Soft PLA and TPU materials have a lot in common. However, there are also a number of differences between them that you should know. Read our soft PLA vs TPU guide to know what to expect of the two materials.
What is Flexible Filament?
3D printing makes it possible to produce items with a wide range of uses. For niche items that require particular properties such as resistance to abrasion, bending, and so on, you will need to use a flexible filament.
Most flexible 3D printing filaments are made from thermoplastic elastomers (a combination of hard plastics and rubber). How flexible a material is depends on the ratio of the hard plastic and rubber,
Therefore, depending on the flexibility of a material, you can print an object that can bend and snap back to its original form like a rubber band. You can also print objects that are as rigid as car tires.
There are different types of filaments on the market. The most common ones are:
- TPE (thermoplastic elastomer). This is a generic term that refers to any flexible filament. The term is used to refer to both soft and rigid-flexible filaments.
- TPU (thermoplastic polyutherane). This is a more rigid type of TPE. The filament is easier to print than most TPEs.
- Soft PLA. This is a flexible type of biopolymer PLA (polylactic acid).
- PCTPE (plasticized copolyimide TPE). This is a type of flexible material that is infused with nylon, which improves its durability. However, the infusion of nylon also sacrifices some flexibility properties of TPE.
- TPC (thermoplastic co-polyester). This filament is partially made from bio-oils. The material should be printed at a very slow speed since it can easily buckle in the extruder.
Tips for Printing Flexible Filaments
Flexible filament are resistant to vibration and impact. Therefore, they are durable and have a long shelf life. However, they are also more difficult to print than rigid filaments.
To improve your chances of success when printing a flexible filament, you need a 3D printer with a direct drive extruder. With this extruder, the distance between the drive gear and the melt zone within the printer is short. As a result, the flexible filament can easily travel through the printer without getting stuck.
What is Soft PLA?
PLA is an organic 3D printing material made from things such as sugarcane, tapioca roots and cornstarch. The pellets of these materials are melted down into a liquid that is dried, shaped and hardened into a thin filament.
Soft PLA is essentially PLA that is treated with additional chemicals to reduce its brittle property as much as possible. When the PLA is infused with the chemicals, it gets the characteristics of rubber. Therefore, soft PLA is bendable while regular PLA is brittle.
Soft PLA is used for items such as tires, which need to keep their shape to work, but are usually exposed to pressures that would crack or break regular PLA.
Let’ see the pros and cons of soft PLA and how the material compares to TPU.
Pros
Durable and Flexible
Soft PLA is flexible, unlike regular PLA that is brittle. You can use soft PLA to make items such as phone covers, tires, and others that need to be strong but flexible.
Vibration Resistant
Soft PLA is flexible, strong and durable. Therefore, it is excellent for making vibration dampening components, such as machine parts that absorb a lot of movement from those around them.
Low Carbon Footprint
The material is infused with more chemicals than regular PLA, which is why it is soft. However, its carbon footprint is way lower than that of other flexible filaments. Moreover, soft PLA remains degradable most of the time.
Ergonomics
Soft PLA has a unique blend of firmness, which gives it excellent ergonomic properties. The material is ideal for making things such as shoe sole inserts and pen grips.
Cons
Soft PLA also has some cons, which mostly are as a result of the improved flexibility. The cons include:
Difficult to Print
During the 3D printing process, soft PLA can act out since its flexibility takes away the tension that filaments require when passing through the extruder. The flexible filament can bubble, clog and bunch together in the nozzle. On the same note, it can be difficult to remove from the print bed since it is extremely sticky.
The good news is that most of these problems can be avoided in simple ways. For example, to prevent bubbling or clogging, reduce the printing speed of your machine.
Need for Special Hardware
There are also various tools and add-ons that can help with printing soft PLA and other flexible materials. For example, using a direct drive extruder is recommended as it reduces the distance that the filament has to travel across the bed, which helps in preventing bending on the way out.
For the printing bed, you can use various printer bed adhesion liquids to make the print bed hold well on the soft PLA during the printing process.
Poor Material Support
Since soft PLA is flexible, it does not offer much support. If you are printing an object with a lot of overhangs or gaps, you will need to use a stiffer filament like regular PLA. For soft PLA, the best models to print are those with unbroken planes.
Soft PLA vs TPU
While soft PLA and TPU have a lot in common, there are also a number of differences. Here is an overview of how the two flexible filaments compare:
Stiffness
TPU is easier to work with than soft PLA mainly because of its stiffness. According to the Shore scale or rigidity, TPU measures 94A to 95A while soft PLA measures 92A. This little difference makes TPU easier to work with.
Food Safety
Soft PLA is made from biodegradable items and is food-safe. Therefore, it can be used to print utensils and food containers. The material is also good for printing items that will touch or can be put in the mouth, e.g., children’s toys.
However, just because PLA is food-safe does not mean easting it is safe.
On the other hand, PUT is infused with many chemicals and is, therefore, not food-safe.
Flexibility
Soft PLA is more flexible than TPU. If you need to print anything to wear, the best material to use would be soft PLA. This filament has softer properties, which makes it easily malleable, e.g., a belt around your waist that doesn’t break when you bend.
Resistant to Abrasion
TPU is more rigid than soft PLA. Therefore, it is more resistant to abrasion. This is why the material is recommended for items such as machine parts.
The above is an overview of how soft PLA compares to TPU.
