What Are Shells In 3d Printing | Infill Pattern And Shells – How To Get The Maximum Strength Out Of Your 3d Prints?

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Infill Pattern And Shells - How To Get The Maximum Strength Out Of Your 3d Prints?


When it comes to the strength of your 3D printed parts, print settings play besides the material. A major roll in what your prints can handle. Unfortunately, I hear and read way, too often that many only use the infill ratio to adjust that property. For this reason, I tested the strength of different infill patterns on tons of these hooks and more importantly, show you how you really should strengthen your prints. Guten Tag Everybody I’m Stefan. And welcome to CNC Kitchen. If you have your material dialed in, you will usually only adjust a small number of settings before each print, depending on the requirements of the part. If you want it to be strong, many will adjust the infill density to a higher value. This will scale the infill Patters density and defines how much of the internal cavity is filled with material, which can go up even to a fully dense part. The other option is increasing the thickness of the outer shell by adjusting the shell thickness, wall thickness, number of perimeters, or, however, it is called in your slicer. Usually for a strong print, you’’ll be adjusting both values. But what really gives you the strongest result? And which is the most economical way meaning? How can you increase the strength of your part with the least amount of material? If you want to print light weight structures, this is something which is really important. In order to properly answer that question, I printed quiet a lot of my trusty test hooks and measured their strength – for science. This is definitely not perfect and doesn’’t include all possible load cases and orientations. But I still think that this is a good real world example and probably one of the best analysis. You’’ll find at the moment. The reason why I use my hook from my filament test series for the investigation instead of standardized axial test specimens is that the critical area is loaded with a more every day load case. Since the location of load application is a little offset, that lever arm will cause an additional bending moment that is superposed with the axial force. In real life, your part will also mostly be loaded by such a combination, so the results I present. Even though not 100% scientific will probably be more usable and proof my point better. As a first investigation, I wanted to find out what difference the infill patterns make on strength of the part and print time. I also wanted to find out if 30% infill really meant that 30% of the internal volume was filled by material. Since I used Simplify 3D as a slicer for these tests, I was trying out the following available patterns: Rectilinear Grid, Triangular Wiggle, Fast Honeycomb and Full Honeycomb Rectilinear is usually the default and prints the fastest, whereas Wiggle is probably more for esthetic purposes. Like for most of my parts, these hooks were printed with only 2 perimeters and 4 bottom and 5 top layers at 02mm layer height. All the parts were printed in PolyLite PLA, by the way. Print time of the Rectilinear infill was the shortest with 48.5 minutes Grid infill took 50.5 minuest and triangular 53. The patterns with lots of direction changes took the longest with 55 minutes for the full honeycomb and interestingly, wiggle and fast. Honeycomb took the longest needing 56.5 minutes. This is not fully representative since the times change due to the geometry and ratio between outer walls and infill, but shows that you can definitely save some time using the standard rectilinear pattern. Taking a look at the real final weight of the parts was pretty interesting because most hook’s weight around the same, resulting in a calculated infill of roughly 33%. Only the hook with the triangular pattern weight, quite a lot more and ended up with a 45% infill instead of the assigned 30% But now, to the most interesting part. What was the strength of the parts. As expected, Wiggle did the worst with only 45 kg until failure. Rectilinear came next and failed at 48 kg. Then there was grid at 52 kg and both Honeycomb patterns failed at 57 kg. The hook with the triangular infill was the strongest failing at 60 kg. But as we have seen before 30% infill in your slicing software, doesn’’t necessarily mean 30% material in the infill. For this reason, let’’s take a look at which infill is the most economic. So we’re do we get the most strength per weight? This is where we see that triangular infill is no more the best, but both honeycomb infill scores the highest values. The order of the rest stays pretty much the same. In the first analysis, we have seen that the full honeycomb seemed to be the most economic solution if you want to increase strength. As a next test, I wanted to find out how the strength of the hooks change, depending on different infill ratios from 0 to 100% I did this analysis with the full honeycomb infill, but also the rectilinear because I wanted to know how my standard infill pattern behaves with different infill ratios. Even though it seemed with the first tests that the honeycomb patter was significantly stronger than the standard infill, taking a look at the all of the values between 15 and 75% They are pretty much the same. The interesting part again is if we also take a look at the print time where the rectilinear pattern starts to shine. At smaller infill ratios, the both infills give you around the same strength in the same amount of print time, But as soon as you go over 50% the rectilinear prints way faster than honeycomb at the same strength. But wait, this is not the end. Let me show you how you really can increase your part strength the right way without worrying about infill ration or infill patterns. I hope this analysis is not too technical, but I think there is too much superficial knowledge around about this topic, so I thought I’’d approach it. At least a little scientific. If you would like to see more in this direction, please let me know in the comments and consider becoming a Patreon. This doesn’’t only help me spend more time on these topics, But You’’ll also get access to all the detailed test reports and test models. All right, so I have already said in the beginning. The critical section of our hook is not only loaded in tension, but also in bending. If you bend a part, just like the piece of foam right here. One side will be stretched. The other sider compressed. The part in the middle is not stretched at all so material, which we place in the core of our part, usually is loaded, not at all or only slightly. The further material is next to the outer shell, the more it contributes to the strength and stiffness of the part. If we take a look at our 3D prints, this is shell of our print, which thickness we can adjust with the number of perimeters, shell’s, wall thickness or similar. In order to find out how this affects the strength of the hooks, I printed more samples with 2 to 6 shells and only a moderate 15% infill. I also increased the number of top and bottom layers to get a constant wall thickness of my part. If we take a look at the results, we can directly see that increasing the shell thickness is way more efficient than varying the infill. At the same weight, a hook that was reinforced with more shells is significantly lighter than a hook. Where only the infill was increased? What’’s also interesting is that a hook with 6 perimeters is already as strong as a part with 2 perimeters and 100% infill. This is due to the reason that in this case. The strands of filament of the shells are in the direction of the internal forces, so in their strongest orientation, making them way stronger than the infill that is rotated all the time. For completeness, let’s also take a look at the print times and here. We see that in my case. I didn’’t save print time with the perimeter method. Print times at the same strength were very comparable to the hooks where the infill was varied. The reason for this is that the outer shell is usually printed slower and with lower accelerations than the infill to improve print quality, Okay. So what is my verdict? If you want to print stronger parts, increase the number of perimeters and also top and bottom layers, Don’t only crank up the infill ratio. I wouldn’’t usually use infill ratios of 100% because at first, this is not economic and second might lead to severe printing problems If only a small amount of overextrusion is happening. Also, don’’t try to get 100% infill with increasing the wall thickness all the way because that can also lead to printing problems. And as I have told you. Before material in the core, mostly doesn’’t contribute a lot to the strength of your designs. For parts that need to be strong, I usually don’’t go above 4 perimeters and 50% infill. That is a good compromise between material usage and strength. Even though Rectilinear infill wasn’t always the strongest I’’m still a huge fan of this pattern because it gives you quite a dense grid even at low infill ratios, which is good for your top layers. I might need to try out the 3D infill patterns that are available in Slic3r and Cura and find out how they faire also considering loads in different directions. But what’’s your approach at the moment if you print parts that need to handle some beating. Let me know down in the comments. I hope I was able to clarify and debunk some myths about infill and part strength. If you liked the video and learned something, then please hit the like button share and subscribe. If you want to support my work and research, consider supporting me on Patreon. Thank you so much for watching auf wiedersehen and I’’ll see you next time.

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