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For most 3D printing needs, the standard PLA and ABS filaments are reliable enough in terms of product quality and processability. However, there can be very specific requirements that require an alternative 3D printing filament material. One such alternative is TPU or thermoplastic polyurethane. In this article we will discuss the unique properties of TPU filaments, their uses, how they work, and the best brands currently available in the market.
What is TPU?
In order to better understand ThermoPlastic Polyurethane (TPU) and its usability, it can be useful to look at its functional ancestor – ThermoPlastic Elastomer (TPE). Until a few years ago, TPE was the material of choice when printing flexible materials.
TPE is essentially a plastic with rubber-like properties. It can be stretched to twice its original length and return to its original shape without permanent deformation. However, the softness of the TPE filament made it difficult to work with. With a bank hardness of only 85A, TPE filaments tended to be poorly handled by extruders that were not designed for flexible filaments.
TPU is the newer and stronger variant of TPE. By combining low polarity segments (or soft segments) and high polarity segments (or hard segments) into a single polymer chain, TPU offers a better combination of elasticity, rigidity and flexibility. The resulting product has a slightly higher Shore hardness of 94A, which makes it easier to use the 3D printing extruder mechanism.
What are the benefits of using TPU?
TPU is a product that offers a number of unique properties. It has a rubbery elasticity that sets it apart from the more common ABS and PLA. It’s also abrasion resistant and has proven to work well even at low temperatures. TPU has generally been used to print products that have to bend or bend during use, e.g. B. sporting goods, medical equipment, shoes, inflatables, external cases for mobile devices and instrument panels for motor vehicles. Because of its resistance to oils, greases and a wide variety of solvents, it has also been used for industrial applications.
In terms of processability, TPU is much easier to handle than TPE. The extremely flexible nature of TPE makes it quite problematic to work with, especially when a Bowden extruder is used. The length of the tube between the extruder and the hot end introduces some complication when using a flexible filament because the filament can contract within the tube when pushed by the extruder. With a more solid structure, TPU solves most problems when working with TPE filaments.
The layer-to-layer adhesion of TPU is usually excellent due to its very soft nature. This means that prints made from TPU should be very durable.
How do you work with TPU?
We recommend using direct extruders when working with flexible filaments. As mentioned earlier, the length of tubing the filament has to traverse in a Bowden extruder makes the process a bit difficult. It is still possible to use a Bowden extruder, but additional adjustments to the printer settings may be required to get good results. Newer 3D printers that use Bowden extruders have been designed to alleviate the problems with flexible filaments. If you are unsure of what your printer will do, the best thing to do is to ask the manufacturer if your particular model is approved for use with flexible filament.
An extrusion temperature of 200 to 220 ° C is recommended for TPE filaments. We also recommend the use of a heated bed platform with a temperature of 80 to 100 ° C. TPE has very good adhesive properties, so surfaces such as glass or aluminum should not pose a problem. For best results, we still recommend using Kapton’s tape or Blue Painter’s tape.
When working with flexible filaments, it is recommended that you print at very low print speeds. Flexible filaments tend to bend and contract under heavy use, so rapid pressure will likely clog your extruder. A setting of 15 mm / s is recommended, but you can print up to 30 mm / s with satisfactory results. This may depend on the specific model you are using. Therefore, you may have to start at a low setting and move up to see what works.
Flexible filaments are not particularly prone to warping when printed. Hence, you can use a medium or high setting fan. This way, you can keep good detail on your prints without sagging or melting in a messy way. We also recommend not using a fan in the first two shifts in order to ensure very good bed adhesion.
Pullbacks are sometimes required when your design requires the extruder to travel long gaps without printing. However, withdrawals can be especially problematic when using flexible filaments as they can be sensitive to rapid movement. We recommend turning retraction off entirely, especially if this is your first time using flexible filaments. If this cannot be avoided, you can set a very low retraction speed or minimize the need for retraction in your design.
