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Everything You Need to Know About Printing CoexFlex™ 60A TPU COEX 3D

Everything You Need to Know About Printing CoexFlex™ 60A TPU

Mark Szymanski

CoexFlex™ is a great series of filament that can truly enable your 3D printing creativity. Our flexible filaments cover a wide range of the shore hardness scale, whether you need something stiff and incredibly durable or extremely soft and squishy. On the softest side of the scale sits CoexFlex™ 60A TPU. It is an amazing material, capable of some of the softest 3D printed parts possible. This is perfect for gaskets, RC car tires, and you could even print custom insoles! This extreme flexibility comes with one downside, though - 60A is quite tricky to print. Its flexibility means it will try to find every gap or crevice to squeeze itself into, so there are many special considerations to make when printing with 60A TPU.

This guide will hopefully serve as an in-depth resource for all the tips and tricks for printing with CoexFlex™ 60A TPU. From slicer settings to what extruder to choose, we hope we can help get you started with this amazing material! If you have any questions this guide doesn't answer, please reach out to support@coex3d.com and we'd be more than happy to help!

Bed Adhesion

One of the great things about 60A TPU is that it actually sticks extremely well to even an unheated print bed. It will also stick to a variety of print bed materials, such as glass, smooth PEI, textured PEI, painter's tape, etc. In some cases, however, it can stick too well, so it is a good idea to use a glue stick or Magigoo as a release agent when printing it. But overall, you likely won't have to worry about parts curling up off the bed or otherwise having adhesion issues.

Part Cooling

Part cooling is another factor that you generally don't have to worry about with 60A TPU. Since you'll be printing it so slowly, the layers will have plenty of time to cool. You can disable your cooling fan entirely when printing 60A TPU.

The Extruder

The most important thing in this whole setup is the extruder itself. You absolutely need a direct drive extruder - and specifically one with as constrained of a filament path as possible. Quite probably the best off the shelf extruder for this purpose is the OmniaDrop. We're not just saying that because we carry it! The OmniaDrop was designed specifically to be able to print even the most flexible materials, and we carry it specifically because it enables our customers to be able to print with our CoexFlex 60A TPU.

This image illustrates what we mean by a constrained filament path. As you can see, there is very little space between the gears and the body of the extruder, meaning there is very little space for the filament to "find" a way to wrap around the extruder gears. This is crucial for printing with 60A TPU.

A cross section view showing the filament extrusion path through the OmniaDrop Extruder.

If you go the OmniaDrop route, make sure you also pick up a PTFE-lined heatbreak. The OmniaDrop comes with an all-metal heatbreak, which is perfect for printing higher temperature materials such as CoexNylex™, but the metal will cause excess friction when printing 60A TPU and will make it much more difficult to print such a soft material.

If you go with another extruder or choose to DIY a different solution - keeping the filament path constrained as tightly as possible is by far the most important thing to consider.

You also need to ensure your nozzle and extruder is clean and free of debris. Any partial clog or contaminant can give 60A TPU a chance to clog up. Performing a cold pull with nylon or a material other than the 60A TPU itself can be a great way to thoroughly clean your nozzle.

Slicer Settings

There are many settings that need to be considered when slicing models to be printed in 60A TPU.

Speed

Probably the most important setting when printing with 60A TPU is printing speed - you will need to print very, very slowly. Start out with a maximum speed of 10mm/s, and work your way up from there if you're able to. Don't expect to get much more than 20mm/s as your max speed, though. You won't be printing a 20 minute Benchy with 60A TPU!

Temperature

Temperature is also very important. At Coex 3D when we print with our 60A TPU, we use a nozzle temperature of 230°C. Beware though, as above this temperature the material can get too hot and start to degrade, so you may want to start out around 220°C-225°C. Ensuring the hotend is up to an even temperature is also important. Uneven temperature throughout the hotend could cause the material to melt unevenly and therefore clog up. A bit of custom G-Code at the start of a print can help with this, specifically the G4 G-Code command. This command is "dwell" - it causes the printer to pause and wait a specified amount of time before continuing. In this case, you could add G4 S60 to your custom starting G-Code, right after the hotend comes up to temperature with the M109 command. This will give the hotend 60 seconds to get to an even temperature before continuing the print, which can help a lot when printing 60A TPU.

