9 Ways How To Fix 3D Prints That Are Not Solid

3D printed parts come in all shapes and sizes, but in some instances they come as not very solid. If you are 3D printing an object that you don’t want to be very solid, then this is perfect, but what about when you want your 3D prints to be solid?

To fix 3D prints that are not solid you should increase your infill percentage, improve your top layer settings by increasing the wall thickness. You should check whether you are experiencing under extrusion issues because this can lead to 3D prints that aren’t solid.

Keep on reading for more information on why your 3D prints aren’t solid in the first place, as well as many fixes that you can implement as soon as possible to finally correct this issue.

Why Are My 3D Prints Not Solid?

For your 3D print to be successful, it has to have a solid exterior that is filled with a grid. The print’s exterior should be smooth and solid.

However, users often find it challenging for the top layer to be flawless and end up producing prints that have gaps in them. This phenomenon is known as pillowing.

There can be a host of reasons why the outside of your print isn’t as solid as it should be. Let’s look at them one by one.

Infill Percentage too Low

Most of the time, what makes 3D prints not solid enough is the low infill percentage. It is one of the most common causes of the first layer not being solid. The low infill density can also be connected to the fewer number of top layers.

If the interior of the print is not solid enough, then the exterior is likely to be the same.

Poor Top Layer Settings

Often, too few top layers can be the leading cause of obtaining 3D prints that are not solid. The solid top layer is to be printed on top of the grid that is supposed to fill the print.

A thin top layer or a few layers cannot bridge the gaps of the infill, thus leading to a 3D print that’s not solid.

Under Extrusion

If you feel that you’re doing everything possibly correct but are still acquiring prints that are not solid, it is very likely that under extrusion is the reason behind it.

When the nozzle of your 3D printer is not extruding as much filament as the software expects it to, under extrusion is said to occur.

The plastic released from the hot end is not hot enough to bond with other layers, making the 3D print not solid enough to stay put.

Printing Speed too Fast or too Slow

If the printing speed of your 3D printer is too fast, there is a higher chance that you will have gaps in them.

Similarly, if the printing speed is too slow, it may cause print deformation since the filament is at a higher temperature for longer, and won’t deal with overhangs and bridging so well.

Both of these scenarios can make your 3D print’s first layer not solid.

Mechanical Issues With Your 3D Printer

Users often face several mechanical issues with their respective 3D printers that hamper the printing process. There can be a vast array of issues that can hinder the possibility of a solid, successful print.

From loose nuts and bolts to poor lubrication to worn-out gears, anything can contribute to a failed 3D print not solid enough.

Filament Quality and Diameter Settings

New users often tend to ignore this aspect of 3D printing, nonetheless, it is important. The quality of filament you are using plays a huge role in determining the quality of the print obtained.

Changes in Temperature

Unexpected temperature changes can also ruin your 3D prints. If there is a temperature build-up, then the top layers may not be cooled well enough. It can lead to spoiled layers and thus cause gaps in the print.

How to Fix 3D Prints That Are Not Solid?

Now that we know the reasons behind what makes your 3D prints not solid, let us look into what you can do to combat this issue.

1. Increase Your Infill Percentage

As mentioned earlier, a low infill density is likely to be a leading cause behind your 3D prints not being solid. The infill acts as the foundation for your top layers.

You need to make sure that the infill density is optimal enough to shoulder the top layers on top of it. Increase your infill density by 10-15% to see what suits your printer best and print accordingly.

You can also increase your “Infill Overlap Percentage” which is the amount of overlap between the infill and the walls as a percentage of the infill line width.

The more overlap you set, the more firm the walls connect with the infill.

2. Change Your Infill Pattern

Certain infill patterns have differing levels of density overall, meaning that a 10% infill percentage with one infill pattern can produce more infill than another pattern with a 10% density.

It’s a good idea to have a play with your infill patterns and “Preview” your layers beforehand to get a good look at how your 3D prints will be made up.

Once you slice your model in your chosen slicer, there should be a place where you can preview each layer from top to bottom, allowing you to see how densely packed the infill is.

One setting that can give you a general idea of your infill is the “Infill Line Distance” which is a setting in Cura that gives the distance between printed infill lines.

For example, a “Grid” pattern with 10% infill density gives an infill line distance of 8.0mm, and a 15% infill density gives 5.33mm.

When you switch your infill pattern to “Gyroid” with a 10% infill density, you get 4.0mm, and a 15% infill density gives 2.67mm.

You would need a 5% infill density with the Gyroid infill pattern to get the same 8.0mm as the 10% infill density on the Grid pattern.

3. Adjust Top Layer Settings

Besides the infill percentage and pattern, the number of top layers plays an important in deciding the quality of your print.

Your top layers are related to the “Wall” or “Perimeter” of your 3D prints, meaning the thickness of the exterior. When your exterior isn’t very thick and sturdy, you are likely to run into issues with your 3D prints not being solid.

