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General Principles And Requirements Of Injection Mold Design
Jul 05, 2018

Core Tip: General Principles and Requirements for Injection Mould Design

 First, the overall principle of mold design

1. Reasonable mold design mainly embodies the quality of the plastic products formed (appearance quality and dimensional stability); it is convenient, rapid and concise when processing and manufacturing, ie provincial capital and manpower, leaving room for correction and improvement; when used It is safe, reliable, and easy to repair; it has short molding cycle and long service life in injection molding and reasonable mold manufacturing process.


2, mold design should pay attention to several aspects:

1) When starting the mold design, more consideration should be given to considering several options to measure the advantages and disadvantages of each solution. One of them is preferred, and the T-mode is also taken seriously. Because of the reason of your understanding of time, at that time, it was considered that a reasonable design would have the potential to be improved after production and use.

2) After handing over the design plan, it is necessary to communicate more with the factory to understand the process and the use of Sino-German manufacturing. Each set of mold should have a fixed analysis experience, summarize the process of gains and losses, in order to continuously improve the level of mold design;

3) When designing, refer to similar drawings designed in the past and draw lessons from them.

4) The mold design department should be a whole, and not every design member should be independent. In particular, the mold design conclusions must have a style.


3, mold design basis

The main basis is the product drawings and templates provided by customers. Designers must carry out careful and detailed analysis and digestion of products and prototypes. At the same time, they must check all the items one by one in the design process.

1) The correctness of the relevant dimensions of dimensional accuracy;

A. high appearance requirements, low dimensional accuracy requirements of clinker products, such as toys, etc., in addition to the specific size of the distribution, the other dimensions as long as the agreement can be good;

B. functional plastic products, strict size requirements, must be within the allowable tolerance range, otherwise it will affect the performance of the entire product;

C. The strict size of the onlookers.

2) whether the demoulding slope is reasonable;

3) Wall thickness and uniformity of products;

4) Plastic types. (Plastic types want to steal the choice of mold steel and determine the shrinkage rate.)

5) Surface requirements.

6) product color. (In general, the color has no direct effect on the mold design. However, when the product is thick and the shape is large, color unevenness is easy to occur; and the darker the color, the more obvious the product defect is exposed).

7) Is there post-processing after molding? (If there are surface electroplated products, and when multiple cavities are in one mold, auxiliary flow paths must be considered to connect the products together until the electroplating process is completed and separated.)

8) Batches of products, (the batch of products is an important basis for mold design, customers must provide a range to determine the number of mold cavity, size, mold selection and life).

9) injection molding machine specifications.

10) Other customer requirements. Designers must seriously consider and check to meet the requirements.


4, mold design general process:

<1> Analysis and digestion of products and templates.

<2> It should be understood whether the customer requests the injection molding machine specifications to determine the mold size range.

<3> The cavity number is determined and ranked.

<4> Partial surface determination.

<5> If there is a row, orthorhombic structure should be first understood.

<6> Casting system design.

<7> Determination of the mosaic structure.

<8> Top out. Reset system design.

<9> Cooling. Heating system design.

<10> Guide. Positioning device.

<11> Determine the mold blank and use standard parts.

<12> mold steel selection.

<13> Complete the structure diagram, mold blank drawing, cutting.

<14> Print out the figure, check it, and hand in the mold design team leader and supervisor.


Second, the mold requirements


<1> The position of the product in the inner mold should be discharged in the form of the best effect. The position of the water and the parting surface must be taken into account. It must be proportional to the size and depth of the product.

<2> Distance from the product to the edge of the precision frame:

A) small parts of the product: the distance between 25mm ~ 30mm, between the finished product is 15mm ~ 20mm, if there is about 25mm, there is a minimum of 15mm flow path between the finished products.

B) Large-size products: 35 to 50 mm from the edge, with a minimum of 35 mm for inserts. If a steel piece contains multiple small products, the distance between them should be about 12 to 15 mm. The length of the finished product should be 200 mm or more. At 150mm or more, the product should be no less than 35mm away from the edge.

