Introduction: Molds are super important in industry today, and the quality of your molds directly affects the quality of your products.

The plastic injection molding molds production process is generally divided into: customer customization, mold design, mold manufacturing, mold inspection and mold trial, mold modification and mold repair, mold maintenance, and the following will explain them one by one.

Customer Customization

The production of plastic molds starts with the customer’s engineering people giving the mold maker product drawings. The mold maker takes the product data, chews it up, and spits it out in the form of a plastic molding production task list. This is customer engineering.

Plastic Parts Production Requirements

You need to understand the technical requirements of the parts, such as whether they can be processed, whether they can be accurately dimensioned, etc.

For example, what are the requirements for the appearance shape, color transparency, and performance of plastic parts? Is the geometric structure, slope, insert, etc. of the plastic parts reasonable? What is the allowable degree of molding defects such as weld marks and shrinkage holes, and whether there is post-processing such as painting, electroplating, silk screen printing, and drilling.

Estimate whether narrow dimensional tolerances and if the plastic part can be molded that meets the requirements. Also, you need to know the plasticization and molten plastic process parameters of the plastic.

Process Information

Understand the requirements of the injection mould method, beer machine model, plastic resin performance, mold structure type, etc.

The molding material should be strong enough for the plastic materials part, flow well, be the same all over, be the same in all directions, and not change when it gets hot.

Depending on what the plastic part is for and if it gets worked on later, the molding material should be good for dyeing, metal plating, looking good, being stretchy and bendy enough, see-through or shiny, sticking together (like with sound waves) or getting welded.

Select Molding Equipment

Injection capacity, clamping pressure, injection pressure, injection unit , mold installation size, ejection device and size, nozzle hole diameter and nozzle spherical radius, gate sleeve positioning ring size, maximum and minimum thickness of the mold, template stroke, etc.

Specific Mold Structure Plan

Two-plate mold, three-plate mold. Whether the mold structure is reliable, whether it meets the process technology (such as geometric shape, surface finish and dimensional accuracy, etc.) and production economic requirements of plastic parts (low part cost, high production efficiency, continuous mold operation, long service life, labor saving, etc.).

Mold Structure Design

To make a good mold, you need good processing equipment and skilled mold makers. But the most important thing is to have a good mold design. Especially for complex molds, the quality of the mold design accounts for more than 80% of the mold quality.

A good mold design is: under the premise of meeting the customer’s requirements, the processing cost is low, the processing difficulty is small, and the processing time is short.

To achieve this, you must not only fully understand the customer’s requirements, but also understand the injection moulding machine, mold structure, processing technology, and the processing capabilities of your own mold factory.

The mold structure is determined by the type of injection molding machine and the characteristics of the plastic parts. When designing, focus on the following aspects: technical specifications of the injection molding machine; process performance of plastics; pouring system, including runners, gates, etc.;

Molding parts; commonly used structural parts; positioning mechanism; ejection mechanism; mold temperature control; exhaust; mold material.When designing a mold, you need to think about a lot of things and pick a good shape that will make the mold work right.

Plastic Parts Ranking

Plastic parts ranking is about putting one or more plastic parts that you need in order, based on how you’re going to make them and what the customer wants.

The ranking of plastic parts complements the mold structure and the plastic processability, and directly affects the subsequent injection moulding process. The corresponding mold structure must be considered during the ranking, and the ranking should be adjusted under the condition of meeting the mold structure.

From the perspective of the injection molding process, the following points need to be considered for ranking:

a. Runner length; b. Runner waste; c. Gate position; d. Glue feeding balance; e. Cavity pressure balance.When it comes to mold structure, you need to consider the following points: a. Make sure it meets the requirements of the sealing glue.

b. Make sure the mold structure has enough space: check if there is enough space for the sprue base, runner, parting line, and other necessary spaces; check if the mold structure is strong enough; check if there is any interference between multiple moving parts; and make sure the location of the bushing does not interfere with the ejector pin location.

c. Take screws, cooling water, and ejector device into account: when ranking, consider how screws and ejectors affect cooling water holes.

d. Make sure the length and width ratio of the mold is balanced: the mold should be as compact as possible, with a good length and width ratio, and consider how it will fit on the injection molding machine.

Parting

Choose the correct parting surface, consider the sealing distance, build a reference plane, balance the lateral pressure, flatten the nozzle contact surface, handle the contact and penetration of small holes, avoid sharp steel, and comprehensively consider the appearance of the product.

Parting Verification And Improvement of Mold Strength

Choose the right parting surface, consider the sealing distance, build a reference plane, balance the lateral pressure, flatten the nozzle contact surface, handle the contact and penetration of small holes, avoid sharp steel, and comprehensively consider the appearance of the product.

To make sure the mold can work normally, we need to check not only the overall strength of the mold, but also the strength of the local structure of the mold.Make some Improvements to the specific mechanism to improve the local strength .

Design of Mold Parts

Mold parts can be divided into two types: forming parts and structural parts. Forming parts are the parts that directly participate in the formation of the cavity space, such as the concave mold (cavity), punch (core), insert, slide, etc.

