Dynamic performance improvement like less vibration, smooth motor torque requirement, etc. of a carpet scrapping machine to enhance productivity and quality of Indian hand knotted carpets is presented. A complete dynamic analysis is carried out, along with optimum balancing of shaking force and shaking moment of the machine. To do this, its inertia properties are re presented by dynamically equivalent systems, referred as equimomental systems, of point-masses to identify the design variables, and formulate the associated constraints. Mass redistribution and counterweights are suggested methods to improve dynamic performances of existing carpet scrapping machine.


Key words: Carpet Scrapping machine, Dynamic performances, Optimization, Shaking force, Shaking moment.


1 Introduction


Carpet weaving is facing a tough competition from other exporting countries of Asia-Pacific region due to market liberalization (1). A project (1, 2) with the aims to improve processes, tools and machines involved in the manufacturing of carpets was initiated by IIT Delhi in 2000. In the project, optimisation of a metallic loom (3) was carried out for its reduced weight and cost. A way to balance any mechanism is to trade-off between all the competing dynamic quantities (4-10). Since shaking force, shaking moment, input-torque, etc., depend on the mass and inertias of each link, and its mass centre locations (8), it is required to optimally distribute the link masses for dynamic balancing. A convenient way to represent the inertia properties of the links is treating them as dynamically equivalent systems of point masses referred to as equimomental system (11). Using the concept of equimomental system, Sherwood & Hockey (8) presented optimization of mass distribution in mechanisms. Using the two point-mass models, Wiederrich & Roth (9) presented momentum balancing of four-bar linkages. Optimum balancing of combined shaking force, shaking moment, and torque fluctuations in linkages was later reported in Lee & Cheng (10), where a two point-mass model was used. In this paper, concept of equimomental system is used to balance the carpet scrapping machine in order to minimize shaking force and shaking moment so that vibrations and fluctuation in driving torque are reduced. Two methods are presented; the first is for the design of new scrapping machine using mass redistribution moving links and the second for reducing the unbalance of an existing one using counterweights. The methodology is quite general and not restricted only to singleloop four-bar linkage as reported in Refs (9, 10, 13). The dynamic analysis presented in Ref (13) is extended in this paper for Carpet scarping mechanism which is a multiloop mechanism.

 

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About the Authors


The authors are associated with Department of Mechanical Engineering, MLV Textile and Engineering College, Bhilwara and IIT Delhi, New Delhi, India, respectively.