Status Update
Where We Are Now
We have manufactured every part of our lotus flower yo-yo thus far! We now have actual parts that we can take measurements from and adjust accordingly. Below is a quick update, part by part of what we have discovered and what still needs to be done.
Initial Shrinkage Measurements
Body
In our attempts so far in injection molding the body, we have not been able to lessen a very visible weld line on the side opposite of the sprue. We are considering adding a runner on the body mold to get hot plastic to the side opposite the sprue quickly to try to mitigate this weld line. We also had some issues with the shoulder bolts not appearing to be flush with the bottom of the cavity - so we will need to re-look at this.
Snap Ring
When measuring the injection molded snap rings, we found that the circumference is too big with the current molds. At first we also thought that the step height that interfaces with the body was also too short, but we have since realized that this is an issue with the body part, not the snap ring. We believe that we scaled the entire snap ring when making the molds instead of keeping the inner diameter as designed (since it will shrink onto the mold core) and only change the outer diameter to compensate for shrinkage.
Lily Pad
We have determined from testing that we like the gradient pattern without radial lines on the solid white, rather than clear, thermoforming plastic. The inner triangle on the current snap rings pushes a bit to far inside in the radial direction, but we believe this might be resolved by changing the scaling on the snap ring. We will make that change first and then will re-look at potentially changing the lily pad die. We also are considering drilling the center hole in the die out a bit more. Right now, the plastic is drawn through until it is very thin, but it does not actually create a hole. It is very easy to push the stigma through the thin plastic, but we may choose to make the hole bigger so that the plastic does tear. Riley also found that the mistake black lines that came out on some of the plastic prints could be helpful in aligning during thermoforming. We'd like to work with Wade to see how we could get alignment marks that are purposeful on the prints.
Petals
We've injection molded the inner petals and they came out great! We are not seeing flash like we did on the outer petals and do not believe that the inner petal molds need to be re-machined. We have not been able to mitigate the flash seen on the outer petal parts simply by tweaking injection molding parameters. Annie would like to explore how to remake the outer petal molds to try and mitigate the flash occurring, as well as potentially remake the molds on the HASS since they take so long to machine. We would like to do the inner petals a lighter color pink than the outer petals for a more realistic look. We will start exploring colors with the next round of injection molding trial runs.
Stigma
We were not able to get rid of the divot in the top of the stigma through the tweaking of injection molding process parameters. We are considering making the top face bowed outwards in the mold instead of flat to try to counteract this shrinkage. We have also found that the clocking between the stigma and petals has some slight give to it, so we will need to edit the core side of the stigma mold to make the triangle feature slightly larger.