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12. Molding and Casting: Kabir Nawaz and Ryan Zhou

Group Assignment

  • Review the safety data sheets for each of your molding and casting materials
  • Make and compare test casts with each of them
  • Compare printing vs milling molds

Safety Datasheets

The first thing we did for this group assignment was take a look at the datasheet(s) that we would be using to cast with. The first one, for the Moldstar 15 Slow, can be found here. The notes we took on this datasheet are listed below.

  • Section 3: No “hazardous materials” are contained in the ingredients.
  • Section 4: This section provides advice on appropriate action if the product is ingested, inhaled, touches eyes, or touches skin. If ingested, do not try to vomit the substance; if inhaled, remove the sources of contamination (the product) and get to fresh air; if eye contact occurs, flush eyes with a large amount of water and seek medicaal attention if irritation remains; if skin contact occurs, wash the affected skin with soap and water and remove/wash contaminated clothes.
  • Section 5: Material is non-flammable, and there are no hazards pertaining to “unusual fire or explosions”. If a fire does break out near the product, protect breathing airways from inhalation and wear a face protection breathing apparatus.
  • Section 6: If spilled, contain the released product and scrape excess into a “suitable” container (which the material will not leak out of). Follow applicable OSHA regultions at all times.
  • Section 7: Store product in a cool and well-ventilated area at around room temperature at all times.
  • Section 8: Wear protective gloves (single-use recommended) and appropriate eye protection when handling at all times (even with contact lenses). Do not eat, drink, or smoke near the product, and make sure to clean appropriately after using the product.
  • Section 10: Incompatible with strong bases and acids. Stable when being stored at room temperature under normal conditions.
  • Section 13: Product must be disposed of in accordance with applical Federal, state, and legal regulations.

3D Printing and Milling Molds: Mold Comparisons

This week, Ryan was assigned to 3D printing a mold, and Kabir was put in the milling group. The main difference between these two methods of creating a mold is the time it takes to get from CAD to actually casting the design. With 3D printing, it is fairly simple to just create a box in CAD and create your design negatively extruded into that box before 3D printing it out. Additionally, 3D printing the mold usually results in the possibility to include smaller details when compared to milling the mold. This is because the smallest bit which worked on the Bantam desktop milling machine was the 1/16 inch bit. While there are smaller bits like the 1/32 and 1/64 inch bits, they are too small to fit appropriately on the larger milling machine. This was especially for my (Ryan’s) mold, as there were several parts of the design which required details that couldn’t be milled out by the 1/16 inch bit.

When it comes to milling out a mold, the process we and most of our classmates followed consisted of using Fusion 360’s manufacturing tab to create a toolpath in gcode for the milling machine. There were other applications we could have used for this, such as Vectric Aspire, but most of us already had our mold CADs in Fusion, so it felt easier to continue using the same file. This process was considerably more complicated than 3D printing a mold, as it had all of the same steps as 3D printing plus many more. The milling job consists of two basic parts: the roughing toolpath, and the finishing toolpath. The basic process for creating a toolpath in Fusion is shown below:

  1. Create the a CAD model of your mold
  2. Change the Fusion tab from “Design” To “Manufacture”
  3. Choose “setup” and choose the selected body as the CAD model you made
  4. Then, install the Bantam tools library in Fusion and choose the Bantam desktop milling machine as the milling machine you are using
  5. Finish the setup; now, you can begin with creating a roughing toolpath
  6. For this step, choose 2D/3D adaptive toolpath or 2D/3D pocket toolpath. Choosing between 2D and 3D depends mostly on whether your design has curves. If it does, choose a 3D toolpath. If not, choose a 2D toolpath
  7. When prompted to, select the tool you will be using from the Bantam tools library
  8. Choose the faces you want to conduct your roughing cut on and tune the tool settings as needed (ex: the rpm of the bit)
  9. Optional: Make sure to enable multiple depths if you are milling a deep design
  10. Finalize your roughing cut and move onto the finishing toolpath; 2D/3D contour is usually good to use for this step
  11. Configure the same settings as in your roughing pass (but for your finishing pass). Again, enable multiple depths if you need to mill out a deep design
  12. Right click on both the roughing and finishing toolpaths and select “simulate”. This will show you what your toolpaths look like and will notify you if there are any errors. Be cautious when simulating your toolpath, however, as the simulation will sometimes give you incorrect errors. Reference the actual bit in your lab instead of the simulated bit if you think the simulation is incorrect, as they may be different sizes.

Cast Comparisons

The first cast that our group did was with Ryan’s design using a 3D printed mold. This design was of Pusheen the cat and was relatively simple, being 0.4 inches tall at its highest with a few 0.5 inch extrudes on the bottom of the mold. We used Mold Star 15 Fast for all of our casting this week. Overall, there were no issues encountered while casting this piece and it came out well. The picture below shows what the casted design looked like.

Next, we compared casting with Ryan’s 3D printed mold to casting with his wax mold and resin printed molds. All 3 casts are shown in the picture below.

The results were actually quite surprising; the cast with the wax printed mold (bottom left in the image) looked quite good and was similar to the cast using the 3D printed mold. However, the wax cast did have an imperfection, which was the fact that the whiskers on the cat design of the cast had been fused together.

On the other hand, the cast using the resin printed mold (on top of the wax block in the image) came out pretty bad. It was very wet upon being taken out of the mold and stayed that way for hours, if not days. Additionally, many details on the cast itself, such as the cat’s face, had been completely obscured and were difficult to make out. Finally, there were many holes in the body of the cast which made it even less desirable.

Printing vs. Milling Molds

After printing, molding, and performing test casts using printed and milled molds, we have come to the conclusion that, for smaller designs like the ones we used during this group assignment, 3D printing molds out of PLA and similar materials is generally easier and leads to better results than milling molds out of wax. The reason for this is because 3D printing molds allows more of the details of these small designs to come out correctly after casting when compared to the wax mold, which lost a few details after having the design casted. However, for larger casts/molds, milling out molds may be more preferable, as the appeal of 3D printed molds retaining more detail is not as important at that scale.

Last update: July 4, 2024