RESEARCH OF A LATERAL REAMER BIT FOR DIGGING PLANTING HOLE IN ROCKY ABANDONED MINE AREA

In the abandoned mine area with Karst landform in China, soils are few and thin but rocks are common, traditional planting hole diggers are unequal to work in rocks for vegetation restoration. A reamer bit with variable lateral drilling radius was designed based on the PDC (polycrystalline diamond compact) bit technology and metamorphic mechanism. Two lateral camber blades with PDC teeth were installed inside the bit body, a screw mechanism was employed as the actuation and a spatial double triangle mechanism was taken for the transmission. The curve of the camber blade was specially defined thus the reaming load was decentralized to 85.7% teeth on the blade. The kinematics of the lateral reamer bit was analysed, the mapping models from the actuation to the reaming radius and speed were established. Concrete samples were reamed indoors from 240mm to 407mm in diameter, the reaming cutting load and time length were measured and analysed. The lateral reamer bit was approved with the experiment results, this study provided equipment support for digging the planting hole in rocky abandoned mine areas and also expanded the PDC bit application.

A Multiscale Accuracy Degradation Prediction Method of Planetary Roller Screw Mechanism Based on Fractal Theory Considering Thread Surface Roughness

The wear problems are vital to the planetary roller screw mechanism (PRSM) as they have a great influence on transmission accuracy, working efficiency, and service life. However, the wear characteristics of the PRSM have been rarely investigated in the past. In this paper, a multiscale adhesive wear model is established by incorporating the effective wear coefficient and considering the thread surface roughness. The variation of surface roughness is characterized by the two-dimension Majumdar–Bhushan (MB) function. The multi-asperity contact regimes are used to estimate microcontact mechanics of the rough interface. Moreover, the influences of surface roughness, material properties, and working conditions on the wear depth and precision loss of the PRSM are studied in detail. The results reveal that as the surface roughness increases, the total actual contact area, wear depth, and precision loss rate rise. In addition, the adhesive wear increases with the growth of the axial load, and decreases with the increase in the material hardness and material elastic modulus ratio to a certain extent. The investigation opens up a theoretical methodology to predict the wear volume and precision loss with regard to thread surface roughness, which lays the foundation for the design, manufacturing, and application of the PRSM.

Optimization of the drive mechanism with lead screw using Isight software

The ball screws are characterized with better positioning accuracy and higher efficiency and load ratings than the same size lead screw, but still cannot fully replace their functionality mostly due to the self-locking. Leads screws are recommended especially for such applications as grippers, lifters, presses and vertical positioning drives. By proper selection of the lead screw geometrical features and application of the modern materials, it is possible to obtain much more advantageous parameters of the drive system. In this paper, the methodology of optimization of the drive mechanism with lead screw using Isight software is presented. The performed sensitivity analysis allowed not only to find the influence of various constructional features such as: size of the thread, length of the screw and material properties, on the maximum load capacity of the drive mechanism and its inertia, but also determine its scale impact. The obtained results can improve the design process of lead screw mechanism.

A review of wear resistance materials used in power-screw mechanism for aerospace applications

In today’s industrial requirement, good wear resistant materials with the same or better mechanical properties are the need of the hour. In the present paper, an actuator that is used to lift the load is under study. It uses a linear actuation mechanism involving a screw-like motion to lift the loads. It employs a stainless steel of high quality. Since there are various types of wearing involved in the system, choice of the materials becomes the prime factor for determining the maintenance cost and the cycle life of the actuator. There are many research advances made in this field which provides us with the best type of material for its particular type of job. The present paper discusses the materials that could be substituted in place of the existing material choice i.e., in place of AMS5659 and aluminium-bronze. The two materials stated above are known for its superior wear handling and excellent mechanical properties.

Design and Fabrication of Wheelchair into Foldable Bed

In this paper lead screw mechanism is used to convert a wheelchair into bed and vice versa. When lead screw mechanism is operated, the foot rest which is downward goes till the level of seat of wheelchair and simultaneously the back support goes down to the same level making, its stretcher and vice versa, when it is converted into wheelchair from stretcher. Below the seat, a defecation system has been provided which is detachable and is operated by sliding mechanism. It is designed and fabricated in such a way that it can be used in hospitals as well as for personal use at home. Below the seat, a defecation system has been provided which is detachable and is operated by sliding mechanism. Also, obstacle avoiding sensor i.e., ultrasonic sensor is used to know if any obstacle will come in front of wheelchair, siren bell will ring. Keywords: Fabrication, Hospital, Mobility Aid, Lead Screw, Design, Wiper Motor, Wheelchair, Battery