Rotary Control Bearing Precision via Injection Molding Positioning
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Solution Overview
Problem
Existing operating devices for vehicle components, such as rotary controls, face challenges with mechanical precision and reproducibility due to manufacturing tolerances in injection-molded plastic parts, leading to issues with haptics, acoustics, and friction-related problems.
Innovation Solution
The method involves producing a rotary operating element and a bearing unit using injection-molded plastic parts with specific die separation planes, where one surface is defined by die-dependent and the other by die-independent mold separations, ensuring precise positioning and reduced tolerance dependence, and incorporating a flange and second bearing element for enhanced mechanical coupling and locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If injection molding dies with die separation planes are used to produce rotary operating element and bearing unit, then manufacturing cost is reduced and production is simplified, but manufacturing precision and mechanical reproducibility deteriorate due to tolerances and contact precision issues
Solution Approach 1:
The invention divides the bearing assembly into two separate injection-molded components: the rotary operating element and the bearing unit. By segmenting the design, each component can be manufactured independently with standard injection molding processes, avoiding the need for complex multi-component molds while ensuring precise radial positioning through dedicated bearing surfaces.
Solution Approach 2:
The invention transitions from axial positioning (along the injection direction) to radial positioning (perpendicular to the injection direction) for the bearing contact surfaces. The bearing surface of the bearing unit and the contact surface of the rotary operating element are both positioned radially, allowing precise concentric alignment independent of die separation plane tolerances.
2Ease of operation
If die-independent mold separations are used, then ease of mold operation is improved, but position precision of contact surfaces deteriorates due to tolerance accumulation
Solution Approach 1:
The invention incorporates preliminary positioning features directly into the injection-molded components: a radially extending flange on the rotary operating element and a corresponding radially extending bearing surface on the bearing unit. These features are formed during the injection molding process itself, establishing precise radial positions before assembly occurs, thereby compensating for any variations in die separation plane positioning.
3Productivity
If standard injection molding processes are used, then productivity is improved and manufacturing time is reduced, but mechanical precision and friction characteristics worsen due to tolerance variations
Solution Approach 1:
The invention changes the critical positioning parameter from axial (along the injection direction, subject to die separation tolerances) to radial (perpendicular to injection direction). The bearing surface and contact surface are both positioned radially, allowing standard injection molding processes to produce components with consistent radial dimensions and minimal friction, thereby maintaining high productivity while improving bearing reliability.
Data Source
AI summary
The operating device, in particular for a vehicle component, is provided with a rotary operating element (18), which can be rotated about a rotation axis (20) and is formed as a plastic injection-molded part, which is produced in a molding die (48) having a die separation plane (46), and with a bearing unit (12), on which the rotary operating element (18) is mounted such that it can rotate about the rotation axis (20). The bearing unit (12) has a first bearing element (14), which is formed as a plastic injection-molded part, which is produced in a molding die (28) having a die separation plane (34). The first bearing element (14) has a bearing surface (26), which extends in a radial plane to the rotation axis (20) and concentrically to same, and the rotary operating element (18) has a contact surface (36), which bears against the bearing surface (26) and likewise extends in a radial plane to the rotation axis (20) and concentrically to same. Either the bearing surface (26) of the first bearing element (14) or the contact surface (36) of the rotary operating element (18) is arranged outside the die separation plane (34; 46) of the injection-molding die (28; 48) for said relevant element (14; 18), and the other of the two surfaces (26; 36) is arranged in the die separation plane (34; 46) of the injection-molding die (28; 48) of said relevant element (14; 18).