Here’s a handy method for quickly creating strong parts using a combination of 3D printing and HMA injection — check out this tutorial by Hunter Nance at MAKE!
Printing a solid object (100% infill) has many advantages, namely strength and rigidity. However, it takes much longer to print with high infill and, of course, takes much more material.
We at Lantern Robotics devised an interesting solution by injecting Hot Melt Adhesive (HMA) into hollow prints (0% infill). HMA, also referred to as hot glue, is a thermoplastic with a melting temperature around 180°C, which allows it to be injected into printed objects without causing them to distort or deform due to excessive heat.
The result is a cheaper, faster printed object that is completely solid, and depending on your shell setting, can be rigid or flexible. Here’s how to try it.
Step 1: Print your object with 0% infill. For our process 3-4 shells is ideal.
Step 2: Drill two holes: one for injections, and one for venting. Make the hole a tight fit for the tip of your glue gun, this allows good back pressure and prevents leakage.
Step 3: Inject HMA into the print until glue seeps out of the vent hole. Let cool.
- This method is best for objects with central voids or large cavities.
- Use a precision metal tip (as pictured). It provides much more control.
- If injecting into PLA use the lowest temperature possible on your glue.
- Isopropyl alcohol breaks HMA’s bond with whatever it is sticking to.
- Keep this in mind for clean-up or if you drip some glue on the outside of the model.
- For larger objects you can drill additional holes.
- You can always add the holes into your design, which allows more precise placement.
- If using outside or in a high heat environment, cover the holes with a bit of ABS+Acetone.