In the cart you need to create a new column, lets call it prodType.
In the add to cart buttons set the prodType column to 1 for Aluminum Signs, 2 for Steel Signs and 3 for Vinyl Decals.
now create 3 shipping charges:
Aluminum Signs Shipping:
Triggers:
Number of Items With a specific Column Value:
If the number of items where "prodType" has a value of "1" is ">" a value of "0"
Calculation:
Based on Items With a Specific Value:
Total Of "Quantity" Where "prodType" has a value of "1" "times" "4.95"
Steel Signs Shipping:
Triggers:
Number of Items With a specific Column Value:
If the number of items where "prodType" has a value of "2" is ">" a value of "0"
Calculation:
Based on Items With a Specific Value:
Total Of "Quantity" Where "prodType" has a value of "2" "times" "6.95"
Vinyl Decal Shipping:
Triggers:
Number of Items With a specific Column Value:
If the number of items where "prodType" has a value of "3" is ">" a value of "0"
Calculation:
Based on Items With a Specific Value:
Total Of "Quantity" Where "prodType" has a value of "3" "times" "0.99"