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3D Printer Infill Not Touching Perimeter? Here’s Why

Almost every 3D printed model is made using a series of perimeters and infills. The perimeter forms the outline and overall shape of each layer, while the infill covers the inside of that layer from one side to the other. But what happens when these lines don’t meet, and why does it happen in the first place?

3D printer infill not touching the perimeter is most often due to under-extrusion, which can be caused by inadequate nozzle temperatures, inaccurate calibrations of the Z-offset, or too-fast printing speeds. Other factors may include insufficient overlap, software issues, or poor infill patterns.

If your 3D printed model has gaps between the infill and perimeter, chances are the print will have weak spots, which could easily lead to breakages. Luckily, many of the causes of this have simple fixes. So, let’s look at some of the most common causes of this and what you can do to fix it.

1. Incorrect Z-Axis Offset

All FDM 3D printers have a Z-axis offset to regulate the distance or height between the hot end and build plate (the nozzle and extruded filament layer). An unusually high Z-axis due to an incorrect or uncalibrated offset generally produces poor finish and causes other printing issues, not necessarily limited to 3D infill and perimeter.

That said, if the Z-axis is a tad too high, the filament or thermoplastic will not be extruded sufficiently for a seamless finish. 

Effectively, the hot end and nozzle may not deposit enough filament at the inner perimeter edges for the 3D infill to touch and fuse properly. 

Also, changing printing speeds as you build up from a base layer to the top will aggravate these problems in the event of an incorrect Z-axis offset. 

How To Fix

Almost every slicer software has default Z offsets. 

So, consider changing this to suit your 3D model and the infill type, be it the pattern, density, or other attributes. For example, if your Z offset default is 1.0 or 0.9, reduce it by a few notches and test. You can go as low as -0.8 to find the appropriate Z offset for that specific design. 

Ideally, you should change the Z-axis offset for: 

  • Complicated models or designs
  • Perimeter shape or contour
  • Layer height
  • Filament diameter
  • Infill pattern & density 

This necessity is one of the reasons many users create multiple profiles and save them on their 3D slicer software.  

2. Too-Fast Printing Speeds

Base layers and the perimeter, especially the outer edges, are usually printed slower than infills.

This is often because the perimeter needs to be more precise, and it’s what you’ll see in the final product. 

In contrast, the infill is typically hidden, so it doesn’t need to be as clean.

How To Fix

If you’re noticing gaps between the infill and perimeter, try reducing the print speed for the infill and check for holes after a few layers. Giving the nozzle more time to connect with the border should help solve the problem.

Reduce the infill speed by approximately 10% and run a test. If you notice an improvement, you can conclude that the printing speed is the primary concern. 

Keep in mind that print speed is not typically an isolated cause, as many external factors influence its impact on 3D infill. Also, it’s possible that you have more than one factor causing the infill to not connect with the perimeter.  

Like the Z offset, you cannot have the same 3D printing speed for every filament, model, layer, and infill. 

For example, a simple line-shaped infill is easier and faster to print than a grid. On the other hand, triangles take much less time and material than gyroid patterns. 

You’ll likely need to review such project-specific issues and go from there. Reducing the print speed may help with one design but not with another.  

3. Too-Low Temperature at the Hot End

The next thing to check is the temperature settings, and there are three you need to worry about:

  • The hot end
  • The ambient temperature
  • Any cooling effects, such as internal fans 

The hot end temperature depends on the filament type. You’ll also see a difference in how they set at ambient temperatures from one material to another. 

If the extrusion temperature is too low, you may see the filament hardening too fast. If that happens, it will struggle to connect properly. 

How To Fix

One easy way to fix this issue is to increase the hot-end temperature. You’ll know if this is a problem when you experience the following:

  • Filament cooling
  • Solidifying
  • Shrinking
  • Curling  

The good news is that most thermoplastics come with a temperature range right on the package. But, of course, if you’re printing in a very hot or frigid environment, you will need to adjust the settings. 

