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Have you ever asked yourself, the layer height setting in the slice software What effect does it have on the strength of 3D printed parts? I printed multiple samples with different layer heights from 0.05mm to 0.4mm And measure its strength on a universal standard testing machine Which one is the strongest? Let’s test it out! Hi everyone, I’m Stefan, and welcome to CNC Kitchen. Most people may use to set the layer height (Layer Height) To adjust the fineness and surface smoothness of the final product in 3D printing. A smaller layer height reduces printing lines, but increases printing time. In fact, the printing time is inversely proportional to the height of the layer thickness, so the printing layer height is half thinner than the original one. More or less doubles the printing time As most of my printouts, not every one of them has to be very meticulous So for many years I have been asking myself, I want to print out better parts strength Do you want to use a thicker or thinner layer height? The strength mentioned here is the bonding strength of the printed layer Refers to how strong the material bonding between each independent layer and layer is But I also analyzed the sample printed while lying down To understand whether the height of the floor also affects its strength If you have conducted research on the Internet, you will find some contradictory results Some claim that the thinner layer has the highest strength, while others claim that the thicker layer has the highest strength. A thinner layer height may be stronger because the molten material is squeezed out more from the nozzle And because the distance between the nozzle and the upper layer is small Will heat up to the previous layer of material during spraying to help it bond In addition, since less plastic is extruded each time, the material has enough residence time in the nozzle Make it longer in the melting zone, so it can be heated and melted appropriately and uniformly. In addition, parts with higher thin layers have higher density because the printed materials The gap between the layers is small There is also a very interesting traffic calculation article on the Slic3r wiki How to calculate the amount of material extrusion, I left a link below Although there is an argument that the material stays in the molten state for a long time It will degrade the plastic, and make the parts with thicker layers have better strength. When printing thicker layer heights, the Z-axis positioning tolerance will not have a big impact Because its tolerance accounts for a smaller percentage of the total thickness This means that, for example, the tolerance of 5 microns (Z-axis positioning tolerance) under the 0.05mm layer height will be very large And may lead to ±10% over-extrusion or under-extrusion. With a layer height of 0.25mm, a tolerance of 5 microns (Z-axis positioning tolerance) gives you only a difference of ±2%. Then in terms of statistics. Use a thicker layer height for printing, and there are fewer layers for objects of the same height. This reduces the risk of problems in one of the layers And that layer may be the location of the strength problem This concept is also called statistical size influence. Longer chains have a higher chance of failure than shorter ones Because the more joints of objects of the same height, the greater the chance that one of the layers is particularly “weak” I have written several articles and reports on the same subject, if you are interested in this You can read further below. In order to answer this question for yourself, which layer height has the highest intensity? I printed dozens of test hooks with different layer heights and directions And test it on my DIY universal testing machine. If you like this type of research, please make sure you have subscribed I entered the channel and clicked on the little bell, because there are still four-fifths of people watching Haven’t followed the channel yet! You can also consider supporting my work on Patreon, which can help me spend more time on this topic The test settings are as follows: As the test pattern, I used the test hook pattern I have also used it for various other researches in the past For me this is a general test part, where the key parts are under tension and bending Therefore, it can measure more realistic working conditions than standard test samples. I did not use the standard tensile test pattern because it is difficult to print standing up In the previous printing, I found that it has a lot of scattered problems, maybe because of the tested machine Some misalignment occurred, but it’s not bad for the print test hook Because it will adjust itself. All parts are used on my original Prusa machine, and use the hardened Prusament PLA i3 Mk2.5 steel nozzle and its initial settings. I chose this material deliberately, because Prusa claimed that the wire diameter of this wire is very accurate after researching. Therefore, the flow rate should not actually change, thereby eliminating another variable in the experiment. I chose the standard 0.15mm preset in Slic3r PE to set 3 outer rings, and then only changed Layer thickness height and adjust the top and bottom layer thickness to make the sample have a consistent wall thickness I finally tested 6 different layer heights 0.05mm, 0.1mm, 0.15mm, 0.2mm, 0.3mm and 0.4mm 50um may be really small, and I have never printed such a thin thickness 0.4mm is beyond the printable range of the same caliber nozzle But I want to see how bad the result is Before proceeding, please click on the info card to vote in the upper right corner Come to find out which floor height you think is the strongest, and leave your thoughts and comments on why this one is the strongest. For standing printing, I print 3 at a time as a record each time And let the layer have enough time for the material to cool down during the printing time. I also want to print all lying samples at once. If you don’t