Pillowing, Stringing and Splitting – What They Are and How to Stop Them

One of the most frustrating aspects of 3d printing is printing defects. We’ve all been there. You’ve got a great design. You’ve sliced it and everything looks good. You start the job, excited to see the results – except the results aren’t so exciting.

Your object didn’t print out the way you thought it would. You’re out the time you spent printing, the material you used to print and all you’re left with are less than stellar results and a feeling of frustration at the whole process.

The good news is that most printing defects are easily solvable once you know where to look and what to do. In this article we’re going to look at three of the most common printing problems – pillowing, stringing and splitting. We’ll talk about what they are, why they occur and the steps that you can take to prevent them from ever happening again.



Image of pillowing, courtesy of Ultimaker's blog

Pillowing occurs on the top surface of an object. It looks like there are gaps in the surface layer, along with little bumps or pillows. In general, pillowing is caused by a top layer that is too thin and/or improper cooling of that layer. Under certain circumstances, insufficient infill can also contribute to the problem. Let’s take a look at what you can do to prevent pillowing from happening.

Increase the Thickness of the Top Layer

The easiest way to prevent pillowing is to increase the thickness of the top layer of your object. In most slicer applications, this can be done by going to the advanced settings tab and looking for “Bottom/Top Thickness”. In most cases you want to have a top layer that is at least 6 layers thick.

This means that if you are printing with a 0.1 mm layer height, you want to set your Bottom/Top Thickness to 0.6 mm. If this doesn’t solve the problem, you can increase the Bottom/Top Thickness setting to 0.8 mm. In general, the thinner your layer height, the more top layers you’re going to need to sufficiently cover the infill on your object.

On the subject of infill, the less you have the more difficult it becomes to lay down a top layer. While not a direct cause of pillowing, insufficient infill can contribute to the problem by causing your top player to droop and sag, especially when you add in additional layers. Therefore, it is always a good idea to slightly increase your infill percentage when attempting to prevent pillowing from occurring.


When you’re printing the top layer of your object, it’s very important that you are cooling the print material properly. If the top layer takes too long to cool, it may sag in between the infill layers and curl up where it touches the infill layers. This is especially true when you are using a thin layer height. The result is an uneven surface that becomes bumpy and uneven as the top layers are added.

Make sure that your cooling fans are operating correctly both prior to printing and as the top layer of your object is being laid down. Make sure that the fans are pointed in the right direction and are circulating air in the direction of the object that you are printing.


Image of Stringing 3D Print

Perhaps the worst case of stringing we've seen, image courtesy of Zheng3's blog

Sometimes your object will have thin strands of material where no printing should be occurring, usually across spaces where the print head has traveled from one printing point to another. This problem is known as stringing and it can be one of the most annoying defects to deal with.

Stringing is usually caused by the print nozzle oozing print material as it moves from one place to another. The oozed material cools and hardens into thin “strings” – hence the name. Let’s take a look at a couple of adjustments that you can make to combat stringing.


Retraction is a slicer setting that is usually activated by default. When retraction is activated, the printing filament is pulled back or retracted into the print head any time the head moves from one print point to another. So, if you’re seeing stringing on your objects, the first thing to do is to check that the retraction setting is indeed active.

If retraction is activated and stringing is still occurring, you can then use the additional settings tab to incrementally increase retraction distance and speed. This will cause the filament to retract farther into the print head more quickly.


A common cause of persistent stringing is a print temperature that is too high. When the temperature in the print head is too high for the material being used, the filament becomes too viscous and watery and leaks out the print nozzle. If you’re still experiencing stringing after checking your retraction settings, try reducing your print temperature in 5C increments to see if that clears up the problem.


If you have lowered your print temperature to prevent stringing, you will also likely need to reduce your print speed to prevent potential problems from under extrusion from occurring. A lower print temperature means that the print material will flow more slowly. Keeping the print speed where it was can mean that gaps and holes can begin to appear in your object in the places where the extruded material couldn’t keep up with the speed of the print head.


Layer Separation and Splitting

Simplify3D reenact the pesky layer separation that plagues poor quality filament

Sometimes a print job will be progressing nicely with no apparent problems. You leave the room, and when you come back you see that your object has developed a split or crack along one of its sides at a point where everything seemed fine before.

As you know, your printer makes an object by laying down layers of print material, one on top of the other. It is imperative that each new layer binds to the previous one. Splitting occurs when one layer bonds inadequately with another layer. When this happens, as the object cools, a split or crack occurs between the two inadequately bonded layers. Luckily there are a couple of things that you can do to prevent splitting from occurring.

