The injection mold making process mainly includes:
- Accept the task
- Mold design;
- Mold manufacturing;
- Mold inspection and tryout;
- Modification and modification;
- Mold maintenance.
1. Accept the task
In the production of plastic molds, the customer engineering staff first provides product drawings to the mold manufacturer. The manufacturer collects, analyzes, and digests product data through the task requirements of molding plastic production. This is the acceptance task.
Plastic parts production requirements
Understand the technical requirements such as the purpose, manufacturability, and dimensional accuracy of the parts. For example, what are the requirements for plastic parts in terms of appearance, color transparency, and performance, whether the geometric structure, slope, and inserts of the plastic parts are reasonable, the allowable degree of molding defects such as weld marks and shrinkage holes, and whether they are coated or not. Post-processing such as installation, electroplating, silk-screening, drilling, etc.
Estimate whether the molding tolerance is lower than the tolerance of the plastic parts, and whether the plastic parts meeting the requirements can be molded. In addition, it is necessary to understand the plasticization and molding process parameters of plastics.
Understand the requirements of glue feeding method, beer machine model, plastic material performance, mold structure type, etc.
The molding material should meet the strength requirements of plastic parts, and have good fluidity, uniformity, isotropy, and thermal stability. According to the purpose of the plastic part and whether it is post-processed, the molding material should meet the requirements of dyeing, metal plating, decorative performance, necessary elasticity and plasticity, transparency or reflection performance, adhesiveness (such as ultrasound) or weldability.
Choose molding equipment
Injection capacity, clamping pressure, injection pressure, mold installation size, ejection device and size, nozzle hole diameter and nozzle spherical radius, gate sleeve positioning ring size, mold maximum and minimum thickness, template stroke, etc.
The specific structure of the mold
Two-plate mold, three-plate mold. Whether the mold structure is reliable, whether it meets the process technology of plastic parts (such as geometric shape, indicating smoothness and dimensional accuracy, etc.) and production economic requirements (low part cost, high production efficiency, continuous operation of the mold, long service life, and labor saving Wait).
Plastic parts ranking
Positioning of plastic parts refers to arranging one or more plastic parts according to a reasonable injection molding process and mold structure according to customer requirements.
The ranking of plastic parts complements the mold structure and the plastic technology, and directly affects the later injection process. The corresponding mold structure must be considered when ranking, and the ranking must be adjusted under the conditions of meeting the mold structure.
From the perspective of injection molding process, the following points need to be considered:
- a. The length of the runner;
- b. Runner waste;
- c. Gate location;
- d. Glue feeding balance;
- e. The cavity pressure is balanced.
From the perspective of mold structure, the following points need to be considered:
- a. Meet the requirements of sealing glue
- b. Meet the space requirements of the mold structure: shovel base, row position, inclined top and other space requirements, whether the mold structure is strong enough, whether multiple moving parts interfere, and the position of the cylinder should avoid the position of the top stick hole.
- c. Fully consider the screw, cooling water and ejector device: For the arrangement, pay attention to the influence of the screw and the ejector pin on the cooling water hole.
- d. Whether the mold length and width ratio is coordinated: the mold is as compact as possible, the length and width ratio is appropriate, and the installation requirements of the injection machine should be considered.
Drawing and ordering of quotation chart
- a. The quotation drawing is the initial design plan of the mold, and also provides reference instructions for mold ordering. The quotation chart is a relatively detailed identification of the mold embryo and its structure and the size of the mold meat based on the original layout.
- b. Material ordering is based on the quotation drawing, drawing a sketch of the die blank and filling in the order form.
When ordering materials, attention should be paid to selecting various mold materials according to the various requirements of the mold.
Mould structure design
The mold structure is determined by the type of injection machine and the characteristics of the rubber parts. The design focuses on the following aspects:
- (1) Technical specifications of the injection molding machine;
- (2) Process performance of plastic;
- (3) The pouring system, including runners, gates, etc.;
- (4) Molded parts;
- (5) Common structural parts;
- (6) Position organization;
- (7) Ejector mechanism;
- (8) Mold temperature control;
- (9) Exhaust;
- (10) Mold material.
Mold design needs to comprehensively consider various factors, select a reasonable structure form, and meet the purpose of mold forming.
a. plastic parts ranking
In the 3D design stage, the ranking is now based on the 2D ranking at the beginning of the design to do more in-depth design.
Choose the correct parting surface, consider the sealing distance, build a reference plane, balance the lateral pressure, flatten the nozzle face, and deal with the penetration of small holes, avoid sharp steel, and consider the appearance of the product.
c. Check and improve the strength of the mold
In order to ensure that the mold can work normally, it is necessary 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 specific institutions to increase local strength:
d. Design of mold parts
Mold parts can be divided into forming parts and structural parts according to their functions. Forming parts refer to structural parts that directly participate in the formation of cavity space, such as concave mold (cavity), convex mold (core), inserts, row positions, etc.; structural parts refer to installation, positioning, guidance, and ejection And the parts that complete various actions during forming, such as positioning ring, pump nozzle, screw, pull rod, thimble, sealing ring, fixed distance pull plate, pull hook and so on.
