Practical 3D Printing: Structural Print Settings

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Structural Print Settings

09.09

00:00	In the previous module we discussed the temperature settings of the printer and the effect that these have on the quality or success of the print.
00:07	In this module we'll discuss a few more settings related to the print quality but also the structural properties of the printed part.
00:15	We'll start with layer height which plays a large role in the print quality.
00:19	The name itself is pretty self -explanatory.
00:22	This is the height of each layer as it's printed onto the bed or the previous layer.
00:27	This is typically between 0.1 and 0.5 millimeters and each printer will have a maximum and minimum value that should be considered.
00:35	This is typically between 0.1 and 0.5 millimeters and each printer will have a minimum and maximum value that should be considered.
00:44	The layer height is controlled by the flow rate and the print speed and of course the z -axis movement as the printer steps up each layer.
00:53	Think of this like the vertical or z-axis resolution.
00:57	A lower layer height will result in more resolution and a smoother surface finish.
01:02	Each layer will be less obvious but there will be more layers needed to build up the part so the print time will also increase.
01:09	The x and y axis resolution are controlled by the nozzle diameter but this can also influence the layer height which usually needs to be within 20 to 80 percent of this diameter.
01:20	The layer line or extrusion width is also an adjustable setting but the best results usually come from this being relatively close to the nozzle diameter so this is best controlled by changing to a different nozzle.
01:33	Back to our main focus.
01:34	While a lower layer height will typically increase the print quality, it does also provide more chances for issues to creep in especially because finer layers require more precise calibration and bed leveling which is something that we'll be discussing soon.
01:49	This should be selected based on the application for the part and the desired outcome.
01:54	Keeping in mind that while a lower layer height will increase the print time, it can also reduce the need to finish the part by sanding it smoothly in some cases.
02:04	So,me printers and slicers can actually vary the layer height continuously to adapt to the geometry of the part and get the best of both worlds.
02:12	This is because in some cases, the layer height won't have an effect on the appearance or print quality, like when the walls of the print are more or less vertical.
02:22	Finally, in regards to the layer height, this can have an effect on the strength of the finished part.
02:28	But there is some contradictory information here as it depends on the printer, material and geometry of the part.
02:34	Basically, greater layer height can provide more strength due to more material on each layer and less chance of layer to layer adhesion issues.
02:43	However, it can also be argued that more resolution and accuracy can provide more strength with a more uniform geometry.
02:51	So, it's a case by case basis and realistically, the other factors we're about to discuss have much more bearing on strength.
02:59	The first of these is the shell thickness, or in other words, the number of wall loops making up each wall of the part.
03:06	The term wall loops is a common one in FDM printing because the printer lays down the material for each layer in a kind of loop, tracing the profile of the walls of the part.
03:17	Each loop builds up the thickness of the walls or shell.
03:21	So, the actual shell thickness is a function of the extrusion width and the number of wall loops, while the area between the inner sides of the walls is the infill.
03:31	For the same overall section thickness, a greater shell thickness and number of wall loops will result in less space requiring infill.
03:39	In some cases, like on thin sections, there may be no requirement for infill.
03:45	The density of the infill is expressed as a percentage, where a hundred percent would be a completely solid infill, essentially just wall loops until each side meets.
03:55	As more wall loops and higher infill density will result in a more solid part, this usually makes the design stiffer and in some cases stronger, however it really depends on the design.
04:07	The infill density will usually be lower than 50% in most cases though.
04:12	This not only helps reduce material usage and print time, but also reduces the weight of the part.
04:18	As you can see, the settings depend on our application.
04:22	For example, a simple prototype that doesn't need to be strong may only need two wall loops and 10% infill to do its job.
04:30	But something more demanding might need five or more wall loops and 30 to 40 or 50 % infill.
04:36	The structure of the infill is another setting that we have control over and it's not uncommon for there to be over 10 options here, so we won't dig into each one.
04:45	The names again are somewhat self -explanatory in describing the structure or shape of the infill in each section.
04:52	Some more complex or basic than others, resulting in more or less strength and print efficiency.
04:58	The seams are another thing to consider when discussing wall loops.
05:02	As each loop for each layer is printed it has a start and finishing point.
05:06	Where these points meet and step up to the next layer form a seam and how these seams align layer to layer can be adjusted.
05:15	For example, we can have them distributed randomly which can look like lots of little pimples on the part.
05:22	We could line them up layer by layer which forms a ridge along the surface.
05:26	I personally like to line the seam up and then change its position to a face of the part that won't be as visible if possible.
05:34	Moving on, we've mentioned support previously which is required to print overhangs.
05:39	The threshold angle determines at what point the overhang will require support and this is typically around 30 degrees or so.
05:47	The structure of this support can also be adjusted like the infill structure, although the options here are usually just normal, which is a basic block like support, or more organic tree like support that branches out and helps reduce material usage.
06:03	In some printers it's also possible to use a different material designed specifically for the supports.
06:09	This should have a similar extrusion temperature to the main material that's being used but will usually be cheaper and easier to print, while the surface finish is less critical as it'll be removed after.
06:20	In some cases it's possible to avoid support and use bridging.
06:26	If done correctly this is achievable for small areas without any sagging of the overhang.
06:32	The slicer will have some built in functions and settings for this and as always some experiment can be used to fine tune the results.
06:40	In basic term the printer needs to move more quickly over the gap for the first layer and cool the material faster.
06:47	If the material is too hot and takes too long to cure it'll sag.
06:52	Finally, let's discuss bed adhesion features such as brims, rafts or skirts.
06:58	Starting with the most basic being the skirt.
07:00	This is simply an outline around the section of the part on the print bed that doesn't actually touch the part.
07:07	The purpose of this is to help the extruder and nozzle establish a smooth flow of material and we can also watch this to detect any potential problems before the print begins.
07:18	Next, is the brim.
07:20	The brim is essentially just a skirt that also extends to touch the edge of the part.
07:24	This serves the same function as the skirt but can also help aid in bed adhesion and prevent warpage.
07:31	A raft on the other hand, as you might have guessed, is a structure printed on the print bed that the part will then be printed on top of.
07:39	Again, this can help with bed adhesion and warpage but also provide support for parts with a small footprint.
07:47	Essentially creating a strong foundation for the part.
07:50	Past these settings that we've discussed, depending on the printer and slicer we're using, there might be minimal settings we can adjust, or there could be a seemingly endless amount.
08:01	We've covered the bulk of them here and while this has been a somewhat introductory look at what they are and the effect they have, we'll be having a deeper look into them in the practical section of this course.
08:12	So, let's recap the main points we've covered.
08:15	The layer height is essentially the z-axis resolution.
08:20	And generally a smaller layer height leads to better print quality, although the print time will increase, so the choice here really depends on our application.
08:29	The shell thickness and number of wall loops and the infill structure and density have the most effect on the structure of the part.
08:36	More of each leads to a more solid part but more material usage and weight.
08:41	The seams at the start and finish of each loop can be positioned with aesthetics in mind.
08:46	And supports used to allow for overhangs, the structure of which can be tailored for efficiency, although in some cases bridging may also be possible.
08:56	Skirts, brims and rafts can help establish material flow, help with bed adhesion and prevent warpage while providing a foundation to build on.