How to Print Perfectly With PLA

PLA, or polylactic acid, is an easy-to-use, renewable, and biodegradable 3D printing material. It is also non-toxic. PLA filament comes in a wide range of colors and can be used to produce great prints with little effort owing to its thermoplastic qualities.

PLA [Polylactic acid] - Pro & Cons

Pros

• Low cost
• High tensile strength
• High dimensional accuracy
• Long-lasting with care

Cons

• Requires more heating precision and lower temperatures than most other filaments
• Prone to oozing without effective cooling
• Can be brittle if not stored/used properly
• Prints not suitable for outdoor exposure

What is PLA?

PLA is a thermoplastic polyester that is commonly derived from fermented plant starches, such as those from corn, sugarcane, or beet pulp. One of the most attractive things about PLA plastic is that it degrades in natural conditions. An item made of PLA plastic decomposes in the ocean within six months to two years. This is a significant improvement to the degradation of conventional plastics, which can take from 500 to 1,000 years to degrade, and they can leach toxic byproducts into the environment.

 It is important to point out that although PLA will degrade in an exposed natural environment, it is very robust when used in normal applications such as models or machining components. This is similar to most metals or heavy-duty materials; when exposed to air and water over time, they degrade. When kept indoors and maintained, however, they will last for a very long time.

PLA plastic is graded according to the industry in which its used; PLA can be food-grade, scientific, and medical for food packaging, machine components, and implant fixtures, respectively. In addition to these grades, PLA is also developed for consumer printing. Its natural melting temperature is around 80°C, but it is mixed with other plastics to make it suitable for 3D printing.

Compared to ABS filament, another common 3D printing material, PLA filament is harder, breaks down more slowly, and melts together more effectively. PLA is also less thermally contractive, and it is easier to print large parts. The primary consideration with this material is that its hardness also means that it is more brittle. Therefore, it is not ideal for parts subjected to strong impacts or consistent sharp pressure.

PLA plastic becomes soft at 70–80 °C and will deform in environments with temperatures above that range for a prolonged period. For parts printed for use near the extruder, ABS filament or a similar material should be used.

Machine Requirements

PLA is a high-quality, sturdy material, but it requires some special considerations.

Bed

A heated print bed should reach the 40–60 °C range to aid in adhesion and removal without allowing the filament to melt upon laying.

Build Surface

The provided print surface will likely not be sufficient for ensuring clean removal. Several tools, such as blue tape, PEI, and glass plates, can help provide a suitable build surface.

Cooling

A part-cooling fan that is integrated with your printer will significantly improve your chances of high-quality, sturdy prints. If your printer is not outfitted with a high-powered fan, you may need to buy an external fan or a community-designed mod to ensure comprehensive cooling of printed parts.

What is PLA Filament Made From?

Beyond its use a thermoplastic polymer, PLA is often mixed with other binding agents in the manufacturing process to produce a variety of filament types. Many of these can be used for similar applications with considerations for manufacturer-recommended print temperatures and care practices. Some common and well-loved PLA types are listed below.

Wood PLA blends

These blends consist of polylactic acid and bamboo, birch, cedar, coconut, and ebony wood fibers that lend a nice scent and produce a sturdy product.

Metal PLA blends

Metal PLA blends consist of polylactic acid and aluminum, bronze, brass, copper, and even stainless-steel particles or powders, creating a solid product with a beautiful sheen and color. Note that many metal-based PLA blends can lead to greater wear on your machine than other blends and should be used with care.

Other natural PLA blends

Some PLA blends include natural materials like algae, beer brewing by-products, coffee, and hemp. Each blend has some unique properties, but all are great for prints that do not require extremely high durability. Speaking of...

