3D Printing Guide

3D Print Stringing: Why It Happens & How To Fix It

Scott Gabdullin

Updated on September 26, 2025

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When we talk about 3D printing, we usually get excited about how smooth our prints look or how precise the details are. But let’s be real, what happens inside the print is just as important, too. Infill gives our prints strength, weight, and overall functionality. Whether we’re making a cool display piece, a strong mechanical part, or something that needs a little flex, picking the right infill type and percentage can make or break our print.

So, let’s go over everything we need to know to get the most out of our infill settings!

What is 3D Printing Infill?

If you’ve spent any time 3D printing, you’ve probably adjusted your infill settings more times than you can count. Infill is the internal structure of a 3D-printed object, providing strength and support while keeping material usage in check. It’s the lattice-like pattern inside your print that you don’t see from the outside but plays an important role in determining its durability, weight, and print time.

But, why do we use infill? Well, unless you’re printing solid blocks, which would be wasteful and take forever, infill allows us to maintain structural integrity while reducing material consumption. The right infill settings can mean the difference between a lightweight, functional part and something that either breaks too easily or takes an unnecessary amount of time and filament to print.

Common Types of 3D Printing Infill

Not all infill is created equal, and if you’ve experimented with different types, you already know they serve different purposes. Some prioritize strength, others focus on speed, and some are just fun to use.

Grid

Grid infill is one of the top basic and widely used options because it offers a balance of speed and efficiency. It’s a fantastic choice when we need a quick print that doesn’t require much strength, like decorative items or lightweight enclosures. Since it prints relatively fast and doesn’t use excessive material, it’s an excellent go-to option when we’re prioritizing speed over durability. However, if we need something that can handle stress, weight, or repeated use, Grid infill might not be the best option. For structural parts, we may find that a different infill pattern provides better support without excessive material use.

Lines

Now, if you want something that prints faster than the grid, Lines Infill can be a great choice when we’re aiming for minimal material use and decent support. Since it only prints in one direction per layer, it allows for fast print times while still adding a bit of reinforcement. This makes it useful for models that don’t need excessive strength but still benefit from some structure, like display models, lightweight covers, or quick prototyping.

However, it doesn’t offer the best overall rigidity compared to other patterns, so if our print needs to withstand significant stress or pressure, we might want to consider a denser infill or a stronger pattern.

Triangle

If you need a strong, rigid print that resists deformation,Triangle infill is one of the best options. The interconnected triangular pattern distributes force evenly, making it an excellent choice for structural components, mechanical parts, or anything that needs extra support.

Compared to Grid or Lines, Triangle infill provides better durability without requiring extremely high infill percentages. That means we can keep print times reasonable while still ensuring our part holds up under pressure. It’s especially useful when printing brackets, supports, or anything that will be under continuous stress.

Cubic

Cubic infill, on the other hand, offers one of the best balances between strength and material efficiency, which is why we often use it for functional prints. Its 3D cube-like structure provides uniform strength in all directions, making it ideal for parts that can withstand force from multiple angles. This infill is perfect for tool handles, brackets, and load-bearing components where we need reliable strength without making the print unnecessarily heavy.

While it does take a bit longer to print than simpler patterns like Grid, the added durability makes it worth it in many cases. If we’re working on a part that needs to be strong but also lightweight, Cubic infill is usually a solid choice.

Gyroid

The next one is the Gyroid infill. It is one of the most impressive and versatile options because it provides both strength and flexibility. Its wavy, organic structure allows for an even distribution of force, making it great for parts that need to absorb impact, such as protective cases or drone components. If we’re working with flexible materials like TPU, Gyroid infill is one of the best choices since it maintains strength without making the print too stiff.

Another advantage is that it uses material efficiently while still offering excellent durability. While it can take a bit longer to print than other patterns, the added benefits often make it worth the extra time.

Honeycomb

Last but not least is the Honeycomb infill, which is the go-to choice when we need the perfect mix of strength and lightweight design. Its hexagonal pattern mimics structures found in nature, making it highly efficient at handling loads without adding too much weight. This makes it ideal for parts that need high strength but must remain light, such as RC airplane wings or structural casings.

The one downside that Honeycomb infill has is that it takes longer to print compared to other patterns due to its intricate design. However, if print time isn’t a concern and we need something that can withstand repeated stress and force, Honeycomb is one of the best choices out there.

How to Choose the Right Infill

Choosing the right infill isn’t just about pattern. It’s a balancing act between strength, weight, and print time. A lot of us default to the usual 20% infill percentage because it’s the standard setting in most slicers, but there’s a lot more to it.

0-15% Infill

If we’re printing something purely for looks and not function, keeping infill between 0-15% is the way to go. This range is perfect for display models, figurines, or cosplay props where strength isn’t a priority. We’ve printed a few lightweight decorative items at 10% infill, and the savings on filament were noticeable without sacrificing the overall appearance.

