The second part of this series will focus on creating models that print well and it will also discuss the most important settings you can change in the slicing and printing software to make sure that your prints turn out the way you want them to.
3D modelling, slicing and printing software
Design with the manufacturing method in mind
This is true regardless of the manufacturing method you choose. However, due to the nature of 3D printing, where one layer gets put down on top of a previous one, the parts will be the weakest where the layers meet. Finished parts are much more likely to break along these seams.
This limitation is defenitely something you’ll have to consider when designing a part for 3D printing, especially when you want to print strong, functional parts. Let’s look at the following example:
Fig. 3 displays a functional part that I designed. There’ll be a significant force pulling the part upwards during regular operation conditions. If I printed the part oriented like this, it’s likely to snap sooner or later. Therefore, I needed to make it larger than absolutely necessary so that I could easily print it oriented differently:
You should make sure, that the area, touching the print bed, is large enough so that the whole part will stick nicely and won’t fall over when printing.
Determining the correct layer height
Once your design is ready, it’s time to slice the model. One important factor, that I used to ignore quite happily, is the layer height. I never thought, that it’d make such a huge difference. I knew, that smaller layer heights make for higher quality prints, but I didn’t know how important this setting is for successful prints in general.
I had huge problems printing PETG: The material oozed out, or it didn’t want to adhere to previous layers properly or the nozzle keept clogging. I learned, that the layer height shouldn’t be larger than roughly 80% of the nozzle diameter. So I changed my nozzle to a 0.6mm one and the layer height to 0.4mm and just like that I never had a print fail because of a clogged nozzle or oozing filament since then.
Therefore remember: If your layer height is too large for your nozzle, it might get clogged.
I don’t think there are general numbers that I can give you here that’ll work with every printer and model. However, I can tell you, that you need to find the right balance and you’ll get a feeling what that means.
You shouldn’t print too fast though. I usually print the first 3 layers with 75% of the speed of the others. Furthermore, I use really slow speeds (15mm/s) for very small diameters and small support material.
However, you shouldn’t go too slow either, otherwise the filament remains in the hot area of the print head for too long and it might start to get destroyed due to the heat (especially PLA). It the looses some of its properties and it might not get printed properly or it might end up clogging the nozzle.
Choose the right Infill value
This is an important setting. A general guideline: If you want very strong, functional parts, you should go with a rather high value, like 60% or up to 75%. I, however, wouldn’t go higher than that. You not only use a lot of material that way, your prints will also take forevery and the printed parts are more prone to warping, especially later in the print.
I acually found that with certain materials, like PETG, a 20% infill was more than enough for functional parts due to the material’s high flexibility.
I usually try to print all parts without support material first. However, sometimes it’s just not possible at all or the printed parts don’t look that good. For example: My most recent project required me to print a decagonal prism (a fancy name for a 10-sided cylinder):
I couldn’t rotate it because it wouldn’t have fit into the printer that way. So as you can imagine, it was a pretty hard to print part due to its size and shape. The overhang on that one forced me to use support material.
So you should definitely use supports whenever you have large overhangs and a small base the object stands on. Furthermore, support material helps to increase the print quality in many cases
Skirts and brim
A skirt is a wall around the object you want to print. The brim is made up from layers of support material underneath the main object.
Both can help when your prints start to lift off during longer prints or when the material doesn’t want to adhere to the print bed.
However, even without those problems, you should always add at least one layer of a skirt to the print job. This will make sure, that the extruder is properly primed (which means that the filament is present at the nozzle) and you won’t have any holes in your first layer.
As you can see, there are a few things you can do to ensure that your model prints well. The most important factor is the slicing software. Make sure, that the settings are appropriate for your model and printer. Don’t try to print too fast but don’t go too slow either. If you’re having problems with warping or sticking, these settings might help you too.
Table of contents
Part 1 – Basics, Maintenance and Cleaning
Part 2 – 3D modelling, slicing, and printing software (You are here)
Part 3 – Choice of material, layer adhesion, and warping
Part 4 – Removing the printed parts
Part 5 – Short summary and cheat sheet (Not published yet)