The task document for molded plastic parts is usually presented by the designer.
1. the formal drawing made by the trial shall be signed, and the grades and transparency of the plastic shall be specified.
2. specification or technical requirements for plastic parts.
3. production production.
4. samples of plastic parts.
Usually, the mold design task book is put forward by the plastic part technician according to the task book of the molded plastic parts. The mould designer will design the mould based on the task book of molding plastic parts and the design task book of the mould.
Two. Collecting, analyzing and digesting the original data
Collect and collate relevant information about parts design, molding process, molding equipment, machining and special processing, so as to make use of mold design.
1. digest the plastic parts drawing, understand the use of the parts, analyze the technological requirements of the plastic parts, dimensional accuracy and other technical requirements. For example, what are the requirements of plastic parts in appearance shape, color transparency, and performance, whether the geometric structure of the plastic parts, the slope, the inlay and so on are reasonable, the allowable degree of the forming defects such as weld marks and shrinkage holes, and the addition of coating, electroplating, bonding, drilling and so on. Select the size of the highest dimensional precision of the plastic parts, to see if the tolerance of the molding is lower than the tolerance of the plastic parts, and whether the required plastic parts can be formed. Besides, it is necessary to understand the plasticizing and molding process parameters of plastics.
2. the data of digestion process, analysis of the molding method, equipment model, material specification, mould structure type and so on.
The molding materials should meet the strength requirements of plastic parts with good fluidity, homogeneity, isotropy and thermal stability. According to the use of plastic parts, the molding materials should meet the requirements of dyeing, plating metal conditions, decorative properties, necessary elastic and plastic, transparent or opposite reflection, adhesively, or weldability.
3. determine the molding method
The direct pressure method, the casting pressure method or the injection method are used.
4. Select the molding equipment
According to the type of molding equipment, mold must be familiar with the performance, specifications and characteristics of various molding equipment. For example, for injection machine, the following contents should be understood in specifications: injection capacity, mode locking pressure, injection pressure, mold installation size, ejection device and size, nozzle hole diameter and nozzle sphere radius, gate sleeve size, maximum thickness and minimum thickness of mold, template stroke, etc. Parameters.
It is necessary to preliminarily estimate the size of the die and determine whether the mold can be installed and used on the selected injection machine.
5. concrete structure scheme
(1) determine the mold type
Such as pressing die (open, semi closed, closed), casting die, injection mold, etc.
(two) determine the main structure of the mold type
The ideal mold structure is chosen to determine the necessary molding equipment, the ideal number of cavity, and in absolute and reliable conditions, the work of the mould itself can meet the requirements of the technology and production economy of the plastic parts. The technical requirements for plastic parts are to ensure the geometric shape, surface finish and dimensional accuracy of plastic parts. The requirement of production economy is to make the cost of plastic parts low, the production efficiency is high, the mold can work continuously, the service life is long, and the labor force is saved.
Three, there are many factors that affect the die structure and individual system.
Type 1. cavity layout. According to the geometric characteristics of the plastic parts, size accuracy requirements, batch size, mold manufacturing difficulties, mold cost and so on, determine the number and arrangement of the cavity.
For injection mould, the precision of the plastic parts is 3 and 3a, the weight is 5 grams, the hardened casting system is adopted, the number of the cavity is 4-6; the plastic parts are the general precision (4-5 grade), the molding material is the local crystallizing material, the number of the cavity is 16-20, the weight of the plastic part is 12-16 grams, the number of the cavity is 8-12, and the weight is 50-10. 0 grams of plastic parts, the number of cavities of 4-8. For amorphous plastic parts, the number of recommended cavities is 24-48, 16-32 and 6-10. When we continue to increase the weight of plastic parts, we seldom use multi cavity mold. For plastic parts with 7-9 grade accuracy, the maximum number of cavity is increased to 50% compared with the 4-5 grade precision plastic.
2. determine the parting surface. The location of the parting surface is conducive to mold processing, exhaust, stripping and molding operations, surface quality of plastic parts, etc.
