Cheers for The New Year 2023!

Last Saturday is the Beginng of Spring, our factory had a big dinner together.

We made a short summary of 2022 and had awards for our excellent colleagues. Even though the year 2022 was hard, our factory still had good performance. Here we appreciate all our customers trust and support to our factory.

After 10+ years cooperation together, our team is more and more stronger now, I believe we will have a bright future together.

Cheers for our good harvest and progresses! Cheers for the new year 2023!


Plastic Injection Molding: The Cooling Rate Process

Plastic Injection Molding


In plastic injection molding, the cooling rate is the last section of the molding cycle.

The cooling rate is a decreasing rate from the time the plastic resin enters the mold until the last cavity of the mold is filled.

When the cooling process is complete, it is safe to remove the part from the mold.

Factors that affect the cooling rate and the final molded part

Mold Cavity Pressure

The cooling rate is monitored, measured, and displayed on a pressure curve. It is displayed this way because as the plastic resin cools, it shrinks, which reduces the mold cavity pressure.

Mold Temperature

In plastic injection molding, the temperature of the mold itself can be a factor in the cooling rate process. Aside from affecting mold cooling lines, mold temperature can affect part blemishes, like:

  • Mold Warpage
  • Sink Marks
  • Jetting

Improper mold temperature can also impact properties, such as:

  • Molded-in Stress
  • Fatigue Resistance
  • Wear Resistance
  • Creep Resistance
  • Molecular Weight
  • Dimensional Stability

The cooling rate can also be affected by the use of metals that conduct heat away.

The cooling process is complete when the temperature is no longer reducing and any additional time spent to cool the part is useless.

When the cooling process is complete, it is safe to remove the part from the mold.

TIP: During the plastic mold design phase, you must consider the best possible cooling channels for the mold. Using a plastic molder with a deep knowledge of cooling rate process optimization will allow for better control over the mold temperature, and thus, the cooling rate. It will also provide the best cycle time and the best outcome for a good, stress-reduced molded part.

How to Calculate Cooling Time?

Cooling time in injection molding is a critical part of the production process. It is the amount of time the molten plastic takes to solidify. An adequate cooling system is required to transfer heat away from the mold and maintain a stable cooling rate, ensuring the highest quality final products.

One of the quickest methods for estimating the cooling time is using a formula that accounts for the thickness of the part in an equation based on the effective thermal diffusivity. The thermal diffusivity estimates the transfer of heat in and out of material.


Since its establishment, WIT MOLD has successfully exported more than 2000 sets of molds with different types of structures and designs, which are applied to a variety of industries.

What is Unscrewing Mold?

One of the most unique types of injection molds is unscrewing molds. Unscrewing molding is a unique injection molding process with mold technology that includes movement and rotation to produce threaded components. Some plastic parts such as caps and closures with detailed threads cannot be removed using standard knock-off methods. After they are molded, parts need to be carefully unscrewed from mold to avoid damaging the threads.

The unscrewing molds are part of everyday use, which may cause you to think that you won’t need to spend much time considering the required design. To demonstrate the wide use of this particular mold type, the following is a shortlist of the types of products that use unscrewing molds in the design:


• Bottle and milk caps

• Condition and shampoo lids

• Prescription medication bottles

• Medical supplies

• Sprinkler and showerheads

• Screws, nuts, and bolts

Here’s How It Works:

• First, the plastic is injected into the tool. After the plastic has cooled, the threaded core starts to unscrew. The unscrewing mechanism works off of a rack and pinion and is powered by a hydraulic cylinder.

• The rack turns three sets of gears which then retracts the threaded core into the ejector box.

• Once the threaded core is fully unscrewed, the mold opens and the ejector system pushes a stripper plate forward to eject the part.

• After the part is fully ejected, the hydraulic cylinder reverses, screwing the threaded core back into the molding position, and the process repeats.

 What is Unscrewing Mold?

What factors need to be considered?

When you need one of these types of plastic molds, there are several things you have to determine to make sure you get the right fit for your product and budget.


The volume of the product will probably determine many different aspects of the final product, including the thread count, the size of the part, and the type of material that will be used during production. While other factors are important, the design of the various unscrewing molds is more complex and costly than many of the other types of molds.