Structural parts are the parts used for installation, positioning, guiding, ejection, and various actions during the forming process, such as positioning rings, nozzles, screws, pull rods, ejectors, sealing rings, fixed distance pull plates, hooks, etc.

When we split the inserts, we mainly consider the following aspects: no sharp steel, thin steel, easy to process, easy to adjust the size and repair, ensure the strength of the molded parts, easy to assemble, no impact on the appearance, and comprehensive consideration of cooling (after the inserts are made, it is difficult to cool locally, and the cooling situation must be considered).

When designing structural parts, the general principle for the layout of ejector pins and cooling channels is to arrange the ejector pins first, then arrange the cooling channels, and then adjust the ejector pins. However, in actual production, mold modification is often taken into account.

After the mold is finished, the cooling channels are not started immediately. They can only be opened after the mold has been modified for a period of time according to the modification situation.

Ejector sleeve arrangement:

Ejector sleeve is generally used for the mold column position. In addition, for the deeper bone position, the ejector pin is easy to be ejected, and the ejector sleeve can also be used to add bone to assist ejection. In general, the wall thickness of the ejector sleeve is >=1mm, and the ejector sleeve and ejector needle are ordered together when ordering.

In the structural design, the height of the column should not be too high, otherwise the sleeve needle is easy to bend and difficult to eject. For the design and selection of other structural parts, such as positioning rings, nozzles, screws, pull rods, sealing rings, fixed distance pull plates, hooks, springs, etc., those who are interested can find some information to understand it by themselves.

Production of Mold Drawings

Mold drawings are important documents that convert design intentions into mold production. Generally, they need to be drawn according to national standards, and they also need to be combined with the customary drawing methods of each factory.

Mold drawings include general assembly structure drawings and their technical requirements, as well as part drawings of all parts including various inserts.

Mold Manufacturing

Programming and Electrode Removal

Once the mold design is done, you need to make CNC programs and decide whether to take out electrodes for EDM based on the processing conditions of each part.

Machining

The mold’s mechanical processing includes CNC processing, EDM processing, wire cutting processing, deep hole drilling processing, etc. After the mold base and materials are ordered, the mold is only in a rough processing state or only steel material. At this time, a series of mechanical processing must be carried out according to the design intention of the mold to make various parts.

CNC machining, also known as computer numerical control machining, is a machining process that requires various machining operations, tool selection, machining parameters, and other requirements. Those who are interested can find relevant information to learn.

EDM machining, or electrical discharge machining, is a machining process that uses electrical discharge to erode materials to achieve the required size, so it can only process conductive materials. The electrodes used are usually made of copper and graphite.

Bench Assembly

Bench work is a very important part of the mold making process, and it is a process that needs to be carried out throughout the entire mold manufacturing process. Bench work, fitting mold assembly, turning, milling, grinding, and drilling are all skilled.

Mold Saving And Polishing

Mold saving and polishing is the process of using sandpaper, oilstone, diamond paste, and other tools and materials to process mold parts after CNC, EDM, and bench processing and before mold assembly.

Mold Inspection

A good mold needs to meet the following acceptance standards .

Appearance Quality

A good mold should look flat and smooth, without obvious scratches, bumps, and deformation. The nameplate of the mold should be clear and complete, with neatly arranged characters and numbers, and should be fixed on the mold foot near the template and reference angle.The content on the nameplate should include important information such as mold model, manufacturer information, and materials used.

Structural Rationality

The mold structure should be reasonable and stable, and all components should be firmly installed without looseness.

The positioning ring, gate sleeve, ejector sleeve, and other components of the mold should meet the design requirements, be installed in the correct position, and have no obvious damage and deformation. At the same time, the parting surface of the mold should be seamless, and the opening and closing actions should be smooth and without abnormal noise.

Dimensional Accuracy

Checking the dimensional accuracy of the mold is important to make sure the product is accurate. So, when you get the mold, you need to check its dimensional accuracy strictly. The dimensions of the mold template and parts should meet the design requirements.

The position accuracy of the positioning holes, gates, ejector holes, etc. should meet the production requirements. Also, the mold’s closing height and maximum mold opening stroke should meet the requirements of the electric injection molding machines.

Manufacturing Details

A good mold should also be refined in manufacturing details. For example, the ball R of the gate sleeve should be larger than the ball R of the injection molding machine nozzle to ensure smooth molten plastic flows; the inlet diameter of the gate sleeve should be larger than the diameter of the nozzle injection port to prevent injection during injection.

In addition, the cooling system of the mold should be designed reasonably to ensure uniform cooling and reduce the internal stress of the product after molding.

Mould Modification

Once the mold is tested, the mold is changed according to the mold test situation. Also, after the engineer confirms the plastic part, the structure of the plastic part should be changed accordingly.

Since the mold has been made, all changes are more troublesome, and sometimes even more difficult than redoing. We must find the best way to change according to the specific situation.

