Why aren’t all 3D printers large? The answer is very simple and is based on that fact that as model scale increases linearly, volume increases exponentially. For example, a 2″x2″x2″ cube has a volume of 8 cubic inches. However, when the model is doubled (by simply “scaling” the model in Slic3r) to 4″x4″x4″, the volume increases to 64 cubic inches. This is an 8-fold increase in printing material and time for only a 2-fold increase in external dimensions! In other words, your original print may have taken 20 minutes to print, while your double scale model will now take almost 3 hours. Therefore, 3D printing large models can take some time.
Unexpected Things Can Happen When 3D Printing Large Models
With increased print time comes other, previously unknown problems. For example, is your printer capable of keeping it’s calibration for extended periods of time? Does your printer sometimes skip steps? One skipped step half way through the print will ruin the job. This is especially true in architectural models. The model below was a 20 hour, high precision print on an AW3D XL model printer (at approximately 900 layers)!
One skipped step (where the stepper motor incorrectly positions the hot end or printed surface) would have been fatal! Skipped steps can be caused by a number of factors, most of which are related to machine design and firmware calibration. If the stepper motors are not sized sufficiently, they will tend to overheat and skip steps. If the acceleration is not set correctly in the firmware, the printer, no matter how strong WILL skip steps. This is why it is critical to choose the right 3D printer loaded with the correct firmware. While Marlin and Repetier are great starting points (we use both in our printers), it is absolutely critical that these firmwares be specifically set up for the particular 3D printer model (taken into account gear sizes, motor capacity, frame rigidity, etc.). Had your 3D printer been susceptible to calibration issues, the towers would have come out crooked, maybe even like the Leaning tower of Pisa:
3D Printing Materials
Assuming you have a strong machine, the next focus should be material. If you want to go big and erase the possibility of cracked parts, you NEED to go with PLA (at least for now). ABS is more susceptible to cracking as the print grows (because of its propensity to “shrink” when cooled) and when you go much over 4 inches in height without enclosing the printer, you may get cracks in your print. Stick with PLA for the best quality large prints:
Good Quality PLA for 3D Printing Large Models
PLA is PLA though, right??? The answer is absolutely NOT. PLA varies from vendor to vendor and color to color. Moreover, there are some fundamentally different forms of PLA. One well known version is 4043D. This can appear almost like ABS-like in appearance. This is a very popular form of PLA and is supplied by several well known vendors. This material tends to be consistent and predictable. On the other hand, vendors like Matter Hackers and The Future is 3D carry what is thought of as more traditional, translucent-style PLA. This second type of PLA is very forgiving for 3D printing large models and small prints alike. Meaning, at least with the AW3D series of printers, there is little to no need to run a fan setup. Conventionally, fans are used to cool the hot end so the PLA does not overheat. There is less of a need for this when running the translucent-style PLA. While fans are almost always beneficial, when you need absolute reliability in these long prints, the chance of a broken fan ruining a print is, in some cases, too big a risk to take. In that case, use translucent-style PLA for an extra margin of safety. In addition to reliability, it looks great!
Using the Right Software
Another area of importance is your choice of host software. While we enjoy using Pronterface for making most of our parts because of its easy-to-use interface, we use Reptier Host for ALL of our big prints. Why? Because Repetier Host allows you to control the speed of the print and the flow rate of the hot end DURING THE PRINT. This is an incredible time saver! Let’s face it-none of us are perfect. Evidence of this is our frequent need to “reslice” parts to get the proper speeds for print. Too slow, and simple prints can keep you up until 3 am! Too fast, and simple prints may become a gooey mess. Striking the right compromise takes time, skill, and a lot of practice. Repetier Host is a shortcut – it allows you to correct things such as speed, temperature, and flow mid-print. Want to go to bed at midnight, tweak Repetier to speed up the print. Have all weekend to get your print perfect? Slow it down through Repetier.
Good luck, and may the force be with you!
This white paper reviews the technical requirements for large format additive manufacturing of parts in acrylonitrile butadiene styrene (ABS) material with fused deposition modeling equipment. Read the white paper to learn:
- Heat requirement
- Power requirements
- The math behind nozzle size