What Is Plastic Mold & Molding Technology

Plastic mold technology is also known as plastic molding technology, which is a process that has been around since 1872, it is a common processing for mass plastic parts production and is often better than other processes, given its capability to economically produce complex plastic products to tight tolerances. Basically any plastic parts can be molded, however, a plastic mold is very complex, must be designed & manufactured by the expert plastic mold manufacturer

The plastic mold is a complex system which must simultaneously meet many requirements imposed by the plastic injection molding process. below there are simple step to make the plastic mold.

  • First, the part designer needs to design the desired model or hire your supplier to design the model according to your requirement,
  • Second, when the part design is approval, you need to find your mold supplier come up with a completely mold design, once mold design has been created, then start to manufacture the plastic mold, the plastic mold manufacturing processing including drilling, CNC machining, EDM, wire cut, lather machining, drilling, grinding machining, polishing, etc.
  • Third, the last step to make a plastic mold is mould fitting, when everything is finished in mold manufacturing, you must do the mold fitting to check if components are in the right position and tight tolerance, mold fitting is important way to check the mold quality.
  • Finally, when mold fitting to finished, the actual injection moulding process can start. at the beginning of the injection molding process we called mold trial, from mold trial to massive production, still needs to take some time and doing several times mold trials, because the first mold trial will have more or less issues that needs to be finished.

After two or three-times mold trial until custom approval the samples, so we could start massive production, there is a simple working procedure to explain from part design, mold design, mold manufacturing to get the perfect ending plastic products. Although plastic molding technology is not something that most will be knowledgeable about.

We all use products that will have been manufactured by using this method. Things like bottle caps, automobile plastic parts, home appliances, furniture components & accessories, bicycle accessories, cosmetics molding & packaging containers, cooking equipment, toys, medical plastic parts, and construction part, etc. We can say everything needs molds & plastic molded parts.

The future of plastic molding

Over the decades, the process of plastic injection molding technology has changed and advanced significantly. Thanks to huge leaps in technology, it is now possible to use 3D printing to use photopolymers for plastic moulding parts.

The advantage of using 3D printing for the plastic parts is that will lower the price for lower volume because make custom plastic mold is very expensive.

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

Plastic mold structure

The plastic product formed into life in the mold. basically, the plastic mold can be designed and produce any plastic parts according to shape. However, if more features and functions are required from the mold, then costs and time will increase during its construction.

A Plastic mold is made by variety of plastic mold plates, inserts, blocks, and other metal components (or similar material). Basically, plastic mold is including of two halves: Fixed half and Ejector half (see below picture), which are consisting of several mold plates and inserts. Due to an easier machinability and interchangeability, the cavity is formed by inserts which are tailored to the surrounding frame plates (A/B plate).


plastic mold

plastic mold

The cavity & core inserts is normally separate blocks (some of plastic molds made in solid) which are then inserted into pockets plate that are machined into the A and B plates (which are also called as cavity retainer plate). The cavity & core inserts are placed in the pockets plate and are left standing above the A/B plate approximately 0.1-0.5mm. This leaves the shut-off area. When both fix half and moving half closing so that there are small gap between A&B plate, this will be better fitting for the cavity and core inserts.

Fixed half include (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 /A plate ( cavity if made in solid), see below picture

fixing half

fixing half

Ejection half include (moving half/core side):

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

moving half

moving half


Plastic Mold Material

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

Mold Steels

1.2344, 1.2343, S136, H-13. This type of steel is used for cavity and core inserts, this is for the high quality of plastic mold, mold life time can be 1 million shots or more. This is a very high toughness, low-hardness steel used for high quality cavity and core requirements. The hardness of those steel can be hardened to HRC 48-60 degree.

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.

P-20, S136H, NAK80, 718H tool steel. Those are pre-hardened steel which has hardness of 28 to 40, which provides moderately high hardness, good machinability. It is used primarily for cavities and cores, as well as stripper plates, mold life-time made in those steel is around 0.5 million shots or more.

What is cost for plastic mold and plastic injection molding products Cost?

In order to know what is cost for your plastic molding project, then you need to get both cost for your plastic mould and moulding parts, there are two type of mold cost, one is export mold cost, one is local mold cost plus the plastic molding parts cost. below we will give your cost guideline on those two options.

