A Comprehensive Guide to PLA Melting Point and How it Influences 3D Printing

Widely used for prototyping and to produce visual models, PLA is one of the most common 3D printing thermoplastics in use today. And for good reason: the filament is both easy to print and affordable. However, in order to unlock the most benefits from PLA when 3D printing, it is important to know the material’s properties, like what is the PLA melting point. 

Having a grasp of the material’s behavior under different temperatures is crucial for achieving optimal printing results. This knowledge allows users to fine-tune their printer settings, troubleshoot issues, and ultimately produce high-quality prints with PLA. In this article, we’ll be going over the properties of PLA, including its melting point and temperature properties, as well as how they influence print settings and best practices.

What is PLA?

Before we dive in, let’s first look at PLA in more depth. Also known as polylactic acid, PLA is a biodegradable thermoplastic polymer derived from renewable resources like cornstarch, sugarcane, or tapioca root. As a raw material, PLA has become popular in various industries due to its low environmental impact and ease of processing, including in the world of 3D printing. In fact, PLA is one of the most widely used polymers for 3D printing applications. 

PLA’s popularity can largely be attributed to its low cost, ease of use, and good print quality. It is considered one of the most beginner-friendly materials for 3D printing, as it requires relatively low printing temperatures and displays minimal warping during the printing process. Additionally, PLA's availability in a wide range of colors adds to its appeal for both hobbyists and professionals alike.

As a thermoplastic material, PLA starts to soften and eventually melts when exposed to high temperatures. And as the material cools, it starts to resolidify.[1] This means that thermoplastics like PLA can be processed and reprocessed, facilitating recycling and reuse. It also enables the material to be processed using methods like 3D printing and injection molding.

The Science Behind PLA Melting Point

A material’s melting point is a critical property in material science, as it represents the temperature at which a solid material transitions into a liquid state. 

Several factors determine a material’s melting point, including its molecular weight and crystallinity. For instance, PLA is a semicrystalline polyester that consists of chains of lactic acid molecules, and its melting point is influenced by the molecular weight of these chains. The molecular weight represents the mass of a single molecule (measured by adding up the weight of each atom in the molecule), and a higher molecular weight generally corresponds to a higher melting point. 

PLA's melting point typically ranges between 150°C and 180°C, although this varies depending on the specific grade of PLA and whether the material has any additives. Manufacturers often incorporate additives into thermoplastics, such as pigments, plasticizers, or stabilizers, to modify the material's properties, including its melting point. These additives can either increase or decrease the melting point of PLA, depending on their specific characteristics and concentrations.

Understanding the science behind PLA's melting point is crucial for optimizing its use in various applications, including 3D printing. Accurate knowledge of the melting point allows users to select the appropriate processing temperatures and techniques, ensuring successful printing outcomes and maintaining the integrity of the final product.

How is PLA Melting Point Determined?

There are several methods used by materials experts to determine the exact melting temperature of a material. While you probably won’t attempt these at home, let’s take a look at how melting point can be determined.

• Differential Scanning Calorimetry (DSC): DSC is the most commonly used method for measuring the melting point of polymers, including PLA.[2] This technique involves heating the PLA sample at a controlled rate while monitoring the heat flow associated with the melting process. The melting point is determined based on the temperature at which the endothermic peak occurs. DSC offers high accuracy and the ability to detect small changes in melting point due to additives or molecular weight variations. However, DSC requires specialized equipment and can be time-consuming.

• Thermogravimetric Analysis (TGA): TGA measures the mass loss of a sample as a function of temperature, allowing for the identification of the melting point as the temperature at which the mass loss rate increases significantly. Although TGA can provide useful information about the thermal stability of PLA, it generally offers lower accuracy for melting point determination compared to DSC.

• Melting Point Apparatus: Traditional melting point apparatuses, such as the Thiele tube or Fisher-Johns apparatus, involve heating a small sample of PLA in a capillary tube while observing its physical state. The melting point is recorded as the temperature at which the solid-to-liquid transition occurs. Although these methods are simpler and more cost-effective than DSC or TGA, they may be less accurate and can be influenced by factors such as sample size and contamination.

Factors Influencing Melting Point Measurements

The methods mentioned above are effective at calculating PLA’s melting point, however they do have a margin of error. There are several factors that can influence the measured melting point, potentially leading to incorrect or inconsistent results. Understanding these factors is crucial for obtaining reliable measurements and ensuring optimal material performance.

