This is a common fault and there are many reasons for gaps in your print, depending on where they’re located. It’s worth checking everything mentioned in this section so that you don’t miss the exact cause.
Signs of gaps & holes:
Probably one of the most obvious problems to spot in a print. There will be visible gaps and holes in your print, like in the image shown.
Explanation:
Unfortunately, there can be many reasons for the gaps and we have broken them down in the ‘How to fix:’ section below.
How to fix:
In the top layer / pillowing
3D printer pillowing occurs when trying to print a solid layer over a coarse infill grid. Depending on your infill percentage and your layer height, it may take a lot of layers to fully close the top surface over infill to produce a nice, smooth surface. Figure at least 1mm of combined layers for your top layer as a rule of thumb. So, if you’re printing with a layer height of 0.2mm use at least 5 top layers to play it safe. Other ways to reduce 3D printing pillowing are:
Print colder or increase fan speeds. Better cooling improves bridging performance, and that’s basically what we’re doing when printing over infill.
Use a higher infill percentage. More infill means smaller gaps, which are easier to cover.
Another possible cause for gaps in your top layer is under-extrusion . See [Under-extrusion].
Holes and gaps in floor corners
These 3D printer errors happen where a horizontal surface meets an inclined one. The top layer(s) looks like the printer could not be bothered to print all the way to the edge. Its causes are similar in nature to pillowing, but it can be more annoying to nail the exact cause when everything else is looking great!
There are a lot of possible causes of this, here’s a list of problem and solutions:
Under-extrusion can cause holes and gaps. Increase the extrusion multiplier/feed rate, also see [Under-extrusion].
Not enough top layers – increase the top layers count so you are printing at least 1mm thick.
Printing too hot – print at a lower temperature so the plastic sets in position faster.
Printing too fast – slow down the print speed. This allows the extruded plastic to cool more before the next pass of the nozzle. If kept too warm, the layer will peel back from where it was printed.
Not enough cooling – if at all possible, increase cooling during the printing of these parts of the object. Always check this is suitable for the material you’re using with the manufacturer.
Too little infill – increasing the infill percentage will help. Also look at the minimum infill length in your slicer and reduce this to allow smaller runs of infill to be printed at the edges of an object instead of being ignored.
The infill outline overlap is too small – all slicers can set how much the infill overlaps the outlines/perimeters of the object being printed. This setting makes sure they go all the way to the edge and fuse together and so help support the layers above. Try increasing this and note the result (too much and you will likely see the infill pattern poking through the object’s visible walls and other such surfaces).
Not enough outlines/perimeters – these also have a support role to fill, so increase these if at all possible.
Too much retraction – causes there to be gaps in positions where retractions take place, so reduce this.
Between infill and outlines
If this happens on your first layer, chances are your nozzle to bed distance is not set properly. Your nozzle is probably too far away from the bed. See chapter [First Layer Issues]. If it happens later in the print:
This could be a result of printing too fast, try printing slower.
It could be a sign of (temporary) under extrusion. See [ Under-extrusion].
Another possibility is wrong extrusion settings in your slicer. Check what was dialled in is correct for your printer and print.
Increase your extrusion multiplier Simplify3D.
Increase extrusion width.
Increase overlap settings.
Gaps between thin walls
When trying to print thin walls that are not multiples of your nozzle width in thickness, there is a common problem with slicers leaving a gap inside walls, severely weakening the structural strength of your wall. It is rather straightforward issue: if you’re trying to print a wall that is 0.9mm thick with a 0.4mm nozzle, an average slicer might end up using 2 lines at 0.4mm each and leave a gap of 0.1mm, as it doesn’t know a way to close the remaining 0.1mm.
Therefore you should always strive to stick to a multiple of your nozzle width when designing thin walls to help alleviate the issue:
Thin wall options – A lot of slicers today have special thin wall options, make yourself familiar with them and see where they can take you.
Adjust line width – Adjust (not necessarily increase) line width or the amount of outlines to force your slicer to construct your wall differently.
You can try increasing your extrusion multiplier to close the gap by intentionally over-extruding.
You can also set a narrower nozzle diameter in your slicer settings than you actually have fitted. If used with care and balanced against the extrusion multiplier, this can overcome some situations that your favourite slicer cannot cope with.
Read more: every way to fix gaps and holes in 3D prints.