Mold fitting is one of the most important steps in the process of making plastic parts. All of the parts that are made or bought must be put together and worked. Mold fitting is a job that requires a lot of knowledge about mold structure and injection molding. The quality of mold fitting determines how well the mold is made and how quickly it can be injected.

In order to make a good product, there are a lot of things that need to be done right. These things include:

Mold Core and Cavity

The design of the core and cavity of the plastic injection mold die is what makes the final product look the way that it does, internal and external shape: Mold core and cavity. Core determines the internal shape and the shape of the mold cavity. The mold cavity determines the external shape.

They are the parts of the mold tool that make plastic products look like they do when they are done. The hot molten material is poured into the core and cavity. Then, it hardens into the shape it was made to be. The way the core and cavity are made is very important to how the product is made.

Essential parts of the Core and Cavity!

Gate

This is the point where the runner meets the core and cavity of the machine. Often, it is made to be a little narrower than the runner so that the plastic there will be thinner when it hardens, making it easier to remove the runners from the floor. If the tool isn’t made correctly, it won’t fill the core and cavity correctly.

Gates need to be put in the right places to make sure that happens. As the gates are always visible on the finished product, the tool also needs to be made so that they don’t detract from the look of the finished product.

Runners

Allow the molten plastic to get to the core and cavity with the help of runners. They can also be hot or cold. Hot runners are more expensive, but they give you more options for where you can put gates because they can make them smaller, and they also save money because the plastic in the runner remains hot inside and can be used for the next part. Mold the core.

You can think of them as the shaped parts of the mold tool on each side that help make the plastic product look its best when it is done. The hot molten material is poured into the core and cavity. Then, it hardens into the shape it was meant to be. The core and cavity design is very important to how the product is made.

Lifter

Many different types of lifters are out there. Different mold makers also have other ideas about how to make the lifters. The lifter is a feature that is part of the molding process of injection molding. The way the machine is built and put together changes depending on the other specifications.

It also depends on how the product is made. But the general way the lifter works is the same in every system. The goal is to make it easier for the product to come out of the mold or lifter. It does this by giving you more room to move. That would not happen in normal ejection systems, but it does now.

Types of Lifters

Lifters are made up of the lifter’s body and the parts that make up the lifter. If they are part of something, they are called “integral” or “not integral.” The integral lifters have one body and all parts that make it up in one piece.

Non-integral Lifters

The non-integral lifters have two separate units for the body and parts. The integrated lifters are better for molding small parts. They are easier to make and move around because they are simple. Non-integral lifters work with bigger pieces. This way, they can be made bigger, making them easier to work with and maintain.

Integral Lifters

A lot of people use integral lifters. They are more durable and more compact. It can also be different in shape. They have cylindrical lifters and T-shaped lifters, so you can choose which one you want. The cylindrical lifter is used more often because it is easier to make. The T-shaped filter is used more often for bigger products that must be molded to very high standards, such as cars.

As the name implies, Lifters give a “lift” to help the product be thrown away. They let the product move to the side as it is ejected. They become part of the mold close and open mechanism in an incline. If you want to put the lifter in the right place, you need to put it in a piece of wood that has an incline.

Lifter and lifter plates move. A block comes between them and lifts them. When the mold has cooled down, it is ready to be opened. At first, the ejector plate moves to push the pins out when the mold is opened. This is called a “conventional system.” These things push the product out of the mold. There are a lot of different types of ejectors, like blades and pins that you can use. But the mechanisms for releasing are the same.

Sliders

A lot of products that are made with injection molding have a lot of different parts. Unique needs slide or move a mold sideways make complex shapes and release the finished product when the mold is opened. Often, a “slide” is used to pull the core out of a piece of wood. It is used to change the vertical movement of the mold closing or opening into horizontal movement. to put it in a more simple way.

Slide mechanisms are usually made up of a forming surface, slider body, guide pin, wedge, press block, and wear plate. Injection mold sliders are subject to wear and tear when they are used, so surface nitriding is often done to keep them in good condition for longer. Even though the most interesting part of working with a slider is making complex geometries, there is also a challenge in making sure that the slider doesn’t move during the injection molding process.