• Sample Preparation: The way a PLA sample is prepared can significantly impact the measured melting point. Proper sample preparation, including consistent sample size, shape, and mass, is essential for obtaining accurate results. Additionally, ensuring the sample is free from contaminants, such as dust or moisture, can prevent errors in melting point measurements.

• Presence of Additives: Additives, such as pigments, plasticizers, or stabilizers, can alter PLA's melting point. These additives can either increase or decrease the melting point, depending on their specific properties and concentrations. 

• Heating Rate: The rate at which a PLA sample is heated can affect the measured melting point. Faster heating rates can lead to higher measured melting points, as the sample may not have sufficient time to reach thermal equilibrium during the melting process. To obtain accurate results, it is crucial to use a consistent heating rate that allows for proper thermal equilibration.

• Testing Method: The choice of testing method can also impact the accuracy of PLA melting point measurements. Different techniques, such as DSC, TGA, or traditional melting point apparatuses, may yield different results based on their inherent accuracy and sensitivity. Selecting an appropriate testing method and following standardized procedures can help minimize variations in measured melting points.

By considering these factors and their potential influence on PLA melting point measurements, users can obtain more reliable results and better understand the material's properties, ultimately leading to improved processing and performance in various applications. Generally, though, this testing is done by the PLA manufacturer, who will indicate the melting point in their material data sheet.

PLA's melting point can vary depending on the grade of plastic and additives present in the material.

PLA Melting Point in 3D Printing

When it comes to 3D printing, a material’s melting point—as well as other material properties—determines the temperature settings users should apply both for the print head and heated bed, as well as the cooling mechanisms needed to prevent warping and ensure optimal print quality. 

Temperature Settings 

PLA filament starts to soften at about 60°C (it’s glass transition temperature) and has a melting point between 170°C and 180°C, depending on the specific material formulation. Most PLA filament brands recommend 3D printing at a temperature slightly higher than this, between 180 and 220°C. We recommend starting with the manufacturer's recommended temperature settings and fine-tune as necessary based on print quality.

Bed temperature is another setting to consider. Generally, PLA does not require a heated bed (the material demonstrates good first layer and interlayer adhesion at room temperature), however it can benefit from a bed temperature between 40°C and 60°C. A heated bed is especially useful when printing larger parts (to stabilize the cooling rate) or when printing in a colder environment. 

Ultimately, proper temperature settings are crucial for ensuring smooth extrusion, layer adhesion, and overall print quality. And because different brands of PLA filament recommend different print temperature settings, it’s a good idea to check the material’s data sheet before printing.

Cooling Settings

Cooling also influences the success of a 3D print: if a part cools too quickly it can be prone to more shrinkage, and if it cools too slowly it can result in deformations, like sagging. Active cooling fans, which help dissipate heat and maintain consistent temperatures across the printed layers, can be beneficial when 3D printing with PLA. 

It is common when using a cooling fan in the 3D printing process for it to initiate after the first couple of layers have been deposited. This is to promote strong adhesion between the first layers and the print surface. Once the first layers have a strong bond with the bed, the cooling fan can be brought up to 100% for the duration of the print. Consistent cooling ensures that each layer of PLA has hardened sufficiently before more layers are applied. 

Recommended reading: PLA bed temperature & print temperature settings

Importance of Using the Right PLA Print Settings

As with any thermoplastic, PLA’s material properties, such as melting point, should be taken into consideration when preparing a print job. In other words, choosing the right combination of print settings has a big influence on your print results, including the following:

1. Layer Adhesion: Layer adhesion refers to the bonding between every extruded layer of melted plastic. As the thermoplastic solidifies upon cooling, the bonds between layers should be strong. Proper layer adhesion is crucial for producing strong, durable prints with minimal risk of delamination or other structural defects, and temperature settings—including print and bed temperatures, as well as cooling—play a big role. Typically, if the print temperature is too low, it can lead to poor layer adhesion.

2. Print Quality: With the right temperature settings, PLA will flow smoothly through the extruder and form consistent, even layers as it is deposited. Printing at temperatures below PLA’s melting point can result in incomplete melting, leading to filament jams and other issues like bad adhesion. Conversely, printing at temperatures too far above the melting point can cause excessive material flow, leading to over-extrusion, oozing, and poor print quality. 

3. Material Compatibility: Understanding PLA's melting temperature is also essential when using it in combination with other materials, such as in multi-material prints or support structures. It is important to ensure that the melting points of both materials are compatible to achieve successful printing and prevent issues such as warping or poor layer adhesion.

