Z-Scar when printing circular tubes

[juanmedina]

For some reason when I print tubes it leaves a bad z-scar. When I print any other parts the prints looks flawless. I can try the random start point but I don't want to have marks all over the part. I found other threads of people having the same issue but with no solution; maybe there is glitch with the software when printing circular tubes.

I am trying to print an intake for my car. Currently I am using PLA but I am going to get some thing more exotic so it can take the heat. Any suggestions on what material to use?

As you can see the intake looks really good other than the nasty z-car.

[andrewk72]

It probably just means you need to adjust your retraction settings. Perhaps add some coasting or use a negative extra restart distance.

[juanmedina]

I tried to change the retraction setting, added coasting etc and it didn't help. It just makes the part worse in other areas.

Can anyone print a small round tube and see if they get a z-scar?

Like said any other parts look really good with not visible scar when changing layers.

[andrewk72]

I've printed many circular objects that came out just fine. I don't get any Z-scar once I set the correct retraction settings.

[juanmedina]

Well I kept playing with the retraction setting and could not get it to fix the issue with bad seam. I decided to just turn off the retraction and it looks way better than it used to. There is no void at all anymore just a little seam that I can sand down with much effort. On the inside of the tube there is barely any seam. I am happy with the way that is printing right now.

As far as material with high temp resistance the polycarbonate seems to be the material of choice but it seems that its is really hard to print. I found this advance PLA and it seems that it is good up to 144°C with out any heat deflection. My understanding is that under hood temperatures will reach around 220°F so I should be good.

http://3d-tools.com/product/fossil-fuel-black-apla/

Does anyone have any experience with this material? I just think it should be easier to print than the polycarbonate.

[dorsai3d]

Most of the high temp PLA materials will need annealing in order to maintain heat resistance at their advertised elevated temperatures. It will still not be very strong at all at that high of temperature, and engines vibrate a lot. I'd strongly recommend nylon over any other material in that application. As a bonus, it's easier to print than polycarbonate. The other molded parts under there are probably fiber-filled nylon as well.

You may also want to consider some sort of coating (I haven't looked into what's good with nylon) in order to reduce the likelihood of it cracking along layer lines after being baked and vibrated for hours.

[juanmedina]

Most of the high temp PLA materials will need annealing in order to maintain heat resistance at their advertised elevated temperatures. It will still not be very strong at all at that high of temperature, and engines vibrate a lot. I'd strongly recommend nylon over any other material in that application. As a bonus, it's easier to print than polycarbonate. The other molded parts under there are probably fiber-filled nylon as well.

You may also want to consider some sort of coating (I haven't looked into what's good with nylon) in order to reduce the likelihood of it cracking along layer lines after being baked and vibrated for hours.

Which nylon filament would you recommend for my application?

[juanmedina]

I found an article from dupont stating that most intake manifolds are made from Nylon 66. Is that material available for 3D printers?

[dorsai3d]

Pretty sure taulman 645 is pretty similar. Most of the stuff in cars is fiber filled 6/6 though, so it will never be an exact match. There's carbon filled nylon filament out there, but that's likely more susceptible to cracking.