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湖 南 科 技 大 學(xué)
英文文獻翻譯
學(xué) 生 姓 名： 郭凱
學(xué) 院： 機電工程學(xué)院
專業(yè)及班級： 機械設(shè)計制造及其自動化六班
學(xué) 號： 1103010603
指 導(dǎo) 教 師： 劉厚才
2015年 5月 28日
Analysis of machining process
Abstract
In the machining process, the machining error due to various reasons are inevitable, if not through the correct, effective way to control these errors, directly affects the machining quality, a serious impact on production. So this paper discusses the practical improvement of machining technology according to the mechanical machining error.
Key words：machine work; error；process technology
Introduction
With the development of modern machining technology, the machining requirement of the parts is continuously improved, and the parts can meet the pattern and improve the machining accuracy.In this paper, the reasons for machining errors are analyzed, and the effective technology for reducing machining errors is proposed.. After machining the machining parts, whether the workpiece meets the requirement, and the accuracy of the workpiece is within the permissible error range first.. It is embodied in three aspects: dimension accuracy, geometry accuracy and position accuracy. When the parts are processed to meet the accuracy requirements, is a qualified workpiece.
A.Arrangement of machining operation
When arranging the processing sequence, pay attention to the following points.
a.When the parts need to be processed in stages, the rough machining of each surface is arranged, and the finishing machining is arranged at the end.
b.In order to shorten the transportation distance in the workshop, to avoid the flow of the workpiece, the processing sequence should consider the arrangement of the workshop equipment.
c.According to the function and technical requirements of the parts: the main parts of the main parts of the main, the main surface of the district separate, and then focus on the main surface of the processing order.
d.Parts processing generally starts with the processing of the finish datum, and then processed the other main and minor surfaces by the reference of the precision.
B.The principle of process planning
The principle of the process is quality, high yield and low cost, that is, the premise of ensuring product quality, to strive for the best economic benefits. In the concrete formulation, should also pay attention to the following questions:
a.Advanced technology
In the development of process planning, we need to understand the development of the technology and technology in the domestic and foreign, and use the advanced technology and equipment as far as possible through the necessary technology test.
b.Economic rationality
Under certain production conditions, there may be some technological plan for the technical requirements of parts of the parts. At this point, it should be through the cost accounting or contrast, choose to determine the most reasonable economic plan, making the product production costs minimum.
c.Good working condition and avoiding environmental pollution
In the formulation of the technical regulations, pay attention to ensure that the workers' operation with good, safe labor conditions. Therefore, in the process plan, to try to take mechanization or automation measures, so as to reduce the heavy manual labor. In addition, to comply with the relevant provisions of the national environmental protection law, to avoid the pollution of the environment.
There are three aspects of product quality, productivity and economy sometimes contradictory, so the reasonable technological process should be handled well, which reflects the unity of the three.
C.Error and its causes of machining
a.Error of machine tool
In machining tool relative to workpiece forming motion is generally accomplished by machine tool. Therefore, the machining accuracy of workpiece depends on the accuracy of machine tool.. The error of machine tool has a great influence on the machining accuracy of the workpiece: (1) the rotary error of the spindle; (2) the rail error; (3) the transmission chain error.
b.Geometric error of cutter
The influence of cutting tools error on machining accuracy varies with the variety of tools.. The tool dimensions forming tool generating machining tool, tool manufacturing error will directly affect the workpiece machining accuracy; and the general tool, the manufacturing error have no direct impact on the machining accuracy of workpiece.
c.Error caused by force distortion in process system
stiffness of workpiece. In the process system if the workpiece stiffness relative to the machine tool, cutting tool, fixture is relatively low, in under the action of the cutting force, workpiece due to lack of rigidity caused by the deformation influence on machining accuracy is relatively large. (3) tool stiffness. Lathe tool surface (y) in the normal direction of the stiffness, the deformation can be ignored. The boring hole with the smaller diameter, the stiffness of the tool bar, the deformation of the cutter bar have a great influence on the machining accuracy.. (3) stiffness of machine tool parts. There are many components in machine tool parts, and there is no suitable calculation method for machine tool parts. At present, the stiffness of machine tool is mainly determined by experiment method.. The deformation is not linear with the load, the load curve and the unloading curve do not coincide, the unloading curve is lagging behind the load curve.. Between two curves contained the area is set on the cyclic loading and unloading of the loss of the energy it consumes in friction work and contact deformation work; first after unloading and deformation to restore to the first loading starting point, indicating that the residual deformation existed. After repeatedly after loading and unloading, loading point of curve to and unloading curves overlap the end, residual deformation gradually decreases to zero.
d.Error caused by heat distortion of process system
The thermal deformation of the process system has a great effect on the machining accuracy, especially in the precision machining and the large machining. The machining errors caused by the thermal deformation can sometimes account for 50% of the total error.
D.Improvement error of technological measures
Through the error analysis, there are inevitable errors in machining process, but it can still be reduced by various means.. The following measures are put forward to improve the processing error.
a.Reduce the original error. Because the machine is a complicated system, there are many influencing factors, the accuracy of the fixture, measuring and cutting tool itself workpiece in machining force, heating, tool wear are the original error, in order to avoid the original error accumulation effect on machining accuracy. It is needed to test them in machining process, and the corresponding solution is adopted according to different error, and the error is reduced.
b.Transfer error method:
Error sensitive directions is refers to through the normal direction of the blade surface is processing the maximum error of the direction and tangential direction for non sensitive direction error, error of non sensitive direction, the effect is small. The essence of the transfer error method is to shift the error from the sensitive direction to the non sensitive direction.. So in the process of processing should try to shift the processing error to the non sensitive direction, improve the processing precision.
c.Error compensation method. For some cannot reduce the original error, by imposing artificial contrary to the direction of the original error equal to the size of the error, through this way to offset the original error, error compensation method to control the impact of machining error.
