Background of Rubber, Silicone, and Synthetic Rubber Molding Processes

For fifty years, our family has produced quality custom rubber and silicone molds to some of the largest brands. Those fifty years have provided us with the knowledge and expertise necessary to fully understand the world of custom molds. In this blog post, we'll go over exactly what custom rubber and silicone molds are, how they're made, and what they're used for. 

There are several techniques used to make custom molds. What a lot of consumers don't realize is that the process has to be adapted to fit the part being made. Some companies will do the opposite and try to make the part fit their pre-established manufacturing process. This leads to lower quality parts and it's something that Rubber Industries avoids. 

What Are Custom Rubber and Silicone Molds? 

In general, molds are the tools used to shape and form a material into a desired product. Typically, the material can be injected, pressed, transferred, or poured into the mold. The method used is largely based off of the type of part being made. 

When people think of molds, they most often think of the old children's toys that involved pouring molten plastic or candy into a small mold and allowing it to harden. While the process is much more complex for manufacturing real parts and items, the general idea is similar. 

What Are The Different Molding Techniques That Rubber Industries Uses To Produce Our High Quality Parts? 

As mentioned above, there are several different types of molds and processes used to create our products. Depending on the product being made and the application that the resulting product will be used for, a different process will be chosen and possibly adapted to ensure that the resulting product is properly made. 

Within the confines of our large, 5 acre, campus, we use a number of methods to produce our quality products: 

• General custom molding for rubber and silicone.
• Overmolding services
• Liquid Injection Molding. 

How Is Each Molding Process Accomplished? 

The general act of creating a custom molded rubber or silicone product requires a mold to be made from scratch. Depending on the method used, the mold will be made differenly. 

Some companies will use a temporary aluminum alloy to create their prototype molds. These are typically cut at a CNC machine under the watchful eye of an experienced CNC machinist. At Rubber Industries, we create our molds a bit differently. Instead of using temporary aluminum to create the tooling for our customer's parts, we utilize stainless, 4130, and 4140 steel. Interestingly, steel tooling from Rubber Industries is not initially more expensive than aluminum, and our stainless/steel based tooling will last much longer. It's not uncommon for custom tooling made of aluminum to be damaged, lose its form or lose it high precision entirely before a project is near completion or not able to manufacture a second longer manufacturing run. With our tooling made from true tool steel, we can produce a customer's entire order with the same tooling and it will almost certainly last for much longer than that. We offer our custom tooling starting at $800 dollars and that's remarkably inexpensive when compared to the amount of replacement tools that would be necessary when using aluminum. 

Injection Molding With Rubber

After the general creation of the mold, a popular process used is rubber or silicone molding. The main idea behind rubber and silicone molding is efficiency and that is something that we've mastered over our fifty years of business. 

To begin, the material used for the desired product has to be processed to maximize efficiency and minimize waste. To do this, Rubber Industries takes a mix of bulk rubber and slices it into approximately two inch wide strips that are a half of an inch thick. These strips are long or continuous in length. 

After the material is properly sized, it's automatically fed into a mechanical screw. The screw forces the material into a barrel and it is then pre-heated to reduce its viscosity. With a lower viscosity, the rubber can fill the cavities of the mold much more quickly and easily. This leads to more efficient use of the material and shorter cure times once the mold cavity is filled. 

After the material is heated, it is pushed into the mold cavity until the cavity is filled. After that, the material is cooled and cured to produce the end product. 

Injection molding is extremely efficient and precise. The items made with it can exhibit extremely tight tolerances when a properly designed mold is used. The products are also made faster since the cycle time of the presses used are shorter for rubber injection presses. Our larger presses are capable of injecting up to fifteen pounds of material in a single cycle. Pre-forms are completely unnecessary for injection molding and this saves production cost by eliminating the need for a staff member to be present to consistently change the pre-forms. 

I bet you didn't realize that we buy truckloads of material just for injection molding, and that's why we are so competitive.  Size matters.... 

Besides the speed and efficiency benefits of injection molding, there are also cost benefits in how the material is acquired. We purchase truckloads of rubber every year to utilize in our injection process and it allows us to lower our manufacturing costs drastically. It's also a flexible process and allows for the creation of overmolded products. 

Liquid Injection Molding Of Liquid Silicone Rubber

Injection molding can also be used to make liquid silicone rubber products. LSR is an incredible material that has a lot of advantages over natural rubber in certain applications. The process for injection molding LSR is fairly similar to that of rubber. Except, liquid silicone is a synthetic material that we can create with thousands of different custom formulas. This gives it an advantage when it comes to flexibility of use. 

Despite the processes injection molding of rubber and LSR being similar, extra precautions need to be made when making products from LSR. 

LSR is resilient to mold, resistant to bacteria growth, UV light, x-rays, extreme temperatures, tearing, and degradation. It's also can be made out of completely non-toxic and FDA, even USP Class VI approved ingredients. This makes it a prime choice of material for medical products and other products that require sterility. Because of this, LSR products have to be made entirely separate from other products in a clean, dedicated, and well-managed area. If the product isn't made in such a place, it can be contaminated and fail to meet the standards of customers, or even cause serious issues if it's used in a medical application or certain consumer products. For this reason, Rubber Industries houses all of their LSR equipment in a dedicated clean area. 

What Type Of Custom Mold Material Is Best For Your Product? 

The material used in the production of a product is entirely dependent on the product being made. For instance, natural rubber wouldn't typically be used to encapsulate a medical device. However, LSR is perfect for overmolding onto something such as an implant to protect it due to its natural resistances to microcrobes and other bacteria. On the other hand, using rubber for something like an overmolded tool handle is perfectly acceptable. It's all dependent on the intended application of the desired product. 

Liquid Silicone Rubber is also the better choice for high heat applications like the manufacturing of automobile engine gaskets. Certain LSR formulas can withstand up to 250 degrees centigrade without becoming unreliable or malfunctioning. LSR is also available in any color. Naturally, it's optically clear. So, it's perfect for use in transparent products. However, it can also be colored via custom color mixtures. 

At Rubber Industries, we have fifty years of experience with the use and production of these materials. When you come to us for your prototyping or production needs, we can easily help you in finding the right material for your product. We will also show you which exact compound will the most effective for your application. 

The Entire Process Is Available At Rubber Industries 

Now, custom molding is a complex topic that consists of a lot of technical jargon and memorization of chemical compounds. Luckily, Rubber Industries can handle the entire process, from start to finish, at our 5 acre campus. We can create the tooling necessary to mold your products, the custom compound that your product will be made of, and then handle the entire manufacturing process. We understand all of the technical jargon and we have decades of experience using the different materials. If you've got something that needs to be made, we can help.