1. Acceptance of 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) The formal part drawings that have been examined and signed, and indicate the brand and transparency of the plastic.
(2) specifications or technical requirements of plastic parts.
(3) production output.
(4) samples of plastic parts.
Usually, the mold design task book is put forward by the plastic parts technician according to the task book of the molded plastic parts, and the mold designer designs the mold based on the molded plastic parts task book and the mold design task book.
second, collect, analyze and digest the original data
collect and sort out the information about the design of parts, molding technology, molding equipment, mechanical processing and special processing for use when designing molds.
(1) digest the drawing of plastic parts, understand the purpose of the parts, and analyze the technical requirements such as manufacturability and dimensional accuracy of the plastic parts. For example, what are the requirements of plastic parts in terms of appearance shape, 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 is post-processing such as painting, electroplating, gluing and drilling. Select the dimension with the highest dimensional accuracy of plastic parts for analysis, and 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.
The molding material 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 metallizing conditions, decorative performance, necessary elasticity and plasticity, transparency or opposite reflection performance, adhesion or weldability.
3. Determine whether the molding method
adopts direct pressing, casting pressing or injection.
IV. Selecting molding equipment
Moulding is carried out according to the types of molding equipment, so you must be familiar with the performance, specifications and characteristics of various molding equipment. For example, for an injection machine, the following contents should be understood in terms of specifications: injection capacity, mold locking 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. See relevant parameters for details.
it is necessary to preliminarily estimate the overall dimensions of the mold and judge whether the mold can be installed and used on the selected injection machine.
V. Specific structural scheme:
(1) Determine the mold type
Such as pressing mold (open, semi-closed and closed), casting mold, injection mold, etc.
(2) Determine the main structure of the mold type
Choosing the 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 technology and production economy of the plastic part under absolutely reliable conditions. The technological requirements for 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.
There are many complicated factors that affect the mold structure and individual 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.
For the injection mold, the accuracy of plastic parts is Grade 3 and 3a, the weight is 5g, and the hardened gating system is adopted, and the number of cavities is 4-6; The plastic parts are of general accuracy (4-5 grades), the molding materials are local crystalline materials, and the number of cavities can be 16-2; The weight of plastic parts is 12-16g, and the number of cavities is 8-12; For plastic parts with a weight of 5-1g, the number of cavities is 4-8. For amorphous plastic parts, the suggested number of cavities is 24-48, 16-32 and 6-1. When the weight of plastic parts continues to increase, multi-cavity molds are rarely used. For plastic parts with grade 7-9 precision, the maximum number of cavities is increased to 5% compared with the plastic parts with grade 4-5 precision.
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 the exhaust system (exhaust method, exhaust slot position and size).
④ select the ejection method (ejector pin, pipe jacking, push plate, combined ejection), and determine the side concave treatment method and core-pulling method.
⑤ determine the cooling and heating modes, the shape and position of the heating and cooling groove, and the installation position of the heating element.
⑥ according to the die material, strength calculation or empirical data, determine the thickness, overall dimensions, overall structure and positions of all connecting, positioning and guiding parts of the die.
⑦ determine the structural forms of main molding parts and structural parts.
⑧ Considering the strength of each part of the mold, calculate the working dimensions of the molded parts.
if these problems are solved, the structural form of the mold will be solved naturally. At this time, we should start to draw a sketch of the mold structure to prepare for the formal drawing.
⑨ Drawing the mould
It is required to draw according to the national drawing standards, but it is also required to combine the factory standards and the factory customary drawing methods not specified by the state.
before drawing the die assembly drawing, the process drawing should be drawn, which should meet the requirements of the part drawing and process data. The size guaranteed by the next working procedure shall be marked with the words "process size" on the drawing. If there is no other mechanical processing except burr repair after molding, then the process drawing is exactly the same as the part drawing.
it is best to mark the part number, name, material, material shrinkage, drawing ratio, etc. under the process diagram. Usually, the process is drawn on the die assembly drawing.
a. Draw the assembly structure diagram
Draw the assembly diagram with a ratio of 1: 1 as far as possible, starting with the cavity, and drawing the front view and other views at the same time.
The general assembly drawing of the mold shall include the following contents:
① Structure of the molding part of the mold
② Structure of the gating system and exhaust system.
③ parting surface and parting method.
④ the external structure, all connectors, positioning and guiding parts.
⑤ mark the cavity height size (not required, as required) and the overall size of the mold.
⑥ auxiliary tools (tools for taking parts and demoulding, calibration tools, etc.).
⑦ Compile the serial numbers of all parts in sequence and fill in the detailed list.
⑧ mark the technical requirements and instructions.
B. Technical requirements of the general assembly drawing of the mould:
① Performance requirements for some systems of the mould. For example, the assembly requirements of ejection system and slider core-pulling structure.
② requirements for mold assembly process. For example, the bonding gap of the bonding surface of the parting surface after die assembly should not be greater than the parallelism requirement of the upper and lower surfaces of the .5mm die, and the size determined by assembly and the requirements for this size are pointed out.
③ mold use, assembly and disassembly methods.