Decrease Layer Height

In order for two layers of print material to bond, the print nozzle needs to apply exactly the right amount of pressure to the layer currently being laid down. Too much pressure and the layer will move off to one side or smear. Too little pressure and the layer can’t adequately meld to the previous print layer. The result is a crack.

In order to make sure that the print nozzle is applying adequate pressure, make sure that your layer height is about 20% smaller than your print nozzle diameter. That ratio insures that the nozzle is pressing down enough on the material being extruded to adequately bond it to the previous layer.

Increase Print Temperature

If your material is being extruded at too cool of a temperature, it cannot easily bond with the material that’s already been laid down. Therefore, as it cools, it will shrink and pull away from the layer below it. The result is a split or crack.

To avoid this from happening, increase you print temperature slightly. The slightly higher temperature will insure that the extruded layer bonds with the previous layer so that both layers essentially cool as one object, thus avoiding the splitting that would otherwise occur.

If you’ve liked this article, we’d love to hear from you about your own experiences. Also, remember to sign up to our blog for a wealth of relevant 3d printing info and absolutely, positively no spam. Thanks and see you next time!

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Top 7 3d Printing Tips for Beginners

3d printing is an amazing technology whose possibilities are only just beginning to be explored by tens of thousands of enthusiasts from around the world. If you’re new to 3d printing, it can seem like there’s a veritable mountain of information to wrap your head around.

However, like all things, the more you print, the better a printer you become. This is especially true if you’re building your knowledge on a solid foundation of best practices that have been gleaned from the experiences of others who have been involved in 3d printing for a longer period of time than you have.

Their familiarity and know-how can be invaluable when you’re just starting out. To that end, this article is going to give you 7 expert 3d printing tips that you can use to start achieving better print results in a shorter amount of time.

  1. Have Patience – You’re dealing with a relatively new technology. While the process was invented and patented in the late 1980s, it’s only been the last three or four years, since the expiration of the original patent, that printer prices have dropped allowing nearly anyone who had an urge to give 3d printing a try. While it’s getting close, 3d printers are not quite an “in a box” solution quite yet. (They’re getting close, though.)They are complex machines that run fairly complex programs to produce increasingly complex objects. This means that you need to have patience when you’re beginning to learn how to print. Mistakes are going to be made, but every mistake adds to your body of knowledge and gets you one step closer to mastering the art of printing beautiful and useful object
  2. Man and Machine – Closely related to the idea of patience is the idea that successful 3d printing is the result of a closely choreographed waltz between you and your printer. You can take advantages of tips like these and the experiences of other people who’ve been printing longer, but in the end you’re going to have to get to know your printer inside and out. The best printing results happen because the person doing the printing knows how to adjust and run their printer so they they’re getting the maximum performance out of it for the material that they are using. The more you know about your printer and the material that you’re using to print, the more successful you’re going to be in getting the end result you want.
  3. Get It Straight – One of the easiest ways to eliminate potential problems before you start a print job is to make sure that your printing axes are properly calibrated. Your printer operates on three separate axes – the x axis that moves the print assembly left and right, the y axis that moves the assembly backwards and forwards and the z axis that moves the assembly up and down. While all are important to a successful print job, the correct calibration of the z axis can spell the difference between victory and defeat when printing. If the z axis is too high or too low, you’re going to experience problems like insufficient adhesion to the print surface, smearing or your print material and clogging of the print nozzle. A properly calibrated z axis and a level print bed will increase the chances that you will have a positive experience every time you print.
  4. Use Quality Printing Materials – A higher quality printing filament can allow you to achieve successful results with fewer problems. Not all filaments are created equal. Some contain impurities that can cause inconsistent melting which results in inconsistent extrusion while printing. Poor quality filament is also not manufactured to exacting tolerances. This means that on a single spool of filament, the diameter can vary widely. This variation can also result in under extrusion and even clogging of the print nozzle. When you choose high quality printing materials, you eliminate these problems and increase the chances that your print job will run smoothly.
  5. Be Safe – You always need to be aware of safety when you’re 3d printing. Some of the surfaces of your printer can get hot and burns can occur if you’re not careful. In addition, all 3d printing thermoplastics give off fumes when heated. Some of materials are more benign than others when it comes to fumes. However, all 3d printing should occur in a well ventilated room to reduce any risk of harmful effects occurring as a result of inhaling these fumes.
  6. Network and Communicate – When it comes to solving 3d printing problems, there is no need to reinvent the wheel. No matter what issue you make be experiencing, the chances are that there is someone else out there who has experienced the same problem and is more than willing to share their solution with you. Take advantage of this experience and knowledge. Join 3d printing forums and groups and introduce yourself. Participate in the community. Ask questions. Any “expert” should be more than willing to take the time to answer your questions and give you the benefit of what may be years of experience. Networking and communicating with other 3d printing enthusiasts is an invaluable resource to someone just starting out.
  7. Don’t Neglect Design – Every three dimensional object started life as a computer assisted design. When you’re first beginning to 3d print, it’s makes sense to use designs produced by other people in order to get to know your printer, the materials that you’re using and the process itself. However, you always have to keep in mind that the designing a 3d object is, in some respects, the heart of 3d printing. This means that in order to really get a feel for how the entire process works, you have to begin designing your own objects as well. There are a number of free CAD programs available that make designing your own stuff easier than you think. After all, there’s nothing more satisfying that successfully printing an object that you designed from scratch.