know, you can actually print samples with different layer heights in the same print job. However, there are some clogging problems when printing at a layer height of 0.05mm So at the end, I separated it for printing. As mentioned at the beginning, the printing time is inversely proportional to the layer height But the first interesting result after printing is: not all hooks are the same weight. The higher the layer height, the lighter the part weight, which may explain The fact that higher thickness layers have larger gaps and therefore lower density. We remember this result in order to follow the strength test. Another interesting result is the quality of printing He did not improve the print quality due to the low layer height as he thought Of course, the sides usually look better because the layer pattern will be smoothed high, but in general, I think the best printing layer height is 0.15mm, the convex corners look the best, and the bridging effect is also great Another thing I noticed is that the color of the parts started to become irregular Especially when the layer thickness is 0.05mm This may be because the material remains molten in the nozzle for a long time High temperature causes deterioration of pigments and even base polymers. I put all the samples into the DIY universal testing machine one by one for testing, It is very important that all tests are loaded at the same speed until the sample breaks, and the load value is recorded at the same time First of all, let’s start with the test lying on the printed sample, the adhesion between the layers actually only plays a minor role in the load bearing of the sample I initially thought that there should be no significant difference in this printing direction. I was wrong, because even samples with a layer height of 0.05mm to 0.2mm are broken in the range of about 80kg The 0.3mm sample is considered to be broken very early, not to mention the 0.4mm hook. If we look at the weight value of each sample, I define it as the failure load According to the load-bearing value of the sample, the images (weight and load-bearing) of the two are very similar, only the thicker layer thickness becomes Better, because of their weight reduction. The fracture surface of the sample is also very interesting, because for thicker layers The gap between the lines is clearly visible, The thinner the layer thickness, the more the cross-section resembles the injection molded part. So the first result is that even if the bearing point of your part is not between layers, You should not print with a layer thickness above 0.2mm, because that will reduce the strength of your parts Next, we will conduct a more interesting investigation, the adhesion between layers Use the standing print hook for testing. First of all, all parts are almost broken at the same height, which means that no serious errors occurred during the printing process. Problems leading to premature breakage It can still be clearly seen that all samples are perfectly broken between layers, So the adhesion between the layers is a major weakness, I honestly say, in other brands of PLA materials I have seen better bonding strength results in the past. In addition, if we take a closer look at some samples, we can see signs of insufficient extrusion, It means that the printing process is not 100% perfect. This may also cause us to see some scattered results. Very similar to the previous test sample, the strength is the best in the layer thickness between 0.05mm and 0.2mm The result at 0.15mm is the strongest, then the strength drops rapidly At 0.3mm layer thickness, the load-bearing capacity is quickly reduced to half, And there is almost no load bearing effect when the layer thickness is 0.4mm Even the weight standard value is helpful for thicker layer thickness samples The last is to display the same image result. However, all test strength results are less than 50% of the strength of the lying sample This shows that we do have some non-uniformity in materials. I used it in one of the papers linked below, and I think it has a better comparison value for layer thickness Because they are compared with the nozzle diameter and the thickness between layers This allows us to summarize the results a little bit better Because not everyone uses 0.4mm nozzles. Applying it to our test results means, The strength of the part will start to weaken from the layer thickness of more than half of the nozzle diameter This means that for the strongest printing effect of the 0.4mm nozzle, the layer thickness of 0.2mm may not be exceeded. Interestingly, I thought the performance would be worse if the thinner layer was thicker this is not the truth Therefore, even if we have seen the color change of the material, The resin itself has not deteriorated. And, at least for “Prusament” PLA The thinner the layer thickness will not cause better adhesion between layers What do you think of these results? In addition to the layer height, there are many parameters that affect the strength of 3D printed parts Especially for layer-to-layer adhesion. The most important thing is the material itself, I have tested many other materials I also checked the adhesion of the layers, which can make a big difference. Then there is the printing temperature. I have tested it for nearly 2 years. You can watch other videos if you are interested. Other important parameters may be printing speed, extrusion width and part cooling I may test it in a future video. If you have other ideas, please leave a message below! Thank you for watching! This test took much longer than expected. I still hope you enjoy watching it and learn new things. Please leave a like and make sure you are subscribed to the channel. If you want to support my investigation, then you can consider sponsoring or Help me in other ways. You can also take a look at other videos on the channel, there are also some interesting researches! I hope to see you again next time! Before that, there will be a period and goodbye!