Why Material's Shore Hardness Will Affect The Cycle Time of Liquid Injection Mold?

Different types of material requires different mold temperature, and usually the mold temperature is higher, the curing time is shorter, on the other hand, the curing time will be logner. For the same type of liquid silicone rubber in different Shore hardness will also affect the curing time, which further affects the cycle time of liquid injection molding production process.

Different types of material in same shore hardness:

For one of our liquid silicone cannular, customer required LR 3003 20A liquid silicone rubber as material, the material needs lower temperature to cure or there will some white dots on the product. So we will need to adjust the mold temperature to be lower to make sure there will not have white dot on it to solve the problem.

LR 3038 40 K1 10993-11 E.PDF

EL LR3003.pdf

FDA-SGS-LR3038 K1 en.pdf

3038-50 ISO10993-10 en(1).pdf

We have test use Genvan liquid silicone 20A,  mold temperature is about 145 °C, the curing time is about 90 seconds; while for Wacker LR3003 20A,mold temperature is about 130°C, curing time needs about 105 seconds, which effect the production efficiency directly. So that’s why we will adjust unit cost after customer confirm the detailed material for production.

Same type of material in different shore hardness:

For the same type of liquid silicone in different Shore hardness will also affect the curing time, which further affects the cycle time of liquid injection molding production process. For common shore hardness 30-50A, the product is easy to demold,while for low hardness such as 10-20A, the product is very soft and will stick on the mold tightly, it’s difficult to demold and take much longer time to demold. Take one of our silicone nose plugs for example. The low shore hardness material has good liquidity and mobility, the venting is easily to be blocked and will cause air trapping issue easily.So during production, will need adjust mold and machine to solve the air trapping issue. That’s why low shore hardness material will effect the cycle time and production efficiency.

What is cycle time?

Cycle time is the total time required to complete all the stages of the liquid injection molding cycle.

What are the components of cycle time?

1. Material Feeding Time:

Liquid Silicone Rubber consists of glue A and glue B, which are controlled to be 1:1 ratio dosing device, and fully mixed by a static mixes and then injected into injection mold chambers & tubes. For compression molding, the cycle time is usually longer than liquid injection molding.

2. Curing Time:

The temperature of the mold will effect the length of curing time. And different type of material, the mold temperature requirement is different, and curing time is also different. Some materials require higher mold temperature for curing, curing time is short, and the production is smooth. While for some materials, required lower mold temperature and curing time is logner. So the prodcution efficiency is different in different materials.

Silicone Parts structure will also affect the curing time. For simple structure product, the curing is 30 seconds, and for some complicated structure products, the thickness is large, the curing time is much longer.

3. Cooling time:

The cooling time is the stage of the injection molding cycle when there is no more pressure being applied to the polymer. The mold is held shut and the polymer continues to cool until the part can be ejected. The cooling stage is normally the longest part of the molding cycle and can account for up to 80 percent of the total cycle time.

Mold open time.

The time for which the mold is open before the next molding cycle begins. This time includes the following: