What Is Plastic Mold/Molding Technology?

Plastic mold technology, also known as plastic molding (or moulding) technology, refers to the various methods and techniques used to shape molten plastic into desired shapes and forms.

This includes processes such as plastic injection molding, blow moulding, rotational molding, compression molding, and others. Each of these methods involves the use of molds and specialized injection molding machines to produce plastic parts and products with consistent quality and accuracy.

Plastic molding technology has advanced significantly over the years, allowing for the production of increasingly complex and precise parts as well as the use of a wider range of plastic materials. Below we will focus on injection molding technology.

Some times we habitually call plastic molding injection molding, a manufacturing process where melted plastic is injected into a mold under high pressure to produce the desired shape. The mold that we mentioned above. The injection molding machine injects the melted plastic into the mold.

Although plastic molding technology is not something that most will be knowledgeable about, We all use products that have been manufactured using this method. Things like bottle caps, automobile plastic parts, home appliances, furniture components and accessories, bicycle accessories, cosmetics molding and packaging containers, cooking equipment, toys, medical plastic parts, construction parts, etc. We can say everything needs custom injection moldsand& plastic-molded parts.

The future of plastic injection molds

The future of plastic injection molds looks promising as manufacturers continually seek ways to optimize the process and make it more efficient.

One of the biggest trends in plastic injection molding is the use of automation and robotics to improve productivity and reduce labor costs. This includes the use of robots to perform tasks such as loading and unloading molds, quality control inspections, and part sorting.

Another important trend is the increasing use of 3D printing technology for mold prototyping and for the production of small batch production runs. This allows mold manufacturers to quickly and cost-effectively create molds with intricate shapes and features and to test and refine designs before committing to larger-scale production.

Sustainability and environmental concerns are also driving innovation in plastic injection molding. New materials and processes are being developed to reduce the amount of waste generated during production and to increase the recyclability of plastic products.

The future of plastic injection molding is likely to see continued growth and innovation as manufacturers seek ways to meet evolving customer demands and address increasing pressure to operate sustainably and efficiently.

If you need only a few plastic parts for your market testing or function test, then using 3D printing or CNC machining instead of plastic moulding technology will be the better option; this will save on mold making costs for you. But finally, when you need high-quality plastic moldings and a high volume of plastic products to speed up your market, you still need to make plastic molds.

Plastic mold structure

The structure of a plastic mold typically consists of two main parts: the mold cavity (fixing half) and the mold core (moving half).

The mold cavity (fixing half) is the part of the mold that forms the outer shape or contour of the plastic part being produced. This part of the mold is designed to define the overall shape and size of the part. It is created using a reverse impression of the part to be molded, using high-precision CNC machines, or through electrode discharge machining and other machining processes.

The mold core (moving half), on the other hand, forms the internal features and shapes of the plastic part being produced. It creates the internal geometry of the part, such as holes, bosses, ribs, and other features. The mold core is also created using reverse impressions of the part using high-precision CNC machines or by electrode discharge machining.

The two halves of the plastic mold, the mold cavity and the mold core, come together inside a mold base that houses the cooling and ejection systems, gating system, and other mechanisms required for the injection molding process.

The choice of materials for the mold structure depends on the specific use case, but typically it is made from metals such as P20, 1.2738, NAK80, S136, 1.2344, etc.

Plastic injection molding requires a high degree of precision and accuracy, and the mold structure is crucial to achieving a high-quality finished product.

Overall, plastic mold is made of a variety of plastic mold plates, inserts, blocks, sliders, lifters, and other metal components. Basically, plastic mold is composed of two halves: the fixed half (cavity side) and the ejector half or core side (see below picture), which consist of several mold plates and inserts.

Due to its easier machinability and interchangeability, the cavity is formed by inserts that are tailored to the surrounding frame plates (A/B plates).

The cavity and core inserts are normally separate blocks (some of which are made of solid material), which are then inserted into pocket plates that are machined into the A and B plates (which are also called cavity or core retainer plates).

The cavity and core inserts are placed in the pocket plate and left standing above the A/B plate, approximately 0.1–0.5 mm. This leaves the shut-off area. When both fix half and move half closing so that there is a small gap between the A&B plates, this will be a better fit for the cavity and core inserts.

The fixed half includes (cavity side):

a: Locating ring; b: basic plate (top plate); c: guide pin; d: insulation plate (for higher mold temperatures or hot runner mold); e: fasten screw; f: frame plate or A plate (cavity if made in solid); see below picture

Ejection half includes (moving half/core side):

a: guide bushing; b: locating bushing; c: supporting bar; d: bottom plate; e: frame plate or B plate (core if made in solid); f: support plate; g: support bar; h: upper ejector plate; i: lower ejector plate.

