First, draw mold map

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

Below process diagram * mark part number, name, material, material shrinkage, drawing ratio, and so on. Usually process picture is on plastic molding manufacturing drawing.

Draw final plastic molding manufacturing drawing as much as possible with a 1:1 ratio, drawing start with cavity, and main view is drawn at the same time as other views.

Plastic molding manufacturing drawing should include following:

  • Mold forming part structure
  • Structure of gating system and exhaust system.
  • Parting surface and parting mode.
  • Outline structure and position of all connectors, positioning and guides.
  • Mark cavity height dimension (not required, as needed) and overall dimensions of plastic moulding.
  • Auxiliary tools (pickup tool, calibration tool, etc.).
  • All part numbers are programmed in order and schedule is filled out.
  • Mark technical requirements and instructions for use.

Technical requirements for plastic molding manufacturing drawing:

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

Requirements for plastic molding manufacturing. For example, fitting gap of mating surface of parting surface after plastic moulding is assembled should be no more than parallelism requirement of upper and lower sides of mold of 0.05 mm, and indicate size determined by assembly and requirement for that size.

Mold use, assembly and disassembly methods.

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

Requirements for test and inspection.

Order of drawing parts from mold assembly drawing should be: first inside and then outside, first complicated and then simple, first forming molding plastic parts, then structural molding plastic parts.

Requirements are as follows:

Graphical requirements

Be sure to draw on scale, allowing zoom in or out. View selection is reasonable, projection is correct, and layout is proper. In order to make processing patent number easy to understand and easy to assemble, graphics should be as consistent as possible with final plastic molding manufacturing drawing, and graphics should be clear.

Dimensioning requirements are uniform, centralized, orderly, complete

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

Surface roughness

A roughness of application is marked on the upper right corner of drawing, as indicated by ” Others 3.2.” Other roughness symbols are marked on each surface of part.

Other content

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

Second, proofreading, review

Relationship between plastic moulding, their molding plastic parts and plastic parts drawings

Whether material, hardness, dimensional accuracy, structure of plastic moulding and molding plastic parts meet requirements of plastic parts drawings.

Molding plastic parts

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

Molding equipment

Injection volume, injection pressure, clamping force are insufficient, installation of plastic moulding, south core of molding plastic parts, mold release have no problem, nozzle of injection machine and mouthpiece are in proper contact.

Mold structure

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

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

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

Method of processing undercut of molding plastic parts, whether mechanism for removing concave side is appropriate, for example, whether slider and the push rod in core pulling mechanism of inclined guide column interfere with each other.

Position of pouring and exhaust system is appropriate.

Design drawings

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

Part number, name, production quantity, part internal or outsourced, part are standard or non-standard parts, part processing precision, correction processing and allowance of parts processing precision, high-precision size of molding plastic parts, material of mold parts, heat treatment, surface treatment, surface finishing degree mark, clear description.

Main parts, working dimensions of molding plastic parts and matching dimensions. Size figures should be correct and should not be converted by plastic molding company.

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

Check processing performance

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

Main working size of recalculation aid

In principle, professional proofreading is carried out according to plastic molding company’s self-calibration project; however, it should focus on structural principles, process performance and operational safety. When drawing, first digest graphics, draw according to requirements of national standard, fill in all dimensions and plastic molding technology requirements. Then proofread and sign.

Base map is handed over to plastic molding company for proofreading. Customary practice is to be reviewed by relevant technical personnel of plastic molding company, sign and check manufacturing process, and then send out.

Writing a manufacturing process card

Manufacturing process card is written by plastic molding company technician and is ready for processing.

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

Third, mold trial and repair

Although mold design is carried out under expected process conditions when selecting molding materials and molding equipment, people’s understanding is often imperfect. Therefore, after mold processing is completed, mold trial must be carried out to see molding plastic parts. How is quality? After problem is discovered, erroneous repair is performed.

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

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

Repairing mold should be more cautious, not very sure not to act rashly. Reason is that once mold conditions are changed, it is impossible to make major modifications and restore original condition.

Whether performance of molding plastic parts is good, only in this way can ensure quality of mold.

Fourth, organize data for archiving

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

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