Liquid Injection Molding (LIM)

Why choose ASH™ for my Liquid Injection Molding Needs?

  • State-of-the-art Equipment:
  • Experts in the process
  • Strict Quality Checks
  • Customer Focused Sales Staff

Liquid injection molding, or LIM, is a production process commonly used to make rubber parts or to make parts that need to withstand extreme conditions, regardless of the industry. The process is an injection molding process at heart, meaning that materials are injected into a pre-made mold, where they're then left to sit and curate. Then, the process repeats itself until the part run is complete.

 

While LIM is best used for short and long run part production, it can also be utilized in the final stages of the prototyping process as well, as the process permits engineers to experiment with different material configurations to fine tune the product before it is green-lit for production. Plus, since a mold needs to be created for the process to take effect, product developers can save time and money by using LIM for both final prototyping and production processes.

 

pic-limThere are two main types of LIM process - injection molding of silicone rubber, or LSR, and injection molding of fluoro liquid silicone rubber, or F-LSR. The former is the most common method that product developers take in producing rubber parts while the latter type is used to craft more high performance parts in industries ranging from automotive to aerospace.

 

LIM, however, is a complex process which relies on a lot of different variables for part runs to be successful. For instance, important components of LIM machines include the likes of:

  • Injectors: These devices pressurize the liquid material.
  • Metering Units: In order for LIM to be successful, there's needs to be a catalyst and a base forming silicone material. Metering units help ensure that these two materials maintain a constant ratio while they're in the process of being released.
  • Supply Drums: These components, which are also commonly referred to as "plungers," are the mixing containers.
  • Mixers: These combine the materials before they're injected into the designated mold.
  • Nozzle: These carry out the injection into the mold.
  • Mold Clamp: This is what secures the mold during the production process, as well as what opens the mold back up when the process is completed.

Here's a further look at the ASH™ LIM process, it's pros and cons, design considerations and other information you can use to determine if the process is the right one for your next product run.


 

Advantages

 

LIM is ideal for creating rubber parts or parts that need to withstand extreme temperatures. Seals, o-rings, isolators, electronic components and other parts in the aerospace and automotive industries are common applications. Here are some of the advantages of the LIM process if your product run:

  • Durable: LIM parts are able to hold up to extreme temperatures, which make them ideal for parts under the hood of cars or near engines on airplanes. LIM parts are also often fire retardant and won't melt away or warp like those that are created via similar injection molding processes, such as plastic injection molding.
  • Tensile Strength: To piggyback off of the above advantage, LIM parts are strong which makes them applicable for a variety of industries.
  • Flexibility: Remember, LIM parts are typically rubber. And one characteristic of rubber is its flexibility.
  • Accuracy: Another big advantage is the high level of accuracy that LIM parts are produced with.
  • Automation: LIM is a process that can run around the clock with minimal supervision.

 

Limitations


Like any production process, LIM isn't without its disadvantages as well. For instance, LIM is a process that takes a high level of expertise to carry out, as there are numerous points during the fabrication process where things can go wrong, potentially dramatically impacting the quality of the part run. Perhaps the biggest concern that must be taken into consideration is the potential for leaks during the process. Remember, LIM is a liquid process, so there's always the chance that the mixture could leak at some point in the process if all of the production components aren't carefully inspected and fine tuned prior to a part run. This often occurs when the part material mixture seeps through cracks or gaps during the process. To help combat this, ASH™ users high quality sealants and sealers to keep everything in place where it needs to be.

 

LIM isn't an ideal process for every part application. For instance, there are greater up front costs for part runs because a mold has to be created. That's why it's best used for short or long run manufacturing and/or to fine tune prototypes prior to manufacturing. The latter is important because engineers are able to experiment with different material configurations, surface finishes and additives to get the part that they want before green-lighting it for production.

 pic-ash guy

Design Considerations

 

Generally speaking, design considerations for LIM are about the same as design considerations for plastic injection molding. However, there are a few points to note:

 

  • Liquid silicone rubber, while it doesn't shrink inside the mold like thermoplastic parts do, it can shrink up to 3 percent after its ejected from the mold and is left to finish curing.
  • Venting: Venting is a crucial part of mold design in the LIM process. That's because it's important to avoid air entrapments, which can lead to flawed parts.

Materials Used

The most common material used in the LIM process is liquid silicone rubber. It's a high-purity platinum core silicone that's able to create the highly durable parts that are utilized in so many industries. For example, liquid silicone rubber is especially cherished in the medical industry, as tools and instruments made from the material are biodegradable, well made and reduce the risk of contamination. Fluoro liquid silicone rubber is another material that is making headway via the LIM process, especially when it comes to automotive parts, smaller parts or parts that require extreme precision.

 

For more information on ASH™ liquid injection molding and if it would be the right method for your part run, contact one of our specialists today.