Plastic mold materials

There are lots of mold materials that can be used for making plastic injection molds for manufacturing plastic parts, including aluminum, steel, brass, copper, and many others. The below materials are some of the common mold materials used in the making of plastic molds.

Basic steel, which we use to make plastic molds:

1. Tool Steel:P20 (1.2311): This is a versatile, low-alloy tool steel with good toughness and machinability. It’s commonly used for low- to medium-volume production molds.
   H13 (1.2344, 1.2343), S136: Known for its excellent heat resistance, this type of steel is used for cavity and core inserts. This is for the high quality of plastic molds, whose mold life can be 1 million shots or more. This is a very tough, low-hardness steel used for high-quality cavity and core requirements. The hardness of those steels can be hardened to HRC 48–60 degrees.
2. Stainless Steel:303 Stainless Steel: This material is known for its corrosion resistance and machinability. It’s suitable for molds used in less demanding applications.
   420 Stainless Steel: Offering higher hardness and wear resistance compared to 303 stainless steel, 420 stainless steel is used for molds where abrasion is a concern.
3. Aluminum:Aluminum Alloys: Some aluminum alloys, such as 7075 and 6061, are used for prototype and short-run molds due to their lightweight nature and good thermal conductivity. However, they may not be suitable for high-volume production.
4. Beryllium Copper:Beryllium Copper Alloys: These alloys, such as C17200 and MoldMAX, exhibit high thermal conductivity and excellent corrosion resistance. They are used in applications where rapid heat removal is essential, especially for some of the deep ribs, which are not easy to cool during molding.
5. Pre-hardened Steel:718H (1.2738H) and 2738HH: Those are pre-hardened steels that have a hardness of 28 to 40, which provides moderately high hardness and good machinability. It is used primarily for cavities and cores, as well as stripper plates. The mold life-time of those steels is around 0.5 million shots or more.
6. Carbon Steel:
   1050 carbon steel: This steel is used for mold bases, blocks, and clamp plates. This steel has 25% greater tensile strength than 1020 and can be easily machined.

When selecting a material for a plastic mold, factors such as the type of plastic being molded, the expected production volume, the required mold life, and cost considerations must be taken into account. Additionally, the surface finish, dimensional accuracy, and ease of machining are critical factors in the choice of mold material. It’s common for mold makers to apply surface treatments or coatings to enhance the performance and longevity of the mold.

What is the cost of plastic molds and plastic injection molding products?

The cost of plastic injection molds and the cost of injection molding products can vary greatly depending on a number of factors, including the size and complexity of the mold, the type of plastic being used, the production volume, and the lead time for production.

These elements, as well as any additional costs for finishing, packaging, and shipping, have an impact on the price of the finished plastic injection molding product. It’s important to work closely with a manufacturer to understand all the costs involved and to get a clear estimate before beginning production.

Below, we will give you some guides on how to get a plastic mold price and a plastic molding price from your mold supplier.

1. How do I get a price for export plastic mold or tooling?

What is an export plastic mold? Which means you will buy the mold only; once the mold is completely finished and ready for massive production, you will take the mold back to your country or your specified manufacturer to mold the parts.

To get a price for export plastic injection mould there are a few things that you are going to provide to your mould supplier. In order to make sure that you have given the manufacturer all of the information that they need to check the price accurately, below are some key points for mold price estimating. This is the most important information for export molds.

• First of all, send the 3D drawing (STP or IGS format is better) to your mold suppliers. If you do not have the drawing, then you need to have some pictures of a sample with an approximate part size and show your supplier that part structure.
• Second, you need to know how many shots of the mold you require, for example. 0.5 million shots of a lifetime or 1 million shots of a lifetime requirement, because those two requirements will cause a different price.
• Third. The number of cavities: you need to specify how many cavities you need for your mold. Because one cavity and multiple cavities have totally different prices, the single cavity is cheaper than the multiple cavities mold. Because this will affect the mold price as well, if you are not sure, you can ask your supplier for some suggestions.
• Forth. Is it a cold runner or a hot runner that you require for your mold? If a hot runner, what brand of hot runners? YUDO, INCOE, etc.—all of that information will have different prices, so you need to specify your requirements. You could still ask your mold supplier for some suggestions as well.

The above items are very import information to get tooling costs for export mold because all of the information will change the mold price. You are welcome to contact us if you need any support.

2. How to get a price for injection molding products

If you only need plastic molding parts, then you only need to tell us (or another plastic molding company) what the plastics will be, how many parts you need per time, what the surface requirements are, and the colors of the parts, and they will take care of the rest for you.

To get the cost of plastic injection molding products, it is much easier than getting the cost of exporting plastic mold. Simple steps as below make getting the plastic injection molding service price easy.

