Advanced Guide to printing PLA Filament

Author: Matt Tyson/Monday, 21 May 2018/Categories: User Guides, Material Guides, PLA

Advanced Guide to printing PLA Filament
Authors Note

Thankyou for taking the time to read our guide on 3D printing PLA. This article has been written to provide both printing and troubleshooting tips along with tips for post-printing processes like painting and support removal. We have highlighted important topics with a star (*) so please don't feel intimidated as sections in this guide may not be relevant to everyone, - Matt Tyson, 3D Printing Solutions

This user guide was last updated - 7th October 2019

With a variety of blends exhibiting different mechanical properties, wide colour range and excellent resistance to warping; PLA has become one of the most popular 3D Printing materials due to its low printing requirements and excellent dimensional stability.

Contents:

Introduction 
  What is PLA?
  Requirements *

Printer Setup
  Feeding path and spooling
  Loading & Unloading Filament *
  Bed Surface *
  Bed Leveling & Nozzle Height *
  Pre-heating
  Enclosure
  Filament Storage

Printer Settings
  Nozzle Temperature *
  Bed Temperature *
  Cooling *
  Rafts
  Supports

Post Printing
  Removing a print after completion
  Removing Layer Lines
  Painting
  Joining

Trouble Shooting
  Blocked Nozzle / Filament Jam
  Heat Creep
  Warping
  Poor Layer Adhesion
  Parts difficult to remove from platform

Filament Links
  Purchase or learn about PLA Filaments
 


Introduction


What is PLA?

PLA (Polylactic acid) is a semi-crystalline plastic and is one of the most popular and easiest materials to 3D print due to its accessible and minimal printing requirements. PLA is a biodegradable and recyclable plastic and PLA filaments are available in a variety of colours including opaque and translucent options.

There are of course many types of PLA which can provide various properties.

PLA (aka regular PLA) is a stiff material exhibiting a high stiffness / modulus however its low impact resistance limits its overall applications. One of the advantages of regular PLA is it is easy to 3D print with near-zero warping, making it a suitable choice for large demonstration pieces, architectural models and product design. PLA exhibits a low chemical resistance and low temperature resistance, softening at 60°C (Glass Transition and Vicat temperature).

PLA+ materials are modified PLA materials exhibiting improved mechanical performance when compared to regular PLA. The term PLA+ can mean various things, but generally PLA+ materials offer some improvement to the already high tensile strength of regular PLA. 

PolyMax™ PLA is a nano-reinforced PLA material exhibiting superior impact resistance and ductility when compared with ABS, PLA+ and regular PLA filaments.

With a toughness / impact resistance 20% stronger than ABS and near-zero warping, low odor and low residual stress during printing, PolyMax™ PLA is a suitable replacement for ABS for many applications. Support and raft removal is easier when compared to PLA+ and regular PLA materials.

There are also a wide selection of PLA filaments manufactured with composites and additives. These composites range from glow in the dark, chopped wood or metal and even carbon fibers.

Filaments manufactured with these composites are highly abrasive and will damage the nozzle. For most users we recommend avoiding PLA materials that use these abrasive composites and opting for alternative materials as the benefits don't always outweigh the hassles. For example printing with a wood-mimic PLA filament that contains no real wood improves user experience.

Requirements *

Most desktop 3D printers are suited to print PLA out of the box. We recommend only printing with a quality PLA filament.

Minimum Extruder Temperature - 190°C (±10°C)  is required (Correct temperature will vary on your printer)
Heated Bed - Not required with some machines but low to medium bed temperatures are certainly beneficial! 
Enclosure - PLA has great dimensional stability but an enclosure will protect print from drafts.
Part Cooling Fan - The ability to control the cooling fan is recommended.
Feeding / Spooling - No specific requirements.
Other Notes - N/A

Most 3D printing slicers (software) have a pre-configured PLA profile. The accuracy of this profile may vary depending on if you are using 1st or 3rd party filament, but we recommend choosing this profile to start with and making necessary adjustments covered in this article.


Printer Setup


Feeding path and spooling

PLA doesn't have any specific feeding path requirements.

As a general tip we recommend avoiding long and complicated feeding paths that can cause bends in the filament, this can introduce drag on the filament that may result in difficulties feeding and extruding.

If you typically have issues with moisture in your filament, you can read our tips and comments on filament storage to determine if a dry box will be beneficial.

