Engineering Analysis and Specification Changes
Initially the container was to be designed to withstand a 10g impact within the confines of the Kodak manufacturing areas and during shipment. The team considered this specification to be applicable to the fully packaged container only. Subsequent conversations with the project customers sparked a review of the initial 10g specification.
If the fork and hand trucks used on the manufacturing lines were not capable of accelerating a full size roll and container to 10g, then the container assembly workflow could be further optimized. Namely, the container horseshoes would not be needed for structural support immediately after placing the roll at Windup. At the same time it was determined by the customer that the horseshoes would not need to prevent film roll telescoping. Therefore the horseshoes would only provide structural support in the final design.
It was determined that testing be carried out to determine the actual roll and cart acceleration. The following results were found:
The fork truck with metal roll cart and 500 lb. roll. Peak acceleration at time of impact = ~4g:
The electric hand truck with metal roll cart and 500 lb. roll. Peak accerleration at time of impact >= 10g:
The electric hand truck with wooden container currently used for inter-Kodak transportation with an 800 lb. roll. Peak acceleration at time of impact > 2.5g:
Specification changes post acceleration testing:
It was decided that due to the wooden container having a boxed in base, that the final design should incorporate such a reinforced base. This would allow for easier saddle attachment implementation and better resistance to the moment about the saddle itself (see below):
Other specification changes prior to Detailed Design Review:
Given the specification changes the analysis for feasibility and simulations performed were revised. This allowed the team to design a less robust and less costly container than previously considered.
With the specification changes the assembly workflow for the container and the pack to ship process was revised. Also, the team determined a feasible workflow for wrapping all targeted film rolls at Windup.
The current plastic sleeves would be cut down the middle, creating a larger wrap than the current belly wraps. The revised wrap enables the roll to be enveloped as the excess plastic is tucked into the cores. This eliminates redundant lifting of the roll at the packaging cell (see below).
Saddle Compression Analysis and Dimension Justification
Finite element analysis was completed in Femap to determine the dimensions of the container saddle. Worst case, expected vertical, and horizontal loading scenarios were considered.
Max Stress Simulation Results for Saddles and Horseshoes:
Results from vertical and horizontal loading analysis drove analysis to justify saddle width. As seen below, a 12" wide saddle is the minimum dimension at which the max stress/G force is reduced, given both loading scenarios.
Given 10g vertical loading the following materials and corresponding saddle widths needed are seen. The team chose to prototype the saddles from Plywood. Final dimensions would be 12x18x2.75".
Revised Engineering Analysis and Final Design
Given the specification changes the container should now only hold up to 4g acceleration between Windup and the packaging cell. Should a 10g impact occur it is expected that the updated "boxed in base" will contain the roll given saddle failure. This spec change altered the maximum sheer stress and bending stress expected to be seen.
This altered the thicknesses of all sub components and materials being considered. After these changes the container became much more feasible.
Proposed final design (see DDR PowerPoint PDF for complete model breakdown):
The proposed final model was then simulated to confirm feasibility of the chosen dimensions and materials under consideration.
Final Model Simulation
The final, loaded container was simulated in Femap. Total roll weight = 1700 lb. Stiffness of roll was unknown. Programmed as being a rubber roll instead. The Horseshoes and Saddles were rigid to the base. The Horseshoes were rigid to the roll to simulate strapping.
Due to the rigid nature of the simulation results are conservative. The simulation does not take into account the nature of the wooden base and the potential ability to absorb a great amount of the energy to be seen at impact.
Although Multi Density Fiberboard (MDF) was not included (team could not find specs on MDF) the current packaging solution uses this for an end board type component, so it was included in prototyping plans. Plywood was chosen to be the primary material for Horseshoes, going into initial testing.
Saddle and Core Stop Selection
The saddle dimensions and material were confirmed for all prototypes. Horseshoe dimensions were confirmed as they are restricted by the chosen base and max container height. A range of Horseshoe thicknesses were given from the Final Design Femap simulation.
The final component to be analyzed was the Core Stop and Saddle key way. Metrics for this analysis were obtained from the Final Model analysis.
This component prevents the core and roll from both dropping into the base and from ejecting out of the saddles during impact. Analysis was performed to determine the shape, thickness, and material for the core stop. Multiple mixtures were selected for prototyping.
Core Stop Assembly:
Expected force applied to the core stop:
The shape of the Core Stop and key way was determined as well. Insert Shape Justification:
By using the Factor of Safety (Strength/Max Stress) seen for all possible mixtures of Horseshoe thicknesses, Core stop thicknesses and materials, and Saddle materials, a data driven selection process was derived.
The most robust mixtures will be those where the factor of safety for Saddle and Core Stops will be approximately equal. This logic was applied for selecting the optimal mixtures to prototype and test with. An iteration of the process is seen below:
Prototypes to Build
From the FOS analysis 6 unique prototypes were selected for prototyping and test:
Bill of Material (BOM)
Initial BOM for all subcomponents considered for Detailed Design Review. Prices and quantities were determined prior to review. Attachment method for Horseshoes and all fasteners were not determined prior to completion of MSD I. Best practices would be determined in MSD II when the team constructed all prototypes. The prototype bases and sets of subcomponents were manufactured for the team during Spring Break 2013.
The following is the initial BOM for prototyping:
Final dimensions for the proposed Detailed Design will be reported in MSD II. Test results must be obtained and analyzed to develop the final product. See DDR PowerPoint for complete container breakdown.