Introduction
Liquid Silicone Rubber (LSR) is a high-performance elastomer that has revolutionized the manufacturing of silicone products.
As a silicone mold and product manufacturer, understanding LSR and its applications can help you deliver superior products to our B2B clients. This guide explores what LSR is, its benefits, and why LSR molding is a game-changer in the industry.
LSR, or Liquid Silicone Rubber, is a special kind of plastic made of silicon, oxygen, carbon and hydrogen. It has a special structure where silicon and oxygen atoms are arranged like a chain. This is what makes it so special. To make it stronger, special chemicals are added while it is being made, joining the siloxane chains together.
Platinum is often used as the curing agent in LSR molding，LSR overmolding, making it platinum-cured silicone rubber.
Compared to peroxide-cured alternatives, platinum-cured LSR has some great benefits, like:
It can be stretched and torn more easily.
It is clearer and more consistent.
It doesn't leave any unwanted substances behind, so the end product is cleaner and safer.
The siloxane bond in LSR is what makes it so versatile. This inorganic backbone doesn't react with biological materials, making it ideal for medical and food-grade applications.Additionally, it can be combined with organic chemical groups to tailor its properties for specific uses.The siloxane bond also contributes to LSR's outstanding mechanical performance and durability, making it a top choice for LSR molding in industries ranging from healthcare to automotive.
Liquid silicone material in the injection lsr moulding process, due to the material's low viscosity and good fluidity, there is often a risk of overflowing glue or trapped air. Therefore, in order to reduce the occurrence of defective products, the processing accuracy control of liquid silicone moulds becomes very important.
In order not to overflow caused by burr phenomenon, the liquid silicone mould parting surface precision requirements are high.
After the precision moldings parting surface is improved, the exclusion of air becomes more difficult, and it is often necessary to install an exhaust channel on the side of the moving mould to accelerate the discharge of gas. In addition, the structure of some silicone products is special, through the exhaust groove can not be good exhaust, then there is a solution, that is, the use of vacuum pumps in the mould cavity through the way of vacuum decompression.
Here we are on the liquid silicone mould several key parts of the precision control analysis.
Processing of the parting surface, the performance of silicone material needs to be recognised before processing. For general performance of liquid silicone material, parting surface precision control in 5μm below, parting surface roughness in 3μm below. For low-viscosity liquid silicone material, its fluidity is better, so the precision moldings of parting surface should be controlled below 2μm, and the roughness of parting surface should be below 0.5μm.
The processing of the exhaust channel is mainly through the grinding machine or precision machine tool. For general liquid silicone material, the depth of the exhaust channel is controlled at 2-5μm; for low viscosity liquid silicone material, the depth of the exhaust channel is 1-2μm.
Liquid silicone mould vacuum design, mainly to reduce the occurrence of trapped air bad, set up sealing in the mould parting surface, with a vacuum pump to make the mould cavity become negative pressure state after injection.
The specification of vacuum pump is chosen according to the actual demand of the mould, and it is generally recommended that the exhaust volume is more than 15m³/h, and the vacuum degree is in the degree of 0.5 torr (1kpa is equivalent to 7.6 torr, and 0.5 torr is about 66.6pa).
LSR is better than compression molding because it is more precise and efficient. LSR, used in injection lsr moulding, flows smoothly into the mold and fills even the tiniest of cavities.
This makes it possible to reproduce the mold's minutest details with precision moldings, reducing the probability of product defects and wastage, which enhances operational efficiency.Compression molding, on the other hand, struggles to offer this level of precision. Compression molding requires the polymer to be manually heated and then loaded into the mold, where it is compressed to shape using heat and pressure. This manual process can lead to inconsistencies, resulting in reduced precision and wastage.
Automation and how much effort is involved in the process:
1.Modern LSR injection molding machines are automated, which means they do most of the work without human intervention. This makes the process more reliable and repeatable. Once the process parameters are set, thousands or even millions of identical parts can be produced with minimal intervention.
2.Compression lsr moulding is often more intensive. This is because it requires manual loading of the material and removal of the product. This can lead to more inconsistencies and variations in the finished product.
Liquid silicone rubber products, usually refers to the A/B two-component 1:1 high temperature injection moulding out of the product, the product can not be recycled, hit out of the product after the test if found that the size and the design of the deviation often products will be bad, the cost will also rise.
Because liquid silicone rubber has very good fluidity, so before the mould processing must do a good job of the mould runner, precision design, and at the same time refer to the material properties of the flow rate simulation analysis, to ensure that the silicone products in line with the process requirements.
When processing lsr moulding, we must strictly control the choice of materials, and precision moldings control, to ensure that there is no error in the process, to reduce the dimensional error of liquid silicone products.
If there is any size deviation during the trial moulding of liquid silicone products, we need to analyse and improve and adjust the following aspects-
If the size is large, then you need to consider whether the shrinkage is small; under normal circumstances, it is necessary to determine the material type in advance and the guests, in accordance with the shrinkage rate of the material for mould design. On the contrary, if the size is small, you need to consider whether the shrinkage rate is too big, and consider replacing the suitable material or adjusting the mould size.
Size is large, also need to consider whether the amount of glue injection is too much, the product overflow caused by glue. You can reduce the amount of glue injection test. When the size is small, use the opposite method.
3, the size of the injection pressure, the size is large, it may also be the pressure of the injection of glue is relatively large, you can reduce the injection pressure. Size is small, increase the injection pressure to test the product.
Size is large, increase the temperature of the mould, so that the shrinkage of the material is appropriately large; size is small, the opposite operation.
Liquid silicone moulding and material, glue amount, pressure, temperature, mould and so on are related, the above for the size of the liquid silicone products with slight differences in some auxiliary adjustment direction. The main thing is to strictly control the processing accuracy, skilled process operation, can be less detour, fast and smooth mass production.
In the field of Liquid Silicone Rubber (LSR) production, precision, efficiency and quality are the keys to success. As a leading company specialising in LSR injection moulding and silicone production, TYM is committed to providing customers with tailor-made solutions to ensure that your production process is efficient and trouble-free.