Loading and Unloading Filament *

Changing between two PLA materials:
If the printer is currently loaded with a PLA material, unload that material at 200-210°C and extrude your PLA filament at the same temperature. Stop extruding the PLA filament after the previous colour is completely purged.

Changing from a higher temperature material:
If the printer is currently loaded with a higher temperature material (for example ABS), unload that material at its recommended printing temperature, and then load and extrude your PLA filament at that same higher temperature. It is important to load the PLA at this higher temperature so the previous material can be pushed out.  Stop extruding the PLA filament after the previous material has been completely purged.

Changing from a lower temperature material:
If the printer is currently loaded with a different lower temperature material, unload that material  at its recommended printing temperature, and then load and extrude your PLA filament at 200-210°C. Stop extruding the PLA filament after the previous material has been completely purged.

Bed Surface *

PLA is one of the easiest materials to print and adheres to most printing surfaces. With PLA we recommend first trying the surface your 3D printer was designed to use.

Platform Material Recommended Surfaces
Glass Bed

Most popular - Straight on glass bed with glue

Other options - Buildtak or FlashForge style sheet | PEI sheet | Blue painters tape

Aluminium Bed

Most popular - Buildtak or FlashForge style sheet 

Other options - PEI sheet | Blue Tape

Perforated Board

Most popular -Straight onto perforated board

Other options - Buildtak or FlashForge style sheet

Flex Plate (possibly magnetic)

Most popular - Buildtak or FlashForge style sheet

Other options - PEI sheet | Blue Tape

Bed Leveling & Nozzle Height *

It is important when printing PLA that your first layer adheres to the printing bed.

  • Your bed must be properly leveled.
  • Your nozzle height must be set correctly. (distance between the nozzle and bed)

The ideal gap between the nozzle and bed is typically a distance of 0.1mm, this is the thickness of two pieces of paper. When changing between bed surfaces it is important to adjust the nozzle height again to compensate for the added thickness of the bed surface.

Pre-Heating

When printing PLA, pre-heating the heated bed is not required.

Enclosure

An enclosure is not required when printing PLA however can be beneficial to protect your 3D print from drafts and external temperature changes.

If your 3D printer is enclosed and you have the option to open remove the top lid we recommend doing so. Keeping the lid open will help to prevent the PLA filament from softening too quickly, this is especially important in summer months.

Filament Storage

When not in use PLA should be stored away from sunlight and in a resealable bag with desiccant.

Like many other plastics, PLA is a mildly hygroscopic material that will over time absorb moisture from its surrounding environment. This process typically occurs over a period of months however in high humidity environments (ie. evaporative air conditioning) this process can occur more rapidly.

Printing with a dry box is generally not a critical requirement to print PLA (in most cases) however a dry box can be beneficial and ensure consistent printing quality and mechanical results throughout the spool.

Effects of Moisture:
When the filament passes through the hot end the moisture rapidly expands creating bubbles in between layers, poor layer adhesion, inconsistent extrusion due to material expansion and thus poor surface quality.

Preventing Moisture Absorption:
To eliminate all possibilities of moisture impacting your 3D prints, you must store and print your PLA materials in their optimum environment (below 20% humidity) to prevent moisture absorption.

Some users will simply dry their filament before use however excessive drying will degrade the filament. We recommend storing all filaments in a resealable bag with desiccant when not in use and we recommend using a filament dry box like the PolyBox™ when printing. The PolyBox™ is a spool holder / dry box that stores filament in their optimal environment while printing.

Removing Moisture:
If your filament has absorbed moisture it can be dried in a convection oven. Visit our 'starters guide to moisture, drying and filament storage' for recommended drying times.


Printer Settings


Nozzle Temperature *

PLA prints at a relatively low temperature, typically printing between 190°C - 220°C.

The optimal printing temperature of a PLA filament will vary depending on which printer you are using and more importantly will vary between filament brands. To find the optimal nozzle temperature we recommend starting with a temperature right in the middle of the manufacturer’s suggested settings. If the manufacturer recommends 190°C - 220°C, printing at 205°C is a good starting point. Based on the quality of the print we suggest adjusting ± 5°C at a time.

Troubleshooting Nozzle Temperature
If the nozzle temperature is too hot, you may experience wisps / stringing on the surface of the print, difficult to remove and fused support material , sagging and poor surface quality on overhangs and a noticeable smell during printing.

