In injection mold design, slide system is a crucial mechanism for handling internal and external undercut structures of product. It not only affects smooth demolding of product but also directly relates to mold's lifespan and quality of finished product. Mastering design and application of slide system is a mandatory course for every mold designer.

 

I. What is a Slide? Why is it so Important?
A slide, commonly referred to as a slider, is primarily used to form internal and external undercut structures of product. Its core function is to facilitate smooth demolding by lateral movement during mold opening, preventing demolding difficulties or product damage caused by undercuts.
Design Key Points:
Slide steel is usually not same material as core mold; if same material is required, nitriding treatment is necessary.
Slide system generally consists of five major modules: power part, locking part, positioning part, guiding part, and forming part.
II. 7 Details Not to Be Overlooked in Slide Design
Depth of retaining block recess should be greater than 1/3 of retaining block height.
Angle of angled guide pin is usually 10°, 15°, 20°, or 25°, and slide angle is usually 2° larger than angled guide pin angle.
Slide stroke needs to be 2-5mm more than actual required stroke to ensure safe demolding.
When slide width exceeds 250mm, it is recommended to add guide strips at the bottom; when it exceeds 100mm, it is recommended to use two angled guide pins.
M6, M8, and M10 screws are commonly used for retaining block, and size should match slide dimensions.
Slide retaining plate dimensions: 5*5 is commonly used for small slides, and 8*8 is commonly used for large slides.
When angled guide pin is too long (exceeding 180mm), consider using a hydraulic cylinder for propulsion to ensure stable movement.
III. Common Slide Types and Application Scenarios

IV. "Small Parts, Big Role" in Slides
Locking Block: Used for slide locking, available in reverse and common forms. When designing, locking height should be greater than 2/3 of slide height.
Spring Positioning: Suitable for upward-facing slides, slides with thin inserts, or those with ejector pins at the bottom, preventing slide from falling due to its own weight.
Slide Latch/Slide Lock: Used for slide positioning; appropriate model should be selected based on slide weight.
Safety Pin and Pre-reset Mechanism: Must be installed when there are ejector pins below slide to prevent damage to mold during mold closing.
V. Slide Insert and Parting Line Design Specifications
Slide inserts should preferably use standard hardened inserts, avoiding irregular structures that cause processing difficulties.
Connection method of insert can be selected according to size of core: integral type, screw fixing, or clamping plate fixing.
Slide parting line (positioning structure) is recommended to be made separately for each molding cavity to improve positioning accuracy.
VI. Calculation Formulas and Verification Points (Brief Version)
Core Pulling Force: Related to plastic shrinkage rate, clamping length, and friction coefficient.
Guide Pin Diameter: Needs to be calculated and verified based on core pulling force, inclination angle, and length.
Puller Block Cross-sectional Dimensions: Bending strength verification is required to ensure stability of mechanism.
VII. Spring Selection and Installation
Yellow springs (light load) are the most commonly used, followed by blue springs.
Spring must be pre-compressed by 10%~15% of its original length. For upward-facing slides, it is recommended to add a spring to prevent falling. Installation method can be divided into built-in and external, depending on available space.

 

Design of guiding system tests both theoretical foundation and practical experience of designer. Only by rationally selecting type of guiding system, accurately calculating motion parameters, and rigorously verifying strength of mechanism can a stable, efficient, and long-lasting mold system be created.