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How to Make a Mold for Plastic

injection molding service

Mold making for plastics are crucial for all types of manufacturing. They help get similar shapes and designs with high accuracy and precision for large-volume productions. Moreover, these molds can be of different shapes and made of numerous materials, i.e. aluminum, steel, iron, plastic, etc. In this article, we will discuss plastic molds. Besides this, we will learn how to make mold for plastic, its applications, and its advantages in different fields.

What are Plastic Molds?

Plastic molds are commonly used in industries to create small products, from utensils to small parts for home appliances and large machines. This is a better approach because it enables the creation of unique molds. Besides, it comes with fewer costs in the long run and creates molds for prototypical commercial or personal projects. This comprehensive article will explain how to make a mold for plastic and consider important factors and tips and tricks that will help you do it without a hitch. Go to plastic mold technology page to know more informatino about plastic molds.

Types of Plastic Molds

Before going towards how to make a mold for plastic, let’s discuss a few types of plastic molds;

1. Injection Molds

Injection molds are applied in industries to create a large number of objects. It’s usually done with the help of injecting a liquid polymer material into a molding cavity. It helps manufacture complicated products such as toys, packaging materials, and detailed auto parts. Moreover, this technique is characterized by high output rates, precision, and negligible time required in post-processing.

plastic injection mold

2. Compression Molds

Compression molds use thermosetting plastics, are put in a mold cavity, and get exposed to heat and pressure. This method is most suited for applications that require quality and heat-stable components. These may include automobile parts and electronic appliances. Thus, it is economical in low-production runs and ideal for creating thicker parts, especially those big ones.

3. Blow Molds

Blow molds have wide-scope applications for molding hollow parts such as bottles and containers. This works in a way in which the plastic is first turned into a tube referred to as a parison. Then it is allowed to get inflated between two molds to form a final hollow product. One of the major applications of blow molds is, that they’re highly used in PVC for making light and empty parts in a big quantity.

Blow molding

 

4. Silicone Molds for Resin

Silicone molds are flexible and more common to beginners and they are used in small DIY projects. Besides this, they have many applications even when working with resin. Such molds can retain fine and complex structures. Moreover, they are reusable, making them suitable for crafting, resin work, and prototyping. They are pleasant to deal with and can be used in many ways for other artistic endeavors.

Silicone mold

Properties of Materials Used for Plastic Molds

 

MaterialPurposeCommon TypesKey PropertiesTypical Values/Range
Mold MaterialIt helps form the mold structureSteel, Aluminum, SiliconeDurability, Heat Resistance, MachinabilityTensile Strength: 250-1500 MPa (steel), 90-300 MPa (aluminum)
Release AgentIt prevents material from sticking to the moldSilicone Spray, Wax, PTFENon-stick, High Heat ResistanceMax Temp: 120°C-200°C, Friction Coefficient: <0.05
Mold base/FrameThis holds mold material in placeWood, Plastic, MetalStrength, RigidityDensity: 0.9-1.3 g/cm³ (plastic), 2.7 g/cm³ (aluminum)
Master Object/CAD ModelIt makes shape for the mold3D Model, PrototypePrecision, Smoothness, ComplexityCAD Accuracy: ±0.005 mm, Surface Finish: Ra 0.8-1.6 μm
Mixing ToolsMixes mold material componentsStirring Rods, Mechanical MixersEven Mixing, No Air BubblesRPM: 300-1200 (mechanical mixers), Volume: Variable

plastic mold

Step-by-Step Guide to Mold Making for Plastics

The following is the complete process for mold making for plastics.

1. Designing the Mold

Get a rough design of the mold and consider the need for the plastic part that you want to generate. When you have complex shapes, use your CAD software to design in a way that will help in the CNC machining of the mold. Some of the features include the geometry of the part, the thickness of the walls of the part, and draft angles. They facilitate the removal of extra material from the mold. The choice of the mold material like aluminum or steel depends on the life span required for the mold. Besides this, the material selection also depends on the quantity of products you want to produce.

How to Make a Mold for Plastic

2. Creating a Mold Box or Frame

For plastic mold fabrication, create a mold box or frame that will hold the material during the casting. Mold boxes for CNC machined molds are usually made of sturdy materials. They may include Metal / hard plastic etc. So, during manufacturing, confirm that the box has been well closed properly to avoid any leakage in the pouring process. Moreover, ensure that the box has been reinforced to withstand pressure and temperature during the molding process.

