New product process analysis - mold forming and post-processing process

2021/11/10


 
"Do it right once, do it right every time", so engineers need to make comprehensive consideration of the molds and processing processes required for the products in the advance planning stage of the products, in order to avoid congenital bad products.
When receiving the mold order from XX company, each engineer needs to analyze the mold forming and post-processing process for the product first, but before the analysis, they need to check whether the following information is available, including but not limited to: product plan, 3D drawing, physical sample, relevant engineering specifications and packaging requirements, annual product (daily output) of the product, function or use of the product, processing process of the original sample, etc.

After confirming that the above information is available, then analyze according to the following three steps and make the "Notice of Mold Making", together with the product drawings, computer drawing files, samples, etc., issued to the mold workshop to start making the mold.


1 Review the product plan and 3D drawing, and analyze the process of the parts
To review and analyze the alloy material, shape structure, dimensional accuracy and other characteristics of the product parts from the point of view of die-casting processability. For those factors that are not suitable for die-casting, consult with the user to rationalize them. Only when it is really necessary to use special mold structure and special process measures. Such as the formation of the inner concave movable inserts, with vacuum die-casting system, etc. Process analysis of the part drawing, the general issues to be noted are listed below.
(1) whether the structure shown on the plan and 3D drawing is consistent; whether the dimensions on the plan are completely marked; whether the marked dimensions are the same as those measured on the 3D drawing; whether the dimensions marked on the plan take into account the rounded transition, the size end produced by the slope of the die.
(2) Alloy type and required technical properties (consider mechanical properties, corrosion resistance, casting properties, processing properties, etc.).
(3) Dimensional accuracy and form accuracy. According to the dimensional accuracy to decide whether to die-cast out or what kind of post-processing process to use.
(4) wall thickness, wall connection, ribs and rounded corners.
(5) parting, out of the mold direction and out of the mold slope.
(6) core extraction parts, with or without core cross and inner concave.
(7) Push out direction, push rod position.
(8) Die casting of holes, deep holes, threads and teeth.
(9) Casting into the clamping position of the inlay and the metal cladding.
(10) patterns, words, symbols and raised patterns.
(11) The datum surface and mechanical processing of the parts.
(12) Surface appearance.

(13) Special quality requirements.


2 Preliminary analysis of the mold structure
(1) select the parting surface, determine the number of cavities (out of the mold number), according to the part outline on the parting projection area plus the area of the pouring overflow system to calculate the die casting projection area, according to which to calculate the clamping force.
(2) Select the inlet position of the internal gate and determine the general arrangement of the pouring system.
(3) Determine the core extraction position and choose a reasonable core extraction scheme.
(4) Determine the position of the push-out element and choose a reasonable push-out and reset program.

(5) For castings with inlay, analyze the way of clamping and fixing the inlay.


3 Selection of die-casting machine
After choosing the type of die-casting machine according to the type of alloy, select the die-casting machine according to the projection area and quality requirements, while taking into account the balance of the existing equipment production load.
(1) Determine the ratio pressure, calculate the clamping force, estimate the mold size, and select the die casting machine type and specification.
(2) estimate the mold need to open the stroke, push out the force, whether the need to push out the return and die hydraulic pumping center.

(3) Select the accessories to be equipped with the die casting machine, such as hydraulic core extractor, applicable die holder, vacuum die casting system, etc.


4 Drawing the blank
After various process parameters are determined and confirmed, die-casting blank diagram is the main basis for detailed mold design, fixture design; casting blank quality judgment basis; demand-side quality approval review inspection basis; subsequent processes such as machining, injection molding, press glue, surface treatment, cold forming, etc. for process equipment basis; die-casting and post-processing costing basis.
The main contents that need to be expressed in the drawing of the blank are as follows.
(1) the shape, size and accuracy of the die casting.
(2) specify the surface with machining allowance, marked with special symbols on the processing diagram.
(3) the positioning of the rough reference surface and measurement reference surface for machining, available with specific symbols to indicate the location.
(4) the mosaic of the figure number and the location and size of the mosaic.
(5) the main parting surface position, slider position, the front and rear die touch through position, moving die and fixed die opening direction, marked with a special symbol.
(6) Coordinates of push rod position and its tip size, ejector pin positioning size and ejector pin diameter.
(7) The location and size of the remaining sprue and overflow groove stump.
(8) die-casting process additional shape and size (such as ribs, tabs, aisles, subsidies, etc.).
(9) the shape, size and location of the pattern, text, manufacturing mark, manufacturer code, production year, etc. on the die casting.
(10) Not specified the value of the die slope and its direction of taking (using the method of adding material or subtracting material to increase the angle of the die).
(11) The value of the radius of the rounded corners is indicated.
(12) does not note the size tolerance level.
(13) the criteria for acceptance of die castings (including thimble marks, the residual material height of the water mouth bit of garbage, the allowable height of the batch front, surface shrinkage, chipping, porosity, shrinkage and other defects allowed standards, non-machined surface surface roughness requirements, etc.)
(14) die castings require special inspection of the content, such as mechanical properties, airtightness test, etc.
(15) alloy type grades and their technical standards code.
(16) die-casting blank weight or control weight.
(17) belongs to the product parts drawing number and name.

(18) customer name or code.


2. Design the basic requirements of die-casting die
(1) the production of die casting, should be in line with the shape and size and the technical requirements specified on the die casting blank diagram, especially to try to ensure high precision and high quality parts to meet the requirements.
(2) mold should be suitable for the requirements of the die-casting production process, and reasonable technical and economic.
(3) in the premise of ensuring the quality of die-casting and safe production, should adopt a reasonable and advanced simple structure, so that the action is accurate and reliable, good rigidity of the components, easy to remove and replace wearable parts, and help to extend the working life of the mold.
(4) Various parts on the mold should meet the requirements of mechanical processing technology and heat treatment process. Appropriate material selection, with reasonable precision selection, with reference to national standards GB844-86 to achieve the technical requirements.
(5) master the technical characteristics of the die-casting machine, give full play to the technical functions and production capacity of the equipment, the mold and die-casting machine connection installation is both convenient and accurate and reliable.

(6) the choice of mold parts as far as possible to promote standardization, generalization, serialization.


3. the design of the fixture required for the post-processing of the product
The fixtures referred to here include cutting fixtures, surface deburring and grinding fixtures, protective fixtures for spraying, etc.. The jigs can be initially designed according to the product blank drawing or the sample provided by the customer, and the jigs can be corrected and adjusted according to the die casting after the first mold test. The following matters should be noted when designing fixtures.
(1) According to the demand plan requested by the customer, develop our own daily output or even hourly output, and then consider the fixture design as appropriate, especially the discharge of the workpiece in the group fixture of CNC machining.
(2) The designed fixture should be able to ensure the requirements of each subsequent processing process and achieve the purpose of stable clamping, safe and reliable positioning.
Under the premise of ensuring product quality, the cost should be reduced as much as possible.