By understanding the melting point of PLA in 3D printing applications, users can optimize print settings, improve print quality, and achieve better results with this versatile and biodegradable material.

Troubleshooting PLA 3D Printing Issues

When encountering issues when 3D printing PLA, it is important to identify the root cause and implement appropriate solutions. This section will explore troubleshooting techniques to address common temperature-related problems that can impact print quality and success.

Issues like oozing and under-extrusion can usually be fixed by decreasing or increasing the print temperature.

Common PLA Melting Point Problems in 3D Printing

• Oozing: If you notice any oozing or blobs in your printed parts, it’s time to take a look at your print temperature settings. This 3D printing issue is typically caused by too high a print temperature, so if you spot this issue, try lowering the hot end temperature by a few degrees at a time until the oozing stops.

• Stringing: Stringing can also occur if the PLA filament's melting point is too high, causing the material to flow more freely than intended. Lowering the extruder temperature can help prevent this issue and ensure cleaner prints.

• Under-extrusion: Under-extrusion, which can lead to poor adhesion and structural problems, can be a symptom of printing at too low a temperature. If you notice thin or missing layers, try increasing the print temperature gradually.

• Poor first layer adhesion: If you notice your PLA print is peeling up from the print bed, it could be a sign that the first layers are cooling too quickly. If this happens, we recommend using a heated print bed. PLA prints best with a heated bed around 50°C.

• Clogged nozzle: A clogged nozzle can occur if the PLA filament's melting point is too low, preventing proper extrusion. Increasing the extruder temperature can help resolve this issue and improve print quality. At the same time, if the printing temperature is too high, it can cause the material to stick inside the nozzle and burn, which can also lead to clogs.

Addressing Filament Quality

While all PLA filaments share many properties, filaments do vary in terms of quality and printability. It can therefore be useful to assess the quality of your filament to understand whether it’s the source of any problems. Let’s take a look.

High-quality PLA filaments generally have a more consistent melting point, which can improve print quality and reduce the likelihood of extrusion issues. Poor quality filaments, on the other hand, are characterized by inconsistent filament diameter and can lead to uneven melting and extrusion. To determine a filament’s quality, you can simply measure the diameter of the filament at several points using calipers. 

PLA filament is also very hygroscopic, meaning that it absorbs moisture from the environment. If you print using “wet” filament, the moisture trapped inside the thermoplastic will evaporate when the material is heated, causing air bubbles within the material. Ultimately, this can lead to problems like stringing and blobbling. It’s therefore advisable to keep PLA dry by storing it in airtight containers with a desiccant or by drying it out before using it.

We should also point out that many PLA filaments contain additives such as colorants or performance-enhancing materials, which can impact the material’s melting point. Ensure that the filament's melting point is compatible with your printer's temperature settings.

Recommended reading: How to Dry Filament

Addressing Cooling Issues

Inadequate cooling can lead to problems during the printing process, such as deformations and sagging. Assess the cooling system and settings to identify and resolve any problems:

• Cooling Fan Functionality: Check that the cooling fans are operating properly and providing sufficient airflow to maintain consistent layer temperatures.

• Layer Cooling Time: Adjust the layer cooling time settings to ensure adequate cooling between layers, which can help prevent warping and improve print quality.

Maintaining Printer Hardware

Regular printer maintenance is also an important part of troubleshooting and ensuring optimal 3D printing performance. For the best results printing PLA, follow these maintenance tips:

• Nozzle Cleaning: Regularly clean the extruder nozzle to prevent clogs and ensure consistent filament flow. Use a nozzle cleaning kit, cleaning filament, or appropriate tools to remove any filament debris.

• Thermistor Calibration: Periodically calibrate the thermistor on your 3D printer to ensure accurate temperature readings. This can help maintain proper extruder and heated bed temperatures, leading to improved print quality and reduced PLA melting point issues.

By following these solutions and best practices, you can effectively address 3D printing problems that may occur when printing PLA, resulting in higher-quality prints and a more successful 3D printing experience.

Other 3D Printing Material Alternatives

While PLA is a popular choice for 3D printing due to its low melting point and good printability, there are many FDM 3D printing materials worth exploring that offer different properties and benefits. This section will discuss the melting points of alternative materials and their advantages and disadvantages compared to PLA.