1. What is cost for export plastic mold

To know the cost of plastic injection mold 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 supplier 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, you need to make sure that you have a 3D part design in your hands, if you do not have the design drawing then you need to have the pictures of a sample with approx. part size and show your mould supplier that part structure by the different side view.
  • Second. You need to know how many shots of the mold your requirement, for example. 0.5 million shots of a lifetime or 1 million shots of a lifetime requirement, because those two requirements will cause different price.
  • Third. It is a cold runner or hot runner do you require for your mold, if hot runner what brand of hot runners. YUDO, INCOE, etc, all of that information will have different prices, so you need to specify your requirement.
  • Fourth. What is a surface requirement, VDI 3400 texture, high glass polishing, MT-lather texture(this texture cost is very high).
  • Finally. The number of cavities, you need to specify how many cavities do you need for your mold. Because of one cavity and multiple cavities mold are totally different prices, the single cavity is low than multiple cavities mold.

The above 5 points are very import information to quote a mold price for export mold (you will bring the mold back to your country for production) because all of the information will change the mold price, if you have no any idea you can contact us so that we could send you a list to check.

2. What is the cost for Injection Molding products and local mold cost

If you only need plastic molding parts, then you only need to tell us (or other molding suppliers) what plastics will be and how many parts do you need per time, what is a surface requirement and the colors of the parts, then they will take the rest for you.

To get the cost for your plastic injection molding products it is much easy than getting a price for export plastic mold, simple steps as below to get plastic injection molding service price easy.

plastic mould

  • What plastics will be? For example PP, PA66, ABS, PC, PMMA?
  • 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 matt) or high polishing? Texture code could take reference 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 idea picture and explaining to us, we still can get the price for you.
  • How many parts do you need per time?
  • If have any special function requirement?

With the above information, you will get a mold cost and unit molding cost, that information is important factors to estimate the plastic injection molding cost. Otherwise, any price will not have any references.

Plastic Mold Issues ( molding troubleshooting )

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

Molding defects appears in the plastic mold, it 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, processing and preventing injection molding defects, and using these approaches, mold manufacturers can create the high-quality injection plastic molds, because if you make a high-quality mold, all other issue is easy to be solved.

To make high quality plastic mold you must know how molding troubleshooting skill, of course find a good mould supplier there will solve this issues for you indeed. Blow are some troubleshooting suggestions to solve the common molding defects 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 defects normally will happen close to the gate area, and the joint area (joint line), 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 defects, during the molding process we need to increase the injection speed, injection pressure, molten material temperature, and the mold temperature, increase the gate size or change the location of the gate is helpful as well (last option).

Below left picture of flow marks defects, we increased the gate size to improve flow marks because of the wall thickness to too thicker (7mm)

2. Dull Areas: The most common is a dull concentric ring that can appear around a halo-like a 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, increase the mould temperature can reduce this issue as well. but there must have a cooling system as the feeding area, especially if it is hot runner systems, otherwise 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,

Dull areas

Dull areas

3. Burns Mark defects: The burns Mark defects often seen on plastic injection molding parts and looks 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 defect: Reducing temperature, reducing cycle time, and reducing injection speed.

Plastic Mould Manufacturers must also ensure that they have the proper gate size and gas vents gloves to resolve the trapped air problem that leads to this defect, because the air trap issue is a most common reason to cause this burn mark issue, and could never be completely solved by adjusting the molding process.

To completely solve this burns Mark defects adding venting is the best solution, like increase the venting grove, add 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 mould surface in some part areas, and sometimes there are lots of ribs at the core side that can increase the gloss changes issue on the textured surface.

It can be corrected by increasing the melting temperature or mold temperature or holding pressure. The longer the holding time, the more likely the mold surface will be replicated accurately, if there ribs design 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 defect is normal, especially the long size molding part, distortion defect is hard to solve, improving the mold design is the mean solution.

It is very limited to solve this issue by adjusting the parameter of the moulding machine, the reason and solution to improve warping, distortion is listed as below for reference.

When the deformation is caused by the residual stress of the molding process, it can reduce the injection pressure, increase the mould temperature to improve this.

