Research on a Novel Method for Measuring Volumetric Error of Coordinate Measuring Machine
CMM (Coordinate Measuring Machine) is used as an accurate measuring instrument in manufacturing and design of products. High accurate CMM is required by the development of super-finish, micro-machinery, micro-electronic mechanical systems (MEMS). The precision of CMM is influenced by its volumetric error and dynamic error. The volumetric error is the major component during slowly probing, but the dynamic error is not omitted during fast probing. Compensating the volumetric error is an effective approach to improve the precision of CMM. The volumetric error in the working space of CMM must be measured and the error model must be set up before compensating. In this paper, a novel method to measure 5 volumetric errors of a guide way at the same time by 3-beam laser interferometer is proposed. The error compensating model is validated by experiment. The method can also be used to measure the dynamical error of CMM and CNC machine in real-time. The research can be referred to design the super higher accurate CMM and the accurate CNC machine.
A New Method of the CMM Probe Radius Compensation
The probe radius compensated is necessary when we measure by the CMM.Based on analyses the existing methods of the probe radius compensation,a new algorithm named "4-point build a sphere" is proposed.The theory of the algorithm is expounded,at the same time,the way of gathering data and its operation speed are offered.And then,the precision of the algorithm is analyzed by computer simulation and how to improve the precision is introduced farther.And it's showed that the algorithm can satisfy a majority of measure and has application value.Finally,the algorithm is verified by an instance again.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.