I’m new to 3D Printing. I’m trying to print with Black Bambulabs PETG-CF but the resultant components are brittle. You see from the photos ho the top of this component just snapped off and you can also distinctly see the lines where the filament was laid down. The pictures below show the before and after. The red arrows point to the breaking surfaces.
I’ve already dried the filament (6 hours in 50c oven - My wife was so pleased!) even though it was brand new out of vacuum bag and I also changed settings after initial failures to those listed here:https://www.themakersphere.com/bambu-lab-x1-carbon-petg-settings/
The only additional change I made was to drop the “Initial layer infill” to 40mm/s on the theory that it was lying the filament down too fast .
I’m not sure if I can attached the 3mf files here?
Any suggestions on next steps greatly appreciated.
In the pictures the top layers look a little rough. Looks like there might be some extrusion issues.
And @3DPrintedCard makes a good point. The part will be weakest at the point that broke off.
I have some experience with BL PETG-CF. It is strong to a point, but if you are putting a lot of pressure on a small 5 wall layer like that, it won’t hold up.
I dry it for about 20 hours at 70C (real 60-65ºC). And to prints and looks great. You will notice the difference in the filament when it’s properly dried.
Yes. I did it just last week for three BL PETG-CF new spools.
Be careful using the oven, as the temperature regulator may be inaccurate. At least put some thermometers (e.g. grill thermometers) to double-check.
You wouldn’t be the first to cook the spool.
Is there a possibly of redesigning that part to allow for 3d layer lines, thickening up that section where I’m assuming a cable-tie goes. Maybe look into different material options as CF isn’t necessarily going to be strong in this situation.
FYI - My PETG-CF is currently being cooked at a pretty steady 60c.
@GenericUser I picked PETG because of its supposed strength along with having a little “give” plus its meant to be very good in an exposed environment. I can’t use PLA because of this. I have ABS (Not tried it yet) and TPU (too soft I think and probably not resistant enough to harsh environment).
Yes I can probably bulk it up a bit around where the cable ties go - I’ll look at doing that. It’s currently 2.5mm thick.
BTW - These are going into a plane wing spar - so no pressure
Sorry for the dumb Q - but what do you mean by “3d layer lines”?
The frame looked like something like that, so vibrations would be the biggest factor. My odd term for the layers basically, as you probably already know and have experienced here the weakest spot is going to be naturally the adhesion between layer sliced horizontally. It can be managed in some designs by the print orientation but its probably better to go for beef in this case
I have no idea about the regulations, if any, you have to adhere to but I’d assume you’ve taken this brittleness into account if it does break off so it doesn’t get jammed in anything critical.
Try upping the nozzle temp by 5c also to help with the adhesion, and keeping the chamber warm and stable also.
Actually, TPU is probably the most reliable in a harsh environment. It’s chemical, vibration, and abrasion resistant and is the strongest out of all of those that you mentioned. It’s just not rigid and a little trickier to print. It would make an excellent cable bushing.
ABS requires more heat and an enclosed chamber to print without warping. You’ll also want adequate ventilation as the fumes are toxic.
Unless there is a reason you need it to be very rigid, I think TPU would be the best material for your current application.
Thanks @Lexi - There is a small risk of fuel getting on the component which was why I was opting for PETG-CF. I think the TPU would have problems with that.
I’ll do some more research to see if it TPU can do the job.
@GenericUser I put the temp up by 5c as you suggested and I got this warning when I went to print
The printer is a new P1S with the standard nozzle (0.4 I believe).
Do I really need to change the nozzle to print PETG-CF?
I’m also wondering why I didn’t see this earlier - probably changing too many things at the same time
The CF will wear things, if you’re ok to sacrifice a stainless nozzle this job will prob not worry it too much. But for the long term it’s easier to go for the hardened one. I’m not sure whether the extruder is hardened (mind on other things), just check. That said, if you’re keen to do more CF work it’s nice material but after a kg or two do a check on your PTFE and connections as they’ll have wear (it’s kind of sacrificial anyhow).
Yes, the filament will snap like cheap spaghetti and often in the worst spot inside the AMS hub. In some cases there are variables, like here where the design can lead to spots where weak layers can break apart.
When you have some time to do some research, you will be pleasantly surprised to find that TPU is fuel resistant. Resistant enough that people have successfully printed their own small engine gaskets with it.
Your layer adhesion is bad because your still printing too fast for petg cf. Slow way down.
first layer- 35
first layer infill - 60
outter wall - 70
innerwall - 90
sparse infill- 100
internal solid infill- 100
top surface- 75
overhang settings good.
normmal printing - 8000
You will be shocked how little this impacts you overall print time. Please post if these settings do help if you use them. Main thing to bond layers is to slow way down. I learned this from running cf nylon on a markforged mark2 machine.
Yes, you would need a hardened steel extruder gear upgrade and HS nozzle. For this part, I would suggest 0.6mm nozzle. PETG-based filaments have way better layer adhesion on .6 vs .4 nozzle, with the additional benefits of less nozzle clogging and residue clamping on that nozzle.
I was also sceptical regarding the recommended 0.4mm nozzle, but I can assure you that it works flawlessly. Despite BL PETG-CF being an easy-to-print filament, I agree with the need for hardened steel.