3. Preparing CAD Models & CNC Machining the Mold

Usually in CNC machining the master object is a CAD file with accurate dimensions and free of undercuts on the mold cavities. So, if the materials you use have different forms and structures. CNC machining will help you clean and undergo surface treatment. A release agent is used to avoid the plastic sticking to the mold. The CNC machine further proceeds to make an accurate cut of the mold to achieve the right milled and finished walls. This is important to minimize the chances of defects. Moreover, it allows the smooth flow of the plastic and easy ejection of the final part.

4. Mixing and Pouring the Mold Material

After molding the mold with CNC, the molten plastic material into the mold cavity. If you’re using thermoplastic or resin, make sure the material that you are using is up to the right temperature and flows well. If you use injection molding, heat and melt the plastic material, present in the pellets. Moreover, ensure that you take your time when pouring to minimize air bubbles which if they get into the mixture will reduce the strength of the final product.

5. Curing the Mold

So, allow the material to cool and form a solid in the mold prepared from the plastic material. Depending on the type of plastic used, curing may take a few minutes to several hours. In this stage, it is important to observe that there is no formation of bubbles or any other defect in the mold. As regards the curing of CNC-machined molds, curing is generally faster and more accurate because molds are cured under controlled conditions.

6. Mold Filling and Mold Release

When the plastic reaches its curing point, take out the part from the mold. If you put the release agent correctly, the part should pop out and not stick to the mold surface. Besides this, you can trim or finish the material depending on their requirement. Additional finishing may be done on items through the machines if further polishing is needed for volume production.

Design and Build Considerations for Custom Plastic Molds

Some of the important aspects that need to be considered in the design and building of especially custom plastic molds include the following;

  • Material Selection: Select the mold material such as steel or aluminum for its durability, cost, and production volume. Steel molds tend to be long solutions for strength and volume production. Whereas, aluminum molds are more inexpensive for less volume productions.
  • Part Geometry: The mold design aspect should be informed by all features of the plastic part, particularly, intricate details, undercuts, and draft angles. So, they can facilitate easy removal from the mold.
  • Cooling Channels: This reduction of the cycle time has to be done while at the same time, cooling channels are integrated into the mold design.
  • Mold Tolerances: Understand that accurate dimensional requirements mean closer control in the mold. So, it can minimize the amount of post-mold finishing required particularly when the design details are intricate.
  • Mold Flow Analysis: Make a brief analysis of the appearance of the cavities and how the mold material will flow in the cavity. Check some of the anomalies that are likely to occur such as warping, shrinkage, or formation of air pockets. This is efficient in aiding the mold design of the automobile and also improves production efficiency.

Selection of Resin for Making Plastic Molds

Let’s explore the different types of resin options to make the plastic molds.

  1. Epoxy Resins: Organic epoxy resins are strong and thus can be used to make molds in industries that require high heat and pressure when molding.
  2. Polyurethane Resins: These are flexible and durable so they are the best for molds that will be used where a moderate amount of production is to be done. So, we can get that resistance and a certain degree of flexibility.
  3. Silicone Resins: Silicone is very flexible and can be very convenient when operating on tight molds that are small and complex as well as suitable for DIYs or a few runs.
  4. Polyester Resins: These are cheaper and preferred for big molds with fewer details. Besides this, they offer fair strength but relatively low elasticity compared to silicone and polyurethane.
  5. Thermosetting Resins: Sometimes called thermosetting plastics, these resins become permanently solid and rigid when exposed to heat. So, they are suitable for tough applications like the engineering industry.

Finishing and Polishing the Plastic Mold

Always follow the following aspects while finishing and polishing the plastic molds.

1. Drilling the mold and polishing

Smooth edges to start making the actual part. Here the mold first undergoes inspections to see whether it has sharp edges or uneven surfaces. Scour carefully using fine paper or special machinery that provides polish to figure out the body of the mold. This results in a smooth finish of the last plastic product and the reuse of the mold without causing harm to the cast parts.

2. Making Repairs if Necessary

There are defects on the substrate surface beforehand, such as small cracks,

unevenness, or visible bubbles.  It is mandatory to eliminate them with the help of appropriate filler materials, i.e. epoxy resins or silicate. Detection and correction of these issues enable a manufacturer to prevent defects in the final molded parts, go to injection molding surface finish page to know more.

molding for plastic

Common Mistakes and How to Avoid Mold making for plastics

Here are some common mistakes we generally make while mold making for plastics.