High-temperature and High-strength/Industrial PLA blends

Several PLA blends are manufactured specifically for higher-impact use than more conventional hobby types. High-temp blends are harder to work with but great for applications in components that are subject to consistent heat over their lifetime (think coffee shop items). Industrial-grade PLA is made with an unknown polymer that provides significant strength with lessened shrinkage and warping capacity while being able to withstand higher pressure/impact applications than conventional PLA. While this filament is typically used in commercial industrial printers, at-home makers can definitely make use of this filament for heavy-duty applications.

The First Layer

The first layer is the foundation of the print, so you should focus on getting it right. There are a few things to consider before laying down the first layer:

• The print bed or print surface must be level.
• The extruder should be calibrated to the correct height from the bed.
• A good base material to which the PLA can adhere must be used.

Printing on Blue Tape

Blue tape, or painter’s tape, is a great base for PLA prints. Following these steps can help ensure that your print is stable:

1. Lay down the tape in an even layer without overlapping the edges. Do not miss any spots.
2. Do not heat the bed when using the tape because the heated tape will not stick well to the PLA filament.
3. Replace any tape strips that are damaged when removing parts.
4. After 5–10 prints, or when parts stop sticking, replace the tape.
5. If the first layer does not stick well, check that the print head is close enough to make a squished line of PLA. If the layer still does not stick, try increasing the first layer temperature by 5 to 10 degrees, starting with 5 and increasing as necessary.

While blue tape is not a perfect solution, it is easy to use, accessible, and typically produces great results. However, sometimes the parts can pull the tape off the glass during printing, which can lead to warping.

Printing on Glass with a Heated Bed

When you have a temperature-controlled bed, using glass can be a great option to improve print adhesion and removal.

The following steps can ensure a clean print when using glass:

1. Level the bed and set the extruder at the right height. This is extremely important when printing on glass. If your extruder is too far from the glass, the PLA will not stick to it, but if it is too low, the glass will completely block the extrusion of material.
2. If the first layer is not sticking, there are a few troubleshooting steps you can take.
3. Check the bed leveling and extruder height.
4. Run the extruder for a short time before beginning the print so filament consistently flows onto the bed. Depending on your printer, its software may have a setting for pre-print extrusion to get the filament going.
5. Make sure the extruder temperature is hot enough to properly melt the filament. Otherwise, the plastic may cool too quickly and lift from the bed. This can cause the nozzle to snag on the first layer when moving around the bed.
6. Setting the first layer's extrusion temperature 5–10 degrees higher than the other layers may help it stick properly.
7. Check your print speed. Printing too fast can cause the plastic to cool too quickly and lift from the bed, causing a failed print. 
8. Clean the glass with denatured alcohol.

Glass is the best surface for printing with PLA owing to the ease with which prints can be removed and the surface can be cleaned.

Other Printing Surfaces

Kapton Tape

Many people have had success printing on Kapton Tape. A heated bed is required to use Kapton Tape as a print surface. Using it is very similar to printing on glass, and the same procedure can be followed for troubleshooting. However, glass is still the best option.

Polycarbonate

Some people have reported success using polycarbonate plates as printing surfaces, but the ease of use and benefits when removing prints are somewhat lacking. You may find that polycarbonate works for you, but it is not the easiest material to work with.

The Right Temperature for Printing

Working with a new roll of filament for the first time can be tricky. It can be helpful to start printing at 205 °C, then adjusting the temperature 5-degree increments until print quality, strength, and stability seem balanced.

Common temperature-related problems

Temperature is too high

When the temperature is too high, you will likely see many strings between the layers or parts of your print. Also, the extruder may leak out heated filament while moving.

To fix this, lower the temperature in 5-degree increments until the extruder does not leak as much.

Some materials are less viscous than other PLA and will leak more at low temperatures. If you increase the retraction by a few millimeters (3-4 seems like a good number for most every PLA we have tried), you may be able to fix this issue.

Temperature is too low

If the temperature is too low, the filament will not stick to the previous layer and the print will be rough. You may also see parts of the print that are weaker or less even. Increasing the temperature by 5-degree increments can help.

