Mold is a kind of industrial product that can make the material take shape in a certain way in a specific structure form. Almost all industrial products, from airplanes and automobiles to tea cups and nails, must be moulded. The high precision, high consistency and high productivity of moulds are incomparable to any other machining methods. Mould determines the product quality, benefit and new product development ability to a great extent. So the mold has the "mother of industry" honorary title.
Mold design refers to the digital design of enterprise mold, including mold and cold stamping die, on the basis of traditional mold design, the full application of digital design tools, improve the quality of mold design, shorten the mold design cycle. Mold designers can be employed in the fields of nc programming and machining of molds, 3d design of molds, and 3d design of product development.
Step 1: analysis and digestion of 2D and 3D drawings of products, including the following aspects:
1, the geometric shape of the product.
2. Size, tolerance and design reference of products.
3. Technical requirements (i.e. technical conditions) of the products.
4. Name, shrinkage and color of plastic used in the products.
5. Surface requirements of products.
Step 2: confirm the injection model
Injection specifications are determined mainly according to the size of plastic products and production volume. When selecting the injection machine, designers should mainly consider its plasticization rate, injection volume, clamping force, effective area of the installation mold (the distance between the pull rod of the injection machine), modulus, ejection form and length. If the customer has provided the model or specification of the injection used, the designer must check the parameters, if not meet the requirements, must discuss with the customer to replace.
Step 3: determine the number of cavities and cavity arrangement
The determination of the number of mold cavity is mainly based on the projection area of the products, geometric shape (with or without side core-pulling), product precision, batch and economic benefits to determine.
The number of cavities is mainly determined by the following factors:
1. Production batch of products (monthly batch or annual batch).
2. Whether the product has side core pulling and how to deal with it.
3. The external dimensions of the mold should be in line with the effective area of the injection mold (or the distance between the pull rod of the injection machine).
4. Product weight and injection volume of the injection machine.
5. Projection area and clamping force of products.
6. Product precision.
7. Color of products.
8. Economic benefits (production value of each set of mold).
These factors are sometimes mutually restrictive, and therefore must be coordinated in determining a design to ensure that its primary conditions are met.
After determining the number of strong, then carry out cavity arrangement, and cavity location layout. The arrangement of cavities involves the design of mold size, casting system, casting system balance, core pulling (slider) mechanism, insert core and hot runner system. The above problems are related to the selection of parting surface and gate location. Therefore, necessary adjustments should be made in the specific design process to achieve the most perfect design.
Step 4: determine the parting surface
Parting surface, in some foreign product drawings have made specific provisions, but in a lot of mold design to be determined by the mold personnel, generally speaking, in the plane of the parting surface is relatively easy to deal with, sometimes encounter three-dimensional form of parting surface should pay special attention to. The selection of the parting surface shall follow the following principles:
1, does not affect the appearance of products, especially for the appearance of products with clear requirements, more attention should be paid to the appearance of the impact of typing.
2, to ensure the accuracy of products.
3, conducive to mold processing, especially cavity processing. First compound mechanism.
4. It is conducive to the design of casting system, exhaust system and cooling system.
5. To facilitate the demoulding of the products, ensure that the products are left on the moving side of the mold when the mold is opened.
6, easy to insert metal.
When designing the side parting mechanism, the safety and reliability should be ensured and the interference with the setting mechanism should be avoided as far as possible.
Step 6: confirm the die frame and select the standard parts
After all the above content is determined, the mold frame is designed according to the content. In the design of the die frame, as far as possible to choose the quasi-die frame, determine the form of the standard die frame, specifications and A, B plate thickness. Standard parts include general standard parts and mold special standard parts two categories. Common standard parts such as fasteners, etc. Mold special standard parts such as positioning ring, gate sleeve, push rod, push tube, guide column, guide sleeve, mold special spring, cooling and heating elements, secondary parting mechanism and precision positioning standard components.
It needs to be emphasized that, when designing the mold, as far as possible to choose the standard mold frame and standard parts, because a large part of standard parts have been commercialized, can be bought at any time in the market, which is extremely beneficial to shorten the manufacturing cycle and reduce the manufacturing cost.
After the buyer size is determined, it is important to carry out the necessary strength and rigidity calculation for the relevant parts of the mold to check whether the selected mold frame is appropriate, especially for large molds.
Step 7: design of the casting system
The design of the casting system includes the choice of the main runner, the determination of the shape and size of the runner section.
In the case of a point gate, attention should also be paid to the design of the sprue runner to ensure the shedding of the runner.
In designing a gating system, it is first necessary to select the location of the gate. The proper choice of gate location will directly affect the molding quality of products and whether the injection process can be carried out smoothly. The selection of gate location should follow the following principles:
1. The location of the gate should be selected on the parting surface as far as possible, so as to facilitate mold processing and the cleaning of the gate.
2. The distance between the position of the sprue and each part of the mold cavity should be consistent as far as possible, and the flow should be the shortest (it is difficult to do in general large sprue).
3, the gate position should ensure that plastic injection cavity against the cavity of the spacious, thick wall parts, in order to facilitate the inflow of plastic.