1. Air Bubbles in the Mold

One of the common problems with mold making for plastics is the entrapment of air bubbles in the mold material. We can avoid it by ensuring the material is added slowly and after pouring escapes the air trapped in it. Another way to remove bubbles is by employing the use of a vacuum chamber, and pressure pot.

2. Inadequate Release Agent Application

An inadequate release agent application is another way to cause damage since the final part may later stick to the mold. It is important to note that the release agent is applied uniformly and in detail with a special focus on the intricate regions.

3. Warping During Curing

Warping is the product deformation that appears as a result of an inaccurate curing process or normal coil cooling procedures. This should be prevented by regulating the curing environment and ensuring the right curing temperature. Besides this, also make sure to allow enough time for the material to cure thoroughly.

Conclusion

In conclusion, how to make a mold for plastic, Mold making has relevance in many creative industries where ideas are hatched and inventions manufactured ranging from industrial manufacturing to home craft. Learning about mold-making, the available materials, and the requirements presented in this article, will assist in manufacturing accurate and long-wearing molds for plastic parts production. In this case, the required finishing and finishing are done to perfection and the custom molds have wide-scope applications in several fields.

Frequently Asked Questions

Q1. What materials are commonly used for plastic molds?

Steel and aluminum are some of the best materials for industrial molds because they are hard-wearing. Silicone rubber is mostly used on a small scale and for do-it-yourself projects.

Q2.How long does a mold last?

The serviceability of steel mold is measured by the fact that it can run for millions of cycles. For instance, aluminum has tens of thousands of cycles, depending on the degree of production intensity.

Q3. How do I prevent air bubbles in my mold?

Choose a slow blending speed for the mold material and pay attention to pouring the material. Afterward, use a vacuum chamber or pressure pot to eliminate trapped air.

Q4. What is the best release agent for plastic molds?

Varnishing or applying silicone sprays also the ones that are composed of PTFE, or polytetrafluoroethylene. They are best-suited releasing agents for avoiding the adhesion of plastic to molds.

Q5. What type of mold is best for mass production?

Injection molds should be preferred for mass production. They enable the creation of large numbers of similar spare parts with high accuracy.

Q6. Can mold be repaired if damaged?

Yes, simple damages such as cracks on the siding, small holes or even roughening of the surface can be easily repaired using epoxy or filler materials. Where the extent of damage is bad, then the only solution that may be available may be to replace the whole mold.

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Plastic Injection Molding Service

plastic injection mold

Looking for plastic injection molding service?

Contact us to get quote, we are A Custom injection mold maker in China that offers plastic injection molding services.

The excellent quality of our plastic molds and molded parts, coupled with our experience and the performance of our services give us today a high international recognition.  Indeed, the company is specialized in International Business and has customers all over the world. SINCERE TECH has very high standards of quality control and always runs long tests to make sure that our Plastic Injection Molding Service reaches all the expectations of our customers. We believe that the quality of a company and its products are seen through time and this is why we like to build strong long-term partnerships with our customer

What is plastic injection molding process?

Plastic injection molding is a manufacturing process in which melted plastic is injected into a mold and then cooled to form a solid part. The mold is created from a metal or plastic tool (1.2344, H13, NDK80, etc.) and is typically made in two halves that are clamped together. The plastic material is heated in a barrel and then forced into the mold under high pressure where it cools and solidifies into the desired shape. This process is used to produce large quantities of identical parts with high precision and repeatability.

When do you need plastic injection molding service?

You may need plastic injection molding service when you require mass production of plastic parts with consistent quality and high precision. This process is ideal for producing large quantities of the same part, as the mold can be used multiple times to produce identical pieces. Additionally, plastic injection molding is well-suited for producing complex and intricate shapes that would be difficult or impossible to achieve with other manufacturing methods. This process is often used in various industries such as automotive, consumer goods, medical devices, and electronics.

plastic injection molding service

plastic molding services

Benefits of plastic injection molding service

The benefits of plastic injection molding service include:

  1. High volume production: Plastic injection molding is ideal for high volume production of identical parts, as the mold can be used multiple times.
  2. Consistent quality: The process is highly repeatable, which leads to consistent quality of parts produced.
  3. Complex shapes: Plastic injection molding can produce complex and intricate shapes that would be difficult or impossible to achieve with other manufacturing methods.
  4. Material flexibility: A wide variety of plastic materials can be used in the injection molding process, including thermoplastics, thermosets, and elastomers.
  5. Cost-effective: The process is efficient and cost-effective for producing large quantities of parts, as the cost of the mold can be spread over many parts.
  6. Precision: The process can produce parts with high dimensional accuracy and minimal tolerance variation.
  7. Automation: Plastic injection molding machines can be automated for increased productivity and reduced labor costs.