Ease of Removal

The ease by which an unscrewing mold should be removed from the final product is an important factor to consider in the design. Water bottles have only a few threads, sometimes only two or three because they need to be easy to remove. To ensure that the tops do not fall off easily, the threads are spaced out a bit more. An unscrewing mold on a medical device will likely need a lot of threads that are evenly spaced and very difficult to pull off of the device. The material required for these two vastly different uses is affected by how easily the part should be removed from the product.

The Threads

The number of threads is going to vary based on the final product. Water bottles do not require a high thread count because they are relatively light and should be easily removed. If the unscrewing mold is for a plastic part under the hood of a car, it needs to have a higher thread count to be more durable. The number of threads required plays a large role in the final cost of production, so it needs to be tested to ensure it meets the needs of the final product.

Applications and Maintenance

High volume, reliable unscrewing plastic injection molds are some of the more complex plastic injection molds that can be manufactured. Unscrewing plastic injection molds are typically utilized for high volume applications where threaded plastic parts are needed for items such as:

ㆍBottle caps

ㆍShampoo bottles

ㆍPharmaceutical Supplies

ㆍAutomotive parts

ㆍNuts and bolts

ㆍCosmetics packaging

ㆍMedical Supplies

ㆍConsumer goods

ㆍSprinkler heads, lawn & garden parts

ㆍContainer lids

What is Unscrewing Mold?


Most threaded plastic parts on standard plastic injection molds are not easy to remove using standard knock-off techniques. Therefore more complex unscrewing plastic injection molds must be utilized to prevent the threads on threaded plastic parts from being damaged while the parts are coming off of the plastic injection mold.

Because these threaded plastic parts are typically needed in high volume applications for items such as bottle caps or cosmetics packaging, the unscrewing plastic injection mold most operate at a high speed to reduce cycle times thus reducing part costs. The unscrewing plastic injection molds must also be high quality and reliable to operate for a large number of cycles while only needing routine preventative maintenance.


WIT MOLD is a highly skilled mold design and manufacturing company in China, certified ISO2009:2015 international quality standard. Contact us today for your threaded plastic parts!


What is Two-Shot Molding?



Two-shot molding, also known as dual-shot, multi-shot, or double-shot molding is a subcategory of injection molding that allows engineers to create multi-material or multi-colored parts without adding extra assembly steps.

The two-shot injection molding process is best understood in terms of the different layers of materials or colors that are created by the injection molding machine. The first material is injected into a mold to create the substrate, around which the other material or materials will be molded. The substrate solidifies and cools before being transferred — by hand, robot arm, or rotary plane — to the other chamber of the mold.

From there, the mold opens and the side with the substrate rotates 180° to meet the other mold chamber and injection molding nozzle. Once the substrate is in place, the second material is injected and bonds with the substrate to form a firm hold.  Once the second layer cools, the final part is ejected.

Engineers should know that two-shot injection molding can be sped up or slowed down based on how the substrate is transferred to the other chamber of the mold. Hand and robot arm transfers take longer than a rotary plane, but rotary platen molding is more expensive and generally only an efficient option for high-volume production runs.

Additionally, it’s critical that molds are made out of materials that will easily bond together and that the molds align correctly to prevent deformities in the part.

Pros and cons of two-shot molding

Two-shot plastic injection molding is an excellent technique for efficient and cost-effective manufacturing. This process also produces highly durable end parts and components.

From a design standpoint, two-shot molding offers designers a lot of flexibility because this process can create complex geometries and accommodate multiple colors, making for more aesthetically pleasing parts.

Further, since one machine makes the whole part and no post-processing is required, engineers can dramatically reduce manufacturing time, which in turn keeps costs low. However, it’s worth noting that the initial two-shot mold costs can be high and the two-shot molding machine is more expensive than a standard injection molding machine. Luckily, these costs are often offset by labor savings and assembly costs on large production runs.


We are a TWO SHOT INJECTION MOLDS manufacturer, please contact us if you need them!

How do you make a plastic mold?

In today’s manufacturing environment, plastics are used to manufacture a variety of items. Each application requires a special manufacturing process, which can shape parts according to their specifications. If you are making plastic parts, the first thing you need to determine is the type of molding that is best suited to your particular application.At WIT MOLD,We focus on custom plastic molding. This paper briefly summarizes five different types, their advantages and applications.