If the nozzle temperature isn't hot enough, you may experience compromised mechanical properties due to the poor layer adhesion, under-extrusion (uneven / rough surface quality) and if the filament is not melting fast enough; nozzle blockages.  

Bed Temperature *

PLA can be printed without a heated bed, however a heated bed up 60°C is recommended for the best results. Success without a heated bed will depend on your printing surface, printing environment and model size.

When printing with a heated bed, do NOT exceed temperatures beyond 70°C unless specified by the manufacturer as this can cause most PLA filaments to crystallize rapidly and actually cause warping.

Cooling *

When printing PLA it is best to print with the cooling fan ON. The cooling fan solidifies the plastic faster which will help improve printing quality of PLA. 

Adequate cooling is also important when printing complex models with unsupported overhangs. To improve overhang print quality you can orientate the model so overhangs are facing the cooling fan.

Rafts

A raft is generally not required when printing PLA materials however with some leveling systems manufacturers may recommend a raft to compensate and improve bed adhesion.

Supports

When printing PLA, supports can either be printed in PLA or with a second dedicated support material. Printing with a secondary material will require a printer capable of multi-material / dual extrusion printing.

PLA Supports - Most users own single extruder 3D printers so they print their model and supports in the same material. When printing both the supports and model in PLA, supports will be harder to remove than with an ABS plastic but should still peel away cleanly. 

Soluble Supports - PLA can be printed with a secondary support material that has been engineered to dissolve in a liquid or solvent. Soluble support materials enable users to print complex geometry with superior surface finish on undersides. PVA is the most popular soluble support for PLA as it can be dissolved in water.

When using soluble supports we recommend having no gap (z distance) between the model and supports.

Break-away Supports - PLA can be printed with a secondary material designed to break-away easily. Break-away supports reduce the risk of model damage that can occur when manually removing supports.

Support Troubleshooting - If supports are fusing to the model, try decreasing the printing temperature by -5°C adjustments or increase the distance between the model and supports.

If your supports are failing / collapsing during the print, try increasing support density and printing with a raft , this will improve adhesion for the supports.


Post 3D Printing


Removing a print after completion

Once your 3D print has completed, it can be removed from the build plate. The best method to remove your PLA 3D Prints will depend on your build platform with some of these methods specific to removing PLA prints. 

Rigid Build Platform
On rigid build platforms like glass or aluminium, a sharp paint scraper can be used to easily remove the model.

Some printers are designed so the platform can be removed from the bed while other printers the build platform may be fixed inside the printer. If the platform is fixed, we recommend supporting the platform with your second hand to prevent uneven pressure on the bed which could affect your bed leveling.

Flexible Build Platform
Some printers on the market print on flexible build plates. With these platforms users can flex the plate to remove prints.

Click here if you are having issues removing prints from the build platform.

Removing Layer Lines

PLA like other materials can be post-processed after printing to remove layer lines and achieve a smooth surface. In addition printing with finer resolutions and using a filler primer can drastically cut down on sanding / post-processing time.

PLA also be chemically smoothed however the chemicals involved for this process are incredibly dangerous and known carcinogens. The process of chemically smoothing PLA is not recommended by 3D Printing Solutions and should only be investigated by industrial customers prepared to follow all strict safety precautions. 

Painting

PLA plastics can be easily painted with acrylic and enamel based paints. Removing layer lines and model clean up are recommended before painting.

Joining

Parts printed in PLA can be joined with a variety of techniques

Glue
Gluing parts printed in PLA is simple, with your choice of CA, Super Glue, Gorilla Glue and Two Part Epoxies. Two part epoxy is in our experience the best glue for PLA. We also recommend sanding contact surfaces with a coarse sandpaper to increase the surface area for the glue, this will result in a stronger join.

Friction Welding

Friction welding is the process of welding two 3D Printed parts together using a short length of PLA filament and a rotary dremel tool. This technique is incredibly simple and an effective way to create strong joins between your printed parts.

1. Cut off a short piece of PLA filament and load the filament in the rotary dremel tool. 
2. Turn on the rotary dremel tool and feed the spinning filament where your two parts meet.
3. The friction from the rotating filament will cut a deep channel between the seam and melt; fusing the two parts together.
4. Continue this process with a new cut of PLA filament and experiment with different directions, pressures and speeds to find the optimal technique for your tool.

