Nathaniel’s guide to high-detail printing
A lot of people have asked me recently how I make extremely high-detail prints, such as this little gnome house:
Using a better firmware (Marlin) and a gcode generator that creates more sensible paths (Slic3r) are the first two things you absolutely must do. Without using both Slic3r and Marlin, you’ll struggle to print your perimeters at more than about 25 mm/sec without seeing severe blobbing on corners and arcs. Let’s assume you’ve followed my advice in Getting all the pieces to fit together and you’re using Marlin and Slic3r. Excellent! Let’s get started.
Low layer height
Layer height is the primary setting that determines the surface detail of your print. The lower the layer height, the greater the “resolution” of the print. A 0.3 mm layer height will display visible layers, while at 0.2 mm layer height, the layers will begin to appear smooth with certain filament colors. The gnome house above was printed at 0.2 mm layer height in silver PLA, which is very forgiving of surface blemishes. Black PLA is similar, and translucent blue PLA is even more forgiving, but white PLA needs lower layers and perfect layer alignment before they need to disappear; 0.15 mm layer heights and below, usually.
As for your nozzle diameter, the truth is, the relationship between your nozzle diameter and your layer height is a very loose one. A bigger nozzle lets you print with a slightly higher layer height, but doesn’t really constrain you that much when you want to decrease it. This is because the nozzle diameter merely determines the width of the extrusion that comes out of it. Even a fairly wide extrusion should react fine to being smooshed down on top of the previous layer. To sum up:
Larger nozzle (0.5 and above):
- Taller (and more visible) layers possible
- Greater maximum speed is possible
Smaller nozzle (0.35 to 0.4)
- Shorter layers (< 0.1 mm ) possible
- More contour on extremely short layers possible
One thing I’ll mention is that I do not recommend a 0.25 mm nozzle. That small of an opening makes it a real challenge to print quickly, and can lead to jams. I really like a 0.35 mm nozzle. I can get great high-detail prints, but I’m also able to print infill at 120 mm/sec without the extrusion getting too sparse. If I go much faster than that, though, I can see it start to string out. A 0.4 or even 0.5 mm nozzle would be better for higher speeds than that, but my focus is maximizing speed given a certain quality I want to achieve, so I’m more than happy to sacrifice a bit of potential infill speed so I can get the benefits of a lower potential layer height. Perimeters, of course, are printed much slower than 120 mm/sec to ensure good surface detail and layer alignment. Which leads me to…
Only maximize speed for the desired quality
In the beginning, I was so excited about pushing my printer faster than I sacrificed quality to ramp up the speed, going as fast as 65 mm/sec for the perimeters on this building. Now I know better. It’s far more sensible to pick a desired quality level and then maximize the speed without diminishing the quality.
Once you have a desired quality (say, 0.15 mm layers), you can set about increasing the speed until you start to see diminished surface quality. The exact speed you can achieve for your target quality will vary from machine to machine, so you’ll need to do some experimentation. Here are some tips:
- Print hollow if you can. This really saves time and filament, and more models than you think can be printed without any infill at all. The real challenge is for models with flat tops; those flats need good bridges. But that’s not too hard if you make sure to keep your number of solid layers at 3 or more.
- Print infill faster than perimeters. After all, nobody sees the infill! If you can’t print hollow, you can increase the infill speed all the way until the extrusion get stringy and begins to lose its structural integrity. For me, with PLA and a 0.35 mm nozzle, this is about 120 mm/sec.
- Don’t print infill for every layer. Again, if you can’t print hollow, this is another good alternative. Skeinforge calls this “Skin”, but Slic3r uses the “Print infill every n layers” setting. Make this 2 or even 3 if your layer height is really low or you have a big nozzle.
- For PLA, use a fan. PLA needs more time to cool than ABS, so the faster you go and the hotter your nozzle, the more imperative it is that you use a fan to cool the extrusion after it hits the previous layer.
- Increase your first layer speed by moving the nozzle closer to the build platform. The only reason you need to go slow for the first layer is to ensure good adhesion. You can also get this by moving the nozzle closer to the platform, ensuring that the extrusion is really smooshed down. But don’t go too close or it can be tough to get the print off the platform!
Once you’ve got good prints with all that, there’s an additional piece of the puzzle that lets you increase the speed even more: a rigid frame. No matter how you slice it, the Prusa Mendel isn’t an especially rigid machine along its X axis. The faster I go, the more I can see the frame triangles wobbling back and forth. That won’t do! There are band-aids such as this brace but a better design is really needed. That design is the MendelMax. I’ve finished my MendelMax’s frame and axes, and the thing is rock solid. Even at very high speeds, I just don’t see it bending or wobbling at all. So get yourself a MendelMax!