4, avoid plastic in the flow into the cavity wall, core or insert, plastic can flow into all parts of the cavity as soon as possible, and avoid deformation of the core or insert.
5, try to avoid products produce welding mark, if you want to produce, so that the dissolution mark produced in the product is not important place.
6. The gate position and the injection direction of plastics should be that the plastics can flow into the mold cavity uniformly along the parallel direction of the mold cavity and be conducive to the gas discharge in the mold cavity.
7. The gate shall be designed to be the most easily removed part of the product, and the appearance of the product shall not be affected as far as possible.
Step 8: design the ejection system
The ejection forms of products can be divided into mechanical ejection, hydraulic ejection and pneumatic ejection.
Mechanical ejection is the last step in the process of injection molding. The quality of ejection will determine the quality of products. Therefore, ejection of products cannot be ignored. The following principles should be observed in the design of the ejection system:
1, in order to make the products will not be due to ejection deformation, the thrust point should be as close as possible to the core or difficult to demoulding parts, such as products on the slender hollow cylinder, push tube ejection. The arrangement of thrust points should be balanced as far as possible.
2. The thrust point should act on the parts with the maximum bearing capacity of the work-in-progress, and the parts with good rigidity, such as the rib, flange, wall edge of shell shape products, etc.
3, try to avoid the thrust point action on the thinner surface of the products, to prevent products top white, top high, such as shell shaped products and cylindrical products with push plate jacking.
4, try to avoid ejection marks affect the appearance of products, ejection device should be located in the hidden surface of products or non-decorative surface. In transparent products in particular to pay attention to the location and the choice of ejection form.
5, in order to make the products in the ejection force uniform, and avoid the deformation of the products due to vacuum adsorption, often use compound ejection or special form of ejection system, such as push rod, push plate or push rod, push pipe compound ejection, or use the intake thing push rod, push block and other device, when necessary should also set the inlet valve.
Step 9: cooling system design
The design of the cooling system is a tedious work. The cooling effect, cooling uniformity and the influence of the cooling system on the overall structure of the mold should be considered. The cooling system design includes the following:
1. The arrangement of the cooling system and the specific form of the cooling system.
2. Determine the specific location and size of the cooling system.
3, key parts such as moving model core or insert cooling.
4. Cooling of slide block and slide core.
5. Design of cooling elements and selection of cooling standard elements.
6. Design of sealing structure.
Step 10:
The guide device on the plastic injection mould has been determined when the standard mould frame is used. In general, designers as long as the mold frame specifications can be used. But according to the product requirements to set up precision guide device, it must be designed by the designer according to the mold structure.
General guidance is divided into: dynamic, fixed mode between the guidance; Push plate and push rod fixed plate guide; Guide between push plate lever and moving template; Set model and push liu bootleg between guide. General guide due to restricted by the machining accuracy or use after a period of time, its precision is lower, will directly affect the precision of the products, so for the products of the high accuracy requirement must be separately designed precision positioning components, have been standardized, such as taper dowel pin, positioning block can choose, but some of the precision guided positioning device must be designed according to the specific structure of the module.
Part xi: selection of steel mold
Mold forming parts (cavity, core) material selection, mainly according to the bulk products, plastic categories to determine. For high gloss or transparent products, mainly choose 4Cr13 type of martensitic corrosion resistant stainless steel or aging hardening steel.
For plastic products containing glass fiber reinforced, hardened steel with high abrasion resistance, such as Cr12MoV, should be selected.
When the product material is PVC, POM or contain flame retardant, must choose corrosion resistant stainless steel.
Twelve steps: drawing the assembly drawing
The assembly drawing can be made after the positioning die frame and related contents are determined. In the process of drawing assembly drawing, the selected casting system, cooling system, core-pulling system and ejection system are further coordinated and improved to achieve a more perfect design in terms of structure.
Step 13: draw the main parts drawing of the mold
When drawing the cavity or core drawing, we must consider whether the given molding size, tolerance and stripper Angle are in harmony, and whether the design datum is in harmony with the design datum of the product. At the same time, the technology and reliability of cavity and core should be considered.
The drawing of the structure parts, when using the standard die frame, out of the standard die frame structure, most can not draw the structure parts.
Step 14: proofread the design drawings
After the mold drawing design is completed, the mold designer shall submit the design drawing and relevant original data to the supervisor for proofreading.
The proof-reader shall check the overall structure, working principle and operation feasibility of the mold systematically according to the design basis provided by the customer and the requirements put forward by the customer.
Step 15: countersign the design drawing
Mold design drawings must be submitted to customer for approval immediately after completion. Only after the customer agrees, the mold can be prepared for production. When the customer has a big opinion to make significant changes, it must be re-designed and then sent to the customer for approval, until the customer is satisfied.
Step 16:
Exhaust system plays a crucial role in ensuring the quality of molding products. There are several exhaust methods as follows:
1, the use of exhaust slot. The vent is usually located at the end of the cavity where it is filled. The depth of the vent varies with the plastic and is basically determined by the maximum clearance allowed when the plastic does not produce flanges.
2, the use of core, insert, push rod with clearance or special exhaust plug exhaust.