<3> The principle of selecting the benchmark for product ranking:

A) preferentially select parts with distinct characteristics (such as column position, perforation, bone position).

B) If you select the PRO/E 3D benchmark, indicate the name of the CSO or CSI or DTM.

C) The shape is special, it is difficult to determine the benchmark of the product, to discuss with the CAM to determine its benchmark.

D) The product reference and the model embryo center must be integers, and when the dimensions are marked, the numbers are boxed to indicate the difference.

<4> The principle of determining the X, Y coordinate direction of the inner frame's precision frame during the positioning: if the difference between the length and the width of the inner model precision frame is obvious, the direction of the longer side must be taken to place the embryo alignment in the direction of the X axis to match the workshop. Machine machining direction, reduce the chance of error.



2, book mold

<1> Try to use the standard model embryo (LKM standard or Hongfeng standard).

A) When the straight body model is changed from the I-shape, do not move the square iron.

B) Non-standard model embryos must be approved by the supervisor and indicated on the bitmap.

<2> Use CH-type and CT-type mold blanks to make pattern pits, height and width of about 25 ~ 35mm, length determined by the height of the mold embryo.

<3> The top bar hole should be processed by one or two or four holes according to the large slender width of the die (when machining more than one top bar hole, the long top bar should be made, and the top bar hole of the die blank center should not be used. ). The aperture is 35mm ~ 40mm. Die height is below 400mm (including 400mm) to make a top hole; die height is above 400mm to do 2 or 4 top stick holes, hole spacing according to data processing.

<4> The diameter of the slingshot hole should be greater than the slingshot diameter of 1~2mm, and the depth of the hidden B board should be at least 20 to 30mm.

<5> The mold processing drawing shall be processed by the supplier of mold blanks to process the mouth (flange), spring hole, square-shaped aid mounting recess or -side nail hole, etc. The large mold blank (800800) is required. Machining the head hole (including the screw hole at the bottom), the sloping side evacuation hole, the beveled bronze insert, the trapezoidal shape, the line position, the line position pressure plate, the carrying water, the transport bucket, etc.; Water outlet rods, slingshot rubber holes, glue holes, tapping screw holes, etc.; Please consult workshop requirements before the mold processing map, according to the actual workload of the workshop to determine the need to process items.

<6> The Daguchi mold is a mold embryo of 2730 or more. The thickness of the A-plate should be the depth of the precision frame plus 25mm~35mm, the thickness of the B-plate is the precision frame depth plus 50mm~70mm, and the mold embryo is 2525. Below, the thickness of the A plate is about 25mm~30mm in the depth of the frame, and 40mm~50mm in the B plate.

<7> The thickness of the fine-walled die blank A is between 30 and 40 mm deep, and the thickness of the B-sheet is between 50 and 60 mm deep. (Specifications for large and small nozzles can be referenced to the dragon's embryo data) .


3, booking

1. Ordering principle:

A) The blank size of inserts that do not need to be ground = actual number + 3~5mm (this number should be consistent with the steel supplier's specifications).

B) Finishing blanking size = actual number + margin

C) Cutting size of Y-CUT insert = actual number + 5mm (one side) + 5mm (adjacent side) + 20mm (opposite side) + 20mm (adjacent side of opposite side).

D) Open size of the insert to be hardened = Actual number + >10mm. (Excluding fine grinding).

2. The mold steel material should be ordered according to the plastic nature of the product (including beer plastic material) as follows:

A) Beer PVC products can use GS083H, S136, S136H, beryllium copper as the internal mold material depending on the structure of the pattern.

B) Beer transparent material, POM material, nylon material, ABS material, K material and other internal mold materials are GS083HS136, S136H and other steel materials. Note: Molds made of steel materials such as S136H, GS083H, and S136 are used under special circumstances. It is best not to weld, if it is to be welded, it is necessary to burn the same material and to temper it.