1>Blow molding – suitable for hollow objects, such as bottles

This process follows the basic steps in glass blowing. The parison (heated plastic block, usually pipe) is inflated by air. The air pushes the plastic against the mold to form the desired shape. After cooling, the plastic is ejected.

The blow molding process aims to produce large quantities of integrated hollow objects. If you need to make a lot of bottles, this is the process for you. Blow molding can produce very uniform thin-walled containers. Moreover, it can do this very economically.


2>Extrusion molding – suitable for long hollow molding applications, such as pipes, pipes and straws

Although other forms of molding use extrusion to put plastic resin into the mold, this process extrudes the molten plastic directly into the mold. The shape of the mold, not the mold, determines the shape of the final product.

Extrusion molding involves forcing molten plastic through a mold to form a shape with a fixed cross-section. This is an effective way to produce multiple shapes. Since plastics are melted from solid form and then re cured, only thermoplastics can be extruded. The extruded “pipe” can be cut or rolled up for shipment after cooling.


3>Injection molding – suitable for high quality and mass parts manufacturing

Injection molding is by far the most widely used of all injection molding technologies. The presses used in this process vary in size and are rated according to pressure or tonnage. Larger machines can inject auto parts. Smaller machines can produce very accurate plastic parts for surgery. In addition, many types of plastic resins and additives can be used in the injection molding process, which adds flexibility to designers and engineers.

The process itself is quite simple; However, there are many enhancement and customization technologies available to produce the required finishes and structures. Injection molds are usually made of steel and contain cavities for forming parts. Molten plastic is injected into the mold to fill the cavity. The mold cools and the parts are ejected through pins. This process is similar to a jelly mold, which is filled and then cooled to make the final product.

This method has high cost of mold making; However, the cost per part is very economical. Low part costs and resin and surface treatment options have contributed to the popularity of injection molding in today’s manufacturing field.


4>Compression molding – suitable for large objects, such as automobile parts

The name of this forming method says everything. The heated plastic material is put into the heated mold and then compressed into shape. Plastics can be in bulk, but usually in sheets. The heating process, called curing, ensures that the final part remains intact. As with other forming methods, once the part is formed, it is removed from the mold. If sheet plastic material is used, trim the material in the mold before taking out the part.

This molding method is very suitable for high-strength compounds, such as thermosetting resins, as well as glass fibers and reinforced plastics. The excellent strength characteristics of the materials used in compression molding make it a valuable process in the automotive industry.


5>Rotomolding – suitable for large, hollow and integrated parts

This process uses high temperature and rotary motion to coat the interior of the die and form parts. The continuous rotation of the die will produce centrifugal force, so as to form a product with uniform wall. Because it is very suitable for large hollow containers, such as cans, it is not a fast-moving process. However, this is a very economical process for specific applications and is cheaper than other types of molding. This process wastes few materials, and the excess materials can usually be reused, making it an economic and environmentally friendly manufacturing process.

Each type of molding has its advantages and disadvantages. Designers and engineers need to understand these differences and available production options, and there are always many ways to make the final solution.WIT MOLD has become one of the best molds in the industry because we combine the essence of the latest technology with proven traditional methods.


With an expert team composed of experienced and knowledgeable experts, we are able to complete custom orders for Custom Plastic Molds and parts that may exceed the capabilities of our competitors. We are also unremittingly committed to improving customer satisfaction, which includes providing comprehensive end-to-end quality assurance for every product we produce.

Successful T1 Mold Trial

We are so glad to share this good news! We did good job again! T1 Mold trial is very successful today! Thanks for all our WIT MOLD Team’s hard working and good skills! We are also truth grateful to the customers who choose us as your supplier in China.


WIT MOLD New CNC Machine Has Started Working

WIT MOLD New CNC machine has started working.

This new machine is focusing on building your optic surface. If you worry about whether it is okay to make the radius 0.1mm for your optics surface or your light guide,  WIT MOLD can help you to complete this job successfully.

New CNC machine

New CNC machine

What Does Mold Saving In The Mold Mean?

What Does Mold Saving In The Mold Mean?

Mold saving refers to the fitting that does not reach the design accuracy when assembling the mold, and abnormalities will occur when the product is produced, and the required accuracy is not reached, and the mold saving process is required for fine adjustment.

