Standardized mold making in injection molds is vital for ensuring consistency, efficiency, and cost-effectiveness in production processes across various industries.

Standardized mold making requires precise engineering, material quality selection, adherence to mold design specifications, and compatibility with injection molding machines. Key benefits include reduced production times and enhanced part consistency.

As you delve deeper into the specifics of standardized mold-making, comprehending the key factors that influence mold performance and longevity will be essential for optimizing your manufacturing outcomes.

What are Mold Design Requirements?

Standardized injection mold making requires precise design criteria to ensure consistent quality and efficiency in manufacturing a wide range of products.

Essential mold design requirements include accurate tolerances, proper material selection, efficient cooling systems, and standardized components to facilitate smooth production and maintain uniform product quality.

Product Analysis

I know a lot about how injection molded products are supposed to look and work. For example, if you want a product to look really good, the mold has to be really smooth. For example, if you’re making a part for the inside of a car, the mold has to be really smooth, like between 0.8 and 1.6 micrometers, so the part looks good.

Analyze the demolding method¹ of the product, according to the shape of the product to determine whether to use the ejector pin demolding, push plate demolding or other ways. For example, for cylindrical products, push plate demolding may be more suitable because it can push out the product evenly and avoid product deformation.

Conception de la structure du moule

Make sure the mold’s parting line is reasonable. The parting line should allow the product to be easily ejected and minimize flash. For example, if the product has a surface requirement, the parting line should be placed where it won’t affect the surface.

Decide where and how to gate. Hot runner gating can reduce waste and improve material utilization, but it costs more; side gating is simpler and works for a wide range of products, but it can leave gate marks on the product surface. For example, for transparent plastic products, pin-point gating might be better because it can reduce weld lines and gate marks and improve product transparency.

Design the mold frame² with enough strength and rigidity. The size of the mold frame should be selected according to the size of the mold and the injection pressure. For example, large injection molds require thicker and sturdier mold frames to withstand greater injection pressure and prevent mold deformation.

Dimension Standard

When marking the dimensions of mold parts, it is necessary to mark them in accordance with national standards or industry standards. For example, when marking the size of the mold cavity, it should be marked according to the processing accuracy and assembly requirements, and the selection of dimensional tolerances should be reasonable. Generally, IT6-IT9 level tolerances are used to ensure the interchangeability of parts and the accuracy of assembly.

Using standard holes, shafts, and other structural dimensions makes it easier to use standard tools and gauges for processing and testing. For example, the guide pillar in the mold should have a standard size, so the guide sleeve hole diameter and outside diameter should also be standard sizes. This makes it easy to buy and replace them.

Conception du système de refroidissement

Le système de refroidissement³ should be able to effectively control the mold temperature, so that the temperature of the mold cavity surface is uniform. Cooling pipe diameter, spacing and distance from the cavity surface have certain requirements. General cooling pipe diameter of 8 – 12mm, spacing for 3 – 5 times the diameter of the pipe, and the distance from the surface of the cavity for 10 – 15mm, which can ensure the cooling efficiency, shorten the injection cycle.

When arranging cooling pipes, make sure they don’t get in the way of other mold structures (like ejector pins, sliders, etc.). For example, if you’re designing cooling pipes near a slider, think about how far the slider moves and make sure the cooling pipes don’t get in the way of the slider moving back and forth.

Ejector System Design

The ejector force of the système d'éjection⁴ should be evenly distributed to avoid deformation or damage to the product. The number, position and diameter of the ejector needles should be determined according to the shape, size and material of the product. For example, for large flat products, more ejector pins are required and the position of ejector pins should be evenly distributed at the bottom of the product to ensure that the product can be ejected smoothly.

The ejector stroke should be long enough to make sure the part is completely out of the mold. Generally, the ejector stroke should be more than 1/3 of the part height. Also, you need to consider the mold opening and closing actions so the ejector system doesn’t hit other parts of the mold.

Slider and Tilt Top Design

The structure of the slider and tilting top should be compact, flexible, and reliable. The guiding precision of the slider should be high, generally using T-slot or dovetail slot guiding.

The angle of the tilting top should be reasonably designed according to the demolding requirements of the product, generally not more than 15°, in order to avoid excessive friction generated by the movement of the tilting top, resulting in the phenomenon of jamming.

Choose the material of the slider and the tilting top properly, with good wear resistance and strength. For example, for high production molds, the slider and the tilting top can be made of quenched steel, such as Cr12MoV, with a quenching hardness of HRC58-62, to improve their service life.

