1. Tim Elsner Nate Vetsch Caleb Glantz Andy Johnson
Silicon Rubber
Tim Elsner
Nate Vetsch
Caleb Glantz
Andy Johnson

2. Silicon Rubber Properties
Mechanical
High tear and tensile strength
Great flexibility
Thermal
Wider range than most other rubbers
Electrical
Exceed similar materials in insulating ability
Non-conductive
Maintains dielectric strength through wide temp range
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3. Silicon Rubber Properties
Chemical
Water resistant
Chemical resistant including:
Some acids
Oxidizing agents
Ammonia
Isopropyl alcohol
Bio-Compatibility
Comply with FDA guideline for medical products
Tasteless and odorless
Doesn’t support bacteria growth
Doesn’t corrode other materials
Most importantly have superior compatibility with human tissue
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4. Tour of MN Rubber Lead by Jeff Amundson, Operations Manager
Thank You Jeff
Litchfield Plant
Horizontal injection molding
Liquid silicone molding (LSR)
Extensive automation
Clean room finishing facilities
Thermo-set silicone injection molding
Standard products: ground rubber balls, o-rings & Quad-Ring Seals
LSR are very automated
One man for 4 machines
Visual inspection machine for 100% defect free
Testing room use six sigma principle to ensure quality
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5. Cool things on tour Automated visual inspection machine for deliver
Cryogenic de-flashing process
DOE to optimize with in the next year
Quality inspection room
Not just a myth, SQC is used!
O-ring defect separator
Overall cleanliness
Baffling ball grinder
Recycling of flash for profit!
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6. Automated Visual Inspection
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7. Cryogenic De-flashing Machine
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8. Pampered Chef Spatulas
Minnesota Rubber
Complete in-house production
Handles injection molded plastic
“scoop” injection LSR
Nearly full automation
One man producing 500/hr
Four machines are run by one person
-all they have to do is load the spatula handles
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9. Liquid Silicon Injection
Two part silicon
Mixed in injection machine
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10. Liquid Silicon Injection
Actual machine
Hopper is replaced by hoses to drums with silicon parts separated
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11. MN Rubber Spatula Process
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12. MN Rubber Spatula Process
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13. MN Rubber Spatula Process
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14. Our Experiment Received pre-mixed HTV gum rubber 9/19/2018
Simplified process
-no need to mix or set pressures or flow rates
-plus don’t have equipment to conduct exact process
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15. Our Experiment Modeled two part injection with compression molding
Heat die
Insert precise amount of material
Compress in machine
Leave for time to set
Remove
Post bake for more complete cure
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16. Our Experiment 24 Full Factorial Die temp 275 & 300°F
Dwell time 4 & 5 minutes
Post bake temp 350 & 600°F
Post bake time ½ & 2 hours
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17. Our Experiment
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18. Our Experiment Results
Response variable is hardness
Durometer Shore A scale
Measured with tensile tester
Force vs. Displacement
Correlated to Shore A scale
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19. Testing methods Ideal Modified Method
Load cell measured force
Distance is measured by the top beam moving down
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20. Results Die time and temp Die time prob>f=.419 insignificant
Die temp prob>f=.272 insignificant
Potentially made insignificant by requiring sufficient cure for ease of release
The die temperature and time were found to be insignificant to the model and our response variable being, hardness/durometer. There was only a 59% confidence that our die temp is significant and only 73% confident that our die temp is significant. During our experiment we made the assumption that we had to get a cured and filled part. Not realizing that we potentially had eliminated these factors.
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21. Results Post bake time and temp
Bake time prob>f = significant
Bake temp prob>f = significant
Interaction prob>f = significant
The post bake time and temp were both found to be significant to our model and the durability of the key chains. As well as both being significant alone, their interaction was also significant.
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22. Interactions
The red line represents the high level of the post bake temp. The black line shows the low setting of the post bake temp. They aren’t parallel which shows that there is a significant interaction.
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23. Conclusions Die time and temp both set to low
Save energy and time
Post bake at high temp and least amount of time possible
Low cycle times
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24. Thank you Jeff Amundson for a good tour
Darryl for making test indentor
Bill for answering never ending questions
Seth for helping with lab equipment
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25. QUESTIONS ?
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