Table of Contents
Prototyping, Engineering Analysis, SimulationWhen we first started testing our 3D printed padding, we compared NinjaFlex vs. FilaFlex filament. Research showed that FilaFlex had higher printing capabilities. As print density increased, FilaFlex allowed for increased energy absorption, far exceeding the limit of NinjaFlex. We also had an easier time 3D printing the FilaFlex material; the nozzle of the printer did not clog as frequently as it did with the NinjaFlex. For these reasons, we chose to eliminate NinjaFlex from our testing and print exclusively with FilaaFlex filament. This decision will decrease variability and simplify our test plan.
We have performed some static testing on the blocks using Finite Analysis Testing. This was initial mode of testing to help us determine which densities would be best to consider and which we should eliminate. You can find some of the virtual testing samples on a couple of the blocks here: ANSYS Testing
For the remainder of the project, we will do virtual testing using the SimulationXpress Analysis Wizard through Solidworks . This will allow us to perform dynamic drop testing on the blocks and it will tell us how much energy is absorbed by the block as well as displacement and stresses applied on the blocks. An example of what kind of results this testing will give us can be found below:
- Comparison of the stress, energy strain, and displacement of a half inch thick solid block: 1/2 Inch Block
- Comparison of the stress, energy strain, and displacement of an inch thick solid block: 1 Inch Block
- Sample report of the results from the drop test performed on the half inch thick solid block: 1/2 Inch Block Results
- Sample report of the results from the drop test performed on the 1 inch thick solid block: 1 Inch Block Results
3D scans of a head and the helmet generated with the Sense Scanner and imported into a combined assembly in SolidWorks can be found here: 3D Scans
Test Rig Designs can be found here: Test Rig
A model of the chosen test rig design can be seen here: Test Rig Simulation
One of our customer requirements was to create a workflow for scanning someones head to sending the foam size to the printer to placing the padding in the helmet. Our preliminary workflow process can be found here: Workflow
The procedures for the workflow have been written up here: Workflow Procedure
Padding placement within the helmet: We have done some research on ideas for this but we have not come up with any ideas yet. We emailed our NFL contact and he said that there is no reasoning for the placement of the padding inside the helmet. We are most likely going to experiment with hexagons, circles, and hour glass shapes. We plan to cover most of the helmet and not leave too many open spaces except where necessary for air flow through the helmet.
Bill of Material (BOM)Our current Bill of Material can be found here: Bill of Material
The Bill of Materials for the Test Rig can be found here: Test Rig BOM
Test PlansThe test plan for the 3D printed blocks can be found here: Test Plan
The test plan for testing prototype blocks is divided up into five main trials. The first trial changes the material and density of the prototype blocks, the second trial changes the infill pattern, the third trial changes the physical design of the blocks, the fourth trial tests multiple layers of blocks together, and the fifth trial adds fillers such as gels to the blocks.
Before each trial, ANSYS modeling is performed to narrow down which parameters we want to test for each variable. The prototype blocks are then designed in Solidworks and printed out by the 3D printer. The blocks are then tested after each trial to determine the force absorbed. These results are then analyzed and compared for each block. A couple of the best designs for each trial are then chosen to be used as constants for the following trial. At the end of all of the trials, we will have chosen two or three designs that we can mass produce and implement into the helmet.
The test results for our test plan can be found in the Prototyping, Engineering Analysis, Simulation section of the Detailed Design page (At the top of this page). These results were generated using a simulation tool found in SolidWorks).
The data generated from our drop test rig can be found on the Test Plans & Test Results page of MSD II.
Additional tests have been written to test sterilization, comfort, durability, and the effects of sweat on the padding.
Compression TestingThe results from the compression test that was performed in the packaging science lab on the first 8 samples we printed are provided below. We placed the blocks, one by one, under the compression machine which compressed the graph to deflect after a certain amount of compression. We determined the amount of compression by setting the deflection rate to be about 1/4 of the thickness of the blocks. When compression was occurring, the force sensor was reading out how much weight was being compressed on top of the block and stopped compressing after the set compression value. The graphs for these results can also be found below.
- Compression test results
- Baseline padding graph
- Block 2 graph
- Block 3 graph
- Block 4 graph
- Block 5 graph
- Block 6 graph
- Block 7 graph
- Block 8 graph
See the test plan above for what the geometries and filaments for the different blocks are. The graphs for block 1 were not provided to us.
Drop TestingWe have been given access to the drop test rig in the packaging science lab until we have built ours. We have drop tested the first 20 blocks that have been printed (we are still working with the printer to try and get the last block printed which will complete trial 2). Below you will find the results from the drop tests which will tell you how much force each block absorbed upon impact. You can see that some of our blocks are comparable to the TPU foam we are testing against from the Schutt helmet. See the updated test plan for what densities and infills the blocks are.
Summary of the results from the testing:
- Drop test data for Trial 1&2 are listed on the graph. The main variable recorded was G force which ranged from 6.1 to 9.5 depending on the block number.
- Printed blocks were at rest on a metal anvil while a ~10kg mass was dropped from a height of 2 meters
- Filaflex Hexagonal Infill with 55% density seemed to absorb the maximum amount of Force at 9.1 G’s.
- FilaFlex with a hexagonal Fill and a high density seems to have the highest energy absorption
- The graphs of the drop test results for each block can be found in this folder: Drop Test Results
- A simplified chart of the maximum peak for each block has been graphed here to clarify which blocks absorbed the most force: Drop Test Data
We have had to raise some of the likelihoods and severity numbers, specifically concerning the 3D printer and the test rig cost. We have run into some issues where the printer will not print our filament due to clogging in the nozzle. Additionally, the test rig is proving to be more expensive than expected. Some of the numbers have decreased though as we have resolved those issues throughout the semester.
- The updated risk assessment can be found here: Current Risk Assessment
- Pre-read: This was sent to our guide and customer before presenting
- The Week 9 Update can be found here: Week 9 Update
- The Week 12 Presentation can be found here:
Detailed Design Review
- Notes from the Week 12 Review:
-When printing a high density sample, the sample will take on the material properties of the elastomer. For low density samples, the air trapped within the geometry will control how the sample responds. Both of these characteristics will affect the compressibility factor of the foam padding.
-Seek a composite expert to determine properties of foam
-Integrate a velocity sensor into the test rig
-Seek out experts for dynamic testing simulations (i.e Dr, Ghoneim, Kempski)
-Perform a full thickness (ex. 1in thick block) FEA Analysis and compare results to thinner pad
-Use a plane to center helmet on head
-Determine pattern for padding within the helmet and how many sections
-Will a protective layer be necessary to eliminate permeability factor of the padding?
- The Week 15 Final Presentation can be found here:
Detailed Design Review
- Notes from the Week 15 Review:
-make modifications to print head--see youtube video
-cement/concrete base for test rig
-add brackets to bottom of test rig for support
-use a high speed camera when doing drop test
-compare thinner sample to thick sample(~1 in)
-compare simulation results to physical drop test results (check for accuracy of data being (collected)
-Meet with George for mating ideas--> head to helmet
-more simulation work instead of just printing and testing
-get information on how to order replacement head for printer
-adding min requirements into workflow (specify exactly how many squares the manufacture needs to print)...ex. Printing 12 instead of 18 squares may not protect athlete
-add attachment mechanisms to protocols so that we can remove these off of the critical testing path
- Action Items: These will include everything that has been addressed to us during the reviews.