Standard PLA is a material that defines the starting point for comparing all other variants. Its properties, printing behavior, and price form the basic benchmark from which the evaluation of all specialized filaments is derived. Understanding standard PLA is therefore crucial for anyone who wants to navigate the wider range of materials.
What is standard PLA and what is it made from?
Polylactide or polylactic acid (PLA) is an aliphatic polyester that, unlike most common plastics (such as ABS), does not originate from petroleum. Its basic building blocks are obtained from renewable, starch-rich sources such as corn, sugar cane, or cassava.
The manufacturing process begins with the fermentation of starch, during which microorganisms convert sugars into lactic acid. This acid is then chemically processed and polymerized, creating long chains of polylactide molecules. The resulting polymer is then processed into granule form, from which filament of a precise diameter (most commonly 1.75 mm) wound on a spool is produced by extrusion. This origin from plant sources is the basis for PLA’s marketing designation as a “bioplastic,” a term whose ecological impacts we will discuss in more detail later.
Advantages and Disadvantages
Every material represents a set of compromises, and standard PLA is no exception. Its popularity stems from properties that significantly simplify the 3D printing process.
Advantages:
- Easy printing: PLA has a relatively low melting and printing temperature, which reduces demands on the 3D printer. It does not require a heated print chamber.
- Minimal warping: Compared to materials like ABS, PLA has a significantly lower coefficient of thermal expansion, meaning it shrinks less when cooling. This minimizes the risk of corners peeling off the print bed.
- Low odor: It does not release a strong and unpleasant chemical odor during printing. Many users describe its scent as sweet, reminiscent of cotton candy or waffles. However, it is still recommended to print in a well-ventilated area.
- Good dimensional accuracy: Thanks to low shrinkage, prints retain their dimensions and sharp details well.
- Wide availability and low price: As the most popular filament, it is available from a huge number of manufacturers in countless colors and at a very favorable price.
Disadvantages:
- Low temperature resistance: This is PLA’s biggest weakness. The material begins to soften and deform at temperatures around 60 °C (glass transition temperature). This makes it unsuitable for use in a hot car, in direct sunlight, or for parts that come into contact with hot liquids.
- Brittleness: Standard PLA has low impact strength. It is stiff and strong in tension, but tends to crack, not bend, on impact or bending. It is therefore not ideal for mechanically stressed parts.
- Susceptibility to moisture (hygroscopicity): PLA absorbs atmospheric moisture. Damp filament during printing manifests as cracking, bubbles, poor layer adhesion, and increased stringing. It must therefore be stored dry.
How much does it cost?
Standard PLA is the most affordable filament on the market. The price for a 1 kg spool in the Czech Republic typically ranges from 400 CZK to 700 CZK. The price varies depending on the manufacturer, quality, diameter precision, and color. Economic packages from lesser-known brands may be at the lower end of the spectrum, while premium filaments from renowned manufacturers like Prusament or Fillamentum approach the upper end of this range.
Best temperatures and settings for printing
Although PLA is considered an easy-to-print material, proper settings are crucial for optimal results.
- Nozzle temperature: Most manufacturers recommend a range of 180–230 °C. The optimal temperature varies depending on the specific filament and printer, but commonly ranges between 190 °C and 210 °C. A lower temperature can lead to better overhang and bridging, while a higher temperature improves layer adhesion.
- Bed temperature: A heated bed is not strictly required for PLA, but it is strongly recommended to ensure reliable first layer adhesion. The ideal temperature ranges between 50 °C and 60 °C. A higher temperature can cause deformation of the bottom layers on tall objects (known as “elephant’s foot”).
- Cooling: Active cooling of the print is crucial for PLA. The fan should be set to 100% power after the first few layers are completed. Strong cooling allows for faster material solidification, leading to sharper details, better overhangs, and less stringing.
- Print speed: Standard PLA can handle a wide range of speeds, typically from 40 to 100 mm/s. For the highest visual quality, it is often recommended to stay within the range of 40–60 mm/s. Modern printers with technologies like Input Shaper can print PLA significantly faster, but this may require specifically adjusted profiles.