3, sometimes in order to prevent the work in process in the top cause vacuum deformation, must design exhaust inserts.
conclusion
Integrated above the mold design process, some of the content can be considered, some of the content you have to consider repeatedly. Because the factors are often contradictory, it is necessary to constantly in the process of design demonstration, coordinate with each other to get better treatment, especially with the mould structure, must be taken seriously, often to do several projects at the same time, to each kind of structure list the advantages and disadvantages of various aspects, as far as possible in one by one analysis, optimization. Structural reasons will directly affect the manufacture and use of molds, serious consequences or even cause the whole set of molds scrapped. Therefore, mold design is a key step to ensure the quality of mold, the design process is a system engineering.
Key points in mold design:
1. The overall layout of the mold is reasonable.
2. Selection of parting surface
3. Layout of flow passage and selection of glue inlet
4. Ejection device
5. Water transportation and arrangement
6. Exhaust selection
7. Pay attention to the drawing Angle, the extraction of inserts, the processing of wiping Angle and the selection of shrinkage of materials when parting
8, processing diagram should be detailed, but simple.
Can release! Easy processing! Ejection is easy!
H13 is the same kind of soft material as the European 2344 and the Japanese SKD61. The hardenability and wear resistance of the material are very good. Generally, it can be used in molds with over 300,000 beers.
For general inclined top material, its surface hardness, and within a certain toughness, so if cavities with H13, after add hard to 52 HRC, inclined top can use NAK80 such hard just, for a big company generally require cavities material cannot with inclined top material, if the customer specify with material, heat treatment must be better than cavities are 5 HRC or negative 5 HRC, burned or bites to prevent forming process, also will change a good wear resistance.
It is generally not recommended to use the 420 class for the inclined roof, as it is stainless steel and easy to burn.
The emphasis is on structure
If possible in order to simplify the structure, but also to ensure the quality of the mould, the company will earn the biggest profit. When we receive a product, the first problem is to find the largest parting surface, presumably to determine after the former mode, and then on the basis of the parting surface analysis before the mould structure, mould structure, inserts, line, inclined top, other auxiliary mechanism. The structure of the clarity, the next step is to consider the processing, to determine the rationality of the structure: the set or not set. Should CNC or wire cutting; It should be CNC or engraving, etc. The structure affects the processing, the cost involved in the processing and the delivery time.
So how can we simplify the mold structure as much as possible?
On the one hand, I reviewed the product with the customer, and I focused on whether to improve the product due to the mold drawing problems: on the other hand, whether to hold a meeting in the company before the mold design to solicit a variety of feasible structural Suggestions. The final plan was determined from the perspective of processing and customer requirements.
1. On the design of mould product feasibility analysis, computer case, for example, using design software components of the product drawing group analysis, the work of the code, make sure the correctness of each product before the mold design drawings, on the other hand can be familiar with the importance of components in the whole case, to determine the key size, so good in the mold design, the specific method of floor here don't do is introduced in detail.
2. After product analysis to the work, analyze the product adopt what kind of mould structure, and the product process, determine the work content, each process and using design software for product development, generally from the following project forward when products, such as a product requirements five process, while the stamping done when products from product drawings to four project, three projects, two projects, a project, and after a graphic before a copy and then to the work of a project, which has completed five engineering products, and then a detailed work, note that this step is very important, Need special care at the same time, this step is done well, will save a lot of time in map mould, was determined by the content of stamping of each project, including in the forming die, product material thickness outside threats, to determine the size of intensive use, method for product launch is no longer here, will be introduced in the product expansion method.
3. Inventories, in accordance with the product expansion plan preparation, determine the template size in the drawings, including the fixed plate, stripper plate, intensive, inserts, etc., pay attention to the direct material in product development, it is of great benefit to draw die is, I see there are a lot of mold design personnel directly on the product expansion plan manual calculation to prepares materials, this method is of low efficiency and draw the template size directly on the drawings, expressed in the form of assembly drawing, on the one hand, can complete the preparation, on the other hand, in the mold the parts work, save a lot of work, Because in the work of drawing each component, only need to add positioning, pin, guide post, screw hole in the spare part drawing.
4. After the completion of the materials can be fully into the mould figure drawing, to make a drawing, the materials of components, such as to join the screw holes, guide pin hole, positioning hole and hole, and various in punching die hole to the cutting wear silk hole, in the forming die, lower die forming clearance, must not forget, so all the work after the completion of a product's mold figure is mostly done by 80%, the other must be noticed in the process of mapping the mould: Each working procedure, refers to the production, such as bench marking, wire-cutting wait for different machining processes are complete is made layer and so on line and drawing management has a lot of advantages, such as color, such as the distinction between the size of the label is also a very important work, is also the most troublesome work, because is a waste of time.
5. In the above drawing is finished, in fact also can't issue drawings, still need to check mold drawings, all the accessories group, different mould for each piece of plate production of different layers, and in the same benchmark as guide pin hole until the mould assembling analysis, and the products in each process graph set into the assembly drawing, make sure that the template hole position is consistent and bending position of the lower die clearance fit is correct.
