Dimensioning Requirements for Injection Mold Assembly Drawings

The assembly drawing must clearly specify all dimensions related to the connection between the mold and the injection molding machine. These include, but are not limited to, the overall mold dimensions (length, width, height), mounting hole positions and sizes, ejection stroke requirements, and any special interface features.

These dimensions ensure that the mold can be properly installed and secured in the intended injection molding machine, aligning critical parts of an injection mold with machine components. Accuracy here prevents damage to both the machine and the mold during installation and operation.

Specifically, dimensions for tie bar spacing accommodation, clamp plate dimensions, and locating ring specifications must be precisely indicated. These connections are vital points where parts of an injection mold interact with the machine, requiring exact tolerances to ensure proper operation and safety.

All parts of an injection mold that do not have separate detailed part drawings must have their complete dimensions specified on the assembly drawing. This primarily applies to mold base machining features that are created during the mold fabrication process.

These dimensions include plate thicknesses, custom machining features, non-standard cutouts, and special modifications to standard mold base components. While standard holes in the mold base do not require dimensioning, any non-standard holes or modified standard holes must be fully dimensioned.

Providing these dimensions ensures that all parts of an injection mold can be manufactured correctly even without individual part drawings. It's essential to include all critical dimensions that affect the fit, form, and function of these components within the overall mold assembly.

The position of each cavity within the mold must be clearly dimensioned using the coordinate system with the mold center as the origin. Whenever possible, these dimensions should be specified as integers to simplify manufacturing and reduce the potential for errors.

Cavity positions are critical for ensuring proper part filling, cooling, and ejection. Accurate positioning also ensures that parts of an injection mold align correctly with each other and with the machine's injection unit.

When multiple cavities are present, both the individual position of each cavity relative to the mold center and the spacing between cavities should be dimensioned. This helps in verifying that all cavities are correctly positioned and evenly spaced, which is essential for balanced filling and consistent part quality across all cavities. The coordinate dimensions for these critical parts of an injection mold should be checked and verified at multiple stages of the manufacturing process.

The exact positions of all gates and sprue bushing screws must be clearly dimensioned on the assembly drawing. These components control the flow of molten material into the cavities and are therefore critical parts of an injection mold that directly impact part quality.

Gate positions should be dimensioned relative to both the cavity features and the mold center, ensuring precise placement for optimal filling. Sprue bushing screw positions must be accurately specified to ensure proper alignment with the injection unit and secure attachment to the fixed half of the mold.

For hot runner systems, additional dimensions for manifold positioning, heater locations, and thermocouple positions should be included. These dimensions ensure that all parts of an injection mold related to material delivery work together seamlessly to produce consistent, high-quality parts. Proper dimensioning here also facilitates maintenance and replacement of these critical components when necessary.

The assembly drawing must include complete dimensions for all template sizes (length, width, thickness) and the sizes and positions of all inner mold inserts. These are fundamental parts of an injection mold that determine the overall mold structure and the final part geometry.

For each template, overall dimensions must be specified along with any critical features such as recesses, steps, or counterbores. Insert dimensions include their overall size, critical forming surfaces, and their exact position within the surrounding plates.

Clearance dimensions between inserts and their receiving plates must also be indicated to ensure proper fit and function. These dimensions are crucial for ensuring that all parts of an injection mold align correctly and maintain the required tolerances during operation. Special attention should be paid to dimensions that affect the shutoff surfaces between different mold components to prevent flash and ensure proper part formation.

All dimensions related to side action (lateral) mechanisms must be fully specified, including the positions and sizes of slides, lifters, racks, pins, and other components involved in侧向抽芯. These complex moving parts of an injection mold require precise dimensioning to ensure proper operation and timing.

Dimensions should include the travel distance of each side action component, the position of guideways, the location of actuation mechanisms (such as hydraulic cylinders or cams), and the clearance required for full movement. The engagement positions of any mating components must be clearly defined.

It's particularly important to dimension the critical positions at both the fully extended (molding) and fully retracted (ejection) states of these mechanisms. This ensures that all parts of an injection mold involved in side action can properly perform their functions without interference. Additionally, dimensions related to the locking mechanisms that secure these components during the injection phase must be clearly indicated to prevent movement during high-pressure molding.

Locating blocks are essential parts of an injection mold that ensure proper alignment between the fixed and moving halves of the mold. Their positions and sizes must be clearly dimensioned to guarantee precise alignment during mold closing.

Dimensions should include the overall size of each locating block, their exact position relative to the mold center and key features, and the fit tolerance between mating locating components. Both the male and female elements of the locating system must be fully dimensioned.

These dimensions are critical for maintaining proper cavity alignment, especially during high-pressure injection when forces can cause slight movement between mold halves. Accurate dimensioning of these parts of an injection mold ensures consistent part quality and prevents damage to the mold during operation. The number and placement of locating blocks should be such that they prevent both translational and rotational movement between mold components.