3. determine the gating system (main runner, runner and gate shape, location, size) and exhaust system (exhaust method, exhaust slot location, size).
4. select the ejection mode (ejector pin, pipe jacking, push plate and combined ejection) to decide the side concave treatment method and core pulling method.
5. determines the cooling and heating mode and the shape and location of the heating cooling trench, and the installation part of the heating element.
6. according to the mold material, strength calculation or experience data, determine the thickness and shape size of the mold parts, the shape and structure and the position of all connections, positioning and guiding parts.
7. determine the structural form of the main molding parts and structural parts.
8. consider the strength of each part of the mold and calculate the working dimensions of the molding parts.
If these problems are solved, the structural form of the die will be solved naturally. At this time, we should draw sketches for the drawing of the die structure to prepare for the formal drawing.
Four. Drawing die drawing
It is required to draw in accordance with national standards for drawing, but it is also required to combine the factory standard and the customary drawing method prescribed by the state.
Before drawing the general assembly drawing, draw up the process diagram and conform to the requirements of the parts drawing and process information. For the size guaranteed by the next process, the word "process dimension" should be marked on the drawing. If there is no other machining process besides shaping the burrs, then the process diagram is exactly the same as the part drawing.
Under the process chart, the number, name, material, material shrinkage, drawing proportion and so on are best marked. The working procedure is usually painted on the mold assembly drawing.
1. drawing general assembly structure drawing
Draw the general assembly drawing as far as possible, using the ratio of 1:1, first draw the cavity, and draw the main view with other views at the same time.
Five. The general assembly drawings of the mold should include the following:
1. mold forming part structure
2. the structure of the pouring system and the exhaust system.
3. parting surface and parting mode.
4. outline structure and all connectors, location and orientation.
5. dimensioning cavity height (not forced, as required) and mold overall size.
6. auxiliary tools (take off tools, calibration tools, etc.)
7. compile the serial numbers of all parts in sequence and fill in the detailed list.
8. mark technical requirements and use instructions.
Six. The technical requirements of the mold assembly drawing:
1. for the performance requirements of some systems of the mold. For example, the assembly requirements of ejection system and slider core pulling structure.
2. requirements for the die assembly process. For example, the closing surface of the mold assembly surface after the die assembly is not greater than the parallelism requirements on the 0.05mm mold and below, and points out the size determined by the assembly and the requirements for the size.
3. use and dismantle die.
4. anti oxidation treatment, mold number, lettering, marking, oil seal, storage and other requirements.
5. the requirements for test and inspection.
Seven. Draw all part drawings
The sequence of drawing the part drawing from the general assembly drawing of the die should be as follows: first, inside and outside, first complex and then simple, first forming parts, then structural parts.
1. graphics requirements: we must draw proportionally, allowing magnification or reduction. The choice of view is reasonable, the projection is correct and the layout is proper. In order to make the processing patent number easy to understand and easy to assemble, the graphics should be consistent with the assembly drawing as far as possible, and the graphics should be clear.
2. dimensioning requirements are uniform, centralized, orderly and complete. The order of dimensioning is as follows: first, mark the size of the main parts and the slope of the mould, then mark the matching dimensions, and then mark all the dimensions. The size of the main parts should be labeled together and all dimensions should be marked.
3. surface roughness. Mark one of the most applied roughness to the top right corner of the drawing, for example, mark the remaining 3.2. "Other roughness symbols are marked on each part of the part.
4. other contents, such as part name, mold number, material brand, heat treatment and hardness requirements, surface treatment, graphic proportion, processing precision of free size, technical specification, etc. should be correctly filled in.
Eight. Proofreading, drawing, depiction, and exposure to the sun
The content of A. self proofreading is:
1. the relationship between the mould and its parts and the drawing of the plastic parts
The material, hardness, dimensional accuracy and structure of the die and mold parts conform to the requirements of the plastic drawing.
2. parts of plastic parts
Whether the flow of plastic flow, shrinkage hole, weld mark, crack, stripping angle and so on affect the use performance, size accuracy and surface quality of plastic parts. Whether there is any shortage in pattern design, whether machining is simple, and whether the shrinkage rate of molding material is correct.