Both 1.75mm and 2.85mm filament can be used to friction weld however this will depend on the rotary dremel tools chuck. Using 2.85mm filament is ideal for this technique as the thicker diameter will allow you to cut longer rods of filament, speeding up the process. 1.75mm filament can also be used however shorter rods will need to be cut to avoid snapping the filament.

In our experience gluing two parts together and then friction welding the surfaces results in the strongest join, these welding marks can be later sanded down and any pits in the surface can be filled with plasti bond.


Trouble Shooting


Blocked Nozzle / Filament Jam

When 3D Printing it is possible to encounter filament jams or nozzle blockages, these blockages can be caused due to a variety of reasons.

Causes and Steps to Prevent Nozzle Blockage and filament jams.
In all of these cases if the filament cannot pass through the extruder, the extruder gear will continue to try push the filament and will eventually 'chew out' the filament. If you hear a clicking or clunking sound coming from the extruder, this is a good sign that the filament is jammed or will be if ignored. 

  • If your extruder temperature is too low during printing, the PLA filament will not flow and will have difficulty extruding. Printing with the correct nozzle temperature will solve this issue.
  • If the filament is softening in the hot end, the extruder will 'chew out' the filament, causing a nozzle jam. This issue is known as heat creep, click here to learn more about this issue.
  • If there is too much friction on the filament, the extruder may have difficulties feeding the plastic. Try feeding the filament with a spool holder in different positions (above, beside, behind the printer).
  • If the nozzle height is set too close to the bed, the filament will have difficulty feeding through the nozzle eventually causing a filament jam. When printing at finer layer heights (0.1 and 0.05mm) the correct nozzle height is even more important. To prevent this issue it is important to print with the bed leveled and the correct nozzle height.
  • If the part is warping or lifting off the bed, the part will be pushing against the nozzle limiting extrusion and material flow, in this case it is important to prevent the part from warping.
  • Filled PLA materials (CF, Metal-filled etc.) are commonly known to cause nozzle blockages. Printing with a different PLA material or cleaning and keeping some spare nozzles is recommended.
  • Nozzle Blockages can occur more commonly with finer nozzles. The majority of 3D Printers are equipped with 0.4mm nozzles, it is important when printing or experimenting with a smaller nozzle (0.2mm) to adjust printing speed and extrusion settings 
  • If the filament is of poor quality is oval shaped or manufactured with an inconsistent diameter, this can cause the filament to jam in the extruder. The industry standard for filament tolerance is ± 0.05 mm. If the filament is 1.75mm an acceptable diameter variance would be between 1.70 - 1.80mm. Premium and higher quality brands can offer ± 0.02 mm tolerance. If you have difficulties printing PLA with only specific brands of filament this could signify issue with their quality control or could also be related to heat creep.

Cleaning a PLA Nozzle Blockage
If the nozzle is blocked with PLA one of the most successful solutions is to feed a tougher / harder and higher temperature material (for example PC) through the extruder. In most cases, the properties of the tougher material and its higher printing temperature help to purge and remove the clogged PLA plastic. It is important when feeding the tougher material at its required printing temperature, for PC this is 250°C and to push the filament into the extruder during this process.

If you cannot remove the blockage of PLA plastic from the nozzle, we recommend swapping to a spare nozzle.

Heat Creep

What is heat creep?

Some users have difficulty printing PLA due to a problem known as heat creep. In essence this issue is caused when heat creeps up the extruder to the extruder gear and softens the filament. Rather than the gear gripping and pushing the filament through the hot end, it will chew the filament out.

Heat creep affects lower temperature materials like PLA due to their low softening temperature of 60°C and the issue is more prominent on printers designed to print high temperature materials, dual extruder printers where a section of filament sits idle for long times or cheap 3D printers with poorly designed extruders.

Solutions to preventing heat creep.

The first step is to make sure the extruder fan is ON and cooling the extruder as intended. If the printer is enclosed, printing with all front doors and top hatches open may help to prevent the filament from softening near the extruder gear.

This issue is also more common when printing parts models with retraction. The filament will feed past the extruder gear multiple times with each retraction, this makes it far easier for the extruder gear to ‘chew out’ the filament. Printing simple parts with little or no retraction are more likely to be successful as the filament will only be passing the gear once.

