Spindle Axis Research Articles

Long-range repulsion between chromosomes in mammalian oocyte spindles.

During eukaryotic cell division, a microtubule-based structure called the spindle exerts forces on chromosomes. The best-studied spindle forces, including those responsible for the separation of sister chromatids, are directed parallel to the spindle's long axis. By contrast, little is known about forces perpendicular to the spindle axis, which determine the metaphase plate configuration and thus the location of chromosomes in the subsequent nucleus. Using live-cell microscopy, we find that metaphase chromosomes are spatially anti-correlated in mouse oocyte spindles, evidence of previously unknown long-range forces acting perpendicular to the spindle axis. We explain this observation by showing that the spindle's microtubule network behaves as a nematic liquid crystal and that deformation of the nematic field around embedded chromosomes causes long-range repulsion between them.

Optimizing apple orchard management: Investigating the impact of planting density, training systems and fertigation levels on tree growth, yield and fruit quality

An experiment was conducted to investigate the comprehensive influence of planting density, training system and fertigation level on the performance of 'Jeromine'/M.9 apple orchards at Dr. YS Parmar University of Horticulture and Forestry, Solan (India) in two consecutive years. Experiment encompasses 12 treatment combinations replicated thrice within a factorial experiment. The treatments included three planting densities (4000, 3200 and 2666 trees ha−1), two training systems (Tall Spindle and Vertical Axis), and two levels of fertigation (100 % and 75 % recommended dose of NPK). The results indicated that lowest planting density of 2666 trees ha−1 produced highest yield per tree accompanied with superior fruit quality. Trees planted at a planting density of 2666 trees ha−1 and trained to Tall Spindle training system notably restrained tree growth, with the latter contributing to higher yields and superior quality fruit. Similarly, 100 % recommended dose of NPK fertigation resulted in significantly higher yields and enhanced fruit quality. Remarkably, the three-way interaction analysis revealed that treatment combination of 2666 trees ha−1 planting density, Tall Spindle training system and 100 % recommended dose of NPK fertigation produced the highest yield of 13.6 kg tree−1, along with superior quality fruits. The study emphasized that increasing planting density decreased yield per tree while concurrently increasing yield per hectare. The most productive combination yielding 42.1 t ha−1, involved 4000 trees ha−1 with Tall Spindle training system and 100 % recommended dose of NPK fertigation. These findings provide valuable insights into optimizing apple orchard management strategies to achieve the delicate balance between tree growth, yield and fruit quality, assisting growers in making informed decisions for improved productivity and fruit quality, thereby contributing to the overall profitability of apple cultivation.

STATIC DEFORMATION ANALYSIS OF A MOBILE CUTTING MACHINE

A study of the special requirements and criteria to portable cutting machines was carried out. Based on the existing approaches to the deformation analysis of spindle units the calculation schemes and mathematical model for the static analysis of the problem were developed. The implemented approach makes use of the Timoshenko beam model. The resulting differential equation of the bent beam axis is solved by the method of initial parameters in the matrix form. The nonlinear equation system for the chosen calculation scheme is formed automatically and is solved iteratively. A special feature of the proposed approach is the nonlinear relation between the stiffness of the bearings and the forces acting upon them. As a model application example, the results of the static deformation analysis of portable boring machine XT7809-0524 are presented. An estimate of the bending stiffness and the corresponding distributions of bending deflections and rotations were obtained for several calculation schemes of the machine. The obtained solution quantities are presented in form of graphs along the spindle axis. It has been found, that the calculated equivalent stiffness of XT7809-0524 machine spindle shaft is lower than the normative value used in the industry. A strength assessment of the spindle shaft was also made and the distributions of internal forces and moments acting on shaft cross sections were obtained. It has been concluded, that under work loads the maximum stress in the shaft is acceptable to provide for the required factor of safety.

Spindle Thermal Evaluation Thermal on Realiability Test of Numerical Controlled Lathe

In the process of designing and manufacturing of CNC machine tools, reliability testing is needed to determine the reliability of the main component design and sub assembly. The precision of machine tools is greatly influenced by the temperature generated when the machine tool operates, both which arise from friction and overload.
 Evaluation of spindle axis errors caused by thermal distortion of the spindle bearing is based on ISO 230-3: 2007, ISO 10791-10: 2001 and ISO 13041-8: 2004. Temperature measurement at several measuring points on the spindle head to determine the increase in temperature on the main spindle bearing when getting more load or cutting process.
 The evaluation results showed that spindle erroneous error with a temperature increase in the spindle head was 16.3 oC by 13 um with no loading, while with loading 71.9 um with a temperature increase of 18.0 oC.

