There is always that debate: which 3D printing technology is best for home/small business use? Is it stereolithography (SLA), like that found in the Formlabs Form1+ 3D printer, or is it fused deposition modeling (FDM), like from the MakerBot Replicator line of 3D printer? There is no precise answer. It really depends on what you need 3D printed. Usually if you want a more detailed print but don’t require a very large build size, SLA is the technology of choice. On the other hand, if you prefer a printer that can print larger items, but you are OK with sacrificing a little bit of detail, an FDM printer would probably be preferable.
One man in Italy, named Mattia Mercante, didn’t allow build size to create any obstacles for him in using his Form1+ SLA-based 3D printer to create a rather large sized bear.
Using an incredibly detailed model from designer Bogi Piroth, Mercante took it upon himself to use his Form1+ 3D printer, which only has a build area of 12.5 x 12.5 x 16.5 cm, to 3D print a 33 cm tall bear. Typically, objects as large as this would be reserved for printing on FDM-based machines such as a MakerBot Replicator or an Ultimaker 3D printer. However, Mercante elected to be a bit different and attempt to create this large bear on his Form1+.
“My goal was to test the Form1 machine with big pieces and check how good it manages those sized pieces,” Mercante tells 3DPrint.com. “The machine isn’t projected for large prints, but more focused on small prototyping parts, jewelry, miniatures, etc..”
The file for the bear needed to be optimized for printing, so Mercante used the .ZTL (ZBrush) file to merge all of the sub-tools into one mesh. He then had to convert all of the surfaces into closed volume surfaces, using re-topology and re-meshing tools. He also wanted to have a separate podium for the bear to stand on, that would be completely removable if desired, so he had to design two blocks that would go under its feet.
In order to print the relatively large sized bear on a printer with a minimal build volume, Mercante had to break it up into seven separate parts: the head, chest, lower body, two arms, and two legs. He also had to take into account other issues that could arise.
“Take in mind that [it] is too hard to print full solid volumes that have large surfaces because [of] the adhesion and vacuum effect[s] generated between the cured resin layer and the resin tank during the peeling rotation steps [of the print process],” Mercante explained to us. “This means that the cured resin could be detached from the metallic building plate and stay stuck on the silicone tank layer (where the laser cures the resin).”
In order to ensure that the bear’s parts would print correctly, there were quite a few steps involved. He created a 2mm wall thickness in order to avoid the vacuum and adhesion effects during the printing process. This saved him on resin as well as time. He also created larger borders along the edges where the pieces would be glued together.
“Because the parts are holed, the bigger risk is to create an empty closed volume inside the objects,” he explained. “The air inside will create a strong vacuum effect after every layer is created, so it is important that the air can flow during printing. For the head, arms and legs, there are other problem[s] to keep in mind. Because the final layers close the shape, the main risk is [that of creating] a ‘cup’ that [would] keep the uncured resin inside. Because of that, I created small holes in some precise places in order to let the resin flow down, in the tank, during the job.”
The parts of the bear were printed at 100 micron resolution, taking a print time of 56.5 hours to complete. The head took 7.5 hours; the chest, 6.5 hours; the body, 10 hours; both arms, 7.5 hours; and both legs, 11 hours. The base for the bear to stand on was too large for the Form1+, so Mercante used his MakerBot Replicator to print that.
The final weight of the 3D printed bear was approximately 500g, and it required quite a bit of patience on Mercante’s behalf. He went through three failed prints before getting it just right, and used an entire liter of resin.
Once finished printing, it was on to washing the pieces in isopropyl alcohol to remove any remaining liquid resin from the cured surfaces. Mercante gave the pieces two separate baths in the alcohol to ensure that all the excess resin was removed. He then used several tools such as sandpaper, small rasps, and a micro motor (i.e., Dremel) to remove the supports and any traces thereof.
In order to glue the pieces together, Mercante used the same resin as the objects were printed with. When combined with a UV lamp, this material is harded and becomes the perfect glue. The UV light also serves to make the surface appearance perfectly matte and bright, making it easier to find all of the little blemishes and small gaps in the print surface. These could then also be filled using the resin.
“Along the cuts, I had reconstructed the shape of the fur’s strands of the bear using a small hard brush and the FormLabs resin,” he tells us. “It is quite easy and fast to ‘sculpt’ with a brush and a laser emitter.”
Once these post processing steps were complete, and the ABS printed base was also processed, Mercante prepared two different acrylic paint colors to begin painting his bear. He used a light grey for the bear itself, and a darker grey for the ground that it stood on. “I chose a warm grey tone in order to have a nicer effect for the fur,” he explained. “When the grey colors dried, I varnished all with matte varnish by aerosol.”
As you can see in the photos provided, the results were quite phenomenal. The bear turned out looking almost exactly how Mercante had envisioned, and the results go to show the potential that a Form1+ SLA 3D printer has in creating larger objects, when done correctly.
What do you think about Mercante’s results? Would you have attempted to take on such a large project or would you have simply used a larger build volume FDM-based 3D printer in its fabrication? Discuss in the 3D Printed Bear forum thread on 3DPB.com. More of Mercante’s work can be found on his deviantart.com profile. Check out some more photos below.
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