Exhaust System Design

The mold should be designed with reasonable exhaust channels to remove the air in the cavity and the gas produced by the plastic melt. The exhaust method can be gap exhaust, exhaust slot exhaust or use of breathable steel. For example, an exhaust gap of 0.02 – 0.05mm can be set at the parting surface of the mold, or an exhaust slot with a depth of 0.03 – 0.08mm can be opened at an appropriate location.

Selection of Mold Material

When you’re deciding on the material for your mold, you need to consider the working conditions and requirements of the mold. For high-pressure, high-wear parts of the mold (like the cavities and cores), you can use high-quality mold steel, like P20, H13, and so on.

P20 steel⁵ has good processability and certain wear resistance, suitable for general injection molds; H13 steel has high toughness and thermal fatigue properties, suitable for high temperature and high pressure injection molds.

For the mold frame and other supporting parts, you can use regular structural steel, like 45 steel, and then heat treat it to make it better.

What are the Mold Manufacturing Requirements?

Standardized injection mold manufacturing is essential for enhancing efficiency, reducing costs, and ensuring consistent quality across various industries.

Standardized injection mold making requires precise tolerances, high-quality steel, consistent cooling systems, and robust design principles. This enhances efficiency, ensures repeatability, and guarantees superior part quality. Industries like automotive, consumer goods, and electronics benefit from these streamlined processes.

Machining Process Planning

Plan a machining process⁶ that makes sense, including roughing, finishing, EDM and other steps. For example, for the machining of mold cavities, first rough out most of the material, then semi-finish, and finally finish to make sure the cavity is the right size and has a good surface.

Decide how much extra material you need to leave on the part for each machining operation. You should decide how much extra material to leave on the part based on the size, shape, and how accurate you need the part to be. In general, you should leave 1-3mm of extra material for roughing, and 0.1-0.5mm for finishing.

Cutting Requirements

The choice of cutting tools⁷ should be appropriate, according to the material of the workpiece, machining accuracy and machining process to select the type of tool, material and geometric parameters.

For example, when processing hardened steel, you can choose carbide tools, which have high hardness and good wear resistance; when processing aluminum alloy, you can choose high-speed steel tools, which have sharp cutting edges and can obtain better surface quality.

Cutting parameters (such as cutting speed, feed, depth of cut) should be set reasonably. Cutting speed should be determined according to the characteristics of the tool and material, feed and depth of cut should consider the machining accuracy and tool bearing capacity. For example, when machining mold steel, the cutting speed is generally 50 – 100m/min, the feed is 0.1 – 0.3mm/r, and the depth of cut is 0.5 – 2mm.

EDM Requirements

EDM electrode design needs to be accurate, and the size of the electrode needs to take into account the discharge gap. The discharge gap is generally 0.05-0.2mm, and the electrode size should be designed to compensate for the cavity size and discharge gap.

EDM parameters⁸ (such as discharge current, discharge time, pulse width, etc.) need to be adjusted reasonably to obtain good surface quality and machining accuracy. For example, the discharge current is generally 10-50A, pulse width is 10-100μs, and it needs to be adjusted appropriately according to different processing requirements.

Traitement de surface des moules

When it comes to controlling the precision of mold parts ,The dimensional accuracy⁹ of the mold parts should be strictly controlled, using appropriate gauges for testing. Such as the use of calipers, micrometers, coordinate measuring machine and other tools for size measurement. For key dimensions, the tolerance control should be within ±0.01mm.

The shape accuracy of parts (such as straightness, flatness, roundness, etc.) should also meet the requirements. For example, the flatness of the parting surface of the mold is generally within 0.03mm to ensure that the mold closes accurately.

Mold Assembly Requirements

Before you put the mold together, you need to clean the parts to get rid of stuff like oil, iron filings, and so on. After you clean them, you need to treat them with antirust. After you clean them, you need to treat them with antirust so they don’t rust.

Based on the assembly drawings and assembly process, you need to make sure that each part is assembled in the right place. For example, when you assemble the guide pin and guide bush, you need to make sure that they are concentric. Normally, the concentricity requirement is within ± 0.03mm. This is to make sure that the mold can open and close accurately.

You should make some adjustments when you assemble the mold, such as adjusting the height of the ejector pin, the position of the slider, and so on. The height of the ejector pin should be adjusted to make sure the product can be ejected smoothly, and the top surface of the ejector should be flush with the bottom surface of the cavity or slightly higher 0.05 – 0.1mm.

