Update Requirements: Execution of print trials and experiments proposed. Carefully document the results of what you proposed during the project proposal phase. This includes pictures, data, mechanical drawings, etc. Were your experiments successful?
The first print was completed with our design submitted in the proposal. It had a low infill count of about 5-10% and short layer height, making the part essentially hollow due to the time constraint presented to us to complete a print within. The print constraint is eight hours and this print was completed in 8 hours and 3 minutes.
After picking up the parts, we attempted to test the watertightness. What we found was that the part was not watertight and it leaked all over when water was placed inside. This is due to the gaps in the layers and many holes. In an attempt to continue on with testing the mold’s strength when frozen, a plastic bag was placed inside as an extra layer of defense against the leaking water. However, the bags did not fill properly so the water did not fill the mold well.
When the mold/plastic bag combination was frozen, it was found that the inner mold was difficult to remove. The ice froze directly to the 3D printed part, making a clean removal impossible. The shape of the inner mold kept poking through the bags and creating holes which was another cause of leakage. The inner mold was also less dense than water which was causing the inner mold to spike above the water, so a downward force was required to hold the mold in place.
Did the results merit a redesign or a reconsideration of the part design, material, or event the chosen AM technology? Include the print time of each print you performed. Indicate how you will improve the design of your part based on what you have learned up to this project report.
The results from our preliminary tests required a redesign. We no longer wanted to have the 3D printed parts hold water to freeze. Instead we are using the 3D printed parts to create a silicone mold. This will have better success of holding water and remaining food safe which are two of our project goals. Silicone is flexible making the removal of ice easier than the removal from a hard rigid plastic like ABS.
Our next steps are printing the updated design for our plastic mold which we will use to form a silicone mold to. In addition, we will laser cut a wood box to contain the mold and liquid silicone as it cures. Once we have the silicone mold we can complete more accurate tests of our desired product.
Two reduce the amount of silicone needed for the mold, an additional 3D printed part will be created to take up the dead space in the silicone mold. An initial calculation of how much silicone was required was carried out by making 3D models in Solidworks. Next, the total volume of silicone that came in a package was calculated. Initially, the silicone package we were looking (Smooth-Sil™ 945) had a volume of 730.8631 cm^3. Our initial design required 867.351 cm^3. After designing a 3D printed piece to reduce the dead space, the total volume required is 422.782 cm^3. This gives us more silicone to work with in the event of an error.
The mold only creates half a bottle. The freezing process will need to be carried out twice to make 1 full bottle. After the two halves have frozen, they will be placed on top of each other and frozen together.
Process to make the mold:
- Box is created.
- 3D printed parts are created.
- “Dead Space” 3D printed part is inserted into the box
- Silicone is poured in around the dead space part
- The 3D printed negative of the bottle is placed into the silicone to make the bottom half of mold
- Silicone is left to cure.
- Silicone is removed and trimmed.
- Bottom mold and negative of bottle is again inserted into the box.
- Silicone is poured over the top to create the top of the mold.
- Silicone is left to cure.
- Silicone is removed and ready to test
Updated Project Schedule
Week of 4/8/19:
- Laser cut a box to house the silicon mold
- Print the second iteration of the bottle mold
- Use the second prototype to create the silicon mold
- Perform water-proof and durability tests
Week of 4/15/19:
- Review takeaways and make improvements from second prototype
- Finalize design and prepare second project update, due April 19th.
- Prepare project presentation
Week of 4/22/19 – 5/1/19:
- Final Report Due May 1st
Figure 1 – Outer Mold (1st prototype)
Figure 2 – Inner Mold (1st prototype)
Figure 3 – Attempt to freeze water
Figure 4 – Failed removal of bottle
Figure 5 – Failed removal of bottle
Figure 6 – New proposed design
Figure 7 – Food safe Silicone