Cleavage furrow positioning in dividing Dictyostelium cells.

Accurate placement of the cleavage furrow is crucial for successful cell division. Recent advancements have revealed that diverse mechanisms have evolved across different branches of the phylogenetic tree. Here, we employed Dictyostelium cells to validate previous models. We observed that during metaphase and early anaphase, mitotic spindles exhibited random rotary movements which ceased when the spindle elongated by approximately 7 μm. At this point, astral microtubules reached the polar cell cortex and fixed the spindle axis, causing cells to elongate by extending polar pseudopods and divide along the spindle axis. Therefore, the position of the furrow is determined when the spindle orientation is fixed. The distal ends of astral microtubules stimulate the extension of pseudopods at the polar cortex. One signal for pseudopod extension may be phosphatidylinositol trisphosphate in the cell membrane, but there appears to be another unknown signal. At the onset of polar pseudopod extension, cortical flow began from both poles toward the equator. We suggest that polar stimulation by astral microtubules determines the furrow position, induces polar pseudopod extension and cortical flow, and accumulates the elements necessary for the construction of the contractile ring.

A novel calibration method for angular misalignment in independently controlled fast tool servo-based diamond turning

With significant technological progress in optics fields, such as VR and 3D sensing technologies, the demand for optical components with complex shapes (e.g., freeform surfaces) has expanded significantly in recent years. Ultra-precision diamond turning is one of the common manufacturing methods used for freeform optics. There are two tool-motion mechanisms for freeform diamond turning: slow tool servo (STS), which moves the entire tool rest, and fast tool servo (FTS), which only drives the diamond tool. In particular, high-frequency and long-stroke FTS units driven by a separate control system from the machine tool controller have recently been developed as a new trend in FTS-based diamond turning. However, this type of independent FTS control system causes a time delay between the machine tool instruction and the FTS tool motion. Even a millisecond-scale time delay can cause a considerable angular misalignment owing to the high rotation rate of the spindle, resulting in a micron-scale form error on the workpiece surface. In this paper, a novel method for precisely measuring the time delay from the machined workpiece surface and compensating for the misalignment based on the measured time delay was proposed. To measure the time delay, spherical dimples were machined on the workpiece surface by using STS and FTS. Subsequently, the angular misalignment and time delay were obtained by comparing the measured surface profiles at specific positions of the spherical dimples. Thus, the time delay can be measured with microsecond-scale accuracy. Based on the measured time delay, the shifted tool position along the spindle axis by the time delay was compensated to the ideal tool position by considering the cutting velocity. Consequently, the angular misalignment was completely eliminated, and submicron-level form accuracy was achieved. This calibration method of angular misalignment for an independent FTS unit is expected to significantly improve the accuracy of ultra-precision machining of freeform optics.

Optimized Design of Source Energy for Manufacturing Machine by Digital Numerical Control

The quality of the power supplied to the machining center is a key factor in determining the accuracy of the machine’s operation. The precision of the machining center is to ensure that the spindle accuracy is less than 3 microns. This study proposes a digital numerical control system to control the quality of the power supply and control the accuracy of the spindle axis of the machining center to monitor the measurement results in real time. The computer vision system is set up according to the artificial intelligent (AI) technique to recognize human face objects and control the position of the processor respectively on each line. The online measurement system follows the digital numerical control (DNC) system applied at each processing line, measuring product dimensions, measuring conditions for setting up machining tools, and measuring machine coordinates. The system operates fully automatically, eliminating dependence on operator skill, and facilitating operation in control of machining conditions. Improve machining center operator satisfaction. After implementation of the improvement options, total cost down 1.740 USD per year, the monthly repair cost due to broken drill, spindle alignment decreased from $5000 to $3,300 per month. The scrap rate related to the hole size decreased from 0.47% to 0.23% (cost down $35 per month). Downtime for repair reduced from 20 hours per month to 7.5 hours per month (cost down $10 per month). Broken drill rate was reduced from 0.20% to 0.06% (cost down $100 per month).

Chromatic confocal sensor-based on-machine measurement for microstructured optical surfaces featuring a self-aligned spiral center.

