First, accept the task book.
The task book of molded plastic parts is usually put forward by the part designer, and its contents are as follows:
1. Approve the drawings of formal parts, and indicate the brand and transparency of plastics.
2. Description or technical requirements of plastic parts.
3. Output.
4. Samples of plastic parts.
Usually, the mold design task book is put forward by the plastic part technician according to the molding part task book, and mold designer designs the mold according to the molding part task book and the mold design task book.
Second, collect, analyze and digest raw data.
Collect and sort out information about parts design, molding technology, molding equipment, mechanical processing and special processing for use in mold design.
1. Digest the drawings of plastic parts, understand the purpose of plastic parts, and analyze the technical requirements such as the manufacturability and dimensional accuracy of plastic parts. For example, what are the requirements of plastic parts in appearance, color transparency and usability, whether the geometric structure, inclination and insert of plastic parts are reasonable, the allowable degree of molding defects such as weld marks and shrinkage cavities, and whether there are post-treatments such as painting, electroplating, gluing and drilling. The dimension with the highest dimensional accuracy of plastic parts is selected for analysis to see whether the estimated molding tolerance is lower than that of plastic parts and whether the required plastic parts can be molded. In addition, we should also know the plasticizing and molding process parameters of plastics.
2. Digest the process data, and analyze whether the requirements such as molding method, equipment model, material specification and mold structure type proposed in the process specification are appropriate and can be implemented.
Molding materials should meet the strength requirements of plastic parts and have good fluidity, uniformity, isotropy and thermal stability. According to the use of plastic parts, molding materials should meet the requirements of dyeing and metallization conditions, decorative performance, necessary elasticity and plasticity, transparency or opposite reflection performance, adhesion or weldability.
3. Determine the molding method
Adopt direct tabletting method, casting pressure method or injection method.
4. Select molding equipment
According to the type of molding equipment, so we must be familiar with the performance, specifications and characteristics of various molding equipment. For example, for the injection machine, we should know the following contents from the specifications: injection quantity, mold locking pressure, injection pressure, mold installation size, ejection device and size, nozzle diameter and nozzle spherical radius, gate sleeve positioning ring size, mold maximum and minimum thickness, template stroke, etc. See related parameters for details.
It is necessary to estimate the overall size of the mold and judge whether the mold can be installed and used on the selected injection molding machine.
5. Specific structural scheme
(A) determine the mold type
Such as compression mold (open, semi-closed, closed), casting mold, injection mold, etc.
(2) Determine the main structural types of the mold.
Choosing an ideal mold structure lies in determining the necessary molding equipment and the ideal number of cavities, so that the work of the mold itself can meet the requirements of the manufacturability and production economy of plastic parts under absolutely reliable conditions. The technological requirements of plastic parts are to ensure the geometric shape, surface smoothness and dimensional accuracy of plastic parts. The requirement of production economy is to make the cost of plastic parts low, the production efficiency high, the mold can work continuously, the service life is long and the labor force is saved.
3. There are many complicated factors that affect the mold structure and a single system:
1. Cavity layout. According to the geometric structure characteristics of plastic parts, dimensional accuracy requirements, batch size, mold manufacturing difficulty, mold cost, etc. The number and arrangement of cavities are determined.
Injection mold, the precision of plastic parts is 3and 3 a, the weight is 5 g, the hardening pouring system is adopted, and the number of cavities is 4-6; The precision of plastic parts is generally (Grade 4-5), the molding material is local crystalline material, and the number of cavities can be16-20; The weight of plastic parts is 12- 16g, and the number of cavities is 8-12; Plastic parts with a weight of 50- 100g have 4-8 cavities. For amorphous plastic parts, the recommended number of cavities is 24-48, 16-32, 6- 10. When the weight of plastic parts is increasing, multi-cavity molds are rarely used. For plastic parts with accuracy of 7-9, compared with plastic parts with accuracy of 4-5, the maximum number of cavities is increased to 50%.
2. Determine the parting surface. The position of parting surface should be conducive to mold processing, exhaust, demoulding and molding operations, surface quality of plastic parts, etc.
3. Determine the gating system (shape, position and size of main runner, branch runner and gate) and exhaust system (exhaust mode, position and size of exhaust chute).
