3D Prints Warping or Curling? – Why It Happens and How to Prevent It

extreme warp

If you’ve used a 3d printer, then it’s likely that you’ve experienced 3D print warping. Warping is one of the most common problems encountered in 3d printing and it’s one of the most annoying.

But luckily, it is easily preventable - depending on your material and printing conditions, there are different remedies we'll cover below. 

3D printing curling doesn’t always cause a catastrophic failure of the object being printed like some other problems can. However, it does cause the object to deform enough to look unacceptable and unprofessional.

Worst case is your warping 3d printing can pop off the heated bed and cause it to fail completely. 

Why has my 3D print warped?

A 3D printer warping problem typically occurs when an object is cooling after printing. Cooling, as you know, causes contraction and this contraction causes stress along the object’s lateral surfaces. The quicker the cooling occurs, the greater the stress on the object.

This stress is greatest at corners where two sides meet. There, the pulling stress exerted on both sides causes the corner of the object to deform and pull up and inward. The result is not pleasing to the eye and usually makes the object unusable.

There are really only two ways to prevent 3D printer curling; increasing ambient temperature to reduce cooling time, or seriously improving your bed adhesion. Luckily there are simple ways to do both, which we'll cover shortly. 

But first, what if it's too late - and you have a warped print right now? Well, maybe not all is lost just yet...

How to fix a warped print?

While not all warped prints can be fixed, if the warp or curling is slight - and your print isn't too thick or large in volume you might just be able to salvage it. 

To do this, you'll need to heat up the print close to it's glass transition temperature (where it'll get just soft enough to mold back down). You'll need a large metal surface, like a frying pan, big enough to place the print in bed side down (just the way up it came off your print bed).

Get a hair dryer and place the print in the pan. Heat it up on full power, and move the dryer around to evenly heat it. After a minute or so, you can turn off the dryer and you should be able to hold the print down to bend it back to a flat shape. You'll need to hold it for a few minutes until it's cooled a bit.

Repeat this process until it works sufficiently. Don't bother just putting the print back on a heated bed, or worse heating the pan - because this will just heat the bottom of the print. You'll need to heat it up evenly all over. 

 

Elephant's Foot

Related to warping, but a slightly different fault is something we call 3D Print Elephant Foot - it's when the based of your print widens out, shaping the object like, well - an Elephants large foot. 

elephants foot
It's got elephants foot AND it's warped? Oh lets all just go home...

You can see the bottom few layers here have spread out wider than the rest of the print. Here's how this phenomenon happens and how to solve it:

Essentially your first few layers are being squashed, causing them to ooze out to the side. This can be caused from one of two things: either your bed is just too close to your nozzle, or on longer, heavier prints, the weight of the model later in the print weighs down on the softer layers still warm from the heated bed. 

To Solve 3D Printing Elephant Foot:

Assuming the elephants foot is happening evenly on all base sides of your print, increase the Z-axis offset slightly, to allow more room for those first layers to settle at the correct height. We recommend starting in 0.1mm increments. Too much and you'll risk there not being enough pressure for the print to have sufficient adhesion to the bed. 

If the elephant's foot is only on one or two sides, you'll need to re-level your bed. 

Finally if you're finding that it's a heavy, large model weighing down those first layers (you'll notice this effect increases the larger the print gets if this is the case) then you'll need to reduce temperature of the heated bed. Too hot and you'll soften the material too much. 

To prevent Elephants foot in a nutshell:

  • Level your heated bed
  • Adjust z-axis offset/or the nozzle height from the bed
  • Correct heated bed temperature  

As we said, warping is one of the most common problems that occurs when 3d printing. The good news is that even though it can be caused for a number of reasons, it is relatively simple to prevent. So, let’s take a quick look at some of the ways that can help you prevent print warping.

Heated Bed

Once upon a time, heated print beds were relatively rare. Because of this, printed objects tended to cool very quickly once a job was underway. This caused high levels of lateral stress and ABS curling was commonplace.

Today, most people are printing on a heated print bed. This causes a printed object to cool much more slowly. This reduces the stress caused by contraction which, in turn, helps to reduce warping. Heated beds are not an all-in-one solution to warping, but when used in conjunction with other preventatives, they do lower the chances that your object will warp.

One thing to note with heated beds, is that the heating element isn't always the full size of the bed - this means the edges might not get hot enough (depending on your printer). The diagram below illustrates the common causes of warping. So it's worth taking this into consideration if large prints warp, but smaller central ones don't. 

 

Why your prints warp

Here you see the print warped, or is curling at the edges.

 

This is also assuming the heat on your bed is even. Still getting ABS warping on a heated bed? It could be because the heating elements are not even under the glass or metal plate. Checkout the thermal image of a very popular model of 3D printer. Can you guess what it might be? 

Thermal Prusa Heated Bed

This is taken from the heated bed on a Prusa MKII

The target temp for this bed is 50C, notice the cooler area in the center. Commonly this is where people normally place smaller prints. So you may be getting small prints warping, but larger prints staying flat and printing fine. 

