EdgeCAM的数控技术在模具加工中的应用

EdgeCAM是一套先进的智能数控编程系统,由于其有多重功能,在诸多领域都发挥了重要作用,在模具加工领域有着不可替代的地位。文章通过分析EdgeCAM智能数控编程系统的特点以及实例来阐释EdgeCAM智能数控编程系统在模具加工中的应用。     

Survey of 1012 moldy dwellings by culture fungal analysis: Threshold proposal for asthmatic patient management

Different countries have tried to define guidelines to quantify what levels of fungi are considered as inappropriate for housing. This retrospective study analyzes indoor fungi by cultures of airborne samples from 1012 dwellings. Altogether, 908 patients suffering from rhinitis, conjunctivitis, and asthma were compared to 104 controls free of allergies. Portuguese decree law no 118/2013 (PDL118), ANSES (a French environmental and health agency) recommendations, and health regulations of Besançon University Hospital were applied to determine the rates of non‐conforming dwellings, which were respectively 55.2%, 5.2%, and 19%. Environmental microbiological results and medical data were compared. The whole number of colonies per cubic meter of air was correlated with asthma (P < 0.001) and rhinitis (P = 0.002). Sixty‐seven genera and species were detected in bedrooms. Asthma was correlated to Aspergillus versicolor (P = 0.004) and Cladosporium spp. (P = 0.02). Thresholds of 300 cfu/m³ for A. versicolor or 495 cfu/m³ for Cladosporium spp. are able to discriminate 90% of the asthmatic dwellings. We propose a new protocol to obtain an optimal cost for indoor fungi surveys, excluding surface analyses, and a new guideline to interpret the results based on >1000 cfu/m³ of whole colonies and/or above threshold levels for A. versicolor or Cladosporium spp.     

Physical modeling and numerical simulation of electromagnetic stirring in a slab continuous casting mold

Through physical modeling and numerical simulation,the flow field in a slab continuous casting mold with electromagnetic stirring is measured under different casting parameters and stirring currents. To qualitatively evaluate the flow field in the mold,two indexes,i. e.,mold flux entrapment and velocity uniformity,are proposed.Based on these two indexes,some optimized stirring parameters under different casting conditions can be determined.     

异型铆钉冲模前、后模的电火花加工

电火花加工在民用,国防生产部门和科学研究、模具生产中已经获得了广泛应用。分析了一种异型铆钉冲模前、后模的结构特点,采用电火花来加工此零件。在加工此零件时,通过采用合理的粗、精加工放电参数,保证了零件的加工质量并提高了加工效率。     

支撑轴精密成形工艺及模具设计

通过对45号钢支撑轴的工艺性分析,提出热挤压成形方案,基于Deform-3D软件对热挤压成形过程进行有限元仿真,分析行程载荷曲线、金属流动和温度场,并对工艺进行优化、预测模具设计中可能出现的问题。在此基础上,设计了一套支撑轴热挤压成形模具,有效缩短了模具设计周期,为该类零件的成形工艺及模具设计提供了一定的参考。     

Interfacial reaction between zirconium alloy and graphite mold/yttrium oxide ceramic mold

Zirconium alloys are active in the molten state and tend to react with the mold during casting. The casting technology of zirconium is not yet well established; especially in selecting the mold materials, which are difficult to determine. In the present work, the interfacial reactions between zirconium casting and casting mold were studied. The zirconium alloy was melted in a vacuum arc skull furnace and then cast into the graphite mold and ceramic mold, respectively. The zirconium casting samples were characterized using SEM, EDS and XRD with an emphasis on the chemical diffusion of elements. A reaction layer was observed at the casting surface. Chemical analysis shows that chemical elements C, O and Y from the mold are diffused into the molten zirconium, and new phases, such as ZrC, Zr30, YO1.335 and Y6ZrO11, are formed at the surface. In addition, an end product of zirconium valve cast in a yttria mold has a compact structure and good surface quality.     

50MVA电炉锰系合金地模浇注技术

云南建水锰矿有限责任公司针对锰系合金生产中铁盆浇注工艺存在的缺陷与不足，通过不断摸索改进，采用地模浇注技术在大型电炉生产中的实践，提高浇注效率，简化了工艺操作，解决了一系列难题，取得了可观的经济效益。     

弧形滑块抽芯机构注射模设计

通过分析对比BDCI塑件中手柄主体的结构特征,设计出弧形滑块抽芯机构中抽芯的典型结构,实现模具结构合理,动作可靠,塑件顺利成型。     

School attendance and daily respiratory symptoms in children: influence of moisture damage

We investigated the effect of weekends and school holidays on the daily frequency and severity of respiratory and other symptoms among children attending schools with (index) or without (reference) moisture damage in Spain, the Netherlands, and Finland. Throughout 1 year, parents of 419 children with a respiratory condition attending index (n=15) or reference (n=10) primary schools completed three symptom diaries. We assessed associations between lower respiratory tract, upper respiratory tract or allergy, and other symptom scores and school day, weekend, or summer holiday using mixed regression models stratified by country and moisture damage. We evaluated interactions between moisture damage and type of day. We combined country‐specific estimates (incidence rate ratios [IRRs] and 95% confidence interval [CI]) in meta‐analyses. Symptom scores were lower during weekends and holiday. Lower respiratory tract symptoms were statistically significantly less common during holiday with strongest effect in index schools (IRR=0.7; CI=0.6–0.8). Reporting of other symptoms was more reduced during holiday in index (IRR=0.6; CI=0.4–0.9) than in reference (IRR=0.95; CI=0.8–1.2) schools (interaction P<.01). In conclusion, symptoms were less frequent and/or severe during summer holiday and weekends. This pattern was stronger among children attending moisture‐damaged schools, suggesting potential improvement in moisture damage‐related symptoms during school breaks.