The method of mold saving generally needs to be carried out in accordance with the standard operating steps. The operator of the mold optical polishing plant needs to strictly follow the following mold-saving operation methods to do the most basic mold-saving polishing for the mold.

  1. When a new mold starts to be processed, it should be cleaned with firewater (kerosene) first, and then all oil stains and unnecessary objects should be wiped off with alcohol so that when the mold is filled with an oilstone, the oilstone surface will not stick to dirt and the cutting function is lost.
  2. When saving molds, the bottom corners, bone pits, and dead corners of the mold should be saved first, and the protrusions and large planes should be saved later.
  3. Some of the modules are embedded in three to four pieces to form a module. Only rough or fire patterns are punched along the edges of the individual die openings, and then all the modules are clamped to be smooth, and the plastic parts are clamped when they are out. The position will be slightly smoother.
  4. For modules with large planes or high protrusions, be sure to use flat steel sheets and the red lead to check whether the modules are uneven or reversed after the rough grains are removed. If there is any unevenness in the finished product, it will stick mold or drag flowers.
  5. If the module is a flat surface and maybe a sealing position in a certain place, we can use double-sided adhesive tape to paste sandpaper on the edges that do not want to save the mold, so as to ensure that there is no place that should not be saved.
  6. Use copper or bamboo to press the sandpaper to save the mold. Keep in mind that the sandpaper should not be larger than the area of the tool or even the place that should not be hit by the extra sandpaper to round the mouth or change the status of unevenness.
  7. For processing with copper or bamboo, the shape of the tool should be similar to that of the mold, so as not to save the mold. For example, flat bamboo should be used for the plane, and small or round bamboo should be used for processing the small or round surface.
  8. When the mold-saving plane is next to the protruding position, sandpaper or oil stone should be struck at 15 to 30 degrees syncline to avoid a deep hole next to the protruding position.
  9. For example, when the crude oil stone is 150#, 180#, 220#, and other oil stones, fire water should not be added, except for light 320# and above. Manual use of copper or bamboo pieces depends on the environment at the time.
  10. If the module is not allowed to have fire patterns, the saver must see them clearly or use different methods to find the fire patterns and remove them. Because there are patterns after each trial of the mold. The module must be assembled and disassembled and tried again mold, it will cost a lot of man-hours and waste materials.
  11. Check the fire pattern method of the module. After the module is cleaned, the surface of the copper acid can be evenly coated with a brush. After about 3 to 5 minutes, the module is washed with water and dried with an air gun. After the test, the molds with no fire patterns on the surface will be darkened, and those with fire patterns on the surface will show shiny spots. Repeat the treatment with oilstone or sandpaper until there is no fire pattern, and it will be completely darkened after the copper acid test.
  12. You don’t need to be more serious about the blister copper male than the young copper male. As long as you omit the protruding parts of the copper male surface or the convex position, you don’t have to save the concave part. We need to find the problem to save the mold.
  13. If the copper male is placed on the bronze fixture of the spark machine, the four benchmark nails below must be placed on the bottom with a soft object (such as cloth, paper) to avoid unnecessary damage when the workpiece is moved, and put it on the table or on the shelf.
  14. Use hand or machine to hit above 400# sandpaper. Pay attention to the clean environment around the module. The sandpaper should be rubbed on the sandpaper rolls before cutting, and the slightly coarse sand particles on the sandpaper should be removed. This will reduce the sudden roughness when polishing.
  15. If the model saver finds an abnormality, he should report it to the supervisor. The manager should be notified when the model is completed, and should not be handed over without completion.

The Difference Between Double Shot Molding And Overmolding

The Difference Between Double Shot Molding And Overmolding

There are a variety of manufacturing methods used to make plastic molded products. The two methods mentioned in this article, double shot molding, and over-molding, are viable manufacturing processes and provide some advantages for many plastic manufacturers. Both of these processes are difficult to master because they require very strict tolerances. Below, we discuss the differences and advantages of double-shot molding and over-molding.

Two-shot molding

Two-shot molding, sometimes called double-shot molding, is a manufacturing process that uses two different materials to produce complex molded parts by molding plastic around preformed metal or plastic inserts. The process is relatively simple; one material is injected into the mold to make the initial part of the product, followed by a second injection of another material that is compatible with the initial injection molded part. The two plastic resins then form molecular bonds, and the multi-resin molding is cooled and ejected.