Chromatic confocal sensor-based on-machine measurement is effective for identifying and compensating for form errors of the ultra-precisely machined components. In this study, an on-machine measurement system was developed for an ultra-precision diamond turning machine to generate microstructured optical surfaces, for which the sensor probe adopts a uniform spiral scanning motion. To avoid the tedious spiral center alignment, a self-alignment method was proposed without additional equipment or artefact, which identified the deviation of the optical axis to the spindle axis by matching the measured surface points and the designed surface. The feasibility of the proposed method was demonstrated by numerical simulation with full consideration of noises and system dynamics. Practically, taking a typical microstructured surface as an example, the on-machine measured points were reconstructed after calibrating the alignment deviation, which was then verified by off-machine white light interferometry measurement. Avoiding tedious operations and special artefacts may significantly simplify the on-machine measurement process, thereby greatly improving the efficiency and flexibility for the measurement.

Studi Komparasi Pengaruh Kecepatan Potong Tinggi dan Konvensional terhadap Kekasaran Permukaan dan Waktu Proses Bubut

The number of manufacturing industry growth in Indonesia is increasing over time. Based on the data obtained, the manufacturing industry in Indonesia recorded growth of 3.9% from July to August 2020. This study aims to analyze the effect of cutting speed on the surface roughness of S45C steel and to find out the production time for high speed cutting machining processes. This study used an experimental method, using a transverse/cylindrical turning method. Transverse turning is a lathe process when the cutting tool moves parallel or linear to the spindle axis. The test specimen will be machining starting with determining the independent parameters; feed (f) 0.2mm/rev, depth of cut (depth of cut) 0.1mm, length of cut (Lt) 100mm, then determine the dependent parameter by varying the speed of cut (Vc) starting from 125m/min to 625m/min. Based on the results of the test data obtained, it shows that (1) The higher the cutting speed, the lower the surface roughness value. This is caused by the process of plastic deformation and thixotropy phenomena. (2) The higher the cutting speed, the lower the cutting time. This is caused by the annealing phenomenon during the turning process.

Frictional behavior of tool-workpiece on surface quality of glow discharge polymer during micro-milling

Machining of concavities and other complex microstructures on glow discharge polymer (GDP) films is critical to its high laser power performance, especially in the inertial confinement nuclear fusion. This study mainly investigated the effect of tool-workpiece frictional mechanism on the quality of machined surface in micro-milling of GDP. A series of milling tests of micro-grooves with different spindle speeds (n) and spindle axis deflection angles (θ) were conducted using a cubic boron nitride (CBN) milling tool. The orthogonal cutting slip line model was adopted to reveal the material removal mechanism of GDP. The wear mechanism and friction coefficient of the contact area between GDP material and the CBN tool were analyzed. The chip thickness and shear stress were innovatively used to characterize the surface roughness. The regression models of milling forces, surface profiles, shear stresses and surface roughness with chip thickness were established. The tribo-performance of the CBN tool on GDP material was characterized using cutting specific energy and a friction coefficient. Research results show that θ has a significant effect on the surface quality than n. At θ of 20° and n of 30,000 rpm, the contour error of the micro-groove structure is about 0.11 μm, a reduction of 93.9% compared with at θ of 0°. Thermal softening and strain hardening are found the keys affecting surface morphology. Chip morphology such as segmental, granular, and crack chips was observed. The adhesion wear on the CBN tool surface was found critical to its machining performance.

STUDY OF THE GEAR CUTTING PROCESS BY THE RADIAL-CIRCULAR METHOD

The results of the study of the radial-circular method of gear cutting are presented. The cutting and shaping of teeth is carried out by a thin disc cutter under conditions of continuous generating, with a combination of axial feed of the cutter and its constructive radial movement due to eccentric installation on the spindle axis. The value of the eccentricity is determined by the gear module. A graph-analytical model was used to calculate the parameters of the cuts, and the cutting force and torque on the cutter axis were modeled using these data. It was found that the cutting process is characterized by significant load variations. The areas of maximum tool wear were predicted. It is shown that for under the same initial conditions, the cutting time using this method is two times less than the time of hobbing. Since a disc cutter can cut gears in a wide range of modules, this process is one of the most versatile. This method opens up great possibilities for the restoration and repair of gears and drives manufactured to standards other than those adopted in Europe.

A Study on 4-Axis Turning for Non-Axisymmetric 3D Surfaces - Creation of high-precision curved surfaces by synchronizing the spindle and rotary tool axis-

A Study on 4-Axis Turning for Non-Axisymmetric 3D Surfaces - Creation of high-precision curved surfaces by synchronizing the spindle and rotary tool axis-

Stiffness-Performance-Based Redundant Motion Planning of a Hybrid Machining Robot