4. Select the ejection mode (ejector pin, pipe jacking, push plate and combined ejection), and determine the side concave treatment mode and core-pulling mode.
5. Determine the cooling and heating mode, the shape and position of the heating and cooling tank, and the installation position of the heating element.
6. According to the die material, strength calculation or empirical data, determine the thickness and overall dimensions of die parts, as well as the overall structure and position of all connecting, positioning and guiding parts.
7. Determine the structural forms of main molded parts and structural parts.
8. Considering the strength of each part of the mold, calculate the working size of the molded part.
When these problems are solved, the structural form of the mold will naturally be solved. At this time, it is necessary to start sketching the mold structure to prepare for the formal drawing.
Fourth, draw a mold diagram.
It is required to draw according to the national drawing standards, but it is also required to combine the factory standards and factory customary drawing methods that are not stipulated by the state.
Before drawing the mold assembly drawing, the process drawing should be drawn, which should meet the requirements of part drawing and process data. The guaranteed dimensions of the next process shall be marked with the words "process dimensions" on the drawing. If there is no other machining except burr repair after molding, then the process drawing is exactly the same as the part drawing.
It is best to indicate the part number, name, material, material shrinkage, stretching ratio, etc. Under the flow chart. Usually, the process is drawn on the mold assembly drawing.
1. Draw the assembly structure diagram.
When drawing the assembly drawing, the ratio of 1: 1 should be adopted as far as possible, starting from the cavity, and drawing the front view and other views at the same time.
Five, the mold assembly drawing should include the following contents:
1. Mould forming part structure
2. Structure of gating system and exhaust system.
3. Parting surface and method.
4. Shape and structure and all connectors, positioning and guiding parts.
5. Mark the height dimension of the cavity (if not required, if required) and the overall dimension of the mold.
6. Auxiliary tools (fetching and demoulding tools, calibration tools, etc.). ).
7. Prepare the serial numbers of all parts in sequence, and fill in the schedule.
8. Mark the technical requirements and instructions for use.
Technical requirements of die assembly drawing of intransitive verbs;
1. Performance requirements of some mold systems. For example, the assembly requirements of the ejection system and the slider core-pulling structure.
2. Requirements of mold assembly process. For example, the joint clearance of the parting surface should not be greater than the parallelism requirement of the upper and lower surfaces of the 0.05mm mold after clamping, and the size determined by assembly and the requirements for this size are pointed out.
3. The use, assembly and disassembly methods of the mold.
4. Anti-oxidation treatment, mold number, lettering, marking, oil seal, storage and other requirements.
5. Requirements for mold testing and inspection.
Seven, draw all the parts.
The order of drawing parts from the die assembly drawing should be: first inside and then outside, first complex and then simple, first forming parts, then structural parts.
1. Graphic requirements: it must be drawn in proportion, and enlargement or reduction is allowed. Reasonable scene selection, correct projection and proper layout. In order to make the processing patent number easy to understand and assemble, the figure should be as consistent and clear as possible with the general assembly drawing.
2. The dimensions shall be uniform, centralized, orderly and complete. The order of dimensioning is: first dimension the main part size and draft angle, then dimension the matching size, and then dimension all dimensions. On the drawing of non-major parts, the matching dimensions are marked first, and then all dimensions are marked.
3. Surface roughness. Mark the most widely used roughness in the upper right corner of the drawing, such as "Other 3.2." Other roughness symbols are marked on each surface of the part.
4. Other contents, such as part name, mold drawing number, material grade, heat treatment and hardness requirements, surface treatment, graphic proportion, free dimension machining accuracy, technical description, etc. , should be filled in correctly.
8. Proofreading, checking, tracking and drying.
A. the contents of self-calibration include:
1. Relationship between mould and its parts and plastic parts drawing
Whether the materials, hardness, dimensional accuracy and structure of molds and mold parts meet the requirements of plastic parts drawings.
2. Plastic parts
Whether the flow, shrinkage cavity, weld mark, crack and demoulding inclination of plastic material flow affect the requirements of plastic parts in terms of performance, dimensional accuracy and surface quality. Whether the pattern design is insufficient, whether the processing is simple, and whether the shrinkage of the molding material is selected correctly.