Two Shot Mold is an ideal process for complex, multi-material, multi-color plastic products; especially in mass production scenarios. Other advantages include:

Lower unit cost.

Reduce costs and waste associated with assembly defects.

improve product quality.


Overmolding is the process of adding an extra layer of material to an existing piece or component. This process is usually used for manufacturing parts, sub-parts of parts, and prototype development. Typically, the substrate material (the first piece of other material that will be bonded and mechanically interlocked) is placed in an injection molding tool, at which point the mold material is shot into or around the substrate. When the over-mold material solidifies, the two materials are combined as a single part.

If you over-molding a metal part with plastic, you can really use any type of plastic. If you are over molding a plastic part with another plastic, there may be some compatibility issues. Your experienced molder will be able to recommend the best material for your project.

By adding textures, colors, and adding necessary functional components, over-molding can be added to change the surface of a piece or product. Other advantages include:

Enhance design flexibility and multi-material components.

Reduce secondary operations; assembly and labor costs.

Improve the strength and structure of parts.

As mentioned above, these processes are relatively easy to understand. However, it is very difficult to master. It requires a high level of technical expertise and attention to detail. When dealing with high-volume production scenarios, the smallest errors can also bring huge losses. This is why it is important to find a high-capacity molding manufacturer. Once you find one, you need to involve them early in the design phase of your part, because they can design value and quality into any problem area.

Two-Shot Molding vs. Overmolding

What is two-shot molding?


Two-shot molding, also known as dual-shot, multi-shot, or double-shot molding is a subcategory of injection molding that allows engineers to create multi-material or multi-colored parts without adding additional assembly steps.
The two-shot injection molding process is best understood, where different material layers or colors are created by the injection molding machine. The first material is injected into the mold to create the substrate, and other materials or materials around the substrate will be molded. The substrate solidifies and cools before being transferred to another cavity of the mold by hand, a robotic arm, or a rotating plane.
Engineers should know that the speed of two-shot injection molding can be accelerated or slowed down depending on how the substrate is transferred to other cavities of the mold. Hand and robot arm transfer takes longer than rotating planes, but rotating platen molding is more expensive, and is usually just an efficient option for high-volume operation.
In addition, it is essential that the materials of the mold will be easily combined and the molds are properly aligned to prevent deformed parts.

Advantages and disadvantages of two-shot molding


Two-shot plastic injection molding is efficient and economical manufacturing technology. This process can also produce highly durable end parts and assemblies.
From a design point of view, two-shot molding provides designers with a lot of flexibility, because this process can create complex geometric shapes and accommodate multiple colors to make parts more beautiful.
In addition, since one machine manufactures the entire part, no post-processing is required, engineers can drastically reduce manufacturing time, thereby keeping costs low. However, it is worth noting that the cost of the initial two-shot mold may be very high, and the two-shot molding machine is more expensive than the standard injection molding machine. Fortunately, these costs are usually offset by saved labor and assembly costs for mass production.

Two-shot moldingWhat is overmolding?


Overmolding, like two injection molding, is a multiple injection molding process that uses two or more different thermoplastics to produce a single final product. This process is ideal for engineers who want to build components that are strong, functional, beautiful, and that will not separate over time.
In order to start the over-molding process, engineers injected a harder over-molding material. Then, the substrate is placed in a complex mold or a complex cavity in the same mold. The molten overmolding material is sprayed into the substrate, or onto the substrate, or sprayed around the substrate. After the molten material is cooled, the substrate and the mold are bonded chemically or mechanically. The entire over-molding process only takes 30 seconds.

Advantages and disadvantages of overmolding


Overmolding and two-shot injection molding have many of the same advantages. They are ideal for the rapid manufacture of durable, reliable, and shock-resistant parts with complex geometries, but over-molding is best suited for low-volume production runs.
Compared with two-shot molding, the design of multiple molds is also easier to carry out, because engineers can use any standard injection molding machine to carry out this process.
In terms of disadvantages, the tolerances of parts manufactured by overmolding are often lower than those of two-shot molding that can be achieved. It is also important to remember that plastic compatibility requirements may limit designers.
We are two-shot molding suppliers. Please feel free to contact us if you are interested in our products.

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