3. molding equipment
The injection amount, the injection pressure and the clamping force are not enough. There are no problems with the installation of the mold, the South core and the mold release of the plastic parts.
4. aspects of die structure
1). Whether the position of the parting surface and the precision of precision machining meet the needs will not occur, and whether the plastic parts can be kept on the side of the mold with the ejector device after the die opening.
2). Whether the mode is correct or not, whether the size, position and quantity of the extension rod and tubing are suitable, the push board will not be stuck by the core, and will not cause the scraping parts.
3). Temperature adjustment of mould. The power and quantity of the heater are suitable for the location, size and quantity of the cooling medium.
4) processing the side concave method of plastic parts, whether the mechanism of the side concave is appropriate, such as whether the slider and push rod of the inclined guide core pulling mechanism interfere with each other.
5) whether the location and size of the casting and exhaust system are appropriate.
5. design drawings
1). Whether the location of each part of the assembly is appropriate, whether it is clear or missing.
2). The number and name of parts, the name, the quantity, the parts made or the purchase are standard parts or non standard parts, the accuracy of the parts and the accuracy of the parts, the modified processing and remainder of the high precision size of the molded parts, and the marking of the material, heat treatment, surface treatment, and the degree of surface finishing of the mold parts. The narration is clear.
3) the working dimensions and matching dimensions of the main parts and forming parts of the parts. The size number should be correct and do not convert the producer.
4) check the location of all parts and assembly drawings, whether the projection is correct, whether the drawing is in line with the national standard for drawing, and whether there is a missing size.
6. checking performance
(all parts geometry, view drawing, size, etc.) is conducive to processing.
The main working dimensions of the 7. compound tool
The proofreading principle of B. is carried out according to the designers self proofreading project, but it should be focused on the structural principle, process performance and operation safety.
When digesting drawings, we must first digest the figures, depict them according to the requirements of the national standard, and fill in all the dimensions and technical requirements. Write and sign after drawing.
C. puts the drawing on the designer to proofread the signature. The customary practice is to check, check and inspect the manufacturing process by the technical personnel of the tool manufacturing unit.
D.. Writing manufacturing process cards
The manufacturing process card is prepared by the technician of the tool manufacturing unit, and is prepared for manufacturing.
In the manufacturing process of mold parts, inspection should be strengthened and emphasis should be placed on dimensional accuracy. After the die assembly is completed, the inspector is inspected according to the mold inspection table. The main thing is to check the performance of the mold parts well, only in this way the quality of the slang mold is made.
Nine, test mold and mold repair
Although it is in the selection of molding materials and molding equipment, the mold design is carried out under the preconceived technological conditions, but peoples understanding is often imperfect, so it is necessary to test the mold after the die processing is completed and see how the quality of the moulded parts is. Discovery is always followed by error correction.
There are many kinds of bad phenomena in the plastic parts, and the reasons are very complicated. There are reasons for the mold and the reasons for the technical conditions. The two are often only together. Before repairing the mould, we should make a detailed analysis and study according to the actual situation of the defective phenomena appearing in the plastic parts, and find out the remedy after the cause of the defect of the plastic parts. Because the molding conditions are easy to change, the general practice is to change the molding conditions first. When changing the molding conditions can not solve the problem, then consider repairing the mold.
It is more prudent to repair moulds. The reason is that once the mold conditions are changed, no major transformation and restoration can be made.
Ten. Filing data for archiving
If the mold is not used for the time being, the mold should be completely erased, such as dregs, dust, oil, etc., coated with butter or other antirust oil or antirust agent, and kept in the storage place.
The design mold begins to the successful process of the mold processing, the inspection is qualified so far, the technical data produced during this period, such as the task book, the piece drawing, the technical specification, the mold assembly drawing, the mold parts drawing, the bottom drawing, the mold design instruction, the inspection record table, the test model repair and recording, etc., are systematically arranged and installed according to the regulations. Order and number for filing. It seems very troublesome to do this, but it is very useful for repairing moulds and designing new moulds later.
