In production, the materials you use are very crucial. A material that doesn’t provide quality is bad. Your production is wrong when you use materials that are not compatible with the product. So, you have to select your material with care. They are to suit your desired product but also to suit your production process.
The more materials you know about, the better your chances of selecting the right one. So, if you are using injection molding, read this. You will become familiar with LSR which is suitable for the injection molding production process. LSR injection molding is like other plastic moldings. They are two materials that follow the same process.
But still have some major differences to note. Some of these are the pressure rate, the injection rate, and the features of the materials. So, knowing about general plastic injection molding would help. However, this article will guide you on LSR molding. But first, let us define LSR silicone. And explain the injection molding process.
What Is LSR Liquid Silicone Rubber?
LSR stands for liquid silicone rubber. It is a material suitable for many industries. Its parts make it ideal for the production of different products. Its chemical parts bring about its unique physical state.
LSR is an elastomer comprising many molecules. It differs from other elastomers. It is stronger with high heat resistance. It is a good electrical insulator with chemical strength. LSR has properties that make it suitable for many applications. It has properties for heat and water resistance.
It is transparent and an electrical insulator. LSR is used in many industries. And some of its products include; gaskets, keyboards, syringe tips. Lighted buttons, steam-sterilized parts are products of LSR. And so much more. LSR is vital for production in top industries.
The Difference Liquid Silicone Rubber And Silicone
Also, note that there is a difference between silicone and LSR. Liquid silicon rubber and silicone have a slight difference. It is difficult to separate their products. LSR is a fluid that is in a liquid state while silicone has no fluid. It is solid, with no form of fluidity.
LSR and plain silicone have different use cases. While industrial products like auto parts are from silicone. LSR has a wider use case. You can use it for baby products. You can use it to make various kitchen gadgets.
You can also use it for medical supplies. In their shaping, they also differ. Silicone is compression-molded with less safety. While LSR is injection molded. And it has a higher safety level.
What Is The Injection Molding Process?
Injection molding is a production process. It is a process for producing items in numbers. It involves the injection of heated substances into a mold. The mold helps create the shape of the desired product. And it is not a manual process.
6 Factors That Determine LSR Molding!
Now, what are those factors that influence LSR molding? The structure, the temperature, and much more are included. If avoided, these factors can damage the production process. This is why you need to know these factors.
And also identify how they affect the molding process. This would save you time and money. And also give you top results. So, the factors that influence the LSR molding include;
This is the first on our list of molding influences. Shrinkage affects LSR injection molding process. Most times, this happens after heating and molding. There are still key aspects during molding that influence it.
LSR is not a substance to shrink much. But after stripping and cooling off, there is shrinking. The liquid tends to shrink by about 2.5% – 3%. And this can alter the desired shape of your product. Or even the desired thickness.
So, you need to consider shrinkage in the process. The content of the rubber affects the level of shrinkage. Still, parts in the mold can be responsible for it. Some of these include; the temperature. The temperature causes the mold to shrink more. Also, the pressure of the mold cavity can cause shrinking.
The temperature of the plastic material is a factor. Especially, when stripping, it can lead to shrinkage. The compression rate of the plastic material is also important. The more compressed the plastic, the more shrinkage occurs. And if you carry out re-vulcanization, expect more shrinkage of about 0.5- 0.7%. So, be careful with shrinkage.
· Mold Material
The mold material is also vital in LSR molding. The mold determines either having a good or bad result. For LSR which has oil resistance. The mold should be of a stronger material. There are unique-designed powder metal and chrome-plated steel. These materials are best for mold.
Sometimes, you might be dealing with high-wear materials. In this case, craft mold with replaceable high friction parts. This helps you save costs. You wouldn’t have to replace the whole mold but only the replaceable parts.
You also have to consider the inner parts of the mold. The mold cavity determines the look of your product. So, let the cavity surface match the desired product. Let them match. And when making transparent products, let the inner mold surface be of polished steel. This would give you a better outcome.
· Temperature Control
No matter the type of electric heater you are using. You have to control the temperature. Unequal distribution of heat produces products that aren’t equal. An electric heater is what molds LSR. So, you have to ensure equal distribution of heat. This will give a cured LSR that is perfect.
If the temperature is low, it will affect the quality. This because will cure at a slower pace. There would be issues bringing the product out of the mold. It is important that you control the temperature. Too much heat can cause air to leak. So, one way to control heat is with the insulating plate. You use the plate as a covering over the mold. This helps to reduce heat and prevent air leakage.
· Cold Runner System
The next influencing factor is the cold runner system. This is very important to the outcome of LSR molding. An effective cold runner system reduced material waste. It also reduces the labor intensity. At other times, it also reduces operation time for molding.
What the cold runner does best in using LSR. There is new tech that allows mass production of rubber. You can get to produce silicone rubber items. But without removing the injection ports, this tech has a cold runner system with an injection point.
It takes up very little space. And enables mass production. You need a balance in the temperature of the cold runner. If it’s too hot, it can cause vulcanization. But if it’s too cold, the cure isn’t pure.
The exhaust is also a vital factor in LSR molding. Exhaust refers to the removal of air after molding. After injection, the air is kept in the mold’s cavity. This air is then compressed after you close the mold and then ejected through the aeration groove during mold filling. This is the exhaust process.
The exhaust process is vital. You need to eject compressed air after molding. If not, it remains within the mold. And this causes your product to have white edges. Thus, causing defects to your product. So, you need to eject compressed air after molding.
Having a vacuum inside the mode creates the best effect. It helps to close the mold. It also starts the injection pressure. Some equipment makes it easier to remove air. While preventing rubber spill or expansion.
· Parting Line
You have to decide the parting line for successful molding. It is vital to the whole process. It even includes the exhaust. The parting line is especially important in LSR molding. This is because the viscosity of LSR is low.
To avoid too much glue, the parting line must be exact. This is one importance of parting line to molding the exhaust relates to the groove of the parting line. And this groove is vital. It must be present at the final stop of the rubber. That is, it must be in the injection pressure.
It helps to prevent bubbles inside the rubber and also to cut glue strength loss. Also, the placing of the parting surface determines break-off. And the plastic chamfering helps allow uniform gluing.
In summary, LSR is a great material for production with high water, heat, and oil resistance. No wonder it is famously used for many appliances. Its qualities are top-notch. But also it does the required job with less stress.
Remember that silicone rubber is different from silicone. Do not also forget the vital steps to consider. These steps are critical to the success of your molding. For temperature, cold runner systems, balance is the key. Find the right balance and everything would be fine.