Role of the Sliders

People use processing holes on different sliders in the process of molding, but they each play a different role. There is a parting line on both the front and back parts of the product. The big slider around the product makes up the front part, and the slider is what makes up the back part. When you put two sliders next to each other, there are four lines that hold them together.

There must be a smooth line between sliders, cavities, and sliders. To do this, you must polish the four sliders and the cavity together with the sliders and cavities. There are a lot of holes that can be made for screws because the four sliders need to be stuck in the cavity.

Each slider has two processing screw holes and two processing positioning holes. The processing positioning holes and screw holes are made at the same place as the cavity. There are two parts of re-polish that we must do. First, we must use a screw to lock the slider into place in the cavity, and then we must use a pin to make sure the slider is where it should be.

Using processing holes in injection molded parts improves the efficiency of the molding and assembly and the quality of the mold. This is based on what we’ve seen in practice. It should be made more popular and used more often.

The Connection between Slider and Core & Cavity!

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You must makes sure that the core and mold cavity can be separated smoothly, so the product comes out of the mold without a problem. At the same time, it makes sure that there aren’t any holes or gaps between the core and mold cavity when it’s closed up. When small gaps start to appear, small effects like burr and flash start to happen. Large effects like mold geometry deformation and product failure start to happen, too.

Grinding in Mold Fitting

Some accessories may not fit into the mold because they are too big. Because the part is 0.01mm bigger than the pipe, it can’t be put in. At this point, it is important to grind off the 0.01mm so that you can put the part into the pipe smoothly.

Most of the time, the mold fits the parting surface and parting line of the product without any problems. The cavity and core are both responsible for how the parts look on the outside and inside. The slider makes sure that the mold cavity and mold cavity can be separated smoothly and that the product can be taken off of the mold cavity smoothly.

It also makes sure there are no gaps between the mold cavity and the mold core when the mold is closed. Once there is a gap, it means that the product isn’t good enough or doesn’t work. A Lifter is a piece of equipment that makes sure that you can throw the product out. The mold must be ground down to make sure parts can be fitting into the mold because they are too big.

As a result, if the mold fitting and assembly aren’t strict enough, the number of product defects or unqualified phenomena will arise. The defective and unqualified products also mean that the mold or parts need to be changed, which increases the cost and lengthens the delivery time, which causes a lot of money to be lost. Putting together a mold in the correct way ensures that the product is good and saves time.

Electrical Discharge Machining (EDM)

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EDM is a process that uses heat to remove extra material from a workpiece. The process does not require mechanical force.

This process makes sure that engineers only use electrical discharges to make the shapes they want. It is a very precise process that doesn’t use a tool on the workpiece. EDM is often the best way to do it when you need to work with hard materials like titanium or make complicated shapes.

After the mold parts are CNC-machined to get the finer details, the geometry of the mold is made even better. This is done with electrical discharge machining (EDM). It can’t be done with a CNC mill. Wire EDM is used when cutting gear teeth with sharp corners inside and square holes.

Then, the core, cavity, sliders, lifters, and inserts go through the sinker EDM process with the copper electrodes that have been made by hand.

Sinker EDM can make very small things like text or internal features that are hard or impossible to make with a CNC machine.

It doesn’t take as much EDM to make this sample part, but it does need to be made on both sides. Once the cavity side is done, it can move right on to polishing to save time while the core side is still being made.

Final Thoughts

Mold fitting has a great impact on the production of the product. The number of product defects usually occurs during the mold fitting step. The sliders, lifters, core and cavity, and inserts are directly connected during the electrical discharge machining. This is where the final steps in the production process start. The corners were smoothened, and everything will go into the sinker with copper electrodes made by hand.

Before starting a project with plastic injection molding, think about all the things that could make your parts more or less expensive. Smart design, the right materials, and careful manufacturer selection can make parts better while keeping costs down.

Step Rapid has many years of experience when it comes to the production of plastic parts. Plastic injection molding is one of their services and has proven to be the best producer, even in bulk orders.