Mold Debugging Requirements

Once the mold assembly is done, debugging should be done, and before debugging, we should check whether the mold opening and closing action is flexible, whether the ejector system is working properly, and whether the cooling system and exhaust system are smooth. For example, open and close the mold action should be smooth, open and close the mold speed should be reasonable, generally open the mold speed of 30 – 50mm/s, close the mold speed of 20 – 40mm/s.

When debugging the injection molding process, we need to observe the plastic melt filling situation, product molding quality, etc. According to the debugging situation, adjust the mold, such as adjusting the gate size, cooling time, etc., until the product quality meets the requirements.

What are the Mold Documentation and Management Requirements?

Proper documentation and management are crucial in standardized injection mold making, ensuring quality, consistency, and efficiency across production.

Mold documentation includes design specs, maintenance logs, and inspection records. Key management requirements ensure compliance with industry standards, efficient workflow, and consistent product quality.

Mould Drawing Specification

Mould drawings should follow national drawing standards, which include the drawing format, scale, view selection, size labeling, and so on. For example, the drawing format is generally the A0 – A4 standard format. The proportion should be chosen reasonably based on the size and complexity of the mold. The view should fully show the structure of the mold and the shape of the parts.

Label the drawings with the material, heat treatment, surface treatment, and other technical parameters. For example, if the material for the mold cavity parts is P20 steel, the heat treatment required is quenching + tempering, and the hardness should be HRC30 – 35, then the surface should be nitrided with a nitriding layer thickness of 0.05 – 0.1mm.

Mould Technical Documents Preparation

Prepare the design specification of the mold, explaining in detail the design idea of the mold, structural characteristics, determination of the main dimensions and so on. For example, in the design specification to explain the location of the gate and the type of selection basis, as well as the cooling system and ejection system design principle.

Preparation of mold processing technology documents, including the machining process route of each part, machining allowances, cutting parameters and so on. Processing technology documents should be able to guide the mold processing production, to ensure processing quality and efficiency. of mold requirements for surface treatment, such as nitriding treatment, hard chrome plating treatment.

Nitriding treatment can improve the hardness, wear resistance and corrosion resistance of the mold surface. For example, after nitriding treatment, the surface hardness of the mold cavity can reach HV900 – HV1200, which can effectively improve the service life of the mold.

The quality of surface treatment should meet the requirements, the thickness of the surface treatment layer, hardness and other indicators to meet the required standards. The thickness of hard chrome plating layer is generally 0.02 – 0.05mm, and the hardness reaches HV800 – HV1000.

Mold Parts Marking

Mold parts should be clearly marked, including part name, number, material and other information. The marking method can be steel stamping, engraving or use of labels, etc.. For example, use steel stamps on the mold cavity parts with the part name “Cavity”, number “CX – 01” and material “P20” to facilitate parts management and assembly.

Mould Archive Management

Establish the mold file, including the mold design drawings, technical documents, processing records, debugging records and other information.

Mould files should be classified and organized for easy inquiry and management. For example, according to the mold number to establish a file folder, the relevant drawings, documents and other information into the folder, and can be digitized through the electronic document management system to improve management efficiency.

Mold Maintenance and Maintenance Documents

Preparation of mold maintenance and maintenance manual, describing the daily maintenance of the mold content, maintenance cycle, replacement of wear parts, etc..

For example, the manual stipulates that the mold should be cleaned after each injection production, the cooling system should be inspected and maintained regularly (e.g., weekly or monthly), and the wear and tear of wearing parts (e.g., ejector pins, sliders, etc.) should be inspected regularly, and replaced in a timely manner when the wear and tear exceeds a certain limit.

What is the Mold Quality and Performance Requirements?

Understanding the quality and performance requirements for standardized injection mold making is essential for ensuring product consistency and production efficiency.

Standardized injection mold making requires high-quality materials, precise machining, and adherence to design specifications to ensure optimal mold performance, durability, and consistent production output.

Mold Life Requirements

Moulds should have a sufficient service life, according to the type of mold and use conditions to determine the life of the mold indicators. For example, the general injection mold life requirements for 300,000 – 1 million times, for high precision, high requirements of the mold, such as optical lens mold, life requirements may be as high as millions of times.

Through reasonable design, high quality materials and correct processing and manufacturing methods to improve the life of the mold. Such as the use of appropriate mold steel, optimize the mold structure, reduce stress concentration, appropriate surface treatment of the mold.

