is moving into unprinted areas, the plastic backs up into the nozzle. The extruder itself is still trying to push more plastic out, thinking you need more so it tries to put more plastic than can fit into a very small area. That causes the plastic to basically hit a solid wall, and stop, which makes the filament grind out. Most people think that their nozzle is actually clogged by something at that point, but it’s usually just the “thumb over the garden hose” effect in action. On a larger model, if you set it to print at something like 75% infill but it is extruding an extra 2-3%

I was looking in Cura for an option to start the line on an inside perimeter and didn’t see that as an option. Is there g code for that setting or am I missing something?

Please post your cura profile for your HIPS box settings. I make a lot of control boxes and yours turned out great. I’d like to give your settings a shot!

-Jim

Sure thing, here you go.

The bottom layer still needs tweaked. I tried lowering the bed temp from 110 to 100 after the first couple layers as suggested on another site and they still look to be off center.
HIPS 1.ini (12.4 KB)