Mold information

What is the standard development process for injection molds?


First, draw the mold map Before drawing the master asse […]

First, draw the mold map

Before drawing the master assembly drawing, the process drawing should be drawn and conformed to the requirements of the parts drawing and process data. The size guaranteed by the next process shall be marked with the words "process size" on the drawing. If, after the molding, no other machining is performed except for the repair of the burrs, the process diagram is exactly the same as the workpiece drawing.

Below the process diagram * mark the part number, name, material, material shrinkage, drawing ratio, and so on. Usually the process picture is on the mold assembly drawing.

Draw a final assembly drawing as far as possible with a 1:1 ratio, starting with the cavity and drawing the main view at the same time as the other views.

The mold assembly drawing should include the following:

Mold forming part structure

The structure of the gating system and exhaust system.

Parting surface and parting mode.

Outline structure and position of all connectors, positioning and guides.

Mark the cavity height dimensions (not required, as needed) and the overall dimensions of the mold.

Auxiliary tools (pickup tool, calibration tool, etc.).

All the part numbers are programmed in order and the schedule is filled out.

Mark technical requirements and instructions for use.

Technical requirements for the assembly drawing of the mold:

Performance requirements for certain systems for molds. For example, the assembly requirements for the ejector system and the slider core structure.

Requirements for the mold assembly process. For example, the fitting gap of the mating surface of the parting surface after the mold is assembled should be no more than the parallelism requirement of the upper and lower sides of the mold of 0.05 mm, and the size determined by the assembly and the requirement for the size are pointed out.

Mold use, assembly and disassembly methods.

Anti-oxidation treatment, mold number, lettering, marking, oil seal, storage and other requirements.

Requirements for test and inspection.

The order of drawing the parts drawing from the mold assembly drawing should be: first inside and then outside, first complicated and then simple, first forming parts, then structural parts.

Requirements are as follows:

Graphical requirements

Be sure to draw proportionally, allowing you to zoom in or out. The view selection 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 as consistent as possible with the final assembly drawing, and the graphics should be clear.

Dimensioning requirements are uniform, centralized, orderly, complete

The order of dimensioning is: first mark the main part size and the draft angle, then mark the fit size, and then mark the full size. Mark the fit size on the non-main part drawing and mark the full size.

Surface roughness

Mark the roughness of the most applied type in the upper right corner of the drawing, as marked "Others 3.2." Other roughness symbols are marked on each surface of the part.

Other content

For example, part name, mold drawing number, material grade, heat treatment and hardness requirements, surface treatment, graphic scale, free size processing accuracy, technical description, etc. must be correctly filled out.

Second, proofreading, review

The relationship between molds and their parts and plastic parts drawings

Whether the material, hardness, dimensional accuracy, structure, etc. of the mold and mold parts meet the requirements of the plastic parts drawings.

Plastic parts

Whether the flow, shrinkage, weld mark, crack, and draft angle of the plastic material affect the performance, dimensional accuracy, surface quality and the like of the plastic parts. Whether the pattern design is insufficient or not, whether the processing is simple or not, and whether the shrinkage rate of the molding material is selected correctly.

Molding equipment

The injection volume, injection pressure, and clamping force are insufficient. The installation of the mold, the south core of the plastic part, and the mold release have no problem. The nozzle of the injection machine and the mouthpiece are in proper contact.

Mold structure

Whether the position of the parting surface and the precision of the finishing meet the requirements, will there be any flashover, and whether the plastic part can be left on the side of the mold with the ejector device after the mold is opened.

Is the demoulding method correct? Is the size, position and quantity of the promotion rod and the push tube appropriate? Will the push plate be caught by the core and will not cause the molded part to be scratched.

Mold temperature adjustment. The power and quantity of the heater; whether the flow line position, size and quantity of the cooling medium are suitable.

The method for processing the undercut of the plastic part is whether the mechanism for removing the undercut is appropriate, for example, whether the slider and the push rod in the core pulling mechanism of the inclined guide column interfere with each other.

The position of the pouring and exhaust system is appropriate.

Design drawings

Whether the placement of each mold part on the assembly drawing is appropriate, whether it is clear or not, whether it is missing;

The part number, name, production quantity, part internal or outsourced part drawing are standard or non-standard parts, part processing precision, correction processing and allowance of high-precision size of molded plastic parts, mold parts Whether the material, heat treatment, surface treatment, surface finishing degree is marked, and the description is clear.

The main parts of the parts, the working dimensions and the matching dimensions of the molded parts. The size figures should be correct and should not be converted by the manufacturer.

Check the view position of all parts drawing and assembly drawing, whether the projection is correct, whether the drawing conforms to the national standard of drawing, and whether there is any missing size.

Check processing performance

Whether the geometry of all parts, view drawing, size mark, etc. is beneficial to processing

The main working size of the recalculation aid

In principle, professional proofreading is carried out according to the designer's self-calibration project; however, it should focus on structural principles, process performance and operational safety. When drawing, first digest the graphics, draw according to the requirements of the national standard, fill in all the dimensions and technical requirements. Self-schooling and signing after the description.

The photographed base map is submitted to the designer for proofreading. The customary practice is to review the technical personnel of the tool manufacturing unit, sign and check the manufacturing process, and then send the sun.

Writing a manufacturing process card

The manufacturing process card is written by the tool manufacturer's technician and is ready for processing.

In the manufacturing process of the mold parts, the inspection should be strengthened, and the inspection focus should be on the dimensional accuracy. After the mold assembly is completed, the inspector performs the inspection according to the mold inspection table. The main thing is to check whether the performance of the mold parts is good. Only in this way can the mold manufacturing quality be guaranteed.

Third, try and repair

Although mold design is carried out under the expected process conditions when selecting molding materials and molding equipment, people's understanding is often imperfect. Therefore, after the mold processing is completed, the mold test must be carried out to see the molded parts. How is the quality? It is always found that after the erroneous revision is carried out.

There are many types of defects in plastic parts, and the reasons are also very complicated. There are mold reasons and process conditions, and the two tend to be together.

Before the mold is repaired, it should be carefully analyzed according to the actual situation of the defective parts of the plastic parts, and the remedy method should be proposed after finding out the cause of the defects of the plastic parts. Since the molding conditions are easily changed, it is common practice to change the molding conditions first, and when the molding conditions cannot be solved, the mold is considered to be repaired.

It is more prudent to repair the mold, and it is not easy to act rashly. The reason is that once the mold conditions are changed, it is impossible to make major modifications and restore the original condition.

Whether the performance of the parts is good, only in this way can the quality of the mold manufacturing.

Fourth, organize the data for archiving

After the mold has been tested, if it is not used for a while, it should be completely wiped off the mold residue, dust, oil, etc., coated with butter or other anti-rust oil or rust inhibitor, and kept in a storage place.

The technical data generated during the period from the start of the design of the mold to the successful processing of the mold, such as the task book, the workpiece drawing, the technical specification, the mold assembly drawing, the mold part drawing, the base drawing, the mold design specification, and the inspection record. Tables, test mold repair records, etc., according to regulations, systematically sorted, bound, numbered for archiving. This seems cumbersome, but it is useful to design new molds for future repairs.