Take PLA, for example, which is one of the most used filaments around. The accepted hot end temperature range is 374 °F to 428 °F (190 °C to 220 °C). So, when you input PLA into your software, the printer will adjust the settings accordingly. 

You’ll want to check the automatic temperature setting, adjust it yourself, and test print the design. For example, if it is set on the lower end of that range, try increasing it to see how that affects the print.

Also, the ambient temperature may prevent the 3D infill from fusing or curing correctly. With that in mind, it’s best to keep your 3D printer in a room where you can control the ambient temperature. 

Furthermore, a 3D printer fan impacts the immediate ambient temperature around the print bed and extruded filament for the infill. To fix this, look at the side of the print that directly faces the fan to see if there are gaps on that side or all sides. 

In most cases, the side near the fan will have gaps as it cools faster than the other sides. Reduce the fan or turn it off altogether and run a test. 

4. Under Extrusion

Under-extrusion is a very common problem causing gaps among 3D infills and the perimeter. 

Unfortunately, many issues could be the root cause, so an elimination process is often the only option. 

Here is a checklist of the aspects that can cause under extrusion:

  • The 3D printer is improperly calibrated
  • The hot end and nozzle have a buildup
  • The thermoplastic is not sufficiently hot
  • Faster 3D printing speeds
  • Faulty hardware components
  • Incompatible software settings

How To Fix

Under-extrusion will often cause more problems than gaps between 3D infills and the perimeter. However, the holes or anomalies may be one of the first symptoms. 

So, begin with a calibration test. Check the feeder, extruder, belts, and recalibrate based on your analysis.

Here’s a helpful video tutorial for 3D printer extruder calibration. Though keep in mind that each make and model will be different:

Calibration errors are not always a user’s fault or due to incorrect settings. In some cases:

  • A 3D printer may have poorly calibrated belts
  • A feeder may malfunction
  • An extruder may not work as expected. 

To that end, here is a video showing a calibration anomaly in a 3D printer belt’s tension:

You’ll also want to check this video to see how to adjust the feeder tension properly:

Finally, clean the nozzle to ensure no thermoplastic buildup in the hot end. The following video will show you how it’s done:

5. Insufficient Overlap

All 3D printer slicers have an infill overlap setting. This is the overlapping area where the perimeter meets the infill. More overlap usually means more connectivity and strength. 

Although, many 3D models have more than one wall, meaning there could be two or three shells as the perimeter. These walls may have gaps between them. Such an issue is not related to infill, but you must ensure the overlap setting is sufficient to allow a seamless fusion of extruded filament. 

How To Fix

Increase this overlap percentage in the slicer software so that the 3D infills touch the perimeter. For example, if your slicer software default is 10%, increase it to 20% or up to 30% if the gap is substantial. Go for more if it is necessary for your 3D model. 

Also, remember that the 3D infill overlap setting will depend on the nozzle width and filament diameter. A wider nozzle does not need an excessive overlap. 

Likewise, a 2.85 mm (0.11 inches) filament needs less overlap than a 1.75 mm (0.07 inches) thermoplastic spool for the same nozzle width. 

6. Incompatible Nozzle Width

The standard 0.4 mm (0.014 inches) nozzle should work fine for most designs. 

However, if a model has intricate details, you may need a finer nozzle with a 0.2 mm (0.007) diameter. If that’s the case, the 3D printer will require a recalibration of hardware components and software settings. 

Also, the nozzle width and filament diameter should influence the temperature & speed settings. 

The standard 3D printer settings that work for the base layer and other model structures may not be perfect for the finer details, such as the alignment of all the infills with the perimeter.

How To fix

If you need to use a different nozzle, you’ll first need to buy an appropriate nozzle – one you know will fit your printer – then change the appropriate settings in your slicer software.