The disassembly of inserts mainly considers the following aspects:
- (1) Cannot produce sharp steel or thin steel
- (2) Easy to process
- (3) Easy to resize and maintain
- (4) Ensure the strength of molded parts
- (5) Easy to assemble
- (6) Do not affect the appearance
- (7) Comprehensive consideration of cooling (partial cooling is difficult after the insert is made, and the cooling situation should be considered)
In the design of structural parts, the layout of the thimble and the layout of the water transportation generally follow the principle of first arranging the thimble, then arranging and transporting the water, and then adjusting the thimble. However, in the actual production process, the situation of mold modification is often considered. After the mold is completed, water transportation is not started immediately, and the mold can only be opened after the modification is completed for a certain amount of time.
The layout of the tube:
The main tube is generally used in the forming column position. In addition, for the deep bone position, the thimble is easy to white when it is ejected, and the main tube can also be used to add bone to assist the ejection. Under normal circumstances, the wall thickness of the cylinder is >=1mm, and the cylinder and needle are ordered together when ordering.
In the structural design, the height of the column should not be too high as much as possible, otherwise the cylinder needle is easy to bend and difficult to eject
For the design and selection of other structural parts, such as positioning rings, pumps, screws, pull rods, sealing rings, fixed distance pull plates, pull hooks, springs, etc., if you are interested, you can find some information to understand by yourself.
e. production of mold drawings
The mold drawing is an important document that transforms the design intent into the mold making. Generally, it needs to be drawn in accordance with national standards, and it also needs to be combined with the customary drawing methods of each factory.
The mold drawing includes the general assembly structure drawing and its technical requirements, and there are also parts drawings of all parts including various inserts.
Edit the program and remove the electrode
After the mold design is completed, the CNC program must be compiled according to the processing conditions of each part and whether it is necessary to disassemble the electrode for EDM processing.
The mechanical processing of the mold includes CNC processing, EDM processing, wire cutting processing, deep hole drilling processing and so on. After the mold base and materials are ordered back, the mold is only in rough machining state or just steel material. At this time, a series of mechanical processing must be carried out according to the design intent of the mold to make various parts.
CNC machining, computer numerical control, that is, CNC machining center, its requirements include various processing procedures, tool selection, processing parameters and so on. Those who are interested can find relevant materials to learn.
EDM machining is electric discharge machining, which is a machining process that uses electrical discharge corrosion materials to reach the required size, so only conductive materials can be processed. The electrodes used are generally copper and graphite.
Wire cutting is used for processing sharp corners.
Deep hole drills are generally used in the processing of large mold water-carrying holes and the processing of thimble barrel holes.
The fitter plays a very important role in the mold making process, and the work needs to run through the entire mold manufacturing process. The fitter’s work, fit mold assembly, car milling and drilling are all proficient.
Saving mold and polishing
Mold saving and polishing are the processing of mold parts using sandpaper, oilstone, diamond paste and other tool materials after the mold is processed by CNC, EDM, and fitter, and before the mold is assembled.
Fourth, mold inspection and test mold
a. Inspection of the mold
The process of fit mold and assembly is actually a mold inspection process. In the fit mold assembly, you can check whether the red lead is in place, whether the thimble cylinder is smooth, and whether the mold has any mistakes or interference.
After the mold is manufactured, in order to check the condition of the mold and whether the structure of the rubber part is completed, the injection machine needs to be tested. Through the trial mold, you can understand the situation of the mold during the brewing process and whether the structure of the rubber part is completed.
Refer to other materials for the requirements of mold trial and the improvement of plastic defects.
4. Modification and Modification
After the mold is tested, corresponding changes are made according to the conditions of the test. In addition, after the engineer confirms the plastic part, the structure of the plastic part must be changed accordingly.
Since the mold has been made, all changes are more troublesome, and sometimes even more difficult than redoing. The best way to change must be found according to the specific situation.
For structural design, the change of the structure must try to understand the mold situation, whether the water or thimble is touched, how to change the easiest, etc., can make relevant changes in combination with the relevant information, and consult the mold team colleagues if necessary .
Processing of cooling system:
For the processing of cooling system (drilling and transporting water), products generally require that the front mold transporting water needs to be processed when the first mold modification data is issued, and the back mold transporting water needs to be processed after the second mold modification data is issued, but it is turned on for water transportation. Whether or not it has a greater impact on beer production, such as PC-based beer production (requiring hot oil beer), try to open it before the first mold trial.
Therefore, various situations should be considered at the stage of structural design drawings, and the workload of mold modification should be minimized, so that the opening of the water transportation can operate normally, and the size of the beer can be determined as soon as possible.
Modification of product structure:
Adding bones, adding pillars, and remodeling the structure with inserts.
Adding and subtracting glue to the original bone, shifting the column, increasing or decreasing the screw column, increasing the height and decreasing the height, trimming the front and so on.
6. Mold Maintenance
Because the mold works under high temperature and high pressure and is in contact with air for a long time, it is easy to rust. Therefore, it is necessary to maintain the mold. When not working, it needs to be painted with anti-rust oil and butter.
In addition, because the mold steel has a certain service life and the mold structure design is unreasonable, some sharp and thin steel structures or tube thimbles may crack and break, and they must be maintained and repaired continuously in the later maintenance.
- Mold manufacturing;
- Mold inspection and tryout;
- Modification and modification;
- Mold maintenance.
Link to this article：Mould Manufacturing