This issue can also sometimes be overcome with a different PLA material. All Polymaker PLA based materials (PolyLite™ PLA, PolyMax PLA, PolyWood™) are manufactured with an innovative Jam-Free™ technology which improves the heat stability of the PLA filament. As a result Polymakers PLA filaments exhibit a high softening temperature of more than 140 °C, so while printing, the filament will never soften in the “cold end” and can melt rapidly once entering the heating zone. It is important to note parts printed in Polymaker PLA filaments still exhibit the same heat resistance as other PLA materials

Warping

PLA materials are considered one of the easiest materials to print exhibiting near-zero warping and excellent dimensional stability. In some rare cases it is possible for PLA materials to warp or lift, lets look at why PLA shouldn't warp and what can cause PLA prints to warp or lift off the bed.

Simply put warping is caused by internal stress in the 3D printed part; this internal stress can be created in two ways for semi-crystalline materials.

1. As the filament is extruded through the small diameter of the nozzle, the polymer chain of the filament is stretched and will want to return back to its ‘normal’ state, much like a stretched elastic band will go back to its position when it is released and will curl / warp. At temperatures moderately close to the materials glass transition temperature (tg), the polymer chain will 'relax', releasing the internal stress and preventing warping. Due to the low (tg) temperature of PLA (60°C), PLA should print with minimal / near-zero internal stress at room temperature.

2. PLA like many other plastics (for example Nylon, PEEK) is a semi-crystalline plastic. Internal stress can be created specifically due to crystallization behaviour during printing, causing warping and cracking. When it comes to printing PLA at room temperature, internal stress caused by crystallization behaviour should be minimal due to how the material crystallizes. 

So if PLA materials generally print with low residual and internal stress, why can they warp?

Preventing warping.

  • Printing with a heated bed at 60°C can help to improve adhesion and heat up the surrounding environment, ultimately minimizing warping and improving printing consistency. 
  • Alternately it is important to note that printing with the bed temperature too high can also cause models to warp. If the heated bed is too hot, the PLA will crystallize when printing and will warp. For this reason we recommend never setting the heated bed above 60°C for PLA unless otherwise stated by the manufacturer. 
  • The most common reason for PLA parts to warp or lift during the print is due to insufficient bed adhesion or an incorrect nozzle height. If the first layer of extruded plastic is not sticking to the bed, a small amount of small residual stress will be enough to lift the part off the bed. It is important to ensure your nozzle height and bed is leveled correctly, you are using the correct printing surfaces for PLA.
  • Drafts, cool air from air conditioners and low environmental temperatures in winter can cause the material to behave differently and will print with internal stress. An enclosure with a closed front door can help to maintain the right printing environment for users having difficulty with parts warping.

Poor Layer Adhesion

Causes and steps to improve poor layer adhesion.

  • If the filament is under-extruding during printing there will be inconsistencies and gaps between the layer, compromising  mechanical strength and layer adhesion. It is important to ensure you are printing the PLA filament at the right nozzle temperature to ensure consistent flow and to minimize drag or tension which may prevent the filament from feeding.
  • Poor layer adhesion can also be caused when printing with a PLA spoiled with moisture. When the filament passes through the hot end, the moisture erupts creating bubbles in the extruded plastic, compromising  the parts mechanical properties. If a spool of filament has absorbed moisture, it can be dried however it is important to store the PLA correctly and prevent this issue from occurring.

Parts difficult to remove from platform

While excellent adhesion between the bed and part is important to achieve a successful print, sometimes it can be difficult to remove models if your adhesion is too good.

Causes and steps to improve print removal experience

  • Some print surfaces specifically manufactured for PLA materials are designed to maintain adhesion with the part when the bed is heated and self-release when the part is cool. Try removing the models when the heated bed is hot or cold to see what method best suits your printing surface.
  • Your heated bed may be operating too hot or your nozzle temperature may be too close to the bed. You can try making slight adjustments to the heated bed temperature or nozzle height if this improves your user experience. Of course this is a fine balance as adhesion between the print and platform is important to achieve successful prints.
  • While not required, in some cases with other materials, some users will use Glue stick on top of their print surface to act as a release agent for part removal.

 


Filament Links

PolyLite™ PLA Introduction
Buy PolyLite™ PLA

PolyMax™ PLA Introduction
Buy PolyMax™ PLA

Number of views (3596)/Comments (0)

Name:
Email:
Subject:
Message:
x

Need Help?

Dont know where to start? Or which filament will suit your application?

We have a broad range of support options including Telephone Support

  Contact Us