ABS vs PET

[Sanju]

I've been having pretty bad luck with warping of ABS and was wondering if PET would be fine to use on spare parts for the printer. Most of the things I plan on printing are models/figures so PLA is fine as my main filament but I need a workhorse filament for occasional things and spare parts. If PET will hold up good what kind would you guys recomend? PET+, PETg, whatever others are out there....

[jimc]

Pet is fine for the parts on the m2. In any plastic be sure you print any of the extruder parts in high infill. 80-90% should be fine. A few guys on the forum are using it for their parts. Either pet+ or petg will work fine. I prefer the petg. For extruder parts i would recommend the colorfabb xt since its about the hardest of all the pet variants. Esun is fine too and alot cheaper. I think tim has his all done in pet+.

[pyronaught]

I just bought a roll of white PET+ from Madesolid after reading some comments about how strong the layer bonding was. Well, after printing a couple parts I must say I am not impressed. I use my propeller guard part as a good test for layer bonding on small pieces since it has the lattice work that is prone to breaking off easily, and they break off just as easily if not MORE easily with PET+ than with ABS. I did a twist test on a small square box printed in PET+ and it delaminated as well, which ABS doesn't do on that test. I figured on that one maybe I printed it at too low a temp (260C) so on the propeller guard test I went to 270C but same brittle results on the lattice. A 1cm square strut with 15% infill snaps in half with about the same amount of force required to snap an identical ABS one in half. The PET+ also weighs 30% more than ABS, which is a big minus when using it for RC aircraft parts. So for something that costs twice as much and takes twice as long to print due to the slower printing speed required, you get absolutely nothing that you can't get with ABS and you lose a few things. With the heavier weight, the scarcity of suppliers and the considerably fewer color choices I really can't see why anyone would use PET+ over ABS. It prints fine, no problems there, but not any easier than ABS. In fact, it doesn't bridge well at all, probably due to coming out of the nozzle so hot, so unlike ABS you'd have to use the cooling fan to bridge with it or resort to using support material-- yet another hassle. ABS is fantastic for bridging, I've done unsupported straight-line spans of almost two inches with no cooling fan used and it worked just fine. With PET+ I couldn't even get it to bridge smoothly over the latticework of a 15% infill when printing the solid layer on top (no cooling fan used). It would sag even on tiny spans like that and make a rough mess.

So that's my 2 cents on ABS vs white PET+ from MadeSolid. I've not tried other types of PET or the translucent version of PET+ though, just that one color. I think even if it were a little stronger than ABS I would still avoid it due to being over twice as expensive and taking twice as long to print. 3D printing is slow enough as it is, so anything that doubles these excruciatingly long print times is a deal breaker for me.

[jimc]

ok, yes you are right. the pet+ has poor layer bonding. [et+ and petg are totally different. i have posted may times before how bad the opaque pet+ layer bonds. the petg variants are totally different and 1/2 the price. this would be the stuff from esun, colorfabb, reprapper and most others. the madesolid stuff is the only oddball of the bunch. petg layer bonds far superior to abs. abs does bridge better however.

[pyronaught]

I've been having pretty bad luck with warping of ABS and was wondering if PET would be fine to use on spare parts for the printer. Most of the things I plan on printing are models/figures so PLA is fine as my main filament but I need a workhorse filament for occasional things and spare parts. If PET will hold up good what kind would you guys recomend? PET+, PETg, whatever others are out there....

I think what most people refer to as a warping problem with ABS is really an adhesion problem. If the part doesn't stay firmly stuck to the bed for 100% of its footprint it is going to start warping in the areas where it has pulled away. This is an easy thing to fix by just using a hold-down system that works, and there are several for ABS. My favorite is solid kapton sheet on a 70C bed using a wipe-on ABS slurry before each print. Glue stick on glass works well too, although it is a bigger hassle to apply and remove before each print and there is a slight risk of it yanking chips out of your glass during cooling. Some have luck with hairspray on glass too, although I find it does not stick as good and also do not like the idea of sticky hairspray vapor getting on the M2 parts and building up over time.

If you are having real warping issues, where your part is 100% stuck to the bed but getting deformed in some areas, then that would require putting a chamber around your machine to keep the part from having too large of a temperature gradient during a long print, or even just not running the printer in cold air like an unheated basement or garage. I've never had this problem myself, but then I've never printed outside of an enclosure either so I really don't know how common this issue is.

Once you dial in a system that works, ABS prints just as easily and reliably as any other filament.

[pyronaught]

ok, yes you are right. the pet+ has poor layer bonding. [et+ and petg are totally different. i have posted may times before how bad the opaque pet+ layer bonds. the petg variants are totally different and 1/2 the price. this would be the stuff from esun, colorfabb, reprapper and most others. the madesolid stuff is the only oddball of the bunch. petg layer bonds far superior to abs. abs does bridge better however.

I'll have to try the PETG then. I could swear it was the PET+ I was reading about somewhere on this forum, but I can no longer find the thread. The PETG has a lot more suppliers and color choices too, so that's good. Does PETG also have the slower printing speed requirement? Normally I print ABS at 4800 mm/min, but the PET+ required 2400 mm/min. I'm seeing 3600 mm/min listed by esun as the upper limit.

[jimc]

yes you will find that petg has more impact resistance and better layer bonding than abs but it is also more flexible so it depends on what you need for the specific part. if you want more ridgid take a look at the new carbon fiber filled colorfabb xt. it supposed to be alot stiffer and stronger. it may weigh more but if you can use less material than abs then you can come out with something lighter or atleast the same weight but stronger. if you dont want to go for that stuff then the standard colorfabb xt is very good. esun stuff is great too. they currently only have 4 translucent colors though. i just did some testing their new white and black opaque which should be out in about a month i guess. that stuff was awesome. neither brand can be broke along the layer lines when its done. here is a link to the carbon fiber stuff.

https://www.printedsolid.com/shop/175-3 ... -fiber-xt/

both the esun and pet+ i run at 4000mm/min with no issues.

edit: looked at my opaque pet+ profile and im running 255deg at 4200mm/min. i have printed probably 4-5 spools of it at those speeds.

[pyronaught]

The main thing I'm looking for right now is something with good layer adhesion that is somewhat flexible. I'm making transparent dome light covers that have thin tabs that allow them to snap in place over a grooved rim, and the problem I'm having with ABS is the tabs break off to easily. The tabs have a 1.5mm wall, so it's a bit of a challenge. I ordered a roll of clear PETG from Gizmo Dorks, so hopefully that works out. I've been messing around with hotter extruder temps and jacking up the extrusion factor on ABS prints to try and get better layer adhesion, which did improve strength somewhat at the expense of having more ooze defects.

[insta]

The main thing I'm looking for right now is something with good layer adhesion that is somewhat flexible. I'm making transparent dome light covers that have thin tabs that allow them to snap in place over a grooved rim, and the problem I'm having with ABS is the tabs break off to easily. The tabs have a 1.5mm wall, so it's a bit of a challenge. I ordered a roll of clear PETG from Gizmo Dorks, so hopefully that works out. I've been messing around with hotter extruder temps and jacking up the extrusion factor on ABS prints to try and get better layer adhesion, which did improve strength somewhat at the expense of having more ooze defects.

Taulman 645 will fit that bill nicely, as well..

[pyronaught]

I think the problem with this part I'm trying to make is that the tabs flex parallel to the layer lines rather than perpendicular to them. It is basically a hemisphere with slots around the bottom to create the tabs, and there is no way of printing that where the layers run in the ideal direction to prevent the tabs from easily cracking off. If PETG allows those to flex without cracking off that would be pretty sweet.