What is Liquid Silicone Rubber Injection Molding (LSR)?
LSR is distinctly known as a two component compound. That is, it has polysiloxane chains which are usually reinforced with polymer. Ideally, it has compounds:
- Platinum catalyst as the first compound
- Methylhydrogensiloxane as the second compound
Liquid injection molding (LIM) LSR, involves mixing and directing two compounds into a mold where curing takes place in presence of a catalyst (platinum catalyst).
Benefits of LSR Injection Molding
Some of the main advantages of injection molding LSR are:
- Short manufacturing cycles
- Potential to automate the molding and demolding processes
- Wasteless production due to direct injection
- Flexible tooling and mold design allows it to produce parts with intricate geometries and functionalities
- Produces parts with standardized dimensions and superior quality.
- High reliability since the molding process employs advanced machinery and tooling technology.
- Meticulous process controls resulting in high-quality parts
- Fast production rates due to shorter manufacturing cycles
- Produces parts that are resistant to degradation by the harmful UV light.
- Hygienic and safer production rooms because it utilizes modern production methods
Injection Molding Liquid Silicone Rubber Disadvantages
- Liquid silicone rubber cannot be remolded, meaning you can’t recycle parts.
- LSR can burn if the temperatures are not adjusted during curing
- Untreated LSR is sticky and attracts dirt and dust particles.
- Liquid silicone rubber can be corroded by alcohol or petrol.
- Substances like latex hinders LSR’s curing.
- Premature curing necessitates disassembling and scrubbing production units, resulting in longer production time.
LSR Molding Vs Conventional Injection Molding Process
Ideally, the two processes are virtually the same. That is, from material preparation, mold design to the point where you inject the material into the mold.
The difference comes in the curing process. In LSR injection molding, you will inject two different compounds in the mold. During the process, material experienced accelerated cooling. Usually, the LSR injection molded product is permanent and cannot be remelted again.
Unique Properties of Liquid Silicone Rubber
1. Extremely Durable:
They can withstand every extreme temperatures. This characteristic explains why you will find liquid silicone rubber parts near engines where combustion takes place, continuously yielding high amounts of heat. Likewise, LSR parts are unaffected by exceedingly cold conditions.
2. Resistance to Microbes and Most Biochemical Substances
Liquid silicone rubber parts remain unaffected by moist conditions, various microorganisms, ozone gas, and most alkaline and acidic solutions.
3. Excellent Mechanical Qualities
LSR is extremely elastic, hard, and has low compression.
4. Superb Insulator
LSR is a common insulator in different electrical and electronic devices. The primary reason for LSR’s widespread use as an insulating material is its ability to withstand extreme temperature conditions.
5. Exceptional Natural Clarity
LSR’s outstanding optical clarity allows manufacturers to produce limitless multicolor of products. Besides, this transparency allows great light illumination.
6. Biocompatibility
Several studies have revealed that LSR is significantly compatible to our body tissues and fluids. Further, it can be sterilized using several techniques to meet the stringent regulatory requirements.
Capabilities in LSR Injection Molding
With LSR, you can achieve a wide range of capabilities such as:
- Production of nano components weighing less than 10mg
- Production of ultra-thin sections and membranes of less than 0.1mm thickness with homogenous quality and dimensions
- Production of delicate parts using automated production and special tooling
- Flash-free, efficient, and cost-effective production resulting in consistent part dimensions
- Forms accurate blind sections
- First-rate precision that can produce varied kinds of surface polishes
- Ability to produce various elbow undercut sizes
Liquid Silicone Rubber Injection Molding Machine
You need an injector and a metered pumping unit to assemble An LSR injection molding production unit. Overall, a typical LSR injection molding setup consists of:
1. Injectors
As the name suggests, this unit injects liquid silicone into the metered pumping unit.
2. Metered Pumping Units
These metering devices pump the primary liquid raw materials in the required ratio. Similarly, it pumps the base silicone and catalyst compound.
3. Plungers
Comprises two drums connected to the metered pumping unit. They are the main material-mixing containers.
4. Mixers
This unit helps mix the materials in the plunger to form a uniform mixture before it is drained into the mold.
5. Nozzle
This unit drains the liquid silicone mixture into the mold. It is fitted with a valve to avert leakages and excessive loading.
6. Mold Clamp
This acts as the clamp’s fastening device. It locks and unlocks the mold during production.
Remember, the choice of material and tooling system affect the liquid silicone rubber injection molding price.
Liquid Silicone Rubber Injection Molding Process
LSR injection molding involves series of processes such as:
Step 1:
Preparing the liquid silicone rubber ingredients by adding the base silicone and the catalyst to the metered pumping unit.
Step 2:
Adjust the pressure rate to enable the injector pressurize and inject the liquid silicone into the pumping units. You should remember that the injection pressure determines the injection rate.
Here, the pumping unit mixes the base silicone and catalyst uniformly to form a homogenous mixture.
Step 3:
In this step, the mixer deposits the catalyst, base silicone, and other additives into the nozzle
The nozzle deposits the homogenous mixture into the mold, where it is appropriately cured. Curing entails increasing the mold temperature to convert the liquid silicone into a solid rubber material.
Step 4:
The last LSR injection molding procedure involves reducing the mold temperature, demolding, and cooling the product.
Common Applications of Injection Molded Liquid Silicone Rubber Parts
LSR is commonly used making different parts and components, including:
- Automotive applications like stoppers, sealing membranes, coverings, and optical couplings
- Electronic applications like LED lenses, keyboards, touchpads, and electric connectors.
- Household merchandise like baby toothbrush, spatulas, and pans.
- Medicare devices and drug delivery equipment like wearable drug pumping systems, flexible tubing, nipple protectors, and syringe stoppers.
- Interior and exterior lighting.