If you’ve liked this article, we’d love to hear from you about your own experiences. Also, remember to sign up to our blog for a wealth of relevant 3d printing info and absolutely, positively no spam. Thanks and see you next time!

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Kitten Mittens

Kitten Mittens. From the TV Show "It's Always Sunny In Philadelphia".



Kitten Mittens

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How to Smooth PLA to a Mirror Finish

Need to make your prints look super smooth? Or perhaps, you just want rid of those layer lines to make your print look more 'factory finished'? Here's how to polish PLA 3D prints to a shine you won't believe was ever 3D printed. 

The best way to smooth 3D prints.

It's often said that ABS is easy to smooth (using acetone baths and similar methods) but that PLA and similar non-acetone-dissolving 3d printer filaments cannot be smoothed the same way. They can, you just need to know the right technique, and have a little time on your hands. 

We recommend smoothing using this technique for your most prized prints, as it can take a little bit of time. Additionally, this technique for you to smooth 3D print (PLA filament) does not work as well on very intricate prints. 

Here's a close up of the finished effect. The filament is our Gold/Bronze PLA. This is a 6cm long 3D Benchy for scale, and we only smoothed one side of the hull to compare. 


Polished 3D Benchy

(it's hard to see just how smooth this surface is, but honestly it's like glass)


What you'll need:

To start, you're going to need a selection of fine grit sandpapers. We suggest the following grit sizes (and if you want a really smooth finish like above, we recommend not skipping any steps): 200, 400, 600, 800, 1000, 1200, 1500, 2000, 2500 and finally 3000. 

It's best if you can use 'wet & dry' paper (black grit as opposed to beige effect) especially with PLA, because if you're sanding fast, heat can build up and effect the smooth surface you're trying to achieve. Wetting the glass-paper will lubricate and cool the surface you're sanding. This is not as necessary with smoothing higher temperature 3D printing materials, but still advisable. 


1. Start with the coarsest sandpaper, approx 200 and smooth the surface until you cannot feel any printing layer lines at all. You've got to sand in a circle motion, as you don't want any lines from the sandpaper effecting the surface later on. 


400 Grit Sandpaper 3D Print

 (this is what your print will look like after using 400 grit sandpaper, you cannot see the layer lines)


 2. Start scaling up the grit number. Once you've got an acceptable result with the 200 or 400 - move higher up and smooth the print in increments. Don't skimp on the time to sand them down, and keep going in the circular motion. Try to be mindful of details so you don't loose definition as you go. 

The good news is with each finer grit, you don't need to spend as much time sanding that layer. 


1000 Grit Smooth

 (after using 1000 grit sandpaper it'll start to look really smooth)


3. Keep working up the sizes, from 400 to 600, then to 800 and upwards. Don't miss out steps when you get to 2000. It'll feel really smooth, and will polish nicely at that level - but if you want mirror finish you need to build to 3000. 


3000 Grit Smoothed 3D Benchy

(here you're at 3000 grit, you can start to see the shine before you've polished)


4. The final and most fun stage is the actual polishing stage. Layering up those sandpaper increments doesn't feel like you've made much progress, but once you polish up - the final finish looks great. 

The polish you need to use to really smooth out 3D prints to that mirror finish we've found is just any good liquid metal polish. Our favorite is the ol' trusty Brasso. 


Brasso To Polish 3D Prints


The technique to polish your prints is simple. Get a soft cotton cloth, and apply a small amount of liquid polish. Then apply to your 3D print surface in small circles until all the polish is rubbed into the surface. 

Once you've finished that, the surface should look reasonable shiny. The final stage is to buff up that surface into that mirror polish shine. Just get an unused area of your cloth, without any polish on and go back over the area you've just worked on to buff up to a shine. And that's it. 

Here's a before and after reminder on the technique: 


Before and after smoothing and polishing PLA prints


Hope you found this guide to smooth out 3d prints useful. If you did, why not subscribe to our blog to receive updates on other helpful 3d printing how-tos. 