Plastic injection molding is a versatile and reliable manufacturing process that can provide significant benefits for producing large quantities of complex and high-precision plastic parts.

Plastic Injection Molding Service in China


We are the manufacturer of our own moulds (toolmaker or plastic injection tooling) and support the production of Injection molded parts allowing reducing your numbers of suppliers. Our injection machines have clamping forces going from 60 to 1050 Tons (2000 Tons outside). Plastic injection molding is the process of producing parts from thermosetting and thermoplastic materials.

Our qualified teams of Designers, Quality controllers and our Research and Development Department allow us to complete our policy: achieving Customer Satisfaction through Improvement and Innovation. The quality of our products and organization permits us to obtain quality certifications (ISO 9001, ) and be awarded numerous times of “Quality Supplier” from different customers. We integrate constantly new resources into our process in order to anticipate any future need of the plastic injection molds market and we became one of the most innovative companies in the sector. The modernity and the organization of our facilities allow us to adapt very quickly to the customer’s needs.

SINCERE TECH has always the objective to stay one of the innovative leaders of the sector and play an important role in our customer’s development. The firm can now propose a total solution from mould design to the semi-finished product (All in-house). SINCERE TECH is always willing to integrate new processes to the solution proposed by staying aware of new technologies. If a customer has a special requirement, we will do everything to fulfill its needs.

Plastic Materials /Commodities

We are used to working with all the classic and less classic plastic materials except PVC (PP, PE, PC, ABS, PC+ABS, PA 6, PA 6.6, PBT, PMMA, TPU, PC+GF, AS, PTFE, POM, PEHD, PEEK…). Our main suppliers are Sabic, Bayer, and Chimei.
About the steel used for our moulds, for export plastic molds we work only with the best steel suppliers like Assab (Sweden), Buderus (Germany), Daido Steel (Japan) LKM( the biggest one in China). For our standard component suppliers, we work with Hasco and DME.

We are used to working with our suppliers the same way we work with our customers. It means good long-term relationships with high-quality policy.

Complex moulds: SINCERE TECH has a rich experience in difficult plastic mould and parts, complex moulds and is an expert in finding solutions to your issues. SINCERE TECH is a real specialist in difficult tooling. To give a classic example: many design companies create plastic products without thinking about mould construction. Then, when the designs are sent to toolmakers, it can be hard for them to make the exact parts (Difficult design, many sliders, many lifters, double injection with materials non-bonding well together, many details in awkward places…).

Most of the classic toolmakers will accept the parts and say that they are able to do it. And then, they will have problems with the plastic injection mould construction, the lead time will be extended and the quality of the tool will not be as expected. Often, these companies have to contact SINCERE TECH to help them to resolve their problems. If you are not sure about the complexity of your part, be sure about your mould maker’s professionalism. SINCERE TECH works closely with its customers in order to resolve any issues.Plastic Injection Molding Service

Thin Wall injection molding: it permits a precise, very accurate molding of plastics and gives better details to the product. This is the name referring to products with a wall thickness lower than 2mm. Usually, the flow is quick, permits a short cycle time and a cost-saving.

Hot runner mold: the special process of injection of plastics where the plastic is kept hot when going through cavities of the mould while the rest of the mould is getting cold to solidify the plastic part and create the molded part: this permits to save plastic material. This is mainly used for parts with medium or large sizes. We are used to working with all popular companies like Yudo, INCOE, Synventive, Husky, HRS… We also have the technology to make our own hot runner systems if the production of the parts (Molding) is made in-house. This again allows our customers to save costs.

Optical Lens Molding: precision molding for glass plastic. This is the technique to produce transparent plastic molded parts (For example Security cameras parts such as the dome cover or also phone frames).

Gas-assist Injection Molding: the plastic parts are gas-assisted molded which means that gas (Most often is nitrogen) is injected at the final stage of the part creation process. It permits to reduce the cycle time, the product weight, the risk of deformation and also the pressure tons injection needed. Moreover, it makes the part’s structure stronger with a better look.

LED/LCD frame molding: injection of plastics used for example to manufacture television screen monitors, computer back-light modules, GPS frames…

IMD, IMF, IML, IMR Molding: In-mold decoration. The decoration of the part is made inside the mould through a film. The film is printed before the molding with the designs wanted. It permits better productivity and extends the decoration’s lifetime. If the customer wants to change the design/decoration of the part, it is not necessary to make another mould but only to change the film. SINCERE TECH is experienced with In-mould forming, in-mold-labeling, and in-mold by roller.

