Creating a precise injection mold involves a blend of engineering know-how, meticulous attention to detail, and innovative use of materials. In this guide, I’ll walk you through how I designed and 3D printed an injection mold using Rigid 10K, one of Formlabs’ highest-performing materials, to achieve a beautifully finished part.
Preparation and Designing the Mold
The journey began with the creation of a mold insert blank, a fundamental part of ensuring reliability. This blank was integrated into my shelf support file, making it possible to strategically incorporate air vents based on the air trap locations identified in my simulations. By cutting these vents into one half of the mold at 0.15 millimeters, I allowed air to escape while preventing any plastic from passing through.
To conserve resin, I intelligently designed cavities in the mold halves where no plastic would be ejected. This step was crucial in maintaining the mold’s strength while minimizing resin usage.
Slicing and Printing the Mold
Once both halves of the mold were ready, I proceeded to the slicing and printing stage using PreForm, the slicer by Formlabs. I set up the print job for our Form 4 printer, opting for a Rigid 10K resin at a layer height of 0.05 millimeters. This configuration ensured a smooth finish and high accuracy, especially essential due to Rigid 10K being resistant to the high temperatures and pressures typical in injection molding.
Choosing the best print orientation was a subject of much debate. I discovered that printing the mold at a 30-degree angle across the X and Y axes provided the best results: maximizing flatness, minimizing peel forces, and preventing distortion. This orientation also facilitated easy mold removal without requiring a flexible build platform.
PreForm’s auto-generated supports were largely sufficient, but for parts necessitating extra precision, I manually added supports to cover critical areas. With the job set, the 10 and a half-hour print began.
Post-Processing the Printed Mold
Upon arriving the next day, I was greeted with a fully printed mold, ready for post-processing. Removing Rigid 10K parts can be tricky, as it doesn’t flex but rather chips or shatters if handled poorly. My tip? Use flush cutters to lift a corner of the raft and a scraper to slowly peel the rest off the build platform.
Afterward, I washed both mold halves in slightly dirty isopropyl alcohol to eliminate most of the resin. The molds were then transferred to our unused wash L, which I filled with fresh 99% IPA to remove any remaining resin. A final hose down with fresh alcohol ensured all residue was gone.
Curing and Final Touches
Drying under a box fan took about 30 minutes, after which I placed the molds into our Cure V2. This device exposed them to heat at 80 degrees centigrade for three minutes, followed by seven minutes of UV light exposure. I allowed them to cool down to 35 degrees centigrade inside the cure to avoid thermal shock.
The last steps in this meticulous process involved removing any supports. Rigid 10K makes this straightforward as the supports easily come off. I clipped off residual taller support pips and sanded the closest corner to the build platform with 120-grit sandpaper.
Conclusion
Compared to FDM parts, working with resin components during sanding is truly delightful. After some careful sanding, the insert reached the desired flushness with the aluminum interface. With this achieved, I was ready to move on to the next phase of the project, confident in the quality and precision of the molds I had fabricated. The Buster Beagle Mark III awaited the next step, a testament to the synergy of design and material prowess.
More in this Injection Molding Series
- Can 3D Printing Make Injection Molding Fast and Cheap for Early Product Testing?
- Designing an Injection-Molded Shelf Support: Draft, Gate Placement, and Runner Best Practices
- Printing a High-Accuracy Rigid 10K Injection Mold Insert on the Form 4
- Dialing In a Desktop Injection Molding Machine: Temps, Speed, and Better Shots
