共查询到16条相似文献,搜索用时 109 毫秒
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铣削加工中最小夹紧力的计算 总被引:1,自引:0,他引:1
提出了一种计算铣削加工中夹紧工件所需最小夹紧力的简洁方法。首先,确定了工件与夹具元件之间的接触刚度;其次,建立了接触变形量与工件位移量的关系;然后,给出了工件的静态平衡方程。通过合并以上方程,建立了线性方程组计算工件与夹具元件之间的切向接触力,并根据最大切向接触力进一步计算出夹具元件与工件之间不发生相对滑动所需理论最小夹紧力。最后,通过算例验证了该方法的正确性。 相似文献
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首先通过分析缸盖与夹具定位元件、夹紧元件之间的接触特点,建立了相应的接触副模型。在假定夹具夹紧点的布局位置以及夹紧顺序固定的基础上,以定位元件与工件接触区域半弹性变形所导致的工件最小位移为第一目标函数,同时以接触点变形最小总余能为第二目标函数。根据工件的具体加工过程静力平衡列出约束条件,构建了夹紧力的多目标优化模型。最后,根据多目标优化模型得到相应的结果。夹具的多重夹紧力经过该模型优化后,对应所需的夹紧力显著降低,这对提高加工精度和减少成本具有重要的意义。 相似文献
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夹具夹紧方案优化设计 总被引:1,自引:0,他引:1
综合分析夹具夹紧误差的各种影响因素及其影响方式,并根据影响方式归纳产生夹紧变形的两大原因,即由夹紧副变形导致的工件位置误差与由外力导致的工件变形,由此建立夹紧副变形与工件位置误差的通用关系模型;以工件位置误差最小为目标,建立了夹紧力的优化模型,可以同时实现夹紧力大小与作用点的稳健优化设计。最后用一典型实例说明了夹紧力的优化结果。所介绍的方法不仅适用于夹具设计,而且对机器人多手指抓取规划同样适用。 相似文献
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夹具布局和夹紧力大小影响切削变形的大小和分布.基于遗传算法和有限元方法,提出一种夹具布局和夹紧力优化设计方法.该方法将同步优化夹具布局和夹紧力大小以及施加变夹紧力相结合,首先以加工变形最小化和变形分布最均匀为目标同步优化夹具布局和夹紧力大小,然后在优化后的夹具布局的基础上求解使得加工变形最小的变夹紧力大小.使用该方法进行底座薄壁零件的夹具优化设计,结果表明优化得到的设计优于经验设计和多目标优化方法,该方法有效地降低了加工过程中工件的变形,提高变形均匀度. 相似文献
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李文玉 《现代制造技术与装备》2010,(4):54-55
本文简述了液性塑料夹具的基本原理和使用优点及其薄壁套筒的设计。并从理论上论述了液性塑料定心夹紧机构中薄壁套筒的受力、变形情况。通过弹性力学和材料力学理论分别论述了液性塑料夹具中工件夹紧力的计算与分析。推导出工件夹紧力的精确解和一般计算公式,并由推导材料力学的使用范围。 相似文献
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阐述在轮毂的数控车削加工过程中,由于受到夹具的夹紧力和切削力的作用,致使工件在加工时产生变形,尺寸精度大大超差,严重时甚至工件会脱落于夹具,导致工件报废。经过本人认真研究,通过改进夹爪、调整工件夹紧位置,适当改变夹头夹紧力及优化加工工艺等,从而大大提高了加工精度和生产效率,降低了劳动强度,节约生产成本。希望以上的方法能对从事相关工作的人员有一定的借鉴作用。 相似文献
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B. Li S.N. Melkote 《The International Journal of Advanced Manufacturing Technology》2001,17(2):104-113
Workpiece motion arising from localised elastic deformation at fixture-workpiece contacts owing to clamping and machining
forces is known to affect significantly the workpiece location accuracy and, hence, the final part quality. This effect can
be minimised through fixture design optimisation. The clamping force is a critical design variable that can be optimised to
reduce the workpiece motion. This paper presents a new method for determining the optimun clamping forces for a multiple clamp
fixture subjected to quasu-static machining forces. The method uses elastic contact mechanics models to represent the fixture-workpiece
contact and involves the formulation and solution of a multi-objective constrained oprimisation model. The impact of clamping
force optimisation on workpiece location accuracy is analysed through examples involving a 3-2-1 type milling fixture. 相似文献
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James N. Asante 《The International Journal of Advanced Manufacturing Technology》2008,39(5-6):578-588
Contact forces between workpiece and fixture define fixture stability during clamping and influence workpiece accuracy during machining. In particular, forces acting in the contact region are important for understanding deformation of the workpiece at the contact region. This paper presents a model that combines contact elasticity with finite element methods to predict the contact load and pressure distribution at the contact region in a workpiece-fixture system. The objective is to determine how much clamp forces can be applied to generate adequate contact forces to keep the workpiece in position during machining. The model is able to predict the normal and tangential contact forces as well as the pressure distribution at each workpiece-fixture contact in the fixturing system. Model prediction is shown to be in good agreement with known industry practice on clamp force determination. The presented method has no limits on the types of materials that can be analyzed. 相似文献
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B. Li S. N. Melkote S. Y. Liang 《The International Journal of Advanced Manufacturing Technology》2000,16(2):79-84
This paper presents a model for analysing the reaction forces and moments for machining fixtures with large contact areas,
e.g. a mechanical vice. Such fixtures transmit torsional loads in addition to normal and tangential loads and thus differ
from fixtures using point or line contacts. The model is developed using a contact mechanics approach where the workpiece