  • If the deformation caused by part sticking, can improve the ejection system or add more draft angle to solve this issue.
  • If the warping defects caused by poor cooling channel or poor cooling time, we can add more cooling channels and increase the cooling time to improve this, for example, add more cooling water closing to the deformation area to improve warping defects, or use different mold temperature to cavity and core, this method could normally solve the small warping defects.
  • If the distortion issue caused part shrinkage, to solve this warping defect must be adjusting the mold design, sometimes we need to measure the distortion size from the molding part and do the pre-deformation design to the part, the resin has a large shrinkage rate, usually crystalline resin (such as POM, PA66, PP, PE, PET, etc.) has more warping rate than Amorphous resin (such as PMMA, polyvinyl chloride (PVC), polystyrene (PS), ABS, AS, etc.).
    Sometimes the gloss fiber material has more deformation issue 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 the only way to solve the distortion issue.

6. Short shot defect: Short shot means not completely full filling to the mold, this molding defect normally happens at the end of the filling area, or 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 cold too fast to cause the liquid material is not able to full fill to the end of the part or some deeper ribs. Increase the mould temperature could solve this molding issue,
  • Material temperature is too low. This issue could also cause the short shots 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.
    Short shot issue

    Short shot defects. after adding venting inserts, the defect completely solved

  • 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, slow flow material will be easy to cold, this will cause the short shot since the material getting 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 we could solve by adjusting the molding parameter.
    If short shot issues caused by venting issue, to completely solve the short shot, the best solution is finding a way to release the air out of the cavity, if the air stuck in the cavity or in the dead-ending area (end of ribs for example) so the short shot issue will happen at that area.
    To solve this issue we need to increase the venting grooves on the parting line and add venting insert to the dead-ending spot to guide the air out.

7. Sink marks: It sinks spot on the molded part, it caused by unbalancing plastic material shrinking in the mold cavity, looks like lack of material on that sink area which is not matching to 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 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 close to the thick wall place

  • Add more holding pressure, holding time, and injecting more material in the mold cavity. When using this method you need to double-check the part dimension is still in the tolerance requirement
  • Increase the cooling time and the cooling channels to improve this issue, plastic has shrinkage rate is normal.
    If the cooling time is too short, the part still warm after the mold opened, then the part shrinks quickly without anything cooling system, this will be easy to have sink mark, increase the cooling time until the plastic moulding part completely cool in the mold cavity, 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, add some insert to the thick area to reduce the wall thickness, this issue could be solved, for this unbalance wall issue.
    We could use software to analysis then and prevent in advance, before mold manufacturing we will make fully DFM report and send to our customers for approval, below is sink mark analysis report samples.

The manufacturing world has been increasingly confusing over the years. If you are in this industry, you probably already have this sense of confusion.

What’s happening is that the global market is really starting to come true. A few years ago, there were a few outsourcing companies in some countries like China, but now it is impossible to track production.

Looking at industries such as injection molds, you can see that this trend has really begun. However, it may be overwhelming at first, but there is no doubt that productivity will increase significantly.

Today, injection molding China has become even more efficient due to a faster turnaround.

Welcome to our Plastic Mold & Moulding Company.

We offer custom plastic injection mold & molding services, post manufacturing, electronic contract manufacturing and assembly service, 40% saving for mold manufacturing and molding production services,

We have over 18 years of experience in plastic injection mold manufacturing services, fluent technical English communication, rich manufacturing experience to handle your project in high quality. Contact us to discuss about your project.

We 100% guarantee your project will be successful. You will be impressed and satisfied with our quality, price, and services. we are willing to share with you some of our customers to let you verify our quality and service.

Send us your requirement for quotation, you will not lose anything but having our competitive price for reference.

To protect your project from copy, We can sign an NDA document to protect your project

In the following, you will find information about plastic injection molding processes, techniques, and specialized moulding technology, defects, troubleshooting solutions, below are some of molds we made before.


Are you ready to start working on your new project and search for your plastic molding supplier? If yes then let’s go.

Today for your plastic molding project to find 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 spending less cost.
Please think about today over 80% of big companies on the world are sourcing goods from China. Like the iPhone and some other famous companies buy things from China.
So what are you worry about? If you are ready then speed up to open your market immediately and join your profits.
If you are looking for some good Chinese plastic molding manufacturing partner you can contact us. We. SINCERE TECH which is a professional precision plastic mold and plastic molding company sell moulds and molding parts to the world.

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 moved the molds to our factory for troubleshooting since their current 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 to [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.