织针生产用仿形铣刀浅析

在叙述了我国织针厂家使用的各种织针仿形铣床之后,分析了织针仿形铣刀的特点;介绍了尖齿仿形铣刀和铲齿仿形铣刀的设计要点,齿背加工机床,铣刀外经变化对工件形状的影响和铣刀刃磨。     

小模数修正摆线铣刀对加工齿轮齿形的影响

提出小模数修正摆线铣刀的径向跳动和端面跳动对被加工齿轮齿形误差影响的理论计算和分析,并且推导出用小模数齿轮仿形铣削加工时的最少齿数,以换向齿轴为例进行分析仿形铣削加工的误差,对齿轮加工具有实际指导意义。图2参9     

外国木工机床专利十则

纵向仿形铣床供作仿形加工方木或在装配现场加工其它零部件之用。机床由固定在任何硬质基座21处的弓形夹19和20,用偏心夹具22和23固定的空心底架11和12,带可驱动刀头4的铣刀滑动架34组成。偏心夹具用以工件9定位。铣刀滑动架条由纵向导向轨铰接在立杆16上。可更换的样板6安装在特殊的立柱8上,另一端则固定在挡板10上。     

尖齿成形铣刀的设计计算

铣刀是木材切削加工中应用最广、种类最多的刀具。它广泛应用于以铣削加工方式的各类木工机庆上,如木工铣床、仿形铣床、镂铣机、四面刨床等。铣刀的分类,根据刀齿齿背形式可分为铲齿铣刀、尖齿铣刀和非铲齿铣刀。铲齿铣刀的齿背为阿基米德螺旋线或圆心与铣刀中心偏移的圆弧曲线;尖齿铣刀的齿背为直线;非铲齿铣刀的齿背为圆弧曲线,后角靠适当的装刀来调整。随着木     

成形铣刀片刃磨机设计原理分析

成形铣刀片是用来加工具有曲线外形轮廓制品的木工刀具，如图1所示。刀体呈平板形，刃口截形为曲线，一般用机械方法夹紧在刀头上。成形铣刀片结构简单，制造容易，价格便宜，在木材加工工业中广泛应用。这种铣刀片存在的主要问题是刃磨比较困难，需要专用的刃磨设备。由于成形铣刀片只能刃磨后刀面，而且刃口成曲线形，因此保证多次刃磨后刃口截形及角度参数仍符合设计要求，是评价刃磨机床性能的关键。一般采用仿形原理，精制的模板和靠模销相配合可以实现刃磨后刃口截形不变。刃口角度参数主要是指后角，即保证刃磨后后角符合设计与工艺…     

播种机械的仿形机构

播种机械的土壤工作部件随着地形的起伏而运动称为仿形。仿形机构是使播种机械的土壤工作部件随地形的变化而始终保持一定的工作深度,并开出深浅一致的沟所必要的机构。仿形的好坏直接影响播种的作业质量。因此,播种机械上没置结构合理的仿形机构是极其必要的。     

整体成型铣刀的角度设计

整体成型铣刀(图1下述简称整体铣刀)与目前行业中采用的组装式成型铣刀(图2)相比。具有下述优点:(1)刀具的刀齿多,整体式铣刀一般由4～6个刀齿组成,而组装式铣刀只有2个刀齿,从而提高了加工表面的平整度;(2)修磨方便,整体铣刀的廊形一般可由机械加工而成,刀具钝化后只     

机器人匀速仿形运动控制方法研究

为了提高工业机器人在仿形运动中的匀速性能,对匀速仿形跟踪运动方法进行了研究:采用自适应NURBS曲线插补方法生成仿形路径点,根据点云数据进行仿形末端姿态的规划,通过连续路径匀速运动方法生成最终轨迹。最后在matlab仿真平台进行了仿真分析,通过插补次数为35次NURBS插补后,通过连续路径匀速运动轨迹规划生成的轨迹的速度波动由5%降至0.2%以内,验证了该方法的有效性。     

机采棉精播机关键部件运动仿真研究

在构建播种机仿形播种机构几何模型的基础上,对其关键部件进行运动仿真,通过仿真分析,得出精播机所有关键部件在上坡与下坡过程中的仿形能力均能达到使用标准的结论。     

木工硬质合金斜齿曲线铣刀设计

近几年来,国际上先进国家制造的木工曲线硬质合金铣刀,已经由直刃曲线形,发展为斜刃曲线形新型刀具.斜刃铣刀具有切削轻快,铣制后的工件表面粗糙度好,备受用户的青睐.我厂从1992年起也积极地开发生产了这种新形铣刀.现将设计方法介绍如下,从铣刀的设计方法上有两种,一种是图解法,当工件曲线精度要求不高时可采用此种方法.另一种是解析计算法.解析计算法     