• What will plastic be? for example, PP, PA66, ABS, PC, PMMA, PC/ABS, PEEK, PPS, etc.
• What color do you require for your molding parts? There are lots of colors; you could take a color reference from pantone color.
• What is the part surface requirement? Texture (graining or matte) or high polishing? The texture code could take references from VDI 3400.
• 3D part design (STP or IGS format file will be great for all of the companies); if you do not have a 3D part design, then send your sample pictures with part size and part weight, or an idea picture and explain it to us, and we can still get the price for you.
• How many parts do you need per time?
• Do you have any special function requirements?

With the above information, you will get a very competitive local mold/tooling cost (at least 40% lower than others) and unit injection molding cost from our side. That information is an important factor in estimating the plastic injection molding cost. Otherwise, any price will not have any references.

Plastic mold issues (molding defects) and troubleshooting

The quality of the plastic mold is as important as the molding process. The plastic molding company you choose to help you with your product will eventually fight common molding issues. If you have high-quality plastic molds and a good plastic injection molding process, that will bring out the kind of results you expect from the end product.

Molding defects appear in the plastic mold; they can be attributed to the type of raw material used in the plastic injection moulding process, as well as the quality of the plastic mould, injection molding process skill, injection molding machine, etc.

Fortunately, by processing and preventing injection molding defects and using these approaches, mold manufacturers can create high-quality injection plastic molds. Once you have a high-quality mold, all other issues are easy to solve.

To make high-quality plastic mold, you must know how to solve this molding issue. Of course, find good mold suppliers; they will indeed solve this issue for you. Blow are some troubleshooting tips to solve the common molding defects, such as weld lines, etc., and ultimately get high-quality molded parts. There are some key defects that most happened during the mold manufacturing and molding process.

1. Flow Marks

This molding defect normally happens close to the gate area and the joint area (joint line or weld lines), which some people call flow lines, common in narrow sections of components and may be considered minor or serious defects depending on the part wall thickness and expected use.

In order to solve appearance flow line defects, during the molding process we need to increase the injection speed pressure, molten material temperature, and mold temperature. Increasing the gate size or changing the location of the gate is also helpful (last option). Below the right picture of flow mark defects, we increased the gate size to improve flow marks because the wall thickness was too thick (7mm).

2. Dull Areas

The most common is a dull concentric ring that can appear around a halo-like sprue. This usually occurs when the material flow is poor and the viscosity is high. Contrary to what many think, this is not a packaging defect, but a defect that occurs at the beginning of the billing cycle.
To minimize the possibility, the injection rate profile should be adjusted to ensure a uniform flow front speed throughout the filling phase. It is also helpful to increase the back-pressure and barrel temperature of the screw to reduce dull surfaces resulting from lower melting temperatures. Increasing the mold temperature can also reduce this issue.
But there must be a cooling system in the feeding area, especially if it is a hot-runner system; otherwise, it is not easy to solve this issue. For dull surfaces generated by design-related issues, this can be improved by reducing the radius between the part and the gate.

3. Burns Mark defects

The burn marks are defects often seen on plastic injection molding parts and look like a light yellow or black discoloration. This may be a minor defect due to excessive melting temperature, overheating in the presence of trapped air, and excessive injection speed.

Corrective actions for this type of burn mark issu: include reducing temperature, reducing cycle time, and reducing injection speed. Plastic mold manufacturers must also ensure that they have the proper gate size and gas vent gloves to resolve the trapped air problem that leads to this defect.

Because the air trap issue is the most common reason for this burn mark issue and could never be completely solved by adjusting the molding process, To mark defects, adding venting is the best solution, like increasing the venting grove, adding venting inserts to the deep ribs, etc.

4. Gloss difference defects

Gloss differences on textured surfaces tend to be more pronounced, and even if the surface texture is uniform, the gloss of the part may appear irregular. This is a problem that occurs when there is insufficient replication of the mold surface in some areas, and sometimes there are lots of ribs at the core side that can increase the gloss change issue on the textured surface.
It can be corrected by increasing the melting temperature, mold temperature, or holding pressure. The longer the holding time, the more likely the mold surface will be replicated accurately. If the design of the ribs caused this issue, to improve this issue, we can add some radius to all of the ribs. This will reduce the internal stress so that the textured surface can be improved as well.

5. Warping defects (deformation) 

Plastic molding parts have warping defects that are normal, especially the long-size molding parts; distortion defects are hard to solve. Improving the mold design is the mean solution, but it is very limited to solving this issue by adjusting the parameters of the molding machine. The reasons and solutions to improve warping and distortion are listed below for reference.

