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[GUIDE] TPU – Features and settings for printing

In this guide we will try to eviscerate this new flexible filament the TPU, trying to snatch as many secrets as possible.

TPU is a thermoplastic polyurethane, also called thermoplastic elastomer. It’s made of a piece of polyurethane, one of the strongest plastic materials, and rubber, which gives it flexibility.

Here are some features:

Smell: it is odourless, or rather does not have a strong smell like the ABS.

Toxicity:TPU is not composed of toxic materials, so it is not toxic when printed. It is not yet clear, like all the other filaments, whether there is evidence of the toxicity of substances emitted during printing, such as micro dust.
Shrinkage rate: It actually has some shrinkage rate. Although not very high, it stands between 0.8% and 1.6%. Nothing that isn’t perfectly manageable by a slight increase in flow.

Hydrophobic: Does not absorb water, and therefore does not substantially deteriorate.

High impact resistance: It has a high percentage of rubber, so shocks are its bread. We can spend days bouncing it around without any damage.

High mechanical resistance: ideal to use for objects subjected to mechanical stress, it is a soft material, extremely resistant and flexible. It has an excellent coefficient of adhesion between layers. It is deformable when subjected to a force. This is the feature you choose for but may make it not suitable for certain applications.

High chemical resistance: extremely resistant to the action of chemical agents, acids, fats, oils, alkalis.

High flexibility: It’s its most interesting feature. It allows us to create gummy objects, with a softness measured in Shore: 94A-95A.

But what does this mean for practical applications? What are the ideal objects to print with TPU?

It is suitable for printing clothing and wearables such as belts, shoes, wallets, slippers, watch straps, bracelets, elastic bands, etc… or for wheels of radio-controlled or static models, mobile phone covers, games for animals, and any other object must have gummy appearance and consistency.
TPU - Caratteristiche e impostazioni di stampa
TPU softness test

How to print the TPU:

You have to approach this material with curiosity and willing to sacrifice a little time to perform tests. Obviously in this article I will try to give you an address but as often happens in 3D printing the parameters can change a lot from manufacturer to manufacturer, as well as from machine to machine.
One advice that is always valid, for all the tests that you will carry out on any type of filament, is to obtain scotch paper and write down directly on the coil the parameters used and results obtained. Some filaments can be at the extremes of the indicated parameters, so finding the optimum can be difficult, with losses of time and material.

It may seem easy to remember the settings but after time and with different materials it may not be. With a minimum of effort you will have a diary of the tests carried out directly on the material, not to repeat the same mistake again!

 

SETUP AND PREPARATION FOR PRINTING

TPU
Model F1 wheel printed in TPU

 

Print surface:

Let’s start by saying that you can successfully print TPU on any surface, on blue tape, glass, steel and aluminum. We can help the adhesion with glues of various types and strong lacquer. I normally mold on glass (with a veil of lacquer), tape paper or PEI without any particular problems.

Pre settings:

Like any other filament, the success of the print is determined by the success of the first layer. The very foundations of 3D printing.
To get a good first layer, you may need to slightly increase the nozzle distance when printing with flexible filaments. The TPU filament tends to compress slightly when crushed. We are in the situation of slight crushing during printing, because after being melted the filament must exit from a 0.4 mm hole starting from an original size of 1.75 mm. This friction should not be added further effort to be extruded and deposited on the plate, so it is good practice to leave a 50% more distance, depending on the layer thickness set in the slicer.

Just like the PETG, you have to set a larger offset (increases the nozzle length flat), even just 0.1 mm.
For this setting you just need to enter the command M851 Z 0.1 in the G-code boot.

You don’t want to save the setting for random prints. At least you will leave the printer set to print PLA, ABS or whatever the “usual” material is.

Flow:

As we said presenting the characteristics of the material, TPU has a small shrinkage rate, normally equal to 1%. In most cases not even noticeable. It may happen, however, that ordering to extrude 10 cm of PLA you will have a certain amount of extruded filament, repeating it with the flexible filament you will have less. It may be useful to estimate the loss of filament through a proportion, and react accordingly.
The best way is to compensate by modifying the flow, and not by recalibrating the engine steps, if they are already properly set. The flow change done in this way is reversible and temporary!

Ventilation:

When slicing, you can decide how to set the fan layer to work. Extruding this material the fan is set according to the result you want to achieve.

Absence of ventilation is equivalent to well-balanced layers, the maximum possible ventilation is around 50% of the maximum power brings a greater definition of the details.

Obviously the fan should not be activated for the first layers. The Cura Settings Guide explains the method of letting the fan layer in gently, thus avoiding a number of problems.

Temperatura:

Now let’s move on to temperatures. The extrusion of TPU varies according to the indications of the manufacturer, from 230°C to 240°C (as a rule). It is certain that the higher temperature corresponds to a more compact object, on the contrary, the lower temperature the object is more defined even if there is a risk of underextrusion. The flexible filaments have their weak point in the poor smoothness in narrow points, combined with absorbing part of the thrust force.
As for the temperature of the dish, follow the recommendations. Normally it is recommended a temperature of about 50°C 70°C even if the new mixtures are printable even at 30°C plate.
Personally I gave myself the rule of printing the first layer at 70°C and turning off the plate for the next. I explain how to set this option in the Third Cura Guide.

Retraction:

Retraction is poison for flexible filaments. So it must always be kept off! Sometimes I tried, just in the scientific spirit to leave the retraction on. The press only holds up if we set a minimal, slow, and rare retraction.

Turning on the retraction can be useful in case we find ourselves with a lot of stringing, such as to ruin the print.
In this case we try to halve the retraction values, using the Celtic cross infill, which minimizes them.
In principle though: Do not use retraction!

Speed:

You must also decrease the printing speed. The elastic composition makes it possible to print without problems up to 35mm/sec and gives more and more problems by increasing this speed.

So I urge you not to exceed the speed of 40mm/sec for a safe and trouble-free printing.

 

TPU - Caratteristiche e impostazioni di stampa
TPU elastic tube joint.

Possible problems:

First of all, we must remember that flexible filaments contract when we apply a force. And they contract the more soft they are. This also affects the attack of the press. I explain…
Starting the press the first seconds of rotation of the motor pusher will serve to contract the filament, and give it the right force to start moving it. This results in a delay in depositing material on the plate. If you happen you will not be afraid! Prepare and double the lines of skirts, to increase the time before getting to the print of the model.

Or even a Brim from 4 to 8 mm, could also help you in adhesion to the plate.

Another common problem of TPU is a tendency to stringing, if only because of the fact that it cannot use the retraction. In this case there is little to do unfortunately. Lowering the temperature could be harmful and should be done by a few degrees at a time.

Conclusions:

The TPU is not a filament of the simplest, but once you find the right parameters will give many satisfactions. The elasticity typical of this material opens to new possibilities and makes many everyday objects printable and usable.
If you are not experts in 3D printing and you want to try your hand at printing this material I suggest you to focus on popular and well-known brands, which give a certain result. This is so as not to combine inexperience with random problems.

Among the most popular and reliable TPU in businesses we find:

TPU Sunlu: easy to print, as it retains its features. It is not the cheapest on the market but provides guaranteed results.

You find it >>> HERE <<<

TPU Novamker: It is one of the cheapest flexible materials on the market, but it is far from evil. Novamaker production is synonymous with quality!

You will find it >>> HERE <<<in 7 different colors!

I hope I have unravelled your doubts about the applications and ways of use of this elastic filament, if you have any questions write in the comments!

 


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