Evolution of the Structural Representation of Sucrose [1]

Following a historical account on the establishment of the constitutional formula of sucrose and of its conformational features, the present possibilities for interactive graphics display of its molecular geometry, based on X-ray structural data, are given. In addition, the MOLCAD program-computed contact surface is presented as well as - in a 16 color code ranging from violet ro red - the electrostatic potential and, most relevant for structure-sweetness relationship considerations, ist hydrophobicity potential profile on the contact surface. Finally, an attempt is made towards a tentative assessment of the computer-generated distribution of hydrophilic and hydrophobic regions over the surface of the sucrose molecule in terms of the “sweetness triangle” AH-B-X concept. Also given are the graphic displays for the contact surfaces and hydrophobicity profiles of leucrose, isomaltulose and its reduction products α-glucosyl-mannitol and -sorbitol.     

Non-invasive objective and contemporary methods for measuring ocular surface inflammation in soft contact lens wearers – A review

Contact lens wear is one of the primary risk factors for the development of ocular surface inflammatory events. The purpose of this review is to examine and summarize existing knowledge on the mechanisms of contact lens related ocular surface inflammation and the evidence for the effectiveness of current objective methods to measure ocular surface inflammation. Contact lens wear is postulated to trigger an inflammatory response on the ocular surface due to mechanical, chemical, hypoxic stress, or by the introduction of microbes and their toxins. Apart from the traditional signs of inflammation, such as swelling, oedema, redness and heat, on the ocular surface, other methods to measure ocular surface inflammation in sub-clinical levels include tear inflammatory mediator concentrations, conjunctival cell morphology, and corneal epithelial dendritic cell density and morphology. Tear inflammatory mediator concentrations are up- or down-regulated during contact lens wear, with or without the presence of associated inflammatory events. There is higher conjunctival cell metaplasia observed with contact lens wear, but changes in goblet cell density are inconclusive. Dendritic cell density is seen to increase soon after initiating soft contact lens wear. The long term effects of contact lens wear on dendritic cell migration in the cornea and conjunctiva, including the lid wiper area, require further investigation. Currently patient factors, such as age, smoking, systemic diseases and genetic profile are being studied. A better understanding of these mechanisms may facilitate the development of new management options and strategies to minimize ocular surface inflammation related to contact lens wear.     

Moisture profile determination in urea prill. II. Fertiliser caking implications

In a previous study, Karl Fischer (KF) titration was used to measure the mass of water in concentric layers of urea prill. The obtained data demonstrated that the grains of this fertiliser have a linear moisture profile. In the present paper, complementary to the previous one, a theoretical analysis of the behaviour of a spherical grain sample with a linear moisture profile during KF titration is presented. The obtained curve of titration fits the experimental data perfectly. The moisture content at the grain centre is four times greater than the average moisture content, and the layer with the highest water content is located at two‐thirds of the radius from the centre. Using this theoretical grain model and assuming that the intensity of caking is proportional to the area and moisture content of the flat contact surface between broken or deformed grains, it is possible to explain many observed experimental data on fertiliser caking. Copyright © 2007 Society of Chemical Industry     

A micromechanical model for extension of a tightly packed bundle of aligned short fibres

Micromechanical models for the interaction between discrete short fibres in idealized bundles are developed and are used to investigate fibre strain profiles, slippage behaviour with increasing extension, bundle load-extension, and tangent stiffness properties. The modeling approach permits abutting fibres to interact by elastic surface shear forces in gripping regions and inelastic frictional slip in slipping regions, where transition from gripping to slipping at a contact position occurs as a linear elastic–perfectly plastic function of the interfibre relative displacement. Results show that for typical staple fibre dimensions and physical properties, a short fibre composite model for the fibre strain profile provides a good approximation to the average fibre strain profile occurring along fibres embedded in bundles. For one fibre assembly considered, results for bundle tangent stiffness indicate that, with increasing extension, average bundle stiffness may be expected to decrease from about 0.8 to 0.5 relative to a bundle of similar but continuous fibres, with 0.5 being reached at the point of collapse by localized slippage.     

