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Print Quality Issue


mcham
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Hi,

Thanks in advance for helping a newbie.

What should I look for to address the pictured issue?

Look at the .stl as the corners of this phone case are open to allow it to snap on phone.

The problems are on only 2 sides (cooling?)

The rounded nature of the design cause overhang, but it does it on 2 sides.

Thanks

Voron-PhoneCAD.png

Voron-Phone4.jpg

Voron-Phone3.jpg

Voron-Phone2.jpg

Voron-Phone1.jpg

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I think the angle of the overhang is just a little too much on some points, just try it with support?

See if that makes it better, and I think it should, I think your lines dont end up where they should and makes it a mess.

Over 70 degrees it its just a no no.. on most printers/settings you wont even get that.. so wont go over 50 degrees, but this design goes way over...

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I think @Buurmanis right on it.  Radiused corners coming off the print bed are just incredibly tough to get nice because of the shallow angles as the radius starts.  Support is your only chance but it still isn't as nice as you would like it to be in my opinion.  That will likely cleanup the "loops" on that other opening just at the edge of the photo - those are being caused by the same issue.

Sometimes you need to alter your design to get good prints - I know how nice a radius would be but if this is your own design, you might want to consider going to a chamfer instead.  You will get a lot of the aesthetics of a radius but a better print as you won't have the very shallow starting angle of a radius.

These printers can do a great job but those types of features are asking it to print on air which is just too much.

How much of a chamfer?  Here's an example.

I've found my V2 can easily do 60 degree ANSI threads without support - here is a nozzle I just designed and printed last night:

image.png.5c5f82a481f25e16bcd938156ade432d.png

image.png.817c5ad09157d0aba57f991bf6940e1f.png

 

That came out sweet - it's some of the PrintLife ABS from the recent group buy, 240C, no part cooling, Voron Revo on an Afterburner.  Those threads came out great!  The entire nozzle is hollow and printed with no supports anyplace - just a brim on the build plate.

Printing larger threads has worked for me but I wouldn't go past that and even do 60 degrees for more than short distances but it is impressive.

 

-- Chris V2.2874 350mm^3

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The other issue to consider is the balance of fan and heat. Fan helps with bridging and overhangs but generates cooling that aggravates warping, splitting, weak layers, and lifting with ABS. You can try a little less heat and a little more fan starting maybe at the 3rd layer. You'll need to experiment a bit. A good technique is to cut out a small section of the side of your model so that you can test different parameters quickly without wasting lots of filament. Then when it gets to your best settings, save that profile under a unqiue name so you can use it for similar situations later. 

The other thing I would note is that different brands of filament get "droopy" at different temperatures. I have found that some filament brands won't hardly extrude at 240 and droop at 247 (Paramount), while others print happily anywhere from 235-260. E-Sun, Sparta3D, KVP, and the new Voron-branded filaments are my go-to brands. Every printer is a little different and you will probably have to "find your groove". My advice to new printer owners is stick to one or two brands and get them working well. Then you will have enough experience under your belt to easily adopt others.

IF you haven't seen it, you should check out Ellis's tuning process: https://github.com/AndrewEllis93/Print-Tuning-Guide

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I think your screenshot is from Cura, but if you happen to be using PrusaSlicer there's an icon in the toolbar for "Variable Layer Height" that can be applied automagically. You select the model, click the icon, and click "Adaptive" in the pop up and it will auto generate smaller layers where it needs to for adding detail and helping to accommodate overhangs and such. But of course it can't defy physics but I have seen it do wonderful slices by adding additional details for shorter layer heights.

Of course, as mentioned above, you could try printing the entire case in, say, 0.15 instead of 0.20 layer heights.

Finally, I've seen a lot of phone cases that seem like they can be printed in TPU (flexible material) - have you thought about that? I haven't done this myself but it seems like it would be a good idea.

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