3. Molding equipment.
Whether the injection quantity, injection pressure and clamping force are sufficient, whether there are problems in mold installation, plastic parts south core and demoulding, and whether the nozzle of the injection machine is in correct contact with the sleeve.
4. Mold structure
1). Whether the position and precision of parting surface meet the needs, whether flash will appear, and whether the plastic parts can be kept on the side of the mold with ejector after mold opening.
2) Whether the demoulding method is correct, whether the size, position and quantity of extension rod and push tube are appropriate, whether the push plate will be stuck by the core, and whether the molded part has scratches.
3). Mold temperature adjustment. Power and quantity of heaters; Whether the location, size and quantity of cooling medium streamline are appropriate.
4). How to deal with the side concave of plastic parts, and whether the mechanism for removing the side concave is appropriate, such as whether the slider and the push rod in the inclined guide pillar core-pulling mechanism interfere with each other.
5) Whether the location and size of the pouring and exhaust system are appropriate.
5. Design drawings
1). Whether the placement parts of each mold part on the assembly drawing are appropriate and clearly expressed, and whether there are any omissions.
2). The part number and name on the part drawing, production quantity, whether the part is self-made or purchased, whether it is standard or non-standard, the matching machining accuracy of the part, the correction machining and allowance at the high-precision dimension of the molded plastic part, and whether the material, heat treatment, surface treatment and surface finish of the mold part are clearly marked and described.
3). Working dimensions and mating dimensions of main parts and molded parts. Size figures should be correct, don't let the manufacturer convert them.
4). Check the view position of all parts drawings and assembly drawings, whether the projection is correct, whether the drawing method conforms to the national drawing standards, and whether there are any missing dimensions.
6. Check the processing performance
(Are the geometric structures, views and dimensions of all parts beneficial to machining? )
7. Recalculate the main working dimensions of auxiliary tools.
B. Professional proofreading shall be conducted in principle according to the designer's self-proofreading project; However, we should focus on the structural principle, process performance and operational safety.
When drawing, you should first digest the drawing and fill in all the dimensions and technical requirements according to the national standard. Self-correcting signature after tracing.
C. Submit the drawn base map to the designer for proofreading and signing. Usually, the relevant technicians of the tool manufacturing unit will review, countersign and check the manufacturing process, and then send it to Sun.
D, writing a manufacturing process card
The technical personnel of the tool manufacturing unit shall compile the manufacturing process card and make good preparations for processing and manufacturing.
In the manufacturing process of mold parts, it is necessary to strengthen inspection, and the focus of inspection is dimensional accuracy. After the mold assembly is completed, the inspector will carry out inspection according to the mold inspection list, mainly to check whether the performance of the mold parts is good, and only in this way can the manufacturing quality of the mold be slandered.
Nine, try to repair the mold
Although the mold design is carried out under the expected technological conditions when selecting molding materials and molding equipment, people's understanding is often imperfect, so it is necessary to conduct a mold trial test after the mold processing is completed to see how the quality of the molded parts is. It's always discovered later, and repairing the mold eliminates mistakes.
There are many kinds of bad phenomena of plastic parts, and the reasons are also very complicated, including mold reasons and process conditions, which are often only together. Before repairing the mold, we should make a detailed analysis and study according to the actual situation of the bad phenomenon of plastic parts, find out the causes of the defects of plastic parts, and then put forward the remedies. Because the molding conditions are easy to change, the general practice is to change the molding conditions first, and then consider mold repair when changing the molding conditions can't solve the problem.
Repair the mold more carefully, and you can't make a move without being quite sure. The reason is that once the mold conditions are changed, it cannot be rebuilt and restored.
Ten, organize data for archiving.
After the test, if the mold is not used temporarily, the mold residue, dust, oil stains, etc. should be thoroughly removed. , coated with butter or other antirust oil or antirust agent, and stored in a storage place.
From the design of the mold to the successful processing and inspection of the mold, the technical data generated during this period, such as the task book, part drawings, technical specifications, mold assembly drawings, mold part drawings, basic drawings, mold design specifications, inspection records, mold trial repair records, etc. , according to the provisions of the system sorting, binding, filing number. This seems troublesome, but it is very useful for repairing molds and designing new molds in the future.