The role of corneo-scleral junction in soft contact lens fitting: Case report on nanophthalmos

BackgroundNanophthalmos is rare developmental ocular condition characterized by a small eye with short axial length, high hyperopia and high lens to eye volume ratio due to arrested development of eye ball as a result of scleral inelasticity.ObservationsA 33 year old woman who presented with a complaint of blurring of distance and near vision in both eyes since childhood came to LV Prasad Eye Institute on July 2017. Best corrected visual acuity was 20/60 using soft contact lens +23.50 diopters for the right and left eyes. Axial lengths of two eyes were markedly shortened along with steep corneal curvatures. Visante anterior segment ocular coherence tomography showed a steep (convex) corneo-scleral junction (CSJ) which might be the reason for ill-fitting with conventionally estimated soft contact lens (SCL) parameters. Finally, selection of the customized hydrogel soft contact lens base curve close to flatter corneal curvature and small diameter showed characteristics of optimal lens fit.ConclusionThe corneo-scleral junction profile plays significant role in soft contact lens fitting. An eye with a profile of convex CSJ would require a lens with steeper curvature compared to conventional measurements. Cases of nanophthalmos would require observation of the profile with the help of optical coherence tomography in addition to measurement of corneal curvature prior to fitting soft contact lenses.     

Optical quality of rotationally symmetrical contact lenses derived from their power profiles

Purpose

To present a methodology for evaluating the optical quality of rotationally symmetrical contact lenses (CLs) from a single power profile.

The influence of surface treatment on hydrophobicity, protein adsorption and microbial colonisation of silicone hydrogel contact lenses.

PURPOSE: To evaluate the influence of surface treatment of silicone-hydrogel CL on lens hydrophobicity, protein adsorption and microbial colonisation by studying several silicone hydrogel contact lenses (CL) with and without surface treatment. The lenses used in this study were Balafilcon A, Lotrafilcon A, Lotrafilcon B and Galyfilcon A. A conventional hydrogel CL (Etafilcon A) was also tested. METHODS: Hydrophobicity was determined through contact angle measurement using the advancing type technique on air. The type and quantity of proteins adsorbed were assessed through SDS-PAGE and fluorescence spectroscopy, respectively. Microbial colonisation was studied by removing the microbes from the lenses through sonication, and counting the colony-forming units on agar plates. RESULTS: Regarding hydrophobicity, both surface and non-surface-treated silicone hydrogel CL were found to be hydrophobic, and the conventional hydrogel CL was found to be hydrophilic. Concerning protein adsorption, different protein profiles were observed on the several lenses tested. Nevertheless, the presence of proteins with the same molecular weight as lysozyme and lactoferrin was common to all lenses, which is probably related to their abundance in tears. In terms of total protein adsorption, silicone hydrogel CL did not exhibit any differences between themselves. However, the conventional hydrogel Etafilcon A adsorbed a larger amount of proteins. Regarding microbial colonisation, Balafilcon A exhibited the greatest amount of colonising microbes, which can be due to its superior hydrophobicity and higher electron acceptor capacity. CONCLUSION: This study suggests that silicone hydrogel lenses adsorb a lower amount of proteins than the conventional hydrogel lenses and that this phenomenon is independent of the presence of surface treatment. Concerning microbial colonisation, the surface treated Balafilcon A, exhibited a greater propensity, a fact that may compromise the lens wearer's ocular health.     

摆线轮齿面接触有限元建模的参数化

利用I-DEAS软件本身的参数化设计功能,编写了摆线轮齿面接触有限元建模程序;在I-DEAS中运行该程序文件,只要输入针摆传动相关参数,就可以建立三维实体模型、接触有限元模型,完成从建模、划分网格到施加边界条件的前处理工作。有限元建模的参数化实现了高精建模,使设计的结果具有了延展性和继承性,大大提高了设计速度,并减少了信息的存储量。     

A Predictive Model for Food Particle interactions with Contact Surfaces

The protein adsorption rate from whole milk onto various surfaces was modeled as a function of contact surface tension, surface temperature, and time. A new kinetic parameter related to the value of contact surface tension which corresponds to a minimal interaction between food components and the solid surface is introduced. This experimentally measurable parameter quantifies the influence of contact surface tension on the activation energy required for irreversible protein adsorption. In spite of its simplicity, the model adequately predicted initial adsorptive behavior under steady flow conditions for a wide range of surface properties.