Help me dial this PETG in...

[MikeWi]

I like PETG for it's ability to flex a little bit but I agree it's not always the best choice for strength. My current favorite for all around strength and UV resistance is ASA, but that took a lot of work to get right! I finally had to break down and build an enclosure for the printer. It needs a warm environment with no drafts to prevent warping and layer separation.

 

[Ken226]

Here are some strength values for various filaments. Sourced from:
ultimaker.com

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Juggerbot

Acrylonitrile Styrene Acrylate (ASA) Filament Review

Acrylonitrile Styrene Acrylate (ASA) is a synthetic, amorphous thermoplastic that works best in material extrusion printing due to its high weather resistance and high impact features.

juggerbot3d.com

PLA
Tensile Strength: 53-59 MPa
Flexural Strength: 97-101 MPa

ABS
Tensile Strength: 34-36 MPa
Flexural Strength: 60-61 MPa

ASA
Tensile strength 35.0 - 50.5 MPa
Flexural Strength 38.6 - 78.6 MPa

PETG
Tensile Strength: 38-44 MPa
Flexural Strength: 75-79MPa

Nylon
Tensile Strength: 63-65 MPa
Flexural Strength: 63-83 MPa

Polycarbonate
Tensile Strength: 43-65 MPa
Flexural Strength: 89-114 MPa

Polypropylene
Tensile Strength: 10-12 MPa
Flexural Strength: 13-15 MPa

 

[weston1968]

Here are some strength values for various filaments. Sourced from:
ultimaker.com

Homepage

Discover UltiMaker's 3D printing solutions: Desktop 3D printers, software, and materials for streamlined production and unlimited innovation.

ultimaker.com

Juggerbot

Acrylonitrile Styrene Acrylate (ASA) Filament Review

Acrylonitrile Styrene Acrylate (ASA) is a synthetic, amorphous thermoplastic that works best in material extrusion printing due to its high weather resistance and high impact features.

juggerbot3d.com

PLA
Tensile Strength: 53-59 MPa
Flexural Strength: 97-101 MPa

ABS
Tensile Strength: 34-36 MPa
Flexural Strength: 60-61 MPa

ASA
Tensile strength 35.0 - 50.5 MPa
Flexural Strength 38.6 - 78.6 MPa

PETG
Tensile Strength: 38-44 MPa
Flexural Strength: 75-79MPa

Nylon
Tensile Strength: 63-65 MPa
Flexural Strength: 63-83 MPa

Polycarbonate
Tensile Strength: 43-65 MPa
Flexural Strength: 89-114 MPa

Polypropylene
Tensile Strength: 10-12 MPa
Flexural Strength: 13-15 MPa

I can significantly increase the strength of PETG by increasing the flow rate to 110%. the downside is that tuning is difficult as it has a very narrow range. With Hatchbox and only Hatchbox I can achieve the same strength as PLA+ doing this.

Reducing the Flow rate to 94% makes PETG fairly easy to print and the parts have a good finish but with PETG's detail limitations. The down side is that these parts are not useful where mechanical strength is needed.

 

[WobblyHand]

After drying the filament in evacuated bags with excess desiccant for a month, the PETG prints better, but there's still some bubbles. I used a filament dryer set to 50C overnight and now there's still some pits in the vertical walls but it is slightly better, ie there are not any blurbs sticking out. Guess I have to bake these reels longer. Kind of surprised at the moisture levels out of these two rolls of Prusament. I'll have to try another brand sometime. I'd not want to sell parts made from this filament. Fortunately, for what I need - prototypes of things that I might machine, the parts are coming out good enough.

This is a prototype DRO read head bracket. Used organic supports, which look really cool. Draft mode, 15% infill, 4 perimeters, PETG. The holes are coming out a bit rough, but that is to be expected, especially with the orientation and 0.3mm layer height. If you zoom in, you can see the pits. From reading, this is still moisture.

 

[slodat]

I never dry PETG. It will sit on my printer for months between prints and I don’t have issues..

 

[WobblyHand]

I never dry PETG. It will sit on my printer for months between prints and I don’t have issues..

What is the RH indoors? How do you keep the PETG? Do you live on the dry side of the state or the wet side? What brand PETG do you use?

I think my filament was stored at the bottom of a lake prior to delivery. There's still residual moisture or voids in it. I'm going to dry it for another 12 hours at 50C. Max RH in my house was 34% when it was raining outside (a couple of days ago).

12hrs of drying of the red:

Going in for another 12hrs of drying.

 

[slodat]

You raise a great point. I live in arid desert. Humidity is low in general, lower since I’m still heating the shop. I keep it open spool on the top of my Prusa. I’ll run a print today. Spool has been open for a few months. I use Overture PETG exclusively. I’ve printed 40+ rolls of it on the Prusa.

 

[WobblyHand]

You raise a great point. I live in arid desert. Humidity is low in general, lower since I’m still heating the shop. I keep it open spool on the top of my Prusa. I’ll run a print today. Spool has been open for a few months. I use Overture PETG exclusively. I’ve printed 40+ rolls of it on the Prusa.

Suspect your lack of issues is your climate. Maybe mine is a bad lot of filament. And the RH is higher here.

I have an unopened roll of Overture PETG that I could try. Never printed with Overture. What settings do you use? I downloaded the latest configuration file for PrusaSlicer and they only have OverturePLA, but nothing for OverturePETG. Generic PETG?

 

[weston1968]

I have found PETG to have a very narrow temp, speed, flow range. I know all three are set correctly when there is no plastic creep up the nozzle. For a given flow rate too slow and the filament comes out faster than the print head is set for and I get blobbing and wicking up the print head. Too fast and I get poor adhesion and wicking up the print head. Temp and speed are co-dependent as when one is increased the other must be increased or you get wicking up the print head. The first thing I try to figure out is the cause of the wicking which takes me a long time for each new brand. Once that is solved my prints look decent and I do minor mods with each print to hone in on optimum. I have found that 94% is a good flow rate to start with although the strength of the parts are not great.

The print head is a weight, the belts are springs and the stepper is a damper. To remove ghosting you have to move the frequency of the movement below the resonance of the system. Speed and acceleration reductions are the best was to rid yourself of ghosting without changing the hardware. GT2 belts come in different thicknesses and stiffness. The stiffer and thicker the belt the less the spring constant and the higher the frequency of resonance hopefully out of the range of what you are printing. I have two identical systems the only difference being the stiffness and thickness of the belts. The thicker, stiffer belts have reduced ghosting. Putting in larger steppers increases the damping effect somewhat and gave me some improvement on ghosting. I also found that sometimes just changing the speed a small amount moves me away from resonance and reduces ghosting.

 

[weston1968]

With PETG and it is important to keep the velocity constant. If I slow down the print speed the filament flows out to fast and I get blobbing. It becomes evident in circles where acceleration limitations govern the speed of the print head. Long lines are gorgeous and circles do not come out well.

Acceleration - Velocity^2/radius of circle

If I am printing a circle with a 3 mm hole and 60mm/sec print speed then.

Acceleration minimum = (60 * 60) / 1.5 = 2400

Printing with Florida Filament PETG my 3.3 mm hole with about 2mm walls prints identically to the straight lines. I put an acceleration max of 5000 into marlin and am running 3000. I am printing at 55 mm/sec.

Strangely III3Dmax PETG does not print well. It does not bridge well and I am probably printing it at too high a temp.