④ anti-oxidation treatment, mold number, lettering, marking, oil seal, storage and other requirements.
⑤ Requirements on mold test and inspection.
C, drawing all the part drawings
The order of drawing the part drawings from the die assembly drawing should be: first inside, then outside, first complex, then simple, first molded parts, then structural parts.
① graphic requirements: it must be drawn in proportion, and enlargement or reduction is allowed. Reasonable view selection, correct projection and proper layout. In order to make the processing patent number easy to understand and assemble, the graphics should be as consistent as possible with the general assembly drawing and clear.
② The dimensions should be unified, centralized, orderly and complete. The order of dimensioning is: first mark the main part size and draft angle, then mark the matching size, and then mark all the dimensions. On the drawing of non-main parts, the matching dimensions are marked first, and then all dimensions are marked.
③ surface roughness. Mark the most widely used roughness on the upper right corner of the drawing, such as "The rest 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 scale, machining accuracy of free dimension, technical description, etc., should be filled in correctly.
D, proofreading, drawing review, tracing and drying
The contents of self-proofreading are:
① The relationship between the mold and its parts and the drawings of plastic parts, and whether the materials, hardness, dimensional accuracy and structure of the mold and its parts meet the requirements of the drawings of plastic parts.
② Plastic parts
Whether the flow, shrinkage cavity, weld marks, cracks and demoulding inclination of plastic material flow affect the requirements of plastic parts in terms of service 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 In terms of molding equipment,
whether the injection quantity, injection pressure and clamping force are enough, whether there are any problems in the installation of the mold, the south core of the plastic part and the demoulding, and whether the nozzle of the injection machine is in correct contact with the sleeve.
④ mold structure
a. Whether the position of parting surface and precision of finishing meet the requirements, whether there will be flash, and whether the plastic parts can be kept on one side of the mold with ejector after mold opening.
B. whether the demoulding method is correct, whether the size, position and quantity of the extension rods and push tubes are appropriate, whether the push plate will be stuck by the core, and whether the molded parts will be scratched.
C. mold temperature adjustment. Power and quantity of heaters; Whether the position, size and quantity of the flow line of the cooling medium are appropriate.
D. 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 core-pulling mechanism of inclined guide pillar interfere with each other.
e. whether the location and size of the pouring and exhaust system are appropriate.
F. Design drawing
G. Whether the placement parts of each mold part on the assembly drawing are appropriate and clearly expressed, and whether there are any omissions
H. Part number and name on the part drawing, production quantity, whether the part is made in-house or purchased, whether it is a standard part or a non-standard part, matching processing accuracy of parts, correction processing and allowance at high-precision dimensions of molded plastic parts, materials, heat treatment and allowance of mold parts.
⑤ Working dimensions and matching dimensions of main parts and molded parts. The size figures should be correct, and do not make the producer convert them.
⑥ check the view position and projection of all parts drawings and assembly drawings, whether the drawing method conforms to the national drawing standard, and whether there are any missing dimensions.
⑦ Check the machining performance: (Whether the geometric structure, view drawing and dimension standard of all parts are beneficial to machining)
⑧ The main working dimensions of recalculation auxiliary tools
Professional proofreading shall be carried out according to the designer's self-proofreading project in principle; However, we should focus on the structural principle, process performance and operation safety. When drawing, you should first digest the figure, draw it according to the national standard, and fill in all the dimensions and technical requirements. Self-correcting and signing after tracing. It is customary for the designer to proofread and sign the sketched base map, which is examined by the relevant technicians of the tool manufacturing unit, countersigned and checked for manufacturing manufacturability before it can be sent to the sun.
pet-name ruby writing manufacturing process cards
the technicians of the tool manufacturing unit write manufacturing process cards and make preparations for processing and manufacturing. In the manufacturing process of mold parts, inspection should be strengthened, and the focus of inspection should be on dimensional accuracy. After the mold assembly is completed, the inspector will inspect it according to the mold inspection form, 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.
(3) mold trial and mold repair
Although 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 carry out mold trial after mold processing to see how the molded parts are quality. It is always found later, and the mold is repaired to eliminate mistakes.
there are many kinds of bad phenomena in plastic parts, and the reasons are also very complicated, including mold reasons and process conditions, and the two are often combined. Before repairing the mold, we should make a detailed analysis and study according to the actual situation of the bad phenomena of plastic parts, find out the causes of the defects of plastic parts, and then put forward remedial methods. Because the molding conditions are easy to change, the general practice is to change the molding conditions first, and then consider repairing the mold when changing the molding conditions can't solve the problem.
you should be more careful in repairing the mold, and you should not act rashly without being quite sure. The reason is that once the mold conditions are changed, it can't be reformed and restored.
VI. Organizing data for archiving
If the mold is not used for the time being after the test, it should be completely removed from the mold residue, dust, oil stains, etc., coated with butter or other antirust oil or antirust agent, and kept in the 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 parts drawings, base maps, mold design instructions, inspection records, mold trial and repair records, etc., shall be systematically sorted, bound and numbered for filing according to regulations. It seems troublesome to do so, but it is very useful for repairing the mold and designing a new mold in the future.