Large-scale components usually have complex structures with high local stiffness, and the holes on them are required to be machined with high precision, which makes it important and challenging to study how to efficiently and precisely drill in the large-scale components. This article presents mobile hybrid machining equipment that consists of a five-axis parallel module, a 2-degree-of-freedom (DoF) robotic, arm and an automated guide vehicle (AGV) connected in series. With the ability of wide-range positioning and precise local processing, it has potential advantages in the drilling processing of large-scale components. Stiffness is one of the most important performances for machining equipment, and it’s highly related to the its configuration. For the discussed equipment, the stiffness is determined by the two-stage-positioning hybrid machining robot, which comprises a five-axis parallel module and a two-DoF robotic arm. The redundant motion of the hybrid machining robot makes it possible to optimize its configuration by reasonably planning redundant motion. Therefore, a redundant motion-planning method based on stiffness performance is proposed. A kinematic analysis of the five-axis parallel module, the robotic arm, and the hybrid machining robot is carried out. A hybrid robot usually consists of several subsystems, and to take the compliance of each subsystem into consideration, the stiffness-modeling method for the hybrid robot with n subsystems connected in series is proposed. The stiffness model of the hybrid machining robot is established by using this method, and the variation of the stiffness magnitude has the same trend as that obtained by using FEA software. Stiffness magnitude and isotropy indices are proposed to evaluate the robot’s stiffness performance along the axis of the spindle and in the plane perpendicular to the axis of the spindle. The redundant motion of the hybrid machining robot is planned by maximizing the stiffness magnitude along the spindle axis, with priority to the stiffness isotropy index. Finally, the drilling experiment is carried out, and the results show that the relative error of the hole diameter obtained under the optimal configuration of the hybrid machining robot is 1.63%, which is smaller than those obtained under the other two configurations for comparison with relative errors of 3.75% and 3.50%, respectively. It proves the validity of the redundant motion-planning method. The proposed stiffness-modeling method and the stiffness-performance indices are also applicable to other hybrid machining robots.

Анализ риска возникновения брака, связанного с погрешностью базирования заготовок при установке в призмы

The paper considers issues of assessing the risk of a product defect due to unacceptable errors in positioning surfaces during machining and caused by deviations in the dimensions of workpieces and sample used in setting up the device. Based on analyzing the published studies devoted to the workpiece positioning errors, the need was revealed to expand approaches to determining the risk of product defects by conducting machine experiments to simulate the contact between workpieces and device mounting elements, as well as to consider the joint quality indicators distribution in analyzing the position deviations. The task was set and an example of risk assessment is provided based on analytical calculation of the workpiece limiting positions, as well as the solid-state computer simulation of the technological system elements contact for the case of processing the tee-type part in a CNC milling operation on a machining center with the vertical spindle axis. Based on the results of solving the problem, examples of recommendations are provided for modifying the technological solution aimed at reducing the risk of product defects.

Posture optimization in robotic drilling using a deformation energy model

Robots have various advantages such as multiple degrees of freedom (DOFs), flexibility, and cost efficiency. Although robots have mostly been utilized for painting, welding, pick-and-place, and assembly tasks, robot machining has been actively introduced in many fields to maximize productivity. The main obstacle to robot machining is the poor stiffness of robots, which is lower than that of conventional machine tools. Low stiffness induces compliance errors that deteriorate machining quality. One effort to improve stiffness is tool path compensation, in which compliance errors are predicted and compensated for by utilizing a stiffness model. Another approach to solving the stiffness problem is posture optimization, in which a performance index is defined based on the stiffness model. Such a performance index evaluates stiffness according to the configuration of a robot. Using this index, one can optimize the posture of a robot to maximize stiffness during machining. In previous studies, optimization was performed for the redundant DOF in the spindle axis direction at a given position, assuming a fixed workpiece and vertical feed direction. However, workpiece placement also has to be optimized in the robot workspace to obtain the optimal machining posture. This study introduced a novel approach to posture optimization. A deformation energy model that can evaluate stiffness from an energy perspective was proposed. With the proposed method, the posture of the robot and the workpiece position can be optimized simultaneously. Global optimization was performed within the entire workspace, and simulations were conducted to verify the optimization results. Additionally, local optimization considering the working environment was performed to deal with the practical problems in real scenarios. The results of optimization were verified experimentally.

A Dual Difference Method for Identification of the Inherent Spindle Axis Parallelism Errors of Machine Tools

A Dual Difference Method for Identification of the Inherent Spindle Axis Parallelism Errors of Machine Tools

The Sister Chromatid Division of the Heteromorphic Sex Chromosomes in Silene Species and Their Transmissibility towards the Mitosis.