The assembly drawing must clearly indicate all dimensions related to cooling water circuits, which are vital parts of an injection mold for controlling temperature during the molding process. This includes the positions of all cooling holes, their diameters, depths, and connections.

Each cooling circuit should be assigned a unique identifier or number to facilitate setup and maintenance. The positions of inlet and outlet connections must be precisely dimensioned to ensure compatibility with the molding machine's cooling system.

For complex cooling systems with baffles, bubblers, or spiral channels, additional dimensions are required to specify the position and size of these components. The spacing between cooling channels and their distance from cavity surfaces are critical dimensions that affect cooling efficiency and part quality. Proper dimensioning of these parts of an injection mold ensures uniform cooling and minimizes cycle time while preventing warpage in the molded parts.

The diameter and exact position of all knockout (K.O) holes must be clearly dimensioned. These holes accommodate the machine's knockout pins that actuate the mold's ejection system, making them critical interface points between the machine and specific parts of an injection mold.

K.O hole dimensions must match the specifications of the intended injection molding machine to ensure proper alignment and operation of the ejection system. Both the primary knockout holes and any secondary or auxiliary knockout holes must be included.

The position of these holes relative to the mold center and ejection system components is crucial for ensuring balanced ejection force distribution. Proper dimensioning here prevents binding or uneven wear on the ejection components, extending the life of these parts of an injection mold. Clearance dimensions between the knockout pins and their respective holes should also be specified to ensure smooth operation without excessive play.

The length and size of ejector plate guide pillars and their corresponding guide bushes must be fully dimensioned. These components ensure smooth, precise movement of the ejection system, making them critical parts of an injection mold's functionality.

Dimensions include the diameter of both the guide pillars and bushes, their overall length, the length of the engaged portion, and any shoulder diameters or locating features. The positional dimensions of these guides relative to the mold center and other ejection components must also be specified.

Clearance or interference fits between mating components should be indicated to ensure proper operation without excessive play or binding. The length of these guides must be sufficient to accommodate the full ejection stroke while maintaining adequate engagement at all positions. Proper dimensioning of these parts of an injection mold ensures the longevity and reliability of the ejection system, which is subject to frequent cyclic movement during production.

Support pillars (S.P) are essential parts of an injection mold that reinforce the mold plates against the high clamping forces encountered during injection. Their positions and diameters must be clearly dimensioned to ensure adequate support.

The diameter of each support pillar should be specified based on the load it is expected to carry, with larger diameters used in areas subject to higher pressures. The exact position of each support pillar relative to the mold center and cavity areas must be dimensioned to ensure optimal load distribution.

The height of support pillars, which determines the gap between the plates they separate, must also be included. These dimensions ensure that all parts of an injection mold are properly supported, preventing deflection or deformation during molding that could affect part quality or damage the mold. The number and placement of support pillars should be such that they evenly distribute the clamping force across the mold plates.

Return springs are critical parts of an injection mold's ejection system, responsible for returning the ejector plate to its home position after ejection. Their dimensions must include the wire diameter, outer diameter, free length, and compressed length under operating conditions.

The spring holes must be dimensioned with both diameter and depth specifications. The spring specification (including manufacturer part number if applicable) should be clearly indicated on the drawing.

These dimensions ensure that the springs provide adequate force to reliably return the ejection system while fitting properly within the available space. The depth of spring holes is particularly important to prevent bottoming out before the ejector plate reaches its fully retracted position. Proper dimensioning of these parts of an injection mold ensures reliable cyclic operation and prevents premature spring failure due to over-compression.

Stop pins (or限位钉) are important parts of an injection mold that limit the forward travel of the ejector plate, preventing damage to delicate components. Their diameter and thickness (or length) must be clearly dimensioned.

The diameter of stop pins should be sufficient to withstand the impact forces when the ejector plate reaches its forward limit. The thickness or length dimension determines the maximum ejection stroke, which must be carefully specified to ensure complete part ejection without excessive movement.

The position of stop pins relative to the ejector plate and other components must also be dimensioned to ensure even distribution of impact forces. These dimensions prevent premature wear of both the stop pins and the surfaces they contact. Properly dimensioned stop pins are essential parts of an injection mold that contribute to the safety and longevity of the ejection system.

In three-plate molds and 2.5-plate molds, the dimensions of the distance-limiting parting mechanisms must be precisely specified. These mechanisms control the sequence and extent of mold opening, making them critical parts of an injection mold with complex parting lines.

Dimensions include the length of guide pins, the position and length of stop pins or chains, and the travel distance of each plate during mold opening. The positions of these components relative to each other and to key mold features must be clearly dimensioned.

These dimensions ensure that the mold opens in the correct sequence, allowing for proper runner removal and part ejection. The length of these components must be carefully calculated to provide sufficient travel for part removal while preventing excessive movement that could cause damage. Proper dimensioning of these specialized parts of an injection mold ensures reliable operation and extends mold life by preventing unnecessary wear and stress on components.