Silicone molds – those clever and practical molds or jars that can be used to prepare practically all kinds of things.
Different approaches can be taken when making a silicone mold.
In this article, we will focus on industrial applications for producing silicone molds using methods such as vacuum casting. This is in contrast to more DIY or amateur approaches to making silicone molds, such as for making items at home.
Instead, we will focus here on prototyping silicone molds, especially for plastic items.
Making a silicone mold: which way is better
When it comes to making silicone molds for larger purposes, two approaches are commonly used.
Firstly, there is silicone injection molding, and secondly, there is vacuum molding.
Both methods have their advantages and disadvantages. Below we will talk briefly about each of them.
Injection molding
As the name suggests, this is a molding process in which melted plastic raw material is injected into the mold.
Benefits:
- Greater flexibility in terms of the materials that can be used.
- Same flexibility in color selection.
- Very high level of accuracy.
- Low waste: Leftover materials can often be reused.
Disadvantages:
- Not profitable for small quantities.
- Initial setup costs can be quite high.
- Relatively longer lead time for production delivery.
Vacuum Casting
As the name suggests, this is a silicone molding technique that uses vacuum.
Benefits:
- Low initial setup costs.
- Shorter delivery time.
- Particularly suitable for producing smaller batches of products such as silicone prototypes.
- Ideal for producing large plastic parts.
Of course, vacuum casting to make a silicone mold also has its disadvantages:
- This method may not be suitable for large orders.
- For more complex items, detailing may be minimal.
Now that we've listed the pros and cons of both methods, we find it much easier to choose between the two:
- If more details are required, injection molding is preferred.
- Vacuum casting makes the most sense for silicone prototypes in small quantities.
- Vacuum casting is ideal for fast production times.
How to Make a Silicone Mold Using Vacuum Casting
The essence of making silicone molds in this way is the use of a vacuum, that is, a space completely devoid of matter.
The process usually starts with using two different molds – one at the top and one at the bottom.
The raw material is mixed separately and then placed into the mold. Vacuum pressure ensures solid casting in the chamber. Final casting is usually done in an oven to ensure complete and even curing.
Despite some small flaws in the process of making silicone molds via vacuum casting that we mentioned earlier, this remains one of the most sought after methods of making silicone molds – despite all the advantages we listed above.
Therefore, in this section we will go into more detail about the silicone mold manufacturing process.
Keep in mind that most of this refers to urethane casting, which is a casting process in which additives, curing agents, or polyurethane resins are poured into silicone molds to create a variety of different plastic items.
First step – masterful skill
The first step in manufacturing a silicone mold through vacuum casting involves the master crafting process, which first involves creating digital renderings using systems such as CAD. They are used to create 3D solids, usually using 3D printing or CNC machining.
Once everything is completed and checked for accuracy, we move on to the next step.
Second step – preparing the molds
In the second stage, silicone molds are made with liquid silicone. The watering box is usually filled halfway with liquid silicone and heated until it hardens completely.
Even after this initial curing process, as already mentioned, additional curing is carried out in an oven. Although times may vary, the typical drying process takes approximately 16 hours.
Once everything is completely dry, the two halves of the template (as mentioned previously) are cut out to reveal the finished master edit.
Third and final step – creating additional copies of the master
After the master edition was created in the previous step, now it's time to make new copies of it. At this point, the empty cavity in the mold would be accurate enough to create accurate replicas of the master, as long as materials other than plastic (e.g., a mix of steel and metal, among several possible options) can be used.
This is where one of the main advantages of producing silicone parts by vacuum casting becomes evident: the fact that the silicone molds in this case can be used repeatedly, at least 20 times or more, to continuously create copies from the master.
A Note About Silicone Rubber
When we talk about making silicone molds, it would be appropriate to briefly discuss silicone rubber.
Please note that regardless of the method used to make these molds (injection molding, vacuum casting or another method), the basic raw material, namely silicone rubber, remains the same.
Due to its flexibility, durability and unique ability to withstand extreme temperatures, silicone rubber is widely used across the world for a variety of applications.
Silicone molding is the right choice for producing plastic parts in small quantities
When it comes to producing smaller quantities of plastic items, such as prototypes for larger orders, silicone molding proves to be the ideal choice.
The main reason for this is reusability; the same silicone mold can be used at least 20 to 25 times (possibly even more) to create accurate replicas of the item in question.
This is directly related to costs as it helps keep them under control. Of course, this also leads to huge time savings!
Another advantage is that silicone is easy to store for long periods of time. This is particularly useful when production needs to be stopped.
Start making silicone molds for your project
Although there are several approaches to making a silicone mold, vacuum casting proves to be the right choice for producing small quantities of silicone prototypes.
In this article we clearly describe how to make a silicone mold using vacuum casting.
As you've probably noticed, the steps to follow are quite simple. Although the production is quite industrial and not comparable to a DIY or homemade approach to making silicone molds, the method we describe is easy to follow and implement.