Overmolding: this technique permits to join several components together with a thermoplastic material. This reduces assembly and labor costs. Because the parts are made together, this allows less risk of improper termination or misalignment and increases the design flexibility. Moreover, thermoplastic provides better resistance to vibration or shocks. This technique permits to increase resistance, reduce costs and weights.

Insert Molding: this is a technique where a small part (Stamping part, optical part…) is added or inserted to the Injection molded part.two shot molding

Two-Shot Molding: 2 independent injection units using 2 different materials and/or colors. The first material is injected; then, the mould rotates and the second material is injected to make 1 part. It permits a 2-colour-molding or also called double injection, 2 shot molding, two-shot injection, overmolding, 2K injection, two colour injection, bi-injection, dual shot molding or multi-component molding.

CNC Technology. CNC is an abbreviation for Computer Numerical Control. This is a machine extremely accurately controlled by computer programs permitting a CAM (Computer-aided Manufacturing) through a CAD (Computer-Aided Design). Any plastic injection tool manufacturer uses it but the value-added of SINCERE TECH is the experience, professionalism, and training of the staff.

FMMS Molding or can be called RHCM (Rapid Heat Cycle Molding): excellence surface appearance: permits to take off the welding line. This process is integrated into the molding to save time. It is used for example for clear plastic parts.

US Welding: Ultrasonic Welding: process to weld/ join/ assemble plastic parts thanks to ultra-sounds.

Silk-Screen Printing:  this is to print logos or designs on parts.

Dip-Coating: this is the process of putting the component inside a liquid solution to apply a thin film on it. It permits to manage, change the hardness, the strength of the part by protecting it and expanding the lifetime of the product. Then, the excess liquid has to be drained and evaporation of the solvent is done to create the thin layer.

Laser Etching: this process is made for cutting a shape, a pattern, an image on the plastic part. It is also called laser graving.

Sputtering coating: this is the process of creating a very thin layer of conducting material on the component. It is also called Plasma Enhanced Chemical Vapor Deposition (PECVD) and can be done with most metals like aluminum, stainless steel, copper…

EMI shielding: protect parts from electromagnetic interferences. It is used to protect electrical signals from the outside world. For instance, we use it with marine radars for Garmin.

Waterproof technology: SINCERE TECH has the experience to make water-resistant parts and is able to ensure in-house tests thanks to the IP68 tests.

Sub-assembly: this is the pre-assembly of a component who will be later on being assembled in a larger product.

R&D: SINCERE TECH has its own Research and Development department in order to work with the customers on their projects, advise them on designs, resolve issues and study the feasibility of those.

Quality Control: We have very high standards of quality control in order to respect any requirements from our customers. We have a 100% quality control on our plastic molded parts, it means we control any part coming out of our production.

At Sincere Tech China mold maker, our unwavering commitment to staying at the forefront of the plastic mold industry drives us to embrace advancements and anticipate future trends. We continuously explore innovative materials and composites that offer enhanced performance and promote sustainability. By investing in ongoing research and development, we consistently deliver cutting-edge solutions that meet the evolving needs of our valued customers. As a trusted injection mold supplier in China, we take pride in our unwavering dedication to excellence.

Aligned with our sustainability goals, we place a high priority on environmentally friendly practices. We actively seek out sustainable alternatives, such as biodegradable polymers, and implement recycling initiatives to minimize the environmental impact of our manufacturing processes. By choosing our custom injection molding services, you can align your brand with sustainable manufacturing practices and contribute to a greener future.

Ensuring quality is our topmost priority, and we maintain rigorous quality control measures throughout the entire manufacturing process. Equipped with state-of-the-art facilities and staffed by skilled technicians, we subject each product to thorough inspection and testing. This guarantees exceptional performance, reliability, and customer satisfaction.

When you choose Sincere Tech as plastic injection molding service partner in China, you can expect the highest level of professionalism, expertise, and innovation. Our dedicated team is committed to helping you bring your ideas to life, delivering superior products that excel in performance, durability, and cost-effectiveness.

Partner with Sincere Tech Mould suppliers for your custom plastic injection molding service, and benefit from our comprehensive capabilities, unwavering commitment to quality and sustainability, and our drive to exceed your expectations at every step of the process. Together, let’s bring your innovative ideas to life.

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