12. Molding and Casting¶

Assignment¶

For this week, we were assigned to mold and cast a design. By my node leader, Mr. Dubick, we were assigned to 3D print a mold on a resin printer, a Prusa 3D printer, and mill it out as well. This mold will then have the mold for our desired final product casted in it, so that the mold for the final product will be made of a more sustainable material.

3D Printing a Mold¶

For my 3D printed mold, I decided to create a chess pawn, as this would be a design which utilized the benefits of molding and casting, while remaining relatively simple.

Designing¶

To create the initial mold, I used Fusion360. I created a box which I shelled out, then imported an 2D image of a pawn. I centered this image in the box, used the spline tool to trace half of it, and, after some difficulty arising with the trace not appearing as a selectable profile, was able to revolve it around 360 degrees in order to make the 3D pawn. I moved this pawn to the correct position, and ended up with this:

However, I soon realized that there would be no way for me to pull out the final pawn from the mold created from this mold. To fix this, I split the box down the middle and added walls so that I could simply pull these two pieces apart when the final product was ready. I also decided to change this to a 2 step mold for the Prusa printed mold, and would do a 3 step for the milled one. It then looked like this.

Resin Printer¶

I printed this my 2 step design on the resin printer in our lab. I go more in-depth about the process to use this printer in my Week 5 Group Documentation, but basically I just used the software for it, printed it, and then washed it. When I went to cure it, the print stuck to the build plate, and stayed stuck even after multiple wash cycles. I eventually had to melt away a corner of it with a heat gun at 400C for a while before I could pry it off the plate. After curing this, I had my final product:

Prusa Printer¶

I also printed this design on a Prusa printer, which I am very familiar with, so this was fairly easy.

Casting Printed Molds¶

I used Mold Star 15 B Slow to cast the 3D printed molds, both resin and filament. I mixed the A and B in a 1:1 ratio as instructed by the data sheet. I continued to stir them together before pouring the combination into the molds. With the holes and extrusions I made one each one, I was able to easily fit them together. Thus, immediately after I poured the Mold Star into both sides, I smushed the two sides together (for both the resin printed and the prusa printed molds) so that the final product would be one, solid piece. I first sprayed this quick release so that each piece would stick together rather than to their respective molds:

This is what the pours looked like separate and then together (with the prusa printed one as the resin mold underwent the same process):

This is the outcome for both:

CAD for Mill in Fusion360¶

To mill my mold, I first inverted my fusion file so that it would be a 3 part mold rather than my previous 2 part molds. This is what that looked like after many failed previous attempts:

To create the actual mill file for this design as I did the previous ones, I navigated to the manufacture tab in Fusion360 and followed this workflow to create two passes, a roughing and a finishing. After creating my setup, I chose a 3D Adaptive Clearing for my roughing pass and a 3D paralell for my finishing, selecting 1/8” ball end mills for both. At first when I tried this, it milled two far down for the first layer and the wax came off of the bed, but after I decreased the step over it worked much better. This is what the two tool paths looked like:

I then milled them on the large Bantam milling machine we have in the lab. This is what it looked like after the roughing pass and then after the finishing pass:

Creating Mold¶

I then had to create a mold to cast the final product into. After trying to do this with a material that ended up being too malleable to into, I used Task 8, a material which undergoes an exothermic reaction and hardens (is described in greater detail in group assignment). After a few failed attempts (due to sticking and other problems), I had the final molds after using a band saw and sanding to clear away excess.

Final Cast¶

After many iterations, I finally casted a pawn by pouring the Task 8 into each side after it became viscous enough to not all fall out when I tried to put the two pieces together, pressing them firmly together so that none would solidify between the two, and quickly thereafter removing the cast before it solidified into the mold.

Week Reflection¶

This week I learned about different moulding and casting materials, their benefits, and applications. Overall, it has the same general applications as 3D printing, only moulding and casting allows for greater variability in materials, from the more flimsy Mold Star 15 Slow to the the more rigid and stable Task 4.

File Downloads¶

To view my files used in this week’s processes, use this link.

Last update: June 27, 2024