is assumed to be elastic in the contact region and the fixture element is treated as rigid. Closed-form contact compliance
solutions for normal, tangential, and torsional loads are used to derive the elastic deformation model for each contact. A
minimum energy principle is used to solve the multiple contact problem yielding unique predictions of the fixture–workpiece
contact forces and moments due to clamping and machining forces. This model is then used to determine the minimum clamping
force necessary to keep the workpiece in static equilibrium during machining. An example is given to demonstrate its effectiveness
in analysing the clamping performance of a mechanical vice during machining. 相似文献
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Guo-hua Qin Wei-hong Zhang 《The International Journal of Advanced Manufacturing Technology》2007,32(1-2):78-91
After being located on a machine bed, a workpiece will be subject to gravity and cutting forces during the machining operation.
In order to keep the locating precision as well as the production safety, it is necessary to maintain the workpiece stability.
In this paper, a linear programming method is proposed for stability analysis of the workpiece. Based on the linear approximation
of the friction cone, a quantitative criterion is established to verify the workpiece stability in association with the rationality
of the clamping sequence, magnitude of clamping forces and clamping placement. This criterion allows designers to plan reasonably
the clamping sequence, magnitude of clamping forces as well as clamping placement. Compared with existing methods, the main
advantage of this approach lies in that the sophisticated computing of contact forces between fixture elements and the workpiece
is avoided. In this work, both friction and frictionless cases can be easily taken into account in stability analysis. Mathematical
formulations of the method are given and some numerical tests are finally demonstrated to validate the proposed method. 相似文献
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Machining fixture layout design using ant colony algorithm based continuous optimization method 总被引:3,自引:2,他引:1
K. P. Padmanaban K. P. Arulshri G. Prabhakaran 《The International Journal of Advanced Manufacturing Technology》2009,45(9-10):922-934
In any machining fixture, the workpiece elastic deformation caused during machining influences the dimensional and form errors of the workpiece. Placing each locator and clamp in an optimal place can minimize the elastic deformation of the workpiece, which in turn minimizes the dimensional and form errors of the workpiece. Design of fixture configuration (layout) is a procedure to establish the workpiece–fixture contact through optimal positioning of clamping and locating elements. In this paper, an ant colony algorithm (ACA) based discrete and continuous optimization methods are applied for optimizing the machining fixture layout so that the workpiece elastic deformation is minimized. The finite element method (FEM) is used for determining the dynamic response of the workpiece caused due to machining and clamping forces. The dynamic response of the workpiece is simulated for all ACA runs. This paper proves that the ACA-based continuous fixture layout optimization method exhibits the better results than that of ACA-based discrete fixture layout optimization method. 相似文献
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B. Li S. N. Melkote 《The International Journal of Advanced Manufacturing Technology》2001,18(10):701-707
This paper presents a fixture layout and clamping force optimal synthesis approach that accounts for workpiece dynamics during
machining. The dynamic model is based on the Newton– Euler equations of motion, with each fixture–workpiece contact modelled
as an elastic half-space subjected to distributed nor-mal and tangential loads. The fixture design objective in this paper
is to minimise the maximum positional error at the machining point during machining. An iterative fixture layout and clamping
force optimisation algorithm that yields the "best" improvement in the objective function value is presented. Simulation results
show that the proposed optimis-ation approach produces significant improvement in the work-piece location accuracy. Additionally,
the method is found to be insensitive to the initial fixture layout and clamping forces. 相似文献