Young sex chromosomes possess unique and ongoing dynamics that allow us to understand processes that have an impact on their evolution and divergence. The genus Silene includes species with evolutionarily young sex chromosomes, and two species of section Melandrium, namely Silene latifolia (24, XY) and Silene dioica (24, XY), are well-established models of sex chromosome evolution, Y chromosome degeneration, and sex determination. In both species, the X and Y chromosomes are strongly heteromorphic and differ in the genomic composition compared to the autosomes. It is generally accepted that for proper cell division, the longest chromosomal arm must not exceed half of the average length of the spindle axis at telophase. Yet, it is not clear what are the dynamics between males and females during mitosis and how the cell compensates for the presence of the large Y chromosome in one sex. Using hydroxyurea cell synchronization and 2D/3D microscopy, we determined the position of the sex chromosomes during the mitotic cell cycle and determined the upper limit for the expansion of sex chromosome non-recombining region. Using 3D specimen preparations, we found that the velocity of the large chromosomes is compensated by the distant positioning from the central interpolar axis, confirming previous mathematical modulations.

Cutting force, Vibration, and Temperature in Drilling on a Thermoplastic Material of PEEK

Polyetheretherketone (PEEK) is one of the semi-crystalline thermoplastic polymers with excellent machinability and chemical stability applied to precise structural plates and electronic components. This study installed multiple sensors to analyze the machining characteristics in the PEEK drilling. According to the time domain signals, the effects of spindle speed and feed rate on the machining characteristics of cutting force and vibration were investigated. In addition, an infrared thermography was installed to record the temperature variation within the drilling area. The experimental hole was 2-mm diameter with a 4.5-mm depth. Experimental results showed that the effect of the feed rate on thrust force is greater than the spindle speed; drilling by a low-level spindle speed with a low-level feed rate can obtain the smallest cutting force and acceleration amplitude in the spindle axis; the temperature within the drilling area is inverse to the feed rate and a high-level feed rate is helpful for forming regular curl chips. When adequate airflow was applied during the drilling operation, the hole’s shrinkage ratio and roundness can be decreased. The data presented in this paper provide valuable references for realizing the drilling of the thermoplastic—PEEK.

Computer simulation of merotelic kinetochore-microtubule attachments: corona size is more important than other cell parameters

The even chromosome segregation between daughter cells during mitosis is crucial for genome integrity and is mostly regulated by proper attachments of spindle microtubules to kinetochores. Abnormalities in this process can lead to chromosome mis-segregation and potentially result in severe developmental disorders such as aneuploidy and cancer. Merotelic attachments when tubulin microtubules captured by the kinetochore of one chromatid originate from both spindle poles are considered as one of the key molecular processes that cause such abnormalities. In this paper, we use computer modeling and the Monte Carlo approach to reveal the reasons for retaining merotelic attachments at the end of metaphase. To this end, we varied, in small increments, the basic cell parameters within ensembles of 100, 500, and 1000 virtual cells. The analysis of configurations that ensure the preservation of the largest fraction of merotelic attachments enabled us to conclude that only a change in the size of the kinetochore corona can significantly increase the number of merotelic attachments and the angle between the centromere axis and the spindle axis. The effect of the other changes in model parameters, if any, was steadily suppressed by the end of metaphase. In addition, our computer model was validated by successfully reproducing the results of third-party theoretical studies as well as some experimental observations. We also found that the orientation of chromosomes and the number of merotelic attachments do not have an explicit correlation with each other and within some limits can change independently.

Sustainable peak power smoothing and energy-efficient machining process thorough analysis of high-frequency data

The reduction of CO2 by moving from fossil to renewable energy sources is currently high on the agenda of many governments. Simultaneously these governments are also forcing the reduction of energy consumption. The primary focus of these agendas is on mobility, building, and industrial sectors. For the latter, energy-efficient shop floors and machining processes assist the reduction of energy consumption. Previous research has focused on energy-efficient machining strategies during machining processes. However, an energy-efficient start-up of these machines or their spindle axis start-up has been neglected until now. This paper focuses on this neglected issue by comparing the energy-efficiency, production time, and cost-efficiency of the CNC (computer numeric control) machine by varying the power input at the spindle axis. This is done by analysing the high-frequency data (500Hz) of the machine from machining operations that is retrieved via the edge device. Concepts of data analytics and especially EDA (exploratory data analytics) were used to interactively visualize the inter-dependencies and develop results. It is shown that optimized reduction of spindle power input value leads to both: peak power smoothing from 20kW to 10kW and lowering of overall energy consumption by approximately 1.4%. Moreover, the costs and production time are marginally affected (0.518% and 0.523% respectively) by this optimized reduction of spindle power input value. Thus, this paper highlights a novel method from data acquisition to process improvement towards energy-efficient and sustainable machining.