Optimisation of a Spindle Body Considering the Vibration Prediction of the Entire Milling Centre Construction

Static and dynamic properties of machine tools have a decisive influence on their accuracy. In case of HSM machine tools, the phenomena associated with them are additionally strengthened by high machining parameters. In order to predict a machine tool behaviour at the design stage, it is necessary to use numerical methods to simulate for its simulation. Thanks to the use of this type of software, it is possible to perform the next step, i.e. the optimisation of the structure. In case of machine tools, due to the multiplicity of factors affecting its accuracy, this should be a multicriterial optimisation. This article presents the results of a vertical milling centre spindle body optimisation using the Finite Element Method. The results of static stiffness and vibration frequency analysis for three bodies (i.e. the body of the form and dimensions proposed by the constructor, the body after parametric optimisation and the body after the form and parametric optimisation including use of different materials) were compared. The optimisation tools available in the ANSYS system were used for the simulation. The calculations were preceded by experimental research and modifications of dynamic parameters performed on their basis using the author's methodology to determine the behaviour of a partially existing structure for different masses of the body being optimised.

UCH-L1 inhibitor LDN-57444 hampers mouse oocyte maturation by regulating oxidative stress and mitochondrial function and reducing ERK1/2 expression

Oocyte maturation is a prerequisite for successful fertilization and embryo development. Incomplete oocyte maturation can result in infertility. Ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) has been found to be implicated in oocyte maturation and embryo development. However, the cellular and molecular mechanisms of UCH-L1 underlying oocyte maturation have not been fully elucidated. In the present study, we observed that the introduction of UCH-L1 inhibitor LDN-57444 suppressed first polar body extrusion during mouse oocyte maturation. The inhibition of UCH-L1 by LDN-57444 led to the notable increase in reactive oxygen species (ROS) level, conspicuous reduction in glutathione (GSH) content and mitochondrial membrane potential (MMP), and blockade of spindle body formation. As a conclusion, UCH-L1 inhibitor LDN-57444 suppressed mouse oocyte maturation by improving oxidative stress, attenuating mitochondrial function, curbing spindle body formation and down-regulating extracellular signal-related kinases (ERK1/2) expression, providing a deep insight into the cellular and molecular basis of UCH-L1 during mouse oocyte maturation.

Assessment of High Speed Spindle Accuracies

The spindle error contributes to 25 percent of the error sources of the work piece in- accuracies. The 70 percent of the spindle errors are due to thermal errors that occurs in the spindle. The heat generation in high-speed built-in motorized spindle is of important concern in high speed machining. It is necessary to predict the heat generation in spindle body virtually so as to judge machine capability. The thermal prediction will also help in taking precautions to avoid inaccurate parts being produced as well to avoid the chances of bearing seizure leading to catastrophic failure of spindle. In this paper the thermal behavior of high-speed motorized spindle is investigated through three dimensional analysis and experimentation validation is given for the same.

Mapping load-bearing in the mammalian spindle reveals local kinetochore-fiber anchorage that provides mechanical isolation and redundancy

SummaryActive forces generated at kinetochores move chromosomes, and the dynamic spindle must robustly anchor kinetochore-fibers (k-fibers) to bear this load. We know that the mammalian spindle body can bear the load of chromosome movement far from poles, but do not know where and how – physically and molecularly – this load is distributed across the spindle. In part, this is because perturbing and reading out spindle mechanics in live cells is difficult. Yet, answering this question is key to understanding how the spindle generates and responds to force, and performs its diverse mechanical functions. Here, we map load-bearing across the mammalian spindle in space-time, and dissect local anchorage mechanics and mechanism. To do so, we laser ablate single k-fibers at different spindle locations, and in different molecular backgrounds, and quantify at high time resolution the immediate relaxation of chromosomes, k-fibers, and microtubule speckles. We find that load redistribution is locally confined in all directions: along the first 3-4 μm from kinetochores, scaling with k-fiber length, and laterally within ~2 μm of k-fiber sides, without neighboring k-fibers sharing load. A phenomenological model constrains the mechanistic underpinnings of these data: it suggests that dense, transient crosslinks to the spindle along k-fibers bear the load of chromosome movement, but that these connections do not limit the timescale of spindle reorganization. The microtubule crosslinker NuMA is needed for the local load-bearing observed, while Eg5 and PRC1 are not, suggesting specialization in mechanical function and a novel function for NuMA throughout the spindle body. Together, the data and model suggest that widespread NuMA-mediated crosslinks locally bear load, providing mechanical isolation and redundancy while allowing spindle fluidity. These features are well-suited to support robust chromosome segregation.

Vibration Response Analysis on Spindle System of Milling Machine

The dynamic characteristics and dynamics parameters of rolling bearings is very important to dynamics and vibration response of rotate machine such as rotor systems, gear systems and Spindle systems. The frequencies of rotate machine are affected by dynamics parameters of rolling bearings at different places. The purpose in the work presented is to research a new approach and multibody model of Spindle systems with equivalent dynamics parameters of rolling bearings. The flexible Spindle body has been constructed by the fixed interface component mode method. The four different models of rolling bearings for Spindle systems have been developed using equivalent spring and damper elements. The experiments of Spindle body and Spindle system have been carried out. Experimental modal frequencies have been got by impulse vibration test and sweep frequency vibration test. The frequencies and vibration response of Spindle systems have been calculated by adjusting equivalent spring and damper elements to minimizing errors between the calculated and experiment frequencies. The results show the errors of frequencies of linear equal and unequal spring and damper models are large except the first frequency. However, the errors of nonlinear equal and unequal spring and damper models are small. The predicted frequencies of nonlinear unequal spring and damper model are the most accurate and agree well with the experiment results. The presented method can be applied to calculate the nonlinear equivalent stiffness parameters accurately for rolling bearings in multibody systems.

Mechanically cut mitotic spindles: clean cuts and stable microtubules

We have discovered an easy way to cut through the mitotic spindle at any desired place. Spindles of demembranated cricket or grasshopper spermatocytes were severed with a microneedle between the chromosomes and one pole, and the cut-off polar piece was swept away. Spindle structure and microtubule dynamics in cut spindles were studied by anti-tubulin immunostaining and electron microscopy. The cut is clean: all microtubules are severed and only a few extend beyond the others. This provides the basis for a clear test of whether traction fibers pull chromosomes to the pole in anaphase, because the putative traction fiber is cleanly severed. Cutting creates new plus ends on microtubules in the cut-off polar piece and new minus ends on microtubules in the main spindle body. The microtubules with new plus ends are unstable, as expected from the dynamic instability of microtubules. However, the microtubules with new minus ends are as stable as uncut microtubules in the same spindle. Our mechanical method of cutting microtubules very likely creates native, reactive ends, and therefore the surprising stability of new minus ends is genuinely interesting, not an artifact of cutting.