We continue our quest to experiment with a wide variety of materials for 3DP. This story starts almost one year ago. While teaching our Advanced RP/RM (rapid prototyping/rapid manufacturing) course, I was discussing the course requirements. One our of requirements is an independent research project and report to be undertaken in teams of two (the project is worth 40% of your grade). As an instructor, I would ask the class at every meeting if they had any ideas for a project.
One of the teams (composed of Juliana Meira do Valle and Michael Storey) approached me after class, “We would like to print in bone as our project!” Juliana is a DXArts/Art major and Michael is a Mechanical Engineering major.
“We’d like to print in bone!”
“I want to print bones or animals that never existed!” “Do you think it’s possible?”
“How do we get started?”
“We’ll need to find the material in the correct powder size and then you will start bench testing it”
It took a couple of days of internet searching to find a supplier of powdered bone and then came the interesting questions.
“Where did the bone come from?”
“Wow, it’s food grade.” “Why would you eat it?”
After we located a good source of powdered bone meal (start with your local health food or vitamin store), they started bench testing the bone with an array of adhesive powder and various binder solutions. This process took place across a five week period. Each week a different set of adhesive ratios was tested against our existing binders. Success!!!
Initial Bone Recipe
Powdered Bone Meal — 5 parts by weight.
12x Powdered Sugar — 1 part by weight.
MaltoDextrin —- 1 part by weight.
We loaded up the 3D printer with a bone powder mixture and used an existing binder solution. Let’s just say our first 3D printing tests were not terribly successful. The parts were so weak that any contact caused crumbling, and we could not remove the parts from the powder bed. However, the bone powder mix spread extremely well, produced a nice surface finish on the printing-bed surface. The parts needed to be strong enough to survive general human handing, depowdering, and post processing. Finally, really results!
But WAIT! After the first parts were printed, there was a long pause and a sigh heard from Juliana.
“I don’t know what to do here.” “I don’t know how I feel about touching these parts.”
“I’m a vegetarian!”
As time has passed in our lab, we’ve found some more interesting (and aggressive) adhesives – namely Urea–Formaldehyde (UF) glue. A urea formaldehyde resin or glue (also commonly called a urea glue or a UF) is also called “plastic resin glue”. This product is sold as a water soluble wood glue. A quick test with bone powder has shown that very strong parts can be produced using UF.
Secondary Bone Recipe
Powdered Bone Meal — 4-5 parts by weight.
UF plastic resin glue — 1 part by weight.