You should increase your top/bottom layer thickness in your slicer by increasing the number of top/bottom layers, as well as setting a good enough overall wall thickness for your 3D prints.

A good wall thickness for a fairly sturdy 3D print is around 1.5mm or around 3x your line width, but to improve the “solidness” of your models, you can increase that.

In Cura, you can directly set what your “Wall Thickness” will be, so you can really increase the sturdiness and durability of your printed objects by changing just this one setting.

You also want to focus on the “Top/Bottom Thickness” setting for the best results.

If you find that your 3D prints have some sagging down through the gaps of your infill, your top layer thickness and infill can easily fix this.

4. Fix Under-Extrusion

After low infill density and poor top layer settings, under-extrusion is the next common problem users face while 3D printing. You need to fix under-extrusion issues to avoid missed layers and gaps in your 3D prints.

Given below are some of the common solutions to this issue –

Increase the hot-end temperature in 5-degree increments
Calibrate your extruder steps for accurate filament extrusion
Check your nozzle for clogs and jams
Replace worn-out parts
Optimize the layer heights according to Magic Numbers
Use good quality filaments

Check out my article on How to Fix 3D Printer Not Extruding Enough (Under-Extrusion) which goes into more details to fix this problem.

The video below takes you through the essential step of calibration your extruder’s e-steps for accurate filament extrusion.

5. Adjusting the Print Speed

Depending on how well-tuned and maintained your 3D printer is, you may be able to reach high printing speeds without it having much negative effects on your print quality.

When your 3D printer hasn’t been properly calibrated, a high printing speed can definitely lead to inaccuracies in your print quality, relating to the infill and the wall thickness.

Make sure your 3D printer can handle the speed that you are using, and most of the time, slowing down your 3D printing speed can help out in this regard.

Your slicer already makes sure to automatically adjust the printing speed when printing certain parts of your model, such as the first layers, wall speed, supports speed, and so on.

A printing speed of 40-60mm/s is the ideal range for most 3D printers, and you can adjust your speeds by 10mm/s to test the differences in print quality and durability for solid prints.

6. Improve the Foundation of Your 3D Prints

One of the more important factors for the success of your 3D prints is just how strong the foundation is from bottom to the top. When you have certain shapes and sizes of models, you might find it hard to get a sturdy print base.

Adjusting the orientation of your model so that most of the bottom is flat increases how well the rest of the print will go.

You can also use brims or rafts to help improve the foundation of your model.

When you don’t have a sturdy foundation, you are more likely to have models slightly moving around during the print, leading to worse dimensional accuracy and potentially prints that aren’t as solid as they can be.

7. Solve Mechanical Issues of the 3D Printer

Users and 3D printing enthusiasts often face mechanical issues that hamper their printing process. Given below are common fixes to the problems –

Proper lubrication for the smooth working of parts and gears
Tighten screws, nuts, and bolts
Replace worn-out gears
Clean the nozzle periodically
Optimize print settings
Check the stability and level the bed

8. Using Good Quality Filament and Checking Diameter

Using good quality filament can go a long way in getting successful prints. You should make sure that the filament diameter you’re using matches with the diameter inserted in the software.

The ideal way to do this is to measure multiple infill diameter points along your filament, then take an average and set that as your filament diameter.

You can easily measure the diameter by using a pair of good quality calipers. The most commonly used filament diameters are 1.75mm and 2.85mm.

The video below by Thomas Sanladerer goes into a really detailed filament measuring video to see how tolerant brands of filament are. He finds that most filament is within a good tolerance.

As long as you aren’t getting the cheapest stuff you can find, and using a reputable brand, you should be fine on your filament quality.

9. Improve Cooling

Increasing the fan speed or just accelerating the cooling process can largely help avoid sagging of top layers. Cooling allows the filament to harden and thus act as a strong base for the top layers.

In this way, you can acquire smooth, solid, and sturdy prints, and minimize pillowing.

Many people recommend that you use a good fan duct to direct the air right to your 3D printed objects.

The Bullseye Petsfang Duct from Thingiverse is a popular one that people use for their 3D printers.

How to Fix 3D Prints That Are Spongy

The main cause for 3D prints that are spongy is from under extrusion. This can happen due to your filament diameter not being set correctly, not having your extruder steps calibrated, a clog or jam in the hotend, or your printing temperature being too low.

Here’s what you should do to fix spongy 3D prints:

Change your filament diameter if it’s incorrect
Check your nozzle size is correct in your slicer
Calibrate your extruder steps
Perform a cold pull to remove any partial clogs
Replace your nozzle if it’s worn out
Increase your printing temperature if it’s too low
Make sure your filament roll is not obstructed and spinning freely
Dry filament that has absorbed moisture
Fix any heat creep issues, which is when heat travels too far up the heat break.

Check out the video below to see one of the fixes. The main fix was changing his filament diameter from 3mm to 1.75mm, since this impacts the flow of filament through the nozzle.