However, one mistake we’ve made before was trying to print a phone stand at 10% infill. It ended up too flimsy and cracked under slight pressure. So, while this infill range is great for saving material, we should always double-check if our print actually needs more structural integrity.

20-40% Infill

This range is what we usually consider the sweet spot for everyday prints that need to hold up but don’t need extreme durability. If we’re making something like a phone stand, small brackets, or tool organizers, 20-40% infill strikes a good balance between strength and material efficiency. We’ve had good results printing mechanical parts at around 30% infill. It’s sturdy enough for regular use but doesn’t take forever to print.

However, if we expect the part to handle a lot of force, it’s worth going toward the upper end of this range. A friend of mine once printed a hinge at 25% infill, and while it worked for light applications, it eventually snapped under stress, which is something to keep in mind when designing parts for movement or weight-bearing tasks.

50-100% Infill

If we’re making something that absolutely needs to be as strong as possible, then this is the range to go for. Parts printed at 50% or higher infill are practically solid, making them perfect for mechanical components, weight-bearing parts, or anything that will see heavy use. We once printed a replacement gear for a small machine at 70% infill, and it held up surprisingly well compared to the original injection-molded part.

On the flip side, going all the way to 100% infill can be overkill in most cases. It significantly increases print time and filament usage. Unless we’re working on something like a high-stress functional part, we can usually get away with 60-80% infill and still get excellent strength while saving time and material.

Keep in mind that it’s always a balance between strength, weight, and print time. More infill means more material and longer prints, so we usually try to find the lowest percentage that still meets our needs.

Patterns, Examples, and Uses

For everyday 3D printing, different patterns work better depending on the type of object being printed. Here’s what we’ve found works best for common prints:

Functional Parts (Brackets, Gears, Tools)

For parts that need to handle stress, we typically go for Cubic or Triangular infill in the 30-50% range. We’ve printed several brackets and tool organizers at 35% infill with cubic patterns, and they held up well under daily use. One time, we tried printing a gear at 25% infill, and while it looked fine, it cracked under pressure—so lesson learned: for mechanical parts, always err on the stronger side.

If the part will be bearing a load, bumping up the infill to 40-50% makes a big difference in durability without drastically increasing print time. We don’t always need solid infill, but reinforcing stress points with a higher percentage is a good strategy.

Miniatures & Cosplay Props

For miniatures, cosplay accessories, or any decorative prints, Lines or Lightning infill at 10-20% works well to save on material while still maintaining structure. When we were making a lightweight cosplay prop sword, we initially went with 15% infill, and it was sturdy enough while keeping the weight manageable. For miniatures, though, we stick to Lines because they print quickly and provide just enough internal support. That said, if we’re working on larger props that might be subjected to handling or drops, increasing the infill to 20% or even reinforcing specific areas is a good call. The goal here is to balance weight and strength without wasting unnecessary filament.

Phone Cases & Flexible Prints

For prints that need some flexibility, like phone cases, Gyroid infill at 10-20% strikes the perfect balance. We’ve printed TPU phone cases using 12% Gyroid infill, and they turned out durable but still had enough give to absorb impacts. The wavy structure of the Gyroid allows the print to flex evenly, which is why it’s so effective for rubbery or shock-absorbing designs.

If we go too low on infill, the case might become too flimsy and lose its protective qualities. On the other hand, going too high can make the case too rigid—so testing within this range helps us get the best feel.

Prototypes & Fast Prints

When speed is the priority, Grid infill at 15-25% is usually the best choice. We’ve used this setting for quick prototypes when testing a design before committing to a full-strength print. One time, we needed to prototype a small hinge mechanism, and at 20% Grid infill, it printed fast while still being sturdy enough for testing. Grid infill gives just enough support without slowing things down too much. If the prototype is purely for fit testing rather than function, lowering the infill to 15% saves material and still provides enough stability for handling.

Can You 3D Print Without Infill?

The short answer is yes, but it depends on what you’re printing. Printing without infill, also known as “shell-only” printing, is totally possible and useful in some instances. Hollow prints can be great for lightweight objects like vases or decorative pieces, especially when using spiral vase mode. Just keep in mind that without infill, the outer walls will need to be thick enough to maintain strength.

That said, for anything that needs durability, skipping infill isn’t usually a great idea. Prints can collapse under pressure, and bridging layers become tricky without the internal support structure.

Create More Efficient 3D Prints With The Right Infill

Infill is what makes our 3D prints both strong and efficient. Choosing the right type and percentage can dramatically affect the outcome of your print, whether you’re after strength, speed, or flexibility. There are many infill patterns to choose from, but using cubic, grid, or gyroid patterns will meet most printing requirements. The next time you adjust your slicer software settings, don’t just default to a 20% density grid infill; consider what your specific print actually needs.

Looking to fine-tune your 3D printing results? Explore more expert tips, troubleshooting guides, and in-depth techniques over at 3DGearZone. We have guides that can help you break down everything you need to get the best performance out of your printer!