Redesign the Mold

To completely solve the problem, you need to redesign the mold. You optimize the mold structure, parting surface, gate position, etc., based on the problems with the original mold. You also need to consider the selection of mold materials and optimize the heat treatment process to improve the mold’s life and durability.

For example, if the parting surface of the mold is uneven and causes insufficient melt filling, you can redesign the parting surface to make the melt filling more even.

Modify Mold Parameters

Changing the mold parameters is a relatively simple and fast method of mold modification. By adjusting parameters such as mold size, precision, and surface roughness, the quality and production efficiency of the product can be improved.

Thus achieving mass production and high volume production . For example, by adjusting the size and position of the gate, the melt filling process can be optimized and the product quality can be improved; by reducing the surface roughness of the mold, the product residue can be reduced and the production efficiency can be improved.

Replace Mold Accessories

Swapping out mold accessories is a popular and relatively cheap way to modify molds. For parts in the mold that are prone to wear and failure, like the cavity, core, gate sleeve, etc., you can choose to replace them with materials or surface treatments that are more resistant to wear and corrosion.

You can also choose more advanced mold components based on your actual production needs to improve production efficiency and product quality. For example, replacing the easily worn cavity with highly wear-resistant materials can effectively increase the mold’s service life.

Mold Repair

Argon Arc Welding Repair

The arc that burns between the wire that keeps getting fed and the thing you’re welding is what you use to heat it up, and the gas that comes out of the nozzle on the welding torch is what protects the arc so you can weld.

Right now, TIG welding is the most common way to do it and you can use it on most of the big metals, like regular steel and fancy steel. MIG welding is good for stainless steel, aluminum, magnesium, copper, titanium, zirconium, and nickel alloys.

It’s really cheap, so people use it a lot for fixing molds, but it has some problems, like it makes a big heat-affected zone and big welds. People are starting to use lasers to fix molds instead of MIG welding because it’s more precise.

Brush Plating Repair

Brush plating technology uses a special DC power supply. The positive pole of the power supply is connected to the plating pen as the anode during brush plating; the negative pole of the power supply is connected to the workpiece as the cathode during brush plating.

The plating pen usually uses high-purity fine graphite blocks as anode materials. The graphite blocks are wrapped with cotton and wear-resistant polyester cotton sleeves. When you’re working, you adjust the power supply component to a suitable voltage.

Then you fill the plating pen with plating liquid. You move the plating pen back and forth on the surface of the repaired workpiece at a certain relative speed. You maintain a certain pressure until you form a uniform and ideal metal deposition layer.

When the plating pen touches the surface of the repaired workpiece, the metal ions in the plating liquid move to the surface of the workpiece because of the electric field force. They get electrons on the surface and turn into metal atoms. These metal atoms deposit and crystallize to form a plating layer. That’s how you get the uniform deposition layer you want on the working surface of the repaired plastic mold cavity.

Laser Surfacing Repair

Laser welding is a welding method that uses a laser beam focused by a high-power coherent monochromatic photon stream as a heat source. This welding method usually has continuous power laser welding and pulse power laser welding.

The advantage of laser welding is that it does not need to be carried out in a vacuum, but the disadvantage is that its penetration is not as strong as that of electron beam welding.

Laser welding can perform precise energy control, so it can achieve the welding of precision devices. It can be applied to many metals, especially to solve the welding of some difficult-to-weld metals and dissimilar metals. It has been widely used in mold repair.

Mold Maintenance

Ensure That the Use Environment of the Mold is Dry And Avoid Moisture

If the environment is humid, the surface of the mold is prone to rust, which will affect the surface quality and service life of the mold. Therefore, when storing the mold, choose a dry and ventilated place, and use moisture-proof materials for protection.

Clean the Mold Surface Regularly

When using the mold, it will be covered with paint, oil and other things, which will affect its use effect. Therefore, the surface of the mold should be cleaned regularly with a detergent to ensure that its surface is smooth and avoid defects that affect quality.

Use the Mold Correctly

The mold is designed and made under certain conditions of use, so special attention should be paid when using it, avoid using excessive amounts during operation, and comply with operating procedures to ensure that the mold will not be damaged or have quality problems during long-term use.

Lubricate And Maintain Frequently

The mold needs the cooperation of the moving parts during use, so the moving parts of the mold should be lubricated frequently to prevent it from getting stuck or jammed due to wear during operation.

Pay Attention to the Storage Method

When you store your mold for a long time, you don’t want it to get all messed up and ruined. So, when you store it, you need to put it on a flat surface and prop it up with something so it doesn’t get all bent out of shape while you’re not using it.

Conclusion

Plastic injection molds are super important in industry today. If you want your final product to be good, you need a good mold. You need to make sure your mold design is good, your mold making is good, and you take care of your mold.

You need to make sure you do a good job with your customer, your mold design, your mold making, your mold trial, your mold modification, and your mold maintenance. If you don’t do a good job with all of these things, your mold won’t be good. So, you need to keep working on your technology and your process to make sure you can make good molds.