In PrusaSlicer, in the Filament settings in Expert mode, you can add Custom G-Code specifically when using that filament preset. Filament-specific G-Code does not appear to be a feature in Cura, so you can customize your printer's custom start G-Code to add the G4 S60 command. Just be sure to remove this command when printing with other filaments so your prints aren't a minute longer than they have to be!

See below for a screenshot showing what setting this up looks like in PrusaSlicer.

Screenshot showing a G4 S60 command for a custom filament G-Code in PrusaSlicer

Retractions

You'll also want to disable retractions when printing with 60A TPU. Moving the filament back and forth in the extruder will just give it more opportunities to clog, so disabling retractions will give you the best chance at a successful print. After you've had some success and if stringing is a problem, you can try using very, very small retraction values, on the order of 0.5mm or less.

Multiple Parts

Overall when printing 60A TPU, you'll want to reduce travel as much as possible. Even if you disable retractions entirely, starting and stopping the filament feed can be troublesome. So if you're going to print multiple parts in 60A TPU, it is a good idea to print them sequentially. Most slicers will allow you to do this, just make sure that there is enough clearance between the parts so the extruder won't collide with the already printed ones. Many slicers allow you to enter in your toolhead size and can automatically calculate if there will be problems with sequential printing. Otherwise, try to only print one part at a time if you're experiencing clogs when printing many parts at once.

First Layer Squish

The first layer is the most important one when printing anything, with any material. When printing 60A TPU, it is crucial that your first layer not only squish enough to adhere nicely to the bed, but it also cannot squish too much. Too much squish will cause excess back-pressure in the extruder, which can cause clogs and jams with something as soft as 60A TPU. This can take some trial and error to get dialed in just right, but if you're getting constant clogs on the first layer, this could be the culprit.

Having a level bed is crucial so that the first layer squish is consistent throughout. This is especially important if printing larger objects (such as an entire insole). A bed leveling probe such as a BLTouch will make your life a lot easier in this regard.

Clearing Clogs

Eventually 60A TPU will very likely clog up on you. It's all part of the process with this material. That said, there are some strategies you can take when clearing out clogs to ensure that they won't keep happening.

First, fully clear the clog and remove the 60A TPU from your extruder. Then, purge through with another stiffer filament, such as PLA or PETG. If you have some around, CoexNylex™ Glass Filled is also really good for purging with - the glass fibers help clean things out. However we wouldn't recommend buying a spool solely for this purpose.

If you're confident with your cold pull skills (it takes practice!) you can do that to fully ensure the extruder is cleared of any clogged material.

Then, re-load your 60A TPU into the extruder. It can be extremely helpful to have an extruder that lets you manually feed filament by turning a gear or thumbwheel (the OmniaDrop extruder has a handy knob for this). This way, you can feel the force it takes to extrude the filament. With practice, you'll be able to tell right away if the filament is just going to clog again when you restart the print. It's difficult to get across in text, but if you feel that the force required to push filament through is increasing, you're just going to get another clog. The filament should extrude with little effort, and should also fall straight down from the nozzle. If the filament comes out at an angle instead of straight down, it could be a sign of a partial clog that will need cleaning.

The next step if you continue to have clogging problems would be to totally replace the nozzle with a clean one. Sometimes there's tricky residue stuck in the nozzle that isn't going to be easily cleared by purging it out.

Another step to consider is replacing the PTFE inside of the heatbreak, if that's present in the type of hotend you're using. PTFE wears out eventually under the temperature stresses of 3D printing and a worn out PTFE heatbreak can cause clogs.

Conclusion

Hopefully this has answered whatever questions you may have about how to get successful prints with our 60A TPU material. It can certainly be tricky, but with patience and systematic troubleshooting, you can make incredible things with it. As always, if you have any questions or need advice, drop us a line at support@coex3d.com. Happy printing!

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