This will include:

  • Print speed
  • Print temperature
  • Number of perimeter walls

However, it’s important to note that the smaller the nozzle, the less surface area you’ll have to work with. That could make connecting the infill to the perimeter even more challenging.

7. Filament Problems

There is no way to generalize filament problems as PLA, ABS, PETG, TPE or TPU, PC, and nylon or polyamides do not have identical characteristics. 

As a result, their default profiles in the slicer software may have a few improper settings for a 3D model’s infill. 

It’s always best to find a brand you like and stick with it; that way, you know how it prints and what general settings you need. 

Also, always run a test print on any new filament, even if it says PLA, which you’ve used before. Some are arguably better in quality, so don’t expect each brand to provide the same results.

How To Fix

Always follow the manufacturer’s guidelines, not only for the 3D printer but also the filaments. 

Review the settings for: 

  • 3D printing speed
  • Temperature
  • Overlap
  • Filament diameter

Change the Z-axis offset according to the nozzle width and filament type or diameter.

8. Infill Pattern and Density

Any infill pattern and density may have gaps with the perimeter due to one or more of the causes discussed in this article. However, the infill pattern and density are correlated to the inner edge of your design. 

Therefore, a more comprehensive infill pattern has a greater chance of making a solid connection to the perimeter.

In other words, a 3D infill pattern or its coverage and density should be appropriate for the perimeter, especially its inner shell or wall and contour. Too many intricate shapes increase the chances of gaps.

How To Fix

If your infill is hidden in the final print, you can get away with adding excess infill with a higher density. This will help to guarantee a solid connection between the infill and perimeter. 

However, you must choose the printing speeds and other settings accordingly. So, if you change a setting in the design or the entire 3D printing guide, you’ll likely need to change other settings to keep everything aligned. 

9. Hardware and Software Glitches

Hardware and software glitches will happen in most appliances and machines. For 3D printers, it’s not uncommon to experience the following problems:

  • Feeder belts may be too tight or loose
  • The extruder or stepper motor may not work properly
  • The idler wheel, screws, and other hardware components may need recalibration 

How To Fix

If you print regularly, you have to check each of these parts to detect the cause of your problem. 

Of course, software glitches are common, too. 

With that in mind:

  • Ensure you are feeding the accurate G-code to the slicer. 
  • Always recheck the customized settings if you are modifying a downloaded or pre-configured G-code. 

Remember that every crucial setting has a ripple effect: layer height, flow rate, or printing speed. But in many situations, it’s a matter of trial and error.

10. Other Facilitating Factors, Such as an Unlevel Print Bed

All complexities aside, you may have a few simple issues at hand:

  • Firstly, check the print bed to ensure it is level. You’d be surprised how often this is the cause of 3D printing problems, and it can happen at any time.
  • Review the 3D printer’s variable settings. This is especially important when changing the slicer’s instructions for the infill pattern, density, printing speed, and layer height. 

How To Fix

Since various 3D printer and slicer settings are interlinked, it’s crucial that you become familiar with each.

For instance, the printing speed and hot end or extrusion temperature influence the flow rate setting and vice versa. These interrelated aspects work in real-time conjunction, so all such settings must be in sync for the perfect print. 

Check for other common 3D printing problems, such as: 

  • Layer shifting
  • Warping
  • Wall separation
  • Poor adhesion 
  • Weak fusion at other inner perimeter edges 

Don’t dismiss these possibilities even if the issues aren’t evident elsewhere on the 3D model. 

Conclusion

When your 3D printer infills are not touching the perimeter, start by ruling out other printing anomalies so you can focus on only the gaps. 

The first checkpoints are:

  • The Z-axis offset
  • Printing speed
  • Extrusion temperature
  • Fan’s cooling effect
  • Flow rate
  • Overlap percentage
  • Infill settings

Eliminate these common problems, then check the 3D printer hardware components and review the slicer settings. An unleveled print bed and other more straightforward issues typically cause more problems than the gaps among the 3D printer infills and perimeter. Still, check everything to be sure.