Product Quality Consistency

The quality of the products produced by the mold should be consistent, and the dimensional accuracy, appearance quality, physical properties and other indicators of the products should be within the specified tolerances.

For example, the key dimensional tolerances of the products should be controlled within ±0.1mm, and the appearance surface should be free from obvious defects such as flying edges, bubbles and shrink marks.

Regular inspection and maintenance of the mold to ensure the stability of product quality. Such as checking the wear and tear of the mold, the cooling effect of the cooling system, etc., to detect problems and deal with them in time.

Injection Molding Cycle Requirements

Molds should be able to meet certain injection molding cycle requirements, shorten the injection molding cycle¹⁰ can improve production efficiency. For example, the general injection molding cycle requirement is between 10 – 60 seconds, through the optimization of the cooling system of the mold, the reasonable design of the gate and runner, etc. to shorten the molding cycle.

Interchangeability of the Mold

The parts of the mold should have good interchangeability to facilitate the maintenance and replacement of the mold. For example, the same type of ejector pins, guide pillar, guide bushings and other parts can be replaced with each other, the dimensional tolerance and fit accuracy of the parts should meet the requirements of interchangeability, and generally use the base hole system or the base shaft system of the fit.

Safety of the Mold

The mold should consider the operation safety, set up the necessary safety protection devices. For example, in the mold opening and closing areas set up guardrails to prevent the operator’s hands or other parts of the body into the mold work area to avoid accidental injury.

The structural design of the mold should avoid sharp edges and corners and structures that may cause parts to eject to prevent parts from flying out and injuring people.

What are the Requirements for Mold Acceptance?

Understanding mold acceptance requirements is crucial in achieving high-quality standardized injection molds, ensuring product precision and manufacturing efficiency.

Mold acceptance requirements include strict tolerances, surface finish standards, and proper functionality checks. These ensure that injection molds produce parts with precision and consistency, reducing defects and enhancing efficiency in manufacturing processes.

Inspection de l'apparence

Check the appearance quality of the mold, including surface roughness, color, marking and so on. The surface of the mold should be smooth and free from obvious scratches, rust and other defects. The marking should be clear, accurate and in line with the design requirements.

Check the assembly of the parts of the mold, the assembly should be tight, no loose phenomenon. For example, check whether the screws are tightened and whether the fit gap between parts meets the requirements.

Dimensional Accuracy Check

Adopt suitable gauges to check the key dimensions of the mold, such as cavity dimensions, core dimensions, guide dimensions and so on. The dimensional tolerance should be in accordance with the requirements of the design drawings, and the exceeding dimensions should be analyzed and processed.

Check the shape accuracy of the mold, such as flatness, straightness, roundness and so on. For example, check the flatness of the parting surface of the mold through the level meter, and check the straightness of the guide pillar through the percentage meter.

Function Check

Check the opening and closing function of the mold, the opening and closing action should be flexible, smooth and without stagnation. Check the function of ejector system, ejector action should be normal, ejector force should meet the requirements.

Check the function of cooling system and exhaust system, the cooling pipe should be smooth, the cooling effect should be good; exhaust channel should be able to effectively exhaust. For example, check the cooling system through the water test, and check the exhaust system through the injection mold test.

Product Quality Check

Conduct a trial molding with the mold to check the molding quality of the product. The dimensional accuracy, appearance quality and physical properties of the product should meet the requirements of the product design. For example, check whether the wall thickness of the product is uniform and whether there are defects such as fusion marks and shrink marks on the surface.

Adjust the mold according to the trial mold situation until the product quality is qualified. Adjustments include gate size, cooling time, ejection position, etc.

Acceptance of Documents

Check whether the design drawings, technical documents, processing records and debugging records of the mold are complete. The content of the documents should be complete, accurate and in line with the relevant standards and requirements.

For example, check whether the design drawings are signed by the designers, and whether the technical documents contain the materials and heat treatment requirements of the mold.

Conclusion

Injection mold standardization requirements include product analysis, mold structure design, dimensional standards, cooling and ejector system design. Mold design needs to consider the function of the product, mold release method, parting surface, gate position, cooling effect, etc. to ensure product quality.

Mold manufacturing requires precise machining, selection of appropriate materials and surface treatment, control of part precision and assembly accuracy. Quality requirements cover mold life, product consistency, molding cycle and safety. Mold acceptance involves visual, dimensional and functional inspections as well as product quality and documentation acceptance to ensure that the mold meets design and production standards.