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Production Life vs. Library Life of a Mold

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FAQ – How many castings can I expect to get out of my
rubber mold before it becomes unusable?
 

Answer: What you are really asking is, “what is the expected production life of my rubber mold?”. 

First, we need to distinguish between the “production life” and “library life” of a rubber mold.

Library Life refers to how long a rubber mold will last in your “mold library”, just sitting on a shelf and not being used.  Some mold rubbers last longer than others.  Below is a chart giving you an idea of the
library life you can expect from various mold rubbers:

Production Life FAQ - How many castings can I expect to get out of my rubber mold before it becomes unusable?
 

Answer: There is no easy answer, but we can identify a few variables that will affect how long your mold will last;

    1. What kind of rubber your mold is made out of?
    2. What material you are casting into the mold to make reproductions?    3. How fast are you “cycling” your molds?
    4. Whether or not you are using a release agent.

The above 4 questions will help you determine the mold rubber to select for your project and ultimately, the mold life you can expect.

Some Examples:

A.       Using a urethane rubber mold to cast resins (such as urethane, epoxy or polyester) will result in a shorter production life of that mold vs. using silicone rubber because silicone rubber generally has the best resistance to the chemical and heat attack of resins.

B.        Using a polysulfide rubber mold to cast concrete will result in a shorter production life of that mold vs. using urethane rubber because urethane rubber has much better resistance to abrasive materials like concrete.

C.       Removing a urethane resin casting from a mold after it has “gelled” and letting it cure outside the mold will minimize exposure to heat generated by the resin, thereby extending the life of your mold.

D.       Using a release agent to release urethane resin castings from a silicone rubber mold will result in double the mold life.

 The above four example are but some of the mold and casting variables that can affect the production life of your mold.  You can contact Smooth-On’s technical help line with specific questions about your project.