Smaller parts often can be more problematic to print than large parts. This guide provides useful insight into getting the best print quality on those troublesome tiny parts. While we will be using ABS filament with APEX slicing software and an Airwolf 3D EVO 3D printer, these principles should work for almost any machine/software combo that is on the market today.
Small parts can be troublesome due to the small area where heat is radiated from the hot end. Deformation and melted-looking parts are common issues for these types of prints.
First, download the 3DBenchy model found here: Thingiverse part # 763622. https://www.thingiverse.com/thing:763622.
Thing #763622, or the 3DBenchy stl file on Thingiverse is a great model to use in order to dial-in small parts.
This file works well to test printing small parts due to its many different print features that make up the model.
Import the model into APEX and select the Standard print setting for ABS material. Make sure the chamber heat and support material is turned off. You will also want to remove the top cover of the printer and leave the front door open to allow heat to escape. For small parts, we want as little heat build up as possible.
Import the Benchy model into APEX.
By removing the top cover, heat can escape easily from the top of the printer, keeping the chamber cooler around the part. In stark contrast to large parts, small parts need to have some ventilation to prevent deformation.
Save the gcode on to a USB drive, then insert the drive into your printer and print the Benchy GCODE file.
The part will most likely look ok, but could be much better. The hull of the boat will be deformed and the part will not look sharp on the corners. There is much that can be done to improve the print before starting the job again.
This image shows what happens when the wrong settings are chosen for a small part. The side walls are uneven, the bottom of the part looks melted and deformed, and the layers throughout the part look messy.
In the image above, you can see that the hull of the benchy is deformed and warped. This is a direct effect of too much heat being applied throughout the bottom of the part. This heat comes from the bed, hot end, or a combination of both elements.
Switch to FINE settings, then try the print again. You should notice much better results this time around. The main reason is that the head is moving slower, and the part cooling fans are now on. Why does this help? Less heat means less warping and deformation, so the part will look cleaner.
After switching to “Fine” settings in APEX, you should notice the warping on the bottom of the hull is almost gone, although further temperature changes may be needed. The top portions of the print are much cleaner as well – another resulting benefit of lower heat. The arch in the cabin, the hole in the front of the hull, and the roof, in general, are much more refined and cleaner than the previous Benchy printed with “Standard” settings.
The hull in this image looks much better. After using the “Fine” settings, the warping has been decreased, and the detail of the entire print is much more refined.
Bed temperature is also something that changes depending on the size of the part. Once the first layers are generated, the bed temp will drop in order to prevent heat build up in the part. The FINE settings also turn on the cooling fans, which cools each layer while it is printing before the head starts on the next layer.
The cooling fans will turn on for small parts to help with heat build up. This especially helps for fine features.
If the print still looks melted or warped, the part is most likely very small, or has some tiny features within the part. ABS usually likes to print between 240°C and 250°C, but for small parts you have some flexibility. The FINE settings print the part with the hot end set to 234°C with a .5mm nozzle, and 246°C with a .35mm nozzle. The higher temp with the smaller nozzle is to fight back pressure that builds up when printing with a smaller orifice. If the Benchy is looking better, but still needs some improvement, you can try adjusting this temperature to 234°C. Just remember that with the smaller nozzle jams are more likely to occur at lower temperatures. Switch to FULL SETTINGS to change the temperature from something other than what is in the QUICKPRINT menu.
Go to FULL SETTINGS in order to manually change print temperatures.
A .5mm nozzle is a great starting point and, even with small prints, usually works perfectly. But if you are still lacking sharp corners, fine edges, and the small features on the part do not look clean enough, you can switch to a finer nozzle size to achieve these results more easily. Install the .35mm nozzle to get the most detail out of small parts.
Decreasing your nozzle size will allow the printer to print sharper edges, cleaner corners, and more refined details. In Figure A, the nozzle produces a more “rounded” corner on small areas of the part. Figure B shows a much sharper corner after switching to a .35mm nozzle. To illustrate this principle, imagine two cars. Car 1 has a wide turning radius, and Car 2 has a narrow turning radius. Car two will be able to make sharper turns than Car 1. Nozzle size works the same way. Changing to a smaller nozzle, however, does not come without limitations. When using a smaller orifice nozzle, be mindful of issues like longer print times and more pressure buildup in the hot end.
Nozzles made by Airwolf 3D are clearly marked with a number which represents the orifice size. 1mm, .8mm, .5mm, and .35mm are sizes now offered by Airwolf 3D.
Another great way to remedy deformation at the base of a print is to add a RAFT. A raft is essentially a small platform printed under your part, which acts as a “buffer zone” between the hot bed and the part itself. The settings in APEX have been fine-tuned so that the raft is easily removed by hand after printing.