Reported problems and their solutions
Despite its simplicity, problems can occur when printing with PLA. Most of them, however, can be easily resolved.
- Stringing: Thin plastic threads stretching between different parts of the model.
- Cause: Material leaking from the nozzle during travel moves. Often exacerbated by moist filament.
- Solution: The first step is to ensure the filament is dry. Then, optimize retraction settings in the slicer – increase retraction distance and/or speed. Slightly lowering the nozzle temperature can also help.
- Warping: Lifting and peeling of model corners from the print bed.
- Cause: Uneven cooling and shrinkage of the material.
- Solution: Ensure the print bed is perfectly clean (degreased with isopropyl alcohol). Use a heated bed (50-60 °C). For large models or in cold environments, adding a “brim” in the slicer, which increases the contact area of the first layer, can help.
- Clogging (nozzle blockage): Interruption of material flow.
- Cause: Can be caused by impurities in the filament, overheating in the “cold end” (heat creep), or incorrect retraction settings.
- Solution: Check that the heatbreak cooling fan is fully functional. Try slightly lowering the print temperature or reducing the retraction distance. Make sure you are using quality filament.
Ecological aspect: The myth of compostability
One of PLA’s biggest marketing appeals is its designation as an “ecological” and “biodegradable” material. However, these claims are very misleading and require detailed explanation. The reality is much more complex and often impractical for the average consumer.
The fundamental problem lies in confusing the terms “biodegradable” and “home compostable.” PLA is indeed biodegradable, but only under very specific conditions found exclusively in industrial composting facilities. For PLA to effectively decompose, it requires a combination of three factors:
- High temperature: Continuously maintained temperature above 55–70 °C.
- High humidity: Constant presence of moisture, which triggers the hydrolysis process, i.e., the breakdown of polymer chains.
- Presence of specific microorganisms: Bacteria that are capable of digesting shorter lactic acid chains.
These conditions are absolutely unattainable in a home compost, in regular soil, or in the ocean. A PLA print thrown into a garden compost will not decompose even after many years. In a landfill environment, where oxygen and proper temperature are lacking, its decomposition can take hundreds of years, potentially releasing methane, a greenhouse gas significantly more potent than carbon dioxide.
Another problem is the lack of infrastructure. Most cities and municipalities do not have industrial composting facilities that would accept PLA waste. Moreover, if PLA is thrown into regular sorted plastic waste, it contaminates the recycling stream because it has a different chemical composition and melting temperature than common plastics like PET or HDPE. For the vast majority of users, the only realistic option for PLA disposal is to throw it into mixed waste, which largely negates its ecological advantage of originating from renewable resources.
Surface finishing
A raw FDM print has a characteristic layer texture. To achieve a smooth and professional appearance, surface finishing (post-processing) is often necessary.
- Sanding: PLA can be sanded, but care must be taken. The heat generated by friction during sanding can easily reach the material’s glass transition temperature (approx. 60 °C), causing it to soften and “drag.” The best results are achieved with wet sanding, where sandpaper is soaked in water. The water cools the surface and simultaneously washes away dust, leading to a smoother result. Proceed from coarser grits (e.g., 200) to finer ones (400, 800, and more).
- Filling and priming: For complete smoothing of layers, especially for models intended for painting, fillers are used. Two-component polyester body fillers or acrylic fillers are suitable. An alternative is to use a spray filler primer, which fills smaller irregularities. After drying, the layer of filler or primer is sanded again.
- Painting: PLA takes paint very well. Before painting, it is crucial to thoroughly clean and degrease the surface. For best paint adhesion, it is advisable to first apply a layer of primer. Afterward, acrylic spray paints or model paints applied with a brush or airbrush can be used. To protect the final coat, it is advisable to apply a layer of clear varnish (matte, semi-matte, or glossy).
- Chemical smoothing: Unlike ABS, for which easily available acetone exists, there is no safe and commonly available chemical for smoothing PLA. Chloroform or dichloromethane are mentioned in specialized discussions, but these are highly dangerous and regulated substances that are unavailable to the average user, and their use is strongly discouraged.
