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[GUIDE] How to print flexible filaments – TPU, TPE and others

 

Today we will be talk about some guidelines for printing flexible filaments. TPU, TPE, Soft PLA, and in general all flexible materials are increasingly present in the laboratories of amateur makers.

This is due to the fact that in the last period (let’s talk about years) the manufacturers of 3D printers have made improvements to printers that have made them more suitable for printing flexible materials.

Once only who owned a direct extruder printer could take into account flexible filaments. But the above-mentioned improvements, first of all the removal of any form of empty space between extruder and hotend, in the Bowden configuration. So now you can print flexible filaments with any printer. Although with some limitation.

To understand what limitations we face may be useful to review materials, with temperatures, composition and uses.

How to print flexible filaments: Materials

Here are the flexible materials on the market, and we are going to analyze one by one.

TPE

Thermoplastic polymer on the market since 1950. It has both thermoplastic properties (softens with temperature) and elastomeric (at ambient temperature you can deform it and then it returns to the original form). This is obtained by mixing plastic polymers to rubber polymers. It is the softest among the flexible filaments.

It’s the only material I’m going to talk about in this review that can’t be printed with a Bowden extruder.

If you looking forward to try it: http://s.click.aliexpress.com/e/0GqqUoY

TPU

TPU is a hermoplastic polyurethane, a polymer much newer than TPE. It is a mixture of polyurethane and rubber polymers. It’s definitely less soft than TPE. If you want a rough idea of how soft this material is, imagine you’re dealing with hardened silicone. The shape of the filament, which resembles the licorice wheel as a consistency, has also the same physical characteristics.

 

If you looking forward to try it: https://amzn.to/2CnIE9B

Flexible PLA

This material is simple PLA combined with specific chemicals and specifications to soften it. It has a consistency similar to TPU but the ease of printing typical of PLA. It is very used by makers for these characteristics. Remember, however, that being PLA the softening temperature remains very low.

If you looking forward to try it: https://www.filoalfa3d.com/it/filo-175mm/296-bioflex-flessibile-27-shore-d-o-175-mm-8050327032385.html

PCTPE

A material that possess the characteristics of TPE and nylon, extremely flexible but resistant. You can easily print PCTPE with any 3D printer, since it requires only 23ºC. Although extremely flexible, nylon ensures linearity and therefore you can print with direct extruder or Bowden.

If you looking forward to try it: https://amzn.to/2AIxlsw

Rubber PETG

The company Tomas3D produced this softened PETG. Easy to print as a PETG with the typical strength of this material. It has a stiffer consistency than TPU, remains soft up to half a centimeter, then becomes stiffer layer after layer, keeping the softness only to the touch.

If you looking forward to try it:  https://www.tomas3d.it/shop/gomma-petg-filamento-3d-luxury-quality/

Let us summarize in a table what has been said so far:

flexible filaments

There are many flexible filaments, even different from those presented here. However, you should follow these rules to print to their best.

How to print flexible filaments: rule 1

Follow the manufacturer’s instructions regarding temperatures. They may also differ from the ones listed in the table above. Always follow the manufacturer’s instructions and then depending on the result increases or decreases the temp. Here are some indications to understand if the temperature is too low, or on the contrary too high.

If the temperature is too high: you will notice material leaks from the nozzle during the movements.  You should change the temperature only if these leaks are huge. Some filament are physiological, given the printing settings, means absence of retraction.

If the temperature is too low: you will notice poor adhesion between layers. In some cases also underextrusion. Because the little loose material will struggle to get out and will already be partially cooled before joining the layer below.

How to print flexible filaments: rule 2

Turn off retraction! The retraction of a flexible filament could be dangerous.

In these terms: if we retract a filament from the extruder to the last part of the pipe, where it has slightly more space, it could solidify slightly larger.

This also happens with normal filaments! But while these have the stiffness that allows you to push the material equally and continue printing, the flexible filaments do not bear the slightest effort.

In fact, if they meet resistance they begin to twist around the pulley of the engine pusher.

flexible filaments
Example of infill that minimizes retractions.

PRO TIP: If printing requires retraction and you are working with a material that is flexible, but quite rigid, the tip I can give you is to use the new Roman cross infill of Cura 3.0+. This particular conformation of the infill minimizes the necessary retraction, keeping them by the necessary points only. Use at your own risk!

How to print flexible filaments: rule 3

Slow down! As explained before, the flexible filament suffers resistance. Therefore, it suffers speed  particularly.
Why that? Simply the extrusive thrust of a flexible material is diminished by its composition. In fact the filament itself captures a percentage of the force of thrust of the extruder, which compresses.

To minimise this loss of load, you must slow the filament so it has time to pass from 1,75mm diameter to the typical diameter of the 0,4 mm extruder. Then the speed to be set will go from 15 mm/s of the TPE, to 30 mm/s of the TPU up to 40/45 mm/s of the rubber PETG.

Obviously, this contraction of the filament subjected to thrust also results in a more or less long delay of extrusion. To overcome this problem you can set a Brim of 1 cm or more. This will kill 2 birds with one stone. We’ll give the filament time to come out and help adhere to the plate.

About adhesion

Flexible filaments do not require special materials to adhere, in most cases the heated bed, that is. However, paper, blue tape, glass, ultrabase, and in general can be printed on all the printing plans covered in this article. 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.This is to create less friction and make sure that the filament runs smoothly. But also avoid having too much distance, which leads to problems of adhesion to the plate.

flexible filamentsIncrease the offset

Just like the PETG, you have to set a larger offset (increases the nozzle distance flat), even just 0.1 mm. For smoothness.

For this setting you just need to enter the command between the G-code boot:

M851 Z 0,1.

You don’t want to save the setting unless you want to print TPU for a while. At least when you reboot you will have the parameters for PLA and ABS again.

Increase the extrusion

It can also happen that some flexible filament has a flow slightly lower than the PLA/ABS. Always for the peculiar characteristics. So if 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 is reversible and temporary!

How to print flexible filaments: Last advice

If you have problems with printing flexible materials remember that if they are composed of PLA, Nylon, and ABS are (more or less) prone to absorb air moisture. And this determines an objective difficulty of extrusion. Before any other test, if the filaments have been open for a while, dry them with a dryer!

You can also dry in the oven, but be careful because too high a temperature can transform the filament coil into a lump of shapeless!

What filaments have you tried? Do you have any advice to add? Do it in the comments!

 


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