PETG your favorite brand?

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airscapes
Posts: 92
Joined: Wed Jan 31, 2018 11:36 pm

Re: PETG your favorite brand?

Post by airscapes » Wed May 30, 2018 8:13 pm

Thanks Phil! Already grabbed some Esun, still have not tried it, but will give MakerGeeks a try next.

airscapes
Posts: 92
Joined: Wed Jan 31, 2018 11:36 pm

Re: PETG your favorite brand?

Post by airscapes » Mon Jun 11, 2018 12:35 am

Starting the process of dialing in the PETG temp .. using eSun White, height and extruder multiplier are good using Ed's Single wall calibration square. Now trying to get temp and retraction correct, starting with temp. First string test was at 245C as per the info with the spool, fairly stingy.. rerunning at 240C.. anyone use eSun who can tell me what temp they normally use and there retraction settings (M2)
Thanks!
Doug

jferguson
Posts: 98
Joined: Mon Mar 30, 2015 7:26 pm

Re: PETG your favorite brand?

Post by jferguson » Mon Jun 11, 2018 3:24 pm

I use the 247C which was built into the PETG profile I got here. 87C for Bed - no fan, 1.2mm retraction distance - also stock.

I'm trying to develop design for wings for r/c aircraft. wingspan will be around 50 inches, chord is 10 inches. airfoil gottengen418 which is fat.

wing is glued together sections about 180mm, structure is spars which run at 45 degree angles - sort of a egg-crate pattern - and they are holed to get weight down. everything is single width - manual to .45 and set to allow single extrusion walls in advanced.

the guys in Brno in Czechia who sell very good files to print 3d planes with recommend PLA, but I like thermal stability of PETG better and it seems to be just as strong. But there are some realtively minor thermal issues.

Under early advice from the Czechs, I used clear PLA because they thought it bonded better. Then I tried black PLA and couldn't see any real difference.

Then I went to clear PETG (all of this Esun) and it worked fine. Then Black Esun PETG and here is where I ran into a problem. I would get some melt-down/distortion of structures lower in the print that i hadn't gotten printing in clear. My take is that black radiates heat more than clear and also abosorbs heat from adjacent structures more than clear.

What I'm coming to, is I like Esun PETG fine and it may be that these thermal problems would occur with any PETG filament. Solution to this if I really want to print with black PETG is to print two or three wing sections at same time so each section has a chance to cool before the extruder revisits it.

Phil
Posts: 171
Joined: Mon Sep 19, 2016 7:49 pm

Re: PETG your favorite brand?

Post by Phil » Mon Jun 11, 2018 4:02 pm

Be aware that ABS, PLA, and PETG have not just differing strengths, but also differing densities, (more than 10% difference). That will definitely play a role in choosing the best material for making flying equipment.

jferguson
Posts: 98
Joined: Mon Mar 30, 2015 7:26 pm

Re: PETG your favorite brand?

Post by jferguson » Mon Jun 11, 2018 8:10 pm

Phil wrote:
Mon Jun 11, 2018 4:02 pm
Be aware that ABS, PLA, and PETG have not just differing strengths, but also differing densities, (more than 10% difference). That will definitely play a role in choosing the best material for making flying equipment.
Apparently ABS is not a good choice for this sort of thin shell fabrication, but I'm not sure why. The Czechs advise against it, but don't say why.
I've been flying planes with 48" wingspan with fuselage components M2 printed, but with carbon fiber sparred balsa moncoque wings - 3 ply ribs with 1/32 blasa skin - very light.

but from a design-effort standpoint the non-wing airframe takes much more time. so I resorted to getting the wings under control first and make 3d printed wings for an existing foam airframe. I'm pretty sure I've got the lightest design now that's stiff enough to work - although there are some oil-canning issues in the space between the stringer/spars. I should have first wing completed with aileron servos installed in about a week.

It isn't hard to adjust cg on the plane it will go on, and I suppose only real question is how much more will it weigh than the foam wing it replaces. battery powered electric and the thrust generally used in these things is a bit more than the all-up weight.

test flights are the anwer to discovering structural adequacy. It's fun, but printing time at 6 hours per section does grow design iteration time a whole lot.

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