To create a raft, go back to the QUICKPRINT menu in APEX and with the FINE settings selected using a .35mm nozzle, go to PLATFORM ADHESION and select RAFT.
The faint yellow markings under the 3DBenchy model show where the RAFT will be placed. You can preview the RAFT in the LAYER VIEW mode within APEX.
The part is almost completely optimized, except you may notice that the small tower on the top of the benchy still looks a little melted and not refined enough. This is due to too much heat built up in a small section of the part.
In order to prevent this, we must look at the geometry of the model, as well as a setting called MINIMUM LAYER TIME. This setting is essentially a way to force the head to take a set amount of time on that layer before going on to the next. In our FINE Settings, we use “10,” or 10 seconds, for the MINIMUM LAYER TIME. This is a good overall setting, but in some cases, it may have to be adjusted. APEX will also add a COOLING TOWER, or a small rectangular part that prints next to the main part and allows it to cool in between layers. This adds print time, but helps with quality, especially on finer features. APEX will add the COOLING tower to parts 2500mm^2 (approximately 2″x2″) or smaller.
The MINIMUM LAYER TIME setting forces the print head to stay on a layer for a set time before moving on to the next layer.
A COOLING TOWER is automatically added to the gcode for small parts to allow cooling in between layers.
To help visualize this concept, think of a model of a cityscape, with many tall buildings and skyscrapers. Next, think of a pyramid. These two geometries feature very similar properties, such as fine points, but differ in the fact that the cityscape has several points and towers, while the pyramid only has one. The cityscape actually has a major benefit in that when a layer is done printing on one building, the head moves to another building, allowing the layer to cool for some time before being printed on again. The pyramid only has one point, or small area, but this time the head will be concentrating in one area for the remainder of the print. This can cause a large amount of heat radiation and the bottom of the pyramid will most likely look great, but will have a melted look at the very top point. Using the proper MINIMUM LAYER TIME will solve this issue.
The cityscape above is a great example of how cooling/MINIMUM LAYER TIME works during a print.
These images show a print using a MINIMUM LAYER TIME of 5 seconds. The tip of the pyramid appears melted and is not refined.
After adjusting the MINIMUM LAYER TIME to 10, the tip of the pyramid appears much sharper. This is due to the layer cooling before moving on to the next layer above it.
The more parts you print, the more time the parts have to individually cool on each layer before the head comes back around to start the next layer. This obviously takes more time to print, but the quality difference may be worth it. Try this with the 3D Benchy and the pyramid model and you will see even greater improvements.
Printing small parts in multiples is a great way to increase the quality of finer details. APEX now automatically includes a cooling tower on smaller parts to create the same effect.
Speed also can be your enemy with small parts. The general rule is, the faster you go, the more inertia builds up in the head when it stops to change direction. Printing slowly on small parts is highly recommended in order to prevent backlash. If you see that details on your model are not coming out clean, and you already have changed over to a .35mm nozzle, you may want to try slowing down your print speed. Just keep in mind that if you go too slow, your head may spend too much time on a single layer (which in turn generates too much heat), so make sure to adjust your MINIMUM LAYER TIME accordingly.
Printing too fast can cause layer shifting as seen on the pyramid above. Slow the print down to get better results.
A great advanced feature to utilize is the TWEAK AT Z plugin in APEX, which allows the user to change certain settings throughout the print job. A pyramid is a great example of a type of part that would benefit from TWEAK AT Z. For the first 60% of the print, we most likely won’t run into any issues. But what will happen if we don’t make any adjustments towards the top of the print? After previous tests, we know that the print will not be perfect unless we adjust the cooling settings.
The TWEAK AT Z plugin can be found in the FULL SETTINGS within APEX.
With the TWEAK AT Z plugin, you can use the default FINE settings and the print will most likely look great. The reason for this is due to the fan turning on later in the print, as well as the hot end and bed temperature dropping to allow even better cooling. The part fans are pointed towards the part, cooling each layer before starting the next. You can change these settings by entering a height (in millimeters) or a layer number. With the “Tweak at Z” plugin, you can also change things like bed temp, flow rate, and print speed.
Within the TWEAK AT Z plugin, you can change settings like print temperatures, flow rate, print speed, and fan speed. You can set these changes to take place anywhere throughout a print.
Different printers require different settings, and not all software works the same way. Some of the setting names may be a little different, but most have settings similar to APEX, and they all work in similar ways. Airwolf 3D has set out to make 3D printing as easy as possible, but knowing how settings can affect your print is a valuable tool in getting the most out of your 3D printer and software.