Changing the Filament

When switching PLA colors, follow these steps to ensure the new filament flows smoothly:

1. Heat the extruder to 80 °C. Do this when the machine is cold, not after it has been running.
2. Remove the current filament from the extruder. This can be done by hand, but you may need to reverse the extruder.
3. If the filament is not easily removable, increase the temperature to 100 °C and try again.
4. Increase the heat and load the new filament normally.
5. Run the new color through the extruder until it comes out cleanly without traces of the old filament. If you are switching from a dark color to a light color, run the filament longer to be sure the dark filament does not color the light filament.
6. Clean the extruder gear and remove any particles from the extruder entrance.
7. Run the extruder for several minutes. It can take up to 15 minutes for the filament to run without contamination of the other color.

I recommend removing the filament when it is soft rather than fully melted to mitigate the possibility of getting melted material on the extruder drive gear or coating the melt chamber entrance. These can cause jamming and be hard to clean up.

Temperature References for PLA Filament

Color	Recommended Temperature	Recommended Range
Black	195 °C	190–210 °C
Glow-in-the-dark	190 °C	185–205 °C
All other colors	210 °C	205–220 °C

These values are derived from manufacturer recommendations as well as user recommendations.

You may need to experiment with temperature to find what works best for your printer. Ambient temperature, humidity, calibration, and the unique characteristics of your printer all affect how PLA will work for you.

Troubleshooting

When prints are not turning out the way you were hoping, it can be frustrating. If you have any of the following symptoms, there are some basic steps you can take to try to fix the issue.

The first layer is not sticking.

1. Check that the extruder is at the right height.
2. Make sure the print bed is level.

The internal layers or overall print structure is unstable or uneven.

1. Check the extrusion temperature, increasing in small increments if necessary.
2. Check the filament tension.
3. Clean the filament drive gear to ensure it is clean and moving correctly.

Part edges are bumpy.

1. Make sure your printer is getting the required data quickly enough to produce a smooth print. If printing from a computer, ensure that the computer can feed the printer commands efficiently without background applications slowing down the process. If the printer is pausing, the data may not be being transmitted consistently.
2. Print from an SD card. Some printers allow you to print from SD cards. This often helps the printer run more smoothly.
3. Use higher quality PLA. Filament quality can directly impact print quality, so overall print quality issues may be associated with low-grade filament. However, replacing filament should be a last-resort option as many printers can produce good parts with lower quality filament with the correct settings.

Parts of the printed object seem melted or squished into each other.

1. If your printer has a fan, turn on "cooling" in the print settings.
2. Get a small fan to provide external cooling. If your printer does not have an integrated fan, use a small desk fan.

The printer is not extruding any material.

1. Check the temperature of the hot end to ensure it is heating properly. If it is not, your printer may need to be serviced. This often happens because of an internal wiring issue.
2. Clean the drive gear and adjust tension. Improper tension or a clogged drive gear can reduce the flow of filament or prevent extrusion altogether. Clean the pinch wheel with a wire brush, and check that there is sufficient tension.
3. Remove the current filament and feed new filament. Sometimes, a piece of hardened material or debris can cause the filament to clump or gum in the extruder nozzle, reducing or preventing flow.
4. Examine the extruder, hot end, and the parts in between for jams. If nothing else works, you will have to disassemble the printer body to access the components joining the extruder and hot end. Sometimes, heat can “travel” up the filament in the extruder and begin the melting process earlier than it should happen, leading to cooled, pooling filament that blocks further extrusion. This usually occurs at the junction between the extruder and hot end. Remove the extruder and take out all the PLA that you can, which may require heating the hot end. If you cannot remove the filament by hand, pushing the filament through the hot end may be necessary; however, if you do this, be sure to use a small tool or object that will not scratch or damage the inside of the component as this can lead to clogging later on. Be sure to take precautions against burning, shock, or injury. If you are not completely comfortable working on your printer at this level, do not try to take it apart. Instead, take it to someone who is trained in fixing 3D printers or contact the manufacturer.