What are the limitations of TPU?
The main disadvantage of using flexible filaments like TPU is the added challenge of handling them during printing. As mentioned earlier, not all 3D printers are designed to use flexible filaments. Printers that use Bowden extruders are particularly problematic. However, newer models should already have taken measures to be more compatible with flexible filaments. The more solid property of TPU should also enable more diverse applications.
TPU can also have poor bridging properties, resulting in multi-blob printing and stringing. You have to determine the “sweet spot” of the combination of print temperature, print speed and retraction speed in order to achieve good print quality with the flexible TPU.
Another disadvantage to making prints with TPU is that they cannot be finished to give a polished and smooth look. Unlike PLA or ABS, TPU does not dissolve in simple chemicals like acetone. To a large extent, TPU printing is about “what you see is what you get”.
What are the best TPU brands available?
Flexible filaments like TPU can serve a niche market because they meet very specific requirements. However, there are very few similar products. Manufacturers have long recognized the demand for flexible filaments and have responded with a variety of products.
Ninjatek’s Ninjaflex TPU line is probably the most famous line of TPU filaments today. They are available in sizes 1.75mm and 3.00mm and are sold in 0.5kg spools. They have a wide variety of fancy colors (Flamingo or Radiant Orchid, anyone?) So that you can let your creativity run wild.
Ninjatek also has another line of TPU filaments. The Cheetah product line is designed to improve the user experience when printing with flexible filaments by allowing them to print at higher speeds of up to 60mm / s. Ninjatek claims that its Cheetah products can be printed on any 3D printer model and at ABS or PLA speeds. If you are not sure whether your printer can handle flexible filament, the Cheetah line of products is the safest choice.
Polymaker’s Polyflex line is another well-known line of TPU filament products. They are sold in sizes 1.75mm and 3.00mm and in 0.75kg spools. There is a good range of colors too, although quite limited compared to others. The feedback on this product has been great all round so you can’t go wrong.
PRILINE has its own line of TPU filaments sold on 1kg spools that are 1.75mm in size. With a choice of 7 colors, you can play those creative muscles as much as you want. PRILINE recommends that you use the TPU filaments with a direct drive extruder and print at lower speeds than normal.
If you are not sure whether you can print comfortably with flexible filaments, you can try out SAINSMART’s small 250g spools for your first time. Their TPU filaments are 1.75mm in size and are available in a small range of colors. If you are satisfied with your product, you can also buy your TPU filaments in 0.8 kg spools.
|material||Thermoplastic Polyurethane (TPU)|
|Applications||– sports goods
– Medical equipment
– Cell phone cases
– automotive instrument panels
|characteristics||– Rubber-like elasticity
– Abrasion resistance
– Resistance to oils, greases and solvents
– Easier to use than TPE
– Excellent layer-to-layer adhesion
|Recommended printing temperature||200 to 220 ° C.|
|Recommended bed temperature||80 to 100 ° C.|
|Print speed||Very low; 15 mm / s to 30 mm / s|
|adhesion||Kapton’s tape or blue painter’s tape|
|cooling||No fan for the first 2 shifts; Fan at medium to high setting for all subsequent shifts|
|retreat||It is recommended that you disable retraction entirely. If this cannot be helped, the retraction should be set to the minimum speed, or the design should be maintained with the minimum retraction in mind|
TPU filament is quite difficult to work with, but they are the best filament products if you want to print flexible and high impact products. Flexible filaments haven’t quite caught up with common filaments like PLA or ABS or even alternatives like PETG just because they can be difficult to work with.
Fortunately, new 3D printers are being developed to work better with flexible filaments. TPU in itself represents an improvement in making flexible filaments more user-friendly. It’s a whole different dimension of plastic filament 3D printing, and we hope we’ve helped you become more open to its exciting possibilities.
Warning; 3D printers should never be left unattended. They can pose a fire hazard.