Hey everyone! For the final project of the class, we created 4 custom chess pieces using advanced molding techniques. We combined different manufacturing skills through strategic use of 3D printing, CNC machining, and precision molding. 

CAD/CAM 3D Planning:

For the first part of our project our goal was to create a 3D printed part positive so that we could create our mold and begin casting later on. But, before we could do this we had to create our design. We chose our design of a roblox “noob” character and found the design on Thingiverse. Link to our design: https://www.thingiverse.com/thing:1069299. 

After choosing our design we had to use the platforms Meshmixer and Solidworks in order to utilize CAD so we could process an STL file of our design. First we went on Meshmixer so that we could cut our piece in half and clean our stl file. Our next step was to move onto Solidworks to add a base to our piece so we could create our molds easier. Originally we designed our piece with a place to pour the silicone we would use for our mold as well as four holes, two extruding outwards (pegs) and two inwards. We downloaded this file as an stl to use for 3D printing! The dimensions of our piece were 50.96mm x 65mm x 8.559mm.

Following steps for Solidworks

3D Printing Process:

We utilized 3D printing as a method for producing one half of the chess piece mold. We printed the processed part using a Bambu Lab 3D printer. We positioned the part on the build plate, ensuring the flat surface made direct contact with the plate and the Roblox character’s face oriented upward (facing the plate caused some errors to the print sadly and this way worked much better). This way we didn’t have to include any supports since there weren’t any overhangs. The print didn’t take long and the piece came out decent enough as we expected. However, we encountered an issue with the narrow pouring channel, and we had to make a manual modification by cutting a rectangular opening using a bandsaw along the bottom edge to enable a more precise mold pouring. We also redesigned the part accordingly and reprinted it so that we don’t have to make a manual adjustment again for the further use of the 3D part.

Bad vs Good 3D prints (pre-bandsaw)

CAD/CAM CNC Planning:

Luckily for us when we had to move on to creating our mold negative using CNC we did not have to go back to Meshmixer and start our process above again because both halves of our piece were identical! So we were able to move straight into our CNC process using the same stl file we used for 3d printing

CNC Process:

We fabricated the second positive half using the CNC machine, following the tutorial in the CNC Machining document. In VCarve Pro, we began by defining the wood block’s precise dimensions and orientation. We maintained the same scale used for our 3D printed piece to ensure dimensional consistency. While creating the toolpath, we selected a ¼” end mill for roughing and a ⅛” end mill for finishing. Given the wood block’s thickness, we made additional clamp holes to secure the material during machining. The entire cutting process took approximately one hour. After machining, we carefully sanded the piece to achieve a smooth surface suitable for the molding process.

Probing Honing Machine

Working in VCarve Pro

Wood Engraving on Shapeoko Pro XXL

Molding Techniques pt.1 :

After creating our halves we directly moved onto the really fun but messy part! To start off we created our silicone mold. First we placed and glued down cardboard along the border of the bases for the halves (had a line to mark pour height). We split up who did the mix and pour and switched roles for each half! We mixed the A and B of the silicone mold with a 1:1 ratio with measurements of 50g each. After mixing for about 3 min we poured the silicone inside the border of the cardboard. We needed to make sure we couldn’t see our roblox friend, which we barely could and this helped us move on! We left our molds to dry overnight so we could take apart our molds from the halves and cardboard.

Pouring silicone for mold

Creation of molds

Molding Techniques pt.2 :

After our molds were dried we prepared our final mold by connecting the pegs and holes and keeping them secure and together with rubber bands. Next was the pour of Polyurethane. We decided on what colors we wanted to use for our four pieces which were light green, yellow, dark blue, and light gray, all fun and unique colors of characters we would see when playing Roblox (also funnily, dark blue and yellow were the colors of Mert’s favorite soccer team). For the A pour we had to add a drop of the dye we wanted to use and mix it with the A Polyurethane (15ml). Then we mixed in 15ml of the B Polyurethane for 20 seconds until we poured it into our newly connected mold. After waiting for 20 minutes we deconstructed the connected molds and took the new cast out! We repeated this process 3 more times for 4 total casts!

Piecing together and curing mold

Post Processing:

After we removed our molds, two sides of the mold weren’t perfectly aligned and there was some excess mold, so we post-processed it using an orbital sander with an attached sandpaper to smoothen the Roblox character. 

Pre-processed piece

This was a really fun project and we got to use so many different processes which was exciting for us! Also, because of this we got to create these cool pieces:

Post-processed pieces

In addition we made sure to clean intensively:

 

Cost analysis

Materials:

• PLA
  • $19.99 (PLA Basic Filament, Bambu Lab)
  • $1.5 for our pieces total
• Wood (3.485” x 5.939” x 1.508”)
  • About $2.87 according to HomeDepot
• Polyurethane (A&B)
  • $36.89 (30oz, Amazon)
• Silicone mold making material (A&B)
  • $22 (37 oz, Amazon)
• Sandpaper (sanded with 120 and 220)
  • 120 grit sand paper $6.98 (Home Depot)
  • 220 grit sand paper $6.98 (Home Depot)
  • Total: $13.96
• Heavy Duty Rubber Bands
  • $8.99 (Pack of 60)
• Hot Glue Sticks
  • $9.29 (Pack of 100)

Labor:

• 3D printer operator
  • Approximately $18 per hour in Texas according to ziprecruiter ($36 for 2 hours)
• CNC operator
  • Approximately $20 per hour in Texas according to salary.com ($50 for 2.5 hours)
• Soldidworks engineer
  • Approximately $25 per hour in Texas according to salary.com ($75 for 3 hours)

Facility:

• Facility Cost (Machine Time) – CNC
  • About $60/hr and for 1.5 hours the cost was $90
• Facility Cost (Machine Time) – 3d print
  • About $20/hr and for 2 hours the cost was $40

The total cost was about $406.49