It should also explain why you maybe getting your PLA curling in some areas of the print but not others, for example.

It's also worth noting that if your bed is made of particularly thick aluminium or glass - the thermometer may be reading full temp before the actual surface of the bed has had chance to fully heat up yet. 

In this instance you're best of waiting a good 10 minutes after your bed is reading the correct temperature before you start to print. This could mean the difference between first layer success and complete failure. 

 

How to Avoid Warping 3D Prints

It’s extremely important to regard how different printing materials are affected. For example, PLA doesn’t require a heated bed. However, when printed on one at around 50C it can help those first few layers adhere a little more consistently. But if you're getting 3D print warping PLA then it's likely at too high a heated bed temperature (eg. over 60C) can cause it to warp.

Rule of thumb for PLA warping on a heated bed - you're likely printing too hot. 

Whereas if you're getting 3D printer ABS warping on a heated bed, a big culprit is likely to be that the heated bed simply isn’t getting hot enough. ABS warping on a heated bed? Usually just turn it up!

Other ways to prevent ABS curling, as it can be a common issue, is to improve the ambient temperature of the printing enclosure to slow down the cooling of the print. Generally it's always best to print ABS in an enclosure, or failing that a warm ambient environment. 

With something very sensitive to cooling too fast, like the UV resistant ASA; you’ll definitely want to make sure it’s printed in a warm ambient area with no drafts or it can warp so badly you see cracks in the print. More on this later.

These rough assumptions are based on you using the correct adhesive or surface for your material. This is also really important to prevent 3D printing warping - but don't worry, more on this below. 

 

So, how to prevent warping:

Use a Build Surface that Promotes Adhesion

This is quite likely the most important step that you can take to eliminate warping in your printed objects. Most printers come with a glass or aluminum build surface that is durable, but also far too smooth. Extruded thermoplastics have nothing to grab onto when they encounter smooth surfaces. The result is that warping caused by cooling becomes more pronounced.

The solution is to start using build surfaces that enhance adhesion. There are a number of things that you can try in order to achieve this. Painter’s tape and Kapton tape both work well to reduce warping in PLA and ABS respectively. Hairspray applied directly to the build surface to increase tackiness is used by many in a pinch, but it is messy and has limited durability.

If you're having persistent issues with your ABS print warping, you may want to use a mixture of ABS slurry or ABS juice on your bed, which should significantly aid adhesion. 

Pritt stick accomplishes the same effect much more efficiently and with much less mess. Finally, a substance like PEI (polyetherimide) comes in sheets that are easily attached to your build surface, are affordable and give excellent adhesion to just about any print material (except Nylon). Find out more about build surface adhesion solutions here.

Clean Your Build Surface

No matter how adhesive your build surface is, dirt and grease will conspire to reduce that adhesion and put you back at square one when it comes to warping. Make sure that your build surface is as clean as possible before you begin printing.

An ammonia based product like Windex or Halford’s Glass Cleaner works great to remover grease and fingerprints from the build surface. An isopropyl alcohol and water solution also works well. When your build surface is clean, your print material has a much greater chance of adhering which will reduce warping.

Cause of adhesion issues

Rounded Corners

Your PLA curling at the corners? One interesting way to reduce warping is to design objects that have rounded corners whenever possible. A rounded corner tends to ameliorate the amount of upward stress that occurs where two or more flat surfaces meet, by distributing that stress over a wider area.

Less stress means less warping and less 3D print curling, which means more successful printing.

Check Your Starting Z Coordinates

Sometimes, printing a good first layer is key to achieving a successful result. One way to increase the odds of putting down a decent first layer is by checking your starting Z coordinates before printing.

If the Z axis is starting too high, extruded print material has a longer distance to travel before contacting the build surface. The longer the distance that the material has to travel, the cooler the material becomes and the greater the chances are that it will not adhere correctly.

If you’ve tried everything and are still experiencing warping, try lowering the Z axis height in 0.05mm increments and see if that corrects the problem. As you do this, keep in mind that you never want your extruder nozzle to come too close to the build surface, as this will cause its own set of problems.

If your print has a low surface area, and is proving hard to stick down it may also be worth printing a brim or skirt around your print to encourage extra adhesion to the bed.

Here's an example:

3d print brim or skirt

 

Eliminate Drafts

The key to controlling warping is a slow and steady cooling process.

The quicker that cooling occurs, the more likely it is that your object will warp, no matter how many steps you’ve taken to prevent it. This is why eliminating all drafts while you’re printing is extremely important if you want to reduce the instances of warping.

The cause of warp

You should consider printing in a room in your house or place of business that provides the steadiest ambient temperature. Remind others in the area that you have a print job running and ask them to stay out of the room in question for the duration.

Having someone open a door while your printer is running can cause the warping that you’re trying to prevent. If your home or office is especially drafty, or if your printer must be located in a somewhat high traffic area, you might want to consider enclosing it so that temperature remains stable, or just significantly hotter while you print.

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. Please post comments or questions below – we’re here to help!

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