C) In addition to beer with acid or transparent rubber, other products used in the mold are P5, P20, 738, 718 model steel.

D) Internal die iron commonly used steel yellow card material.

E) Line material, hatching material and row pressure plate are usually 738 materials (except inserts do not insert).

F) The alloy molds are all 8407 (including inner molds) for easy hardening.

G) The material must be 738 steel when the bottom or oblique position is to be inlaid with hardware.

3. Communicate with the workshop, carefully fill in the billing form and verify the delivery.


4, parting surface

<1> Selection principle of parting surface:

A) Products that do not affect the appearance of the product, especially those with clear requirements for appearance, should pay more attention to the influence of the appearance of the product.

B) help to ensure the accuracy of the product;

C) is conducive to the processing of molds, especially the processing of embryos;

D) is conducive to the design of the pouring system, exhaust system, cooling system;

E) It is beneficial to the demoulding of the product, so as to ensure that the product stays on the side of the movable mold when the mold is opened;

F) easy installation of metal inserts;

<2> When the parting surface is a large curved surface or the height and height of the parting surface are large, the upper and lower mold materials can be used to match the tiger's mouth. The size of the tiger's mouth is determined according to the mold material. The length and width are below 200mm, and the tiger mouth is 15mmX8mm high. , Slope is about 10%% d. If the length and width of the mold material exceeds 200mm, the tiger's mouth should do 20mmX10mm degree is about 10%% d. If the length and width of the mold material exceeds 200mm, the tiger's mouth should do 20mmX10mm High or above tiger's mouth, the number of which depends on the rank (can be set to stay).

<3> When drawing, clearly indicate the position of the mold opening line, whether the sealing surface has been extended or not.



5, other design, processing requirements

<1> The clearance between plate A and plate B is 0.1mm (ie, the total height of the mold material is greater than the sum of the depth of the precision frame of plate A and plate B, 0.1mm). The large mold A and B plates have a clearance of 0.5mm. The height should be smaller than the AB plate clearance by 0.05~0.2mm. (ie stool height + B plate height + clearance height - clearance 0.05~0.2mm - bottom needle plate and rubbish nail height = back needle length.)

<2> The top surface of the mold (drawing hole that is hanging mold hole) should be marked with the <<factory and customer number comparison table>> number, typing at least use 12mm word mark, marking the word to neat.

<3> The corners of the dies are all placed on the four corners of the B-plate and are equilateral triangles with a depth of 4 to 5 mm and an inverted R or chamfer.

<4> All the water inlets and outlets on the mold must be marked with 1 IN----1 OUT ~ 2 IN----2 OUT.

<5> The distance between the mold hole and the size of the teeth is determined by the specifications of injection molding.

<6> The requirements for the upper and lower mold materials and the mold blank are as follows:

A) 45%%d chamfer of about 1mmX1mm at the bottom of the mold material and the frame.

B) A, B board mold surface according to the amount of mold material in the box edge out of 5mm a diameter of 1/2 "mm, depth of 0.5mm round position, with the number of playing the mold, easy to install the number, A board press 1,2,3----Seal the word mark, B plate press 01,02,03----Seal the word mark. The upper and lower mold material must face the A plate, B plate word mark position must make the factory number (XXXX ), the upper mold number is XXXX----1, 2, 3----, the lower mold number is XXXX----01, 02, 03----. The upper and lower mold numbers must be symmetrical (ie the upper mold is 1, the lower mold is 01 as a box). The upper and lower molds are for the length of 30mm, width is 8mm, and the depth is 0.5mm. It is marked with a 5.0mm mark. The internal model number should be provided on the customer's engraving or marking. Numbering.

C) The allowable difference between the upper and lower mold frames is %%p0.02mm, the allowable tolerance of the upper and lower mold material rulers is %%p0.02mm, and the tolerance of the upper and lower mold materials is %%p0.02mm.

<7> When moving the mold, the appearance should be clean and the inner mold should be sprayed with anti-rust oil.