Week 2: LR-14 DOE

Hello again!

This week I will take a small step away from hydration because a customer wanted an "emergency" DOE analysis of the LR-14 press. Because the pressure exerted by the press can cause bending in the mold, we wanted to run an experiment to find evidence of this in the LR-14 mold.

Here's a little bit of background on the mold before I talk about the experiment: a mold is the object that allows the injected plastic to take the correct shape, in this case the shape of an LR-14 battery seal. This mold is placed in a molding press that injects plastic into the mold at the desired pressure, velocity, and temperature.

The LR-14 mold has 32 cavities meaning every injection of plastic, or shot, creates 32 LR-14 sized battery seals. Because the mold and the press can never be perfect there will always be variance between each cavity. However, we are trying to find the best combination of factors for the molding press to create the least variability from cavity to cavity and shot to shot.

Therefore an DOE on the LR-14 must be run to find any discrepancy in the molding press. We did two DOE's on the LR-14 mold. The first one consisted of 10 shots in which we weighted all 32 cavities in each shot and looked for the correlation in weight from shot to shot and cavity to cavity. After running a grouped box plot graph, we found little variance from shot to shot however the cavity to cavity variance was unclear. We decided to run a second DOE analysis of 5 new shots to compare the variance from cavity to cavity. We found that the LR-14 mold has negligible variance from cavity to cavity and therefore the parameters on the molding press are adequate for the particular mold. However we look to improve the parameters on the mold to make it more efficient for not only variance but also functional and cosmetic problems.