PETG Settings!?

[reservecuts 0]

Need help setting up a generic PETG Profile. Nothing special. Everything I have tried has failed horribly. 

[Dim3nsioneer 557]

Was the generic CPE profile among your tests?

[JazekerXX 0]

try 235 nozzle, 70-90 bed (higher temp gives better bed adhesion) and fan 30%

those are the most important settings, you could play with retraction distance (2-7mm) and speed (25-50mm/s)

the petg i use is Verbatim black and even at 180C it stil prints but looses it's gloss and has bad layer adhesion, so it has to shine at least. petg always strings a bit but i love it way better then PLA

[geert_2 557]

I usually print PET at: nozzle 215...225°C, bed 90°C, speed 25...30mm/s, layers 0.06...0.20mm thick, and no cooling if there are no overhangs and bridges. If bridges/overhangs, then a little bit of fan is needed, but that reduces layer bonding. And yes, expect more stringing and worse bridging than with PLA.

 

These are PET: the left one is as-printed, the right one is smoothed with dichloromethane. The thumbscrew is a standard nylon M4, with 16mm head.

[JazekerXX 0]

6 hours ago, geert_2 said:

speed 25...30mm/s

i'm curious, why do you print so slow?
i guess because you don't use cooling, it has time to cool?

[geert_2 557]

53 minutes ago, JazekerXX said:

i'm curious, why do you print so slow?
i guess because you don't use cooling, it has time to cool?

 

Because most of my models are small, or have fine details that I want to preserve. For example in the models above, the yellow bar has to slide smoothly in the red clamp, without too much tolerance. They are for medical use, hence the smoothing to remove layer lines and make desinfection easier. And I don't want to spend hours and hours of post-processing on filing and grinding. So, printing slower, and in thinner layers, removes most of the need of post-processing. Then I have less ringing, less thickening at corners (due to the head slowing down to take the corner), less stringing, less blobs, less unevenness due to layer lines, less risk of underextrusion, it is easier to remove the supports because they melt less together, etc....

 

Printing slow also greatly improves layer bonding: the next layer then has twice as much time to melt the underlying layer and bond well.

 

The cooling is mostly achieved by printing two at the same time, plus a dummy tower for the top part, where there is very little material to print. So the dummy takes the nozzle away for some time.

 

I would recommend you try several test pieces that are designed to show the effect on corners, overhangs, holes, rods, etc..., to find out what works best for you. Embed your typical model aspects in the test pieces.

 

For PLA I normally print at 50mm/s, unless the models need to be very fine too. For PET, that is often just too fast with my models, my printer, my brand of PET; but this could be different for you of course.

 

This drawing shows the dummy cooling tower to provide cooling when printing the tiny top area. It is a different model from the ones above, but the concept is the same. This dummy greatly improves quality of the top part.

 

 

Below are testprints of a block of 10mm x 20mm x 10mm, transparent PET. Top row is printed at 50mm/s, bottom row at 10mm/s. Layer thickness is from left to right: 0.40mm, 0.30mm, 0.20mm, 0.10mm, and 0.06mm, printed with a 0.4mm nozzle. Watermark is sitting halfway in the model, as hollow text. Obviously, thinner layers, and printing slower, gives far less air inclusions in-between the extruded sausages, and thus better transparency. The brown discoloration is from sitting too long in the nozzle. Thus when printing slow, you have to print much cooler than otherwise, to prevent decomposition or burning.

 

 

 

 

[JazekerXX 0]

thanks for this in depth reply, interesting!

maybe i have something for you too, it's blob prevention. when do blobs occur? in my opinion when the printer has micro stutters due to too many commands per second. the printer stops for a split second but the extruder extrudes at a constant speed, and a blob is created. this mostly occurs at round surfaces with very high detail. i found a setting in cura wich helps to reduce the commands per second. see image below. so if a curved line of 0,5mm has less deviation then 0,05mm, then it's considered a straight line. so the difference is neglectable but it removes all the blobs.

hope this helps you too.

best regards