• When the deformation is caused by the residual stress of the molding process, it can reduce the injection pressure and increase the mold temperature to improve it.
• If the deformation caused by parts sticking can improve the ejection system or add more draft angle to solve this issue,.
• If the warping defects are caused by a poor cooling channel or a poor cooling time, we can add more cooling channels and increase the cooling time to improve this. For example, we could add more cooling water to the deformation area to improve the warping defects, or we could use different mold temperatures for the cavity and core.
• If the distortion issue caused part shrinkage, to solve this warping defect, we must adjust the mold design. Sometimes we need to measure the distortion size from the molding part and do the pre-deformation design on the part. The resin has a large shrinkage rate; usually, crystalline resin (such as POM, PA66, PP, PE, PET, etc.) has a higher warping rate than amorphous resin (such as PMMA, polyvinyl chloride (PVC), polystyrene (PS), ABS, AS, etc.).
  Sometimes the gloss fiber material has more deformation issues as well. This is the hardest solution because you may need to adjust the part design two or three times to completely solve this issue, but this is the only way to solve the distortion issue.

6. Short shot defect

A short shot means not completely filling the mold; this molding defect normally happens at the end of the filling area, the end

of the rib, or some thin wall area. There are some reasons to cause this defect below.

• The mold temperature is too low. When material fills in the mold cavity since the mold is too cold, the liquid material is not able to fill to the end of the part or some deeper ribs. An increase in mold temperature could solve this molding issue.
• The material temperature is too low. This issue could also cause the short shot issue; this reason is similar to the issue of low mold temperature. To improve this issue, we can increase the melt temperature of the material to solve this molding defect.
• • The injection speed is too slow. The injection speed is directly related to the filling speed. If the injection speed is too low, the liquid material filling speed will be very slow, and the slow flow material will be easy to cold. This will cause the material to get cold in advance. To solve this issue, we could increase the injection speed, injection pressure, and holding pressure.
  • Venting issue. This is the most common molding defect we meet during the mold trial; all other defects could be solved by adjusting the molding parameter. If short-shot issues are caused by a venting issue, the best solution is to find a way to release the air out of the cavity. Sometimes reducing the clamping force can help a little, but it is not able to completely solve these defects.
    If the air is stuck in the cavity or in the dead-ending area (the end of the ribs, for example), the short-shot issue will happen in that area. To troubleshoot this issue, we need to increase the venting grooves on the parting line and add a venting insert to the dead-ending spot to guide the air out.

  7. Sink mark: It is a sink mark on the molded part caused by unbalancing plastic material shrinking in the mold cavity. It looks like there is a lack of material in that sink area that does not match the part geometry. This issue happens to the thick wall area or lack of cooling system in the mold. The mean reason to have this sink mark issue is the uneven wall thickness on the part design.

  If some ribs or some area have a thicker wall than the other place (rib thickness should be around 1/2–7/10 max of the mean wall), then this thicker area will be easy to have a sink mark issue. Below are some suggestions to improve this defect.

• Change the gate location to be close to the thick wall.
• Add more holding pressure and holding time, and inject more material into the mold cavity. When using this method, you need to double-check that the part dimension is still within the tolerance requirement.
• Increase the cooling time and the cooling channels to improve this issue. Plastic shrinkage rate is normal. If the cooling time is too short and the part is still warm after the mold is opened, then the part shrinks quickly without any cooling system. This will make it easy to have a sink mark. Increase the cooling time until the plastic molding part completelycoolsl in the mold cavity, and this defect will be solved.
• If the part design has a serious thick wall on some of the ribs or bosses, to solve this issue, we need to improve the part geometry and add some inserts to the thick area to reduce the wall thickness. This issue could be solved. For this unbalanced wall issue, we could use software to analyze it and prevent it in advance. Before mold manufacturing, we will make a fully DFM report and send it to our customers for approval. Below are sink mark analysis report samples.

Are you ready to start working on your new project and search for your plastic molding supplier? If yes, then let’s go. For your plastic molding project, finding a reliable Chinese mold company is more important. Because this will bring your market up very quickly, and you will win more profits on your project with less cost,

Today, over 80% of big companies are sourcing goods from China. Like the iPhone, some other famous companies buy things from China. So what are you worried about? If you are ready, then speed up to open your market immediately and share your profits.

SINCERE TECH is a professional precision custom plastic mold and plastic injection molding company that sells molds and molding parts worldwide. We guarantee you will be 100% happy with our service and quality.

We have a very professional technical team to handle your project very carefully and make the perfect plastic molds and parts for you. Some of our customers have moved the molds to our factory for troubleshooting since their current plastic mold supplier is not as professional as us. We can send you some of our current customers for you to verify our service, quality, and price.

Send us an email at [email protected] to get a price. We will never share your design with others. We are willing to sign an NDA to protect your project.