Please comment below if you have any tips to add or questions, we'll be only too happy to help. 

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6 Key 3D Printing Slicer Settings You Need To Know

As you may know, a slicer is a piece of 3d printing software that takes a digitized 3d model and converts it into printing instructions that your printer can then use to turn the model into a physical object.

In essence, the slicer takes the CAD model and “cuts” it into layers. It then calculates how much material needs to be used for that layer, where the material should go and how long it will take.

It then converts all of the information for each layer into one GCode file which is sent to your printer. You set up the job and, voila! Sometime later you have a physical representation of the 3d CAD model.

As you can see, the slicer plays an integral role in helping turn your 3d ideas into reality. Therefore, how you use the slicer, specifically how you use the settings, is often a critical difference between printing success and failure.

In this article, we’re going to look at 6 key slicer settings that are common to all the major slicer programs. We’ll tell you what they’re for and we’ll explain how to use them to increase your chances of producing beautiful and useful objects each and every time you print.


1. Layer Height

Layer height is the setting that establishes the height of each layer of filament in your print. In some sense, layer height in 3d printing is akin to resolution in photography or videography.

When you choose a thicker layer height, your object will have less fine detail and the layers will be more viable. When you choose a thinner layer height, a higher level of detail is possible and your layers will tend to blend into one another.

However, keep in mind that the thinner you make the layer height the more time it will take to print the object in question, since there will be more layers to print.

An object with less detail, on the other hand, will print faster with a thicker layer height. It will also have a less smooth surface. Thicker layer height is often chosen for making a prototype of an object, since detailing and surface texture usually don’t matter.


2. Shell Thickness

A shell is the outer wall of a designed object. Shell thickness refers to the number of layers that the outer wall will have before infill printing will begin. The higher the setting is for shell thickness, the thicker the outer walls of your object will be.

Obviously, thicker walls make for a sturdier object, so if strength is a quality that you’re after, it pays to increase the shell thickness appropriately. Obversely, delicate or decorative designs do not usually require strength. Increasing the shell thickness in these instances provides no real benefit and will likely distort the design of the object being printed. 


Slicer Settings

3. Retraction

This setting is used to pull the filament slightly back into the print head during times when the head is traveling from one print point on an object to another. This stops the filament from leaking out of the print nozzle and leaving strings of material across otherwise empty space.

If your CAD design has a discontinuous surface, you slicer program should automatically enable the retraction setting.


4. Fill Density

Fill density or infill is a measure of how much material will be printed inside the outer shell of the object in question. Fill density is usually measured as a percentage of whole, as opposed to a unit of measure.

This means that if 100% fill density is selected, the printed object will be solid, with no empty space inside the outer shell. Likewise, if 0% is selected, the printed object will be empty inside. Fill density is used to conserve filament while printing and speed up printing times.

However, an object with more infill will be stronger and heavier than an object with less infill. Therefore, if either of these properties will benefit the printed object, consider increasing the fill density as needed.


5. Print Speed

Print speed is how fast the print head travels while extruding filament. Therefore, optimal speed depends on the object you are printing and the filament material that you are using to fabricate the object.

In general, simple objects with less detail can be printed faster without complication.

On the other hand, more complex objects with more detail will benefit from a slower print speed. Print speed can also affect adhesion to the print surface, cause under or over extrusion and other problems. Because of this, it pays to experiment with your print speed to see what works best for the job you’re printing.


6. Bottom/Top Thickness

This setting determines how much material will be laid down before the infill printing starts and how much material will be laid down after the infill printing is finished. The thickness of the material at the top and bottom of your object is important for two reasons.

First, thicker material at the bottom of your object will provide a stronger and more stable base. Second, thicker material at the top of your object will prevent sagging and pillowing from occurring when the top layer of material is laid down over the infill lattice.

This especially important if you are using a smaller layer height setting. In such a case, the thinness of the layer can be insufficient to completely cover the infill unless multiple layers are used. Setting the bottom/top thickness to be 6 to 8 times greater than the layer height insures that there is enough material being laid down to adequately cover the infill without complications.

It is useful to remember to only change on slicer setting at a time so that you can see the effect that the change is having on your print. If the change is beneficial, write down the change that was made and proceed, if necessary, to change another setting.

Changing multiple settings at the same time can cause chaotic conditions and a positive effect can be canceled out by one or more negative effects.

If you’ve liked this article, we’d love to hear from you about your own experiences. Also, remember to sign up to our blog for a wealth of relevant 3d printing info and absolutely, positively no spam. 

Any questions or comments? Please post below and we'll get back to you as soon as we can!

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