Had a Brainwave. For a single 3D print I have been using multiple nozzle temperatures for trickier-to-print materials, like Co-Polyester, and getting beautiful results. No more stringing!

Transcript

Hey gang, Tim here at Core Electronics and I'm going to teach you exactly how to get beautiful prints like these whenever you're utilizing copolyester. And I'm going to show you my special trick that I've been using to do it. 

Before going any deeper, all PETG filaments exist under the banner of copolyesters. Copolyester is an astounding material in terms of its properties. It has all the best features of tough PLA and ABS and then both are dialed up just that extra little bit in terms of ruggedness and durability. Ultimaker offers two versions of copolyester filament, CPE and CPE+, with the main difference being CPE+ has a higher impact resistance. Both filaments are formulated for chemical and UV resistance, high toughness and reliable dimensional stability. All this means is that Ultimaker CPE material is an ideal choice for 3D printing functional prototypes and mechanical parts.

All of these great factors, so why doesn't everybody use it? It's challenging to print. The two main challenges with this material are its desire not to stick to a build plate unless extruded at a hot enough nozzle temperature and its large inclination to string at every possible opportunity. Strings are the little cobwebs that you can see on 3D prints. The best way to get stringing to stop is to lower the temperature, but one of the best ways to lose that build platform adhesion with CPE is by not having a high enough nozzle temperature. Stringing sucks as it leads to longer post-processing and furthermore, these little stringing blemishes can bunch up and end up making little burns and marks in the subject. It is as if there's these two competing factors, both with advantages and disadvantages and to achieve one means you lose out on the other one. So I ended up doing both.

For the first couple of layers, depending on the CAD model, but normally in the first 10 layers, I would use a much, much higher nozzle temperature, around 260-degrees Celsius with my 0.4 millimetre nozzle. Then once those layers are firmly attached to the build platform, I bring that nozzle temperature drastically down by over 30-degrees to around 233-degrees. This results in a copolymer 3D print that adheres to the glass build plate very well and has a much better final finish. To do this in practice, you can either manually change the nozzle temperature while printing or depending on your slicer and how easily you can get to the G-code, you can create a printer recipe that does this temperature change automatically. This means you don't need to hover over your printer like a hawk waiting for the right moment to strike. I created a guide which teaches exactly how to change the nozzle temperature automatically mid-print by directly altering the G-code using a software called Rapiter Host. See the description below.

To put emphasis on why this is worth it, I have brought to the table three examples of what I believe highlight exactly the line being walked. The clamshell model on the left was tried to be printed at 230-degrees nozzle temperature. The model on the right was printed at 260-degrees, which shows heaps of stringing and the model in the middle was printed using my trick. 260-degrees for the first 10 layers and then dropping the nozzle temperature right down to 233-degrees. Do you see what happened to me on the left? I don't want that to happen to you. So if you take anything from this, just change the default nozzle temperature a little bit higher when first printing with Ultimaker CPE.

Now for the astute out there who like a good dabble of mechanical properties, they will know that printing in this manner will cause internal stresses along that layer that the temperature change occurs. So far, I've been doing one large temperature drop in my prints. However, to create the strongest possible part, you will want to change the temperature slowly and incrementally over multiple layers. If you take a look at this clamshell case from this angle, you will notice, but only if you look really, really close that there is a slight colour change which occurred when this temperature change happened. This technique would work well for other challenging printing materials like TPU or polycarbonate and I cannot wait to try it out.

A quickie note on the build platform when printing with this material, whenever I 3D print Ultimaker CPE Plus, nowadays I always use a bed adhesion sheet. This filament is infamous for ripping chunks out of glass beds. The chunk gets pulled off when the print is complete as the adhered print will shrink more rapidly and at a different amount than the glass plate. Ultimaker CPE, on the other hand, the stuff here, does this no more than tough PLA.

The best surface finishes come from glass beds and I did not want to limit myself when using this material. I do not use PVA glue on the build platform when printing for CPE as this completely ruins the surface finish. Instead, I make the bed as clean as possible using isopropyl alcohol and allowing it to evaporate off completely to achieve reflective finishes on the final pieces.

And this is an example of what is possible when your 3D printer is dialed in perfect. The exact setting profile I have dialed in for an Ultimaker 3 and an Ultimaker S5 printer can be found down below in the description. Now a quick caveat, each 3D printer, even the same model of 3D printer is a unique creature. So my exact settings may not work instantaneously for you, but I have no doubt I'll be able to get you very similar results.

If you do download and use my profile, you're going to notice that I have some custom tree supports in there that will work for both organic and engineering models, future content on what's going on with that real real soon. There are some other tasty nuggets in that profile for those willing to explore. And with that, I hope I've given you some good ideas for your next print with CPE. And until next time, stay cozy.

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