Folding Core Diameter Changes for Ball Bearing Groove Quality
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Solution Overview
Problem
The production of ball bearing rings with running grooves in plastic injection molding is hindered by protruding separating markings caused by folding cores, which can impair the movement of balls in the bearing.
Innovation Solution
A device and method that modify the folding core design by incorporating diameter changes, such as raised wedges or notches on mold segments, and radially displaceable cylinders to prevent protruding separating marks, ensuring smooth and even material accumulation and shaping, and using a rotatable carrier profile with a stepper motor to achieve a solid cross-section without impairing ball movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If folding cores with segments are used to produce ball bearing rings with running grooves, then undercuts can be formed in the injection molding process, but protruding separating markings are created at the abutting edges of segments that impair ball movement
Solution Approach 1:
The patent applies local quality by introducing diameter changes (raised wedges or notches) at specific locations on the dividing edges of mold segments. These localized modifications create inner curvatures or material accumulation zones that prevent separating markings from protruding into the running groove, while maintaining the overall folding core structure needed for undercut formation.
Solution Approach 2:
The patent implements preliminary action by pre-forming diameter changes (raised wedges or notches) on the mold segments before injection molding. These pre-formed features ensure that material accumulates in controlled locations during molding, creating smooth transitions that prevent protruding separating markings before the defect can occur.
2Ease of operation
If folding core segments are collapsed inwards during axial movement for demolding, then ball bearing rings can be removed from the mold, but separating markings are formed at the abutting edges
Solution Approach 1:
The patent applies local quality by introducing diameter changes (raised wedges or notches) at specific locations on the dividing edges of mold segments. These localized modifications create inner curvatures or material accumulation zones that prevent separating markings from protruding into the running groove, while maintaining the overall folding core structure needed for undercut formation.
Solution Approach 2:
The patent converts the harmful effect of separating markings into a beneficial feature by using the dividing edges to create material accumulation zones. The notches or raised wedges cause material to accumulate at the dividing edges, forming smooth transitions and reinforcements that actually improve the running groove surface quality and prevent ball movement impairment.
3Manufacturing precision
If material is accumulated smoothly and evenly by rotating the carrier profile, then separating markings can be formed into reinforcements, but additional process steps and device complexity are required
Solution Approach 1:
The patent applies dynamics by making the carrier profile rotatable about its axis using a stepper motor. This dynamic capability allows the mold segments to be rotated to specific angular positions after injection molding, enabling precise material accumulation and smoothing operations that transform separating markings into beneficial reinforcements.
Solution Approach 2:
The patent implements parameter changes by rotating the carrier profile to specific angular positions (e.g., 15 degrees) after injection molding. This parameter change allows the molding compound in the grooves to be pressed against the cylinder and leveled, creating hardened zones and smooth running groove surfaces with reinforcements.
4Manufacturing precision
If radially displaceable cylinders are used to reduce material thickness at dividing edges, then wall can be moved for smooth shaping, but additional mold components and complexity are introduced
Solution Approach 1:
The patent applies local quality by introducing diameter changes (raised wedges or notches) at specific locations on the dividing edges of mold segments. These localized modifications create inner curvatures or material accumulation zones that prevent separating markings from protruding into the running groove, while maintaining the overall folding core structure needed for undercut formation.
Solution Approach 2:
The patent uses radially displaceable cylinders as intermediary elements between the folding core segments and the injection mold. These cylinders with indentations corresponding to the arched sections of segments act as mediators that shape the material at the dividing edges, creating smooth transitions and preventing protruding separating markings.
Data Source
AI summary
The device has running grooves formed in a plastic injection molding process and comprising an injection mold (1) with a folding core (2) that is formed by mold segments (3). The mold segments are axially arranged on a carrier profile, and include outwardly curved sections to form the running grooves. The mold segments include diameter deviation on division edges (31) after the outwardly curved sections. The diameter deviation is arranged in form of a raised wedge on the division edges of the mold segments. The carrier profile is connected with a stepping motor in a rotatable manner. An independent claim is also included for a method for manufacturing an outer ring of a radial ball bearing.