Automatic press-fit assembly of small precision interference fitting parts: armature of electro-hydraulic servo valve

Abstract

Purpose The purpose of this paper is to design an automatic press-fit instrument to realize precision assembly and connection quality assessment of a small interference fitting parts, armature. Design/methodology/approach In this paper, an automatic press-fit instrument was developed for the technical problems of reliable clamping and positioning of the armature, automatic measurement and adjustment of the attitude and evaluation of the connection quality. To compensate for the installation error of the equipment, corresponding calibration method was proposed for each module of the instrument. Assembly strategies of axial displacement and perpendicularity were also proposed to ensure the assembly accuracy. A theoretical model was built to calculate the resistant force generated by the non-contact regions and then combined with the thick-walled cylinder theory to predict the press-fit curve. Findings The calibration method and assembly strategy proposed in this paper enable the press-fit instrument to achieve good alignment and assembly accuracy. A reasonable range of press-fit curve obtained from theoretical model can achieve the connection quality assessment. Practical implications This instrument has been used in an armature assembly project. The practical results show that this instrument can assemble the armature components with complex structures automatically, accurately, in high-efficiency and in high quality. Originality/value This paper provides a technical method to improve the assembly quality of small precision interference fitting parts and provides certain methodological guidelines for precision peg-in-hole assembly.

Classification and Recognition of Operators’ Mental Load Under Repetitive High-precision Tasks Based on BP Neural Network

“…Before the comprehensive evaluation of the mental load of operators, it was necessary to determine the primary weight model of the mental load evaluation, as shown in Equation (1).…”

“…With highly mechanized and automated manufacturing workshops of today, although modern equipment can complete the majority of manual operations, numerous repetitive and high-precision manual assembly operations, persist, including precision assembly of armature parts [1] and precision parts assembly with small tolerance range [2]. While the automated machinery requires operators to maintain high attention and invest significant cognitive resources; it also requires them to possess better finger control ability to ensure precise pickup, movement, and manipulation of objects from a place [3,4], thereby resulting in a significant upsurge in the mental and physical load of operators during the task.…”

Connection force measurement of precision small interference components using ultrasound

“…However, since the TCT ignores the influence of the non-contact regions, the analytical models constructed based on TCT have prediction errors. 9 To overcome this problem, Wang et al 10,11 proposed a deformation resistance model and combined it with TCT to obtain a press-fit curve model considering the influence of the non-contact regions. However, the connection strength not only depends on the material, dimension, and interference amount of the mating members but also the friction coefficient and form error.…”

Press-fit process fault diagnosis using 1DCNN-LSTM method

“…Press-fit joining method has been widely used in fully automated assembly lines, and its principle has attracted the attention of many researchers. It is common practice to use the thin wall model to calculate the joining force generated by the mating parts (Wang et al , 2019). Generally, fitting quality depends on various parameters such as the amount of overlaps, material property, physical dimension, geometrical design and friction coefficient of contacting surfaces (Seifi and Abbasi, 2015).…”