Injection Unit Axial Vibration Control
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Solution Overview
Problem
Injection molding machines experience failures due to axial vibration of the screw with respect to the drive shaft caused by clearance in the coupling, leading to abnormal wear or deformation.
Innovation Solution
An injection unit design featuring a coaxial screw shaft and spline shaft with a fitting groove, a receiving member, a pushing member, and a pressing ring that fastens the spline shaft axially, eliminating axial clearance and vibration by forming gaps between the coupling and pressing ring, and using a ring-shaped pushing member and integral pressing ring to secure the spline shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a coupling connects the drive shaft and screw, then the screw can be driven to rotate and move, but axial clearance in the coupling causes vibration and abnormal wear
Solution Approach 1:
A spline shaft is introduced as an intermediary component between the drive shaft and screw. The spline shaft features a fitting groove that receives a receiving member, while a pushing member presses against the spline shaft from the opposite side. This intermediary structure eliminates axial clearance and prevents vibration without compromising the driving function.
Solution Approach 2:
The coupling structure is segmented into multiple functional components: the drive shaft, spline shaft, receiving member, and pushing member. This segmentation allows each component to perform its specific function - the receiving member stabilizes one end of the spline shaft while the pushing member prevents axial movement from the other end, collectively eliminating clearance issues.
2Reliability
If a rigid coupling structure is used to eliminate axial clearance, then vibration is reduced, but the structure becomes more complex
Solution Approach 1:
The coupling structure employs dynamic elements - the receiving member and pushing member can move axially within their respective spaces to accommodate thermal expansion and manufacturing tolerances, while still maintaining continuous contact to eliminate clearance. This dynamic design achieves stability without requiring an overly rigid and complex fixed structure.
Solution Approach 2:
The spline shaft structure serves multiple functions simultaneously: it transmits rotational motion, provides axial positioning through the fitting groove, and accommodates the receiving and pushing members that eliminate clearance. This multi-functional design reduces the need for additional separate components, simplifying the overall structure while maintaining reliability.
Data Source
Figure 1~2
AI summary
An injection unit capable of reducing failures is provided. The injection unit includes a screw (42) in which a screw shaft (421) and a spline shaft (422) are formed to be coaxial with each other and a fitting groove (423) is formed between the screw shaft (421) and the spline shaft (422), a receiving member (47) configured to receive an end portion opposite to the fitting groove (423) in both end portions of the spline shaft (422), a pushing member (53) configured to press the spline shaft (422) from a side opposite to the receiving member (47), and a pressing ring (54) configured to fasten the spline shaft (422) in an axial direction using the pushing member (53) and the receiving member (47) by pressing the pushing member (53) toward the receiving member (47). The pushing member (53) is formed in a ring shape, and is divided into a plurality of ring pieces (531, 532) in a circumferential direction, each ring piece is fitted into the fitting groove (423), and the pressing ring (54) is integrally formed over the entire circumference, and presses each ring piece to a side surface of the spline shaft (422) side in both side surfaces of the fitting groove (423).