ABS (Acrylonitrile Butadiene Styrene)

ABS is a thermoplastic that has a higher printing temperature than PLA, typically ranging between 220 and 250°C. Interestingly, ABS does not have a melting point due to its amorphous nature.[3] This material is known for its durability, impact resistance, and heat resistance, making it suitable for applications requiring mechanical stability. Compared to PLA, ABS is more prone to warping and requires a heated bed and enclosed print chamber to maintain consistent printing conditions. Additionally, ABS emits fumes during the printing process, necessitating proper ventilation.

Recommended reading: ABS print temperature considerations: Nozzle, bed, enclosure

PETG (Polyethylene Terephthalate Glycol)

PETG has a relatively high melting point around 260°C and prints best at a temperature range between 220°C and 260°C. This material is known for its good printability, durability, and resistance to warping, making it suitable for a variety of applications, including prototyping and functional parts. PETG has better adhesion (and less warping) compared to ABS and does not require an enclosed print chamber. However, it may be more challenging to print with than PLA due to its increased stringing and oozing tendencies.

Recommended reading: How PETG melting point influences 3D printing

Nylon (Polyamide)

Nylon is a high-performance material with a print temperature ranging from 220°C to 265°C. It offers excellent strength, durability, and flexibility, making it suitable for heavy-duty applications and parts requiring good fatigue resistance. Nylon is also highly hygroscopic, meaning it readily absorbs moisture from the air, which can affect print quality. It requires proper storage and drying before use. Moreover, nylon tends to be more challenging to print with than PLA due to its increased tendency to warp and requires a heated bed (between 70-90°C) and, in some cases, an enclosed print chamber.

ASA (Acrylonitrile Styrene Acrylate)

ASA is a thermoplastic similar to ABS but with a higher resistance to UV radiation and weathering. Its ideal printing temperature is in the range of 220°C to 250°C. ASA is suitable for outdoor applications and parts exposed to the elements, as it maintains its mechanical properties and color under prolonged UV exposure. Like ABS, ASA requires a heated bed and an enclosed print chamber to minimize warping, and proper ventilation is necessary due to emitted fumes during printing.

In conclusion, while PLA is a popular choice for 3D printing due to its ease of use and low melting point, alternative materials such as ABS, PETG, nylon, and ASA offer different properties and benefits, depending on the specific application requirements. By understanding the characteristics of these materials, 3D printing users can make informed decisions about the best material for their projects.

Key Takeaways

Understanding the importance of PLA melting point in 3D printing is essential for achieving optimal print quality and avoiding potential issues. By optimizing print temperature, troubleshooting common problems, and implementing best practices, users can effectively manage the melting point and enhance the performance of their prints. Furthermore, being aware of alternative materials and their respective melting points enables informed decisions when selecting materials for specific applications.

Frequently Asked Questions

1. What is the typical melting point range for PLA in 3D printing?

The melting point range for PLA typically lies between 170°C and 180°C. However, this range may vary depending on the specific formulation of the PLA filament, additives, and colorants used.

2. How can I determine the optimal print temperature for my PLA filament?

To determine the optimal print temperature for your PLA filament, start by referring to the manufacturer's recommended temperature range. Perform a temperature tower test by printing a test model that varies the nozzle temperature in increments. Analyze the results to determine which temperature provides the best print quality and strength.

3. Why is my PLA filament not melting or extruding properly?

If your PLA filament is not melting or extruding properly, it could be due to an incorrect temperature setting, a clogged nozzle, or a problem with the filament itself. Check the temperature setting, ensure the nozzle is clean, and verify the quality of the filament. If necessary, try a different spool of filament to determine if the issue is material-related.

4. Can PLA be mixed with other materials to change its melting point?

Yes, PLA can be mixed with other materials, such as additives or reinforcing fibers, to modify its properties, including its melting point. However, mixing materials may require adjustments to the print settings and may result in different mechanical properties and print characteristics. 

5. What are some common signs that my PLA print temperature is not optimized?

Some common signs that your PLA print temperature is not optimized include poor layer adhesion, stringing, oozing, excessive warping, or weak and brittle prints. Adjusting the temperature setting and implementing best practices can help resolve these issues and improve print quality.

Resources

[1] The Polymers [Internet]. Britannica. Accessible from: https://www.britannica.com/science/plastic/The-polymers 

[2] Slough, Gray. What is Differential Scanning Calorimetry? [Internet]. TA Instruments. February 7, 2022. Accessible from:   https://www.tainstruments.com/what-is-differential-scanning-calorimetry/ 

[3] ABS Material Datasheet [Internet]. LORRIC. 2023. Accessible from:

https://www.lorric.com/en/WhyLORRIC/Material/material-chemical-resistance-chart-ABS