Exactly What is the Direct Injection Process (DIP) in shoemaking?

In this blog post, you will read: This blog provides an in-depth look into the Direct Injection Process (DIP) in shoemaking, also known as Direct Soling.

Shoe manufacturing is a complex process that can involve various techniques.

In this blog post, we will take a look at the DIP (Direct Injection Process) of shoe making and explore what makes it so special.

We will also discuss the benefits of this process and provide some tips on how to distinguish shoes made with DIP construction.

So, if you are interested in learning more about this unique shoemaking process, be sure to keep reading!

1. What is the direct injection process (DIP)?

The DIP is short for Direct Injection Process, known as Direct Soling in Shoemaking, which is a technique used to inject the liquid sole material (normally a polymer) directly onto the upper and quickly molded. This results in a seamless bond that creates a very strong and durable shoe.

pu direct injection method to attach sole with upper body
PU direct injection method (image from DESMA website)

The DIP process is typically used for athletic footwear, as it provides a strong bond that can withstand the rigors of activities such as running and jumping.

The direct injection process is also used in the construction of safety, hiking, and military boots, as it provides a durable bond that can resist abrasion and wear. 

ecco shoes
Ecco shoes

2. How does the DIP process work in shoemaking?

The specific direct injection moulding process begins with the finished shoe upper (hold with the lasted) being placed over a sole-shaped mould at the injection moulding machine.

dip direct injection process
dip direct injection process

The mold is then heated to a temperature that is slightly below the melting point of the liquid sole material.

The liquid is then heated and injected into the aluminum sole mould cavity instantly around the upper, with a high mixing speed of over 18000RPM creating a better grain structure and it rapidly moulded to the upper directly resulting in a permanent bond.

multiple injection machines positioned

3. What materials are best for DIP in shoemaking?

The best materials for DIP in shoemaking are those that have a high melting point and a low viscosity.

This ensures that the material will be able to flow easily and will not solidify too quickly.

Some of the most common materials used in the direct injection process include polyurethane (PU) and Polyvinyl Chloride (PVC) in the footwear industry.

Polyurethane offers superior material physical properties compared with PVC in the footwear industry.

It is more durable and resistant to abrasion and wear, making it a better choice for shoes that need to withstand strenuous activities.

It is also less likely to tear or rip, making it a more durable material overall.

Additionally, polyurethane features a very low density between 220 and 230 g/l than PVC, making shoes made with this material lighter overall.

PVC is a cheaper alternative to PU, but it is not as durable and is more likely to tear or rip. They also tend to be heavier than shoes made with Polyurethane. It is often used in the construction of budget-friendly shoes.

For these reasons, polyurethane is often the material of choice for shoes made with the direct injection process.

However, PVC can be a choice for budget-friendly shoes that do not need to withstand as much wear and tear.

4. What are the benefits of using the DIP process in shoemaking?

injection point
injection point

There are several benefits of using the direct injection process in shoemaking.


Without adhesives or stitching, the direct injection process creates a seamless and completely water-resistant bond between the upper and sole. This results in a shoe that is much more durable than those constructed with other methods.


Shoes made with direct soling construction are often more comfortable and provide better arch support than their traditional counterparts.


The direct injection process also provides greater outsole design flexibility, as it opens up new possibilities for incorporating different curves into the silhouettes of the sole. This allows for a more personalized shoe that can better meet the needs of the customer.


In addition, It is more environmentally friendly. The lack of adhesives reduces the amount of VOC on the shoes and the high production efficiency, less energy, and low material wastage, resulting in fewer carbon footprints during the manufacturing process.

5. Challenges to using the DIP process in shoemaking?

direct soling
direct soling, image from https://www.desma.de/en/machines/direct-soling/
dip mould
dip outsole mould

One of the challenges of using the DIP process in shoemaking is that it requires specialized equipment and a high level of expertise. This requires considerable initial investments in injection molding machinery, mould and last, and it can make it challenging to find shoemakers who can properly execute the construction technique. Additionally, the direct injection process is not well suited for small batch production, making it difficult to produce custom or limited edition shoes.

Another challenge of direct soling is that it can be difficult to achieve a perfect fit between the mold gap and the finished shoe’s upper thickness. This is because the upper and sole are injected together in one piece, so any inaccuracies in the direct injection process can result in blemished soles.

Eg. if the upper is too thick, there will be some shortage on the outsole side edges.

This is why it is important to work with a shoemaker who has experience in the direct injection process and who can ensure that the direct moulding process is done correctly.

Despite these challenges, the direct injection process offers several advantages that make it a popular choice for many shoemakers. When executed properly, shoes made with this process can be some of the most comfortable and durable on the market.

6. How to distinguish the shoes made with DIP construction?

There are several ways to distinguish between shoes made with direct soling construction and those made with other methods. 

One way is to look at the mould nip line. In the directly injected construction, this line will be very clear, as the mould is closed by hydraulic pressure. In other construction methods, the mould closing line is not obvious.

Another way to tell the difference is by looking at the outsole. In DIP construction, the outsole will be one piece with no seams or glued areas. In other construction methods, the outsole will usually be made of multiple pieces that are glued or sewn together.

Tips for PU DIP construction shoes:

You may find some small bubbles holes on the surface which are caused by gas not being able to escape during the molding process. These are normal and will not affect the durability or good performance of the shoe.

And normally the PU material is always with less density and lower weight.

7. Why did we choose DIP to produce all of our kid’s shoes? 

DIP is a great fit for our mission to produce professional kids’ footwear for those who care about children`s Wearing Secure, Well Fitting, Comfort, and Innovation.


DIP construction results in lighter-weight shoes. This is important for kids, who often have to carry their shoes around with them all day. 


the one-piece outsole means that there are no weak spots or areas that can come apart. This is important for kids’ shoes because they often get put through a lot of wear and tear. 


the shoes are made to be more flexible and comfortable. This is important for kids because they are constantly running, jumping, and playing. 


the shoes are made to be more durable. This is important for kids because they often outgrow their shoes before they have a chance to wear them out. 

If you’re looking for a shoe manufacturer that uses the DIP process? Look no further than Changzhou TopUnion Shoes Co., Ltd! We are a leading kids’ shoe manufacturer in China with over 20 years of experience. We use the latest technology and equipment to produce high-quality shoes for kids.

Contact us today to learn more about our products and services!

Top Union Automatic Production Line
Top Union Automatic Production Line

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