(1) error compensation method: this method is artificially created a new original error, thus compensation or offset the original process system inherent in the original error, to reduce the machining errors, improve machining accuracy.
(2) error canceling method: use the original a primitive error to partially or completely offset the original original error or another original error
d.Differentiation or homogenization of the original error
(1) the original error (packet) differentiation method: differentiation of the original error method is break up the whole into parts. For complex workpiece, if in the machining process, the misalignment errors of corresponding processing, the error in every process of accumulation, the error will continue to expand, directly affects the machining accuracy. Therefore, the corresponding means should be taken, the rough or workpiece size by segmentation for the N group, the size of the workpiece size range reduced to the original 1/n. The error range is also reduced to the original 1/n. Then, in the small range, adjust the accuracy of the relative workpiece, and reduce the impact of the original error to the processing part.
(2) are the original error method: for the fit precision requirements very high shaft or hole, the lapping tool in the tool and workpiece relative motion, through surface friction and wear, to the workpiece for trace cutting error will continue to reduce. The error method is to find out the differences between them, and then to modify the processing or benchmark.
E.Development of machining technology
The mechanical processing technology will develop along the trend of automation, and it plays a very big role in the future society, and the main force of the national economic development lies in the motive of the mechanical technology.. However, in the actual situation, the mechanical machining need to change the resources of the daily gradient, which becomes a stumbling block for the development of mechanical technology toward the direction of automation. However, with the advent of the new century, the popularization and application of computer will be flexible and applied in the development of mechanical technology.. When the computer gradually replaces the human, this also alleviates the problem of the shortage of resources in a certain degree.
At the same time, it is also a good direction to realize the eco - development of machining process, which can promote the sustainable development of the society, and make the development more green and pollution-free.. Now the technology has become increasingly mature, basically have a complete set of their own system. In our country has many enterprises of satellite mechanical processing technology for the research in many aspects and find their own way out of the new skills, but also for the future development of micro mechanical laid the foundation.
Conclusion
In this paper, the reasons of machining errors are analyzed, and some methods and measures of improving machining accuracy are given.. For the vast majority of mechanical processing and technical personnel, how to reduce the errors of mechanical process, we must first clear influence of machining error of several pathways and factors. Therefore, this paper for the study of machining error is has a certain practical application value, for machining error control has good instruction significance. This also lay a good foundation for the development of machining technology in the future.
8
淺析機械加工工藝
摘要
在機械加工中，加工誤差由于各種原因不可避免地存在，如不通過正確、有效地方式來控制，這些誤差直接影響加工質(zhì)量，嚴重影響生產(chǎn)。因此本文根據(jù)機械加工誤差產(chǎn)生的原因來探討機械加工工藝的實際改善。
關(guān)鍵詞：機械加工；誤差；加工工藝
引言
隨著現(xiàn)代加工技術(shù)的發(fā)展，對零件的加工要求也在不斷提高，保證零件符合圖樣，提高加工精度。本文針對機械加工產(chǎn)生誤差的原因進行剖析，并提出減少加工誤差的有效工藝措施。對加工件進行機械加工后，加工件是否滿足要求，先檢驗工件精度是否在允許誤差范圍內(nèi)。具體體現(xiàn)在三個方面：尺寸精度、幾何形狀精度、相互位置精度。當零件加工后滿足這些精度要求時，才是一個合格的工件。
一、機械加工工序的安排
在安排加工順序時，應(yīng)當注意以下幾點。
（1）當零件需要分階段進行加工時，首先安排各表面的粗加工，其次安排半精加工，最后再安排主要表面的精加工與光整加工。
（2）為了縮短工件在車間內(nèi)的運輸距離，以避免工件的往返流動，加工順序應(yīng)當考慮車間設(shè)備的布置情況。
（3）根據(jù)零件的功用與技術(shù)要求：先把零件的主、次要表面進行區(qū)分開，然后再著重考慮主要表面的加工順序。
（4）零件加工一般首先從精基準的加工開始，然后再以精基準定位進行加工其他主、次要表面。
二、工藝規(guī)程制訂的原則
工藝規(guī)程制訂的原則是優(yōu)質(zhì)、高產(chǎn)與低成本，即在保證產(chǎn)品質(zhì)量的前提下，來爭取最好的經(jīng)濟效益。在進行具體制定時，還應(yīng)當注意以下問題：
1、技術(shù)上的先進性
在制訂工藝規(guī)程時，需要了解國內(nèi)外本行業(yè)工藝技術(shù)的發(fā)展，通過必要的工藝試驗，盡可能的采用先進適用的工藝與工藝裝備。
2、經(jīng)濟上的合理性
在一定的生產(chǎn)條件下，可能會出現(xiàn)幾種能保證零件技術(shù)要求的工藝方案。此時，應(yīng)當通過成本核算或者相互對比，選擇確定經(jīng)濟上最合理的方案，使得產(chǎn)品生產(chǎn)成本最低。
3、良好的勞動條件、避免環(huán)境污染
在制訂工藝規(guī)程時，要注意保證在工人操作時有良好的、安全的勞動條件。所以，在工藝方案上，要盡量的采取機械化或者自動化措施，從而減輕工人繁重的體力勞動。此外，要符合國家環(huán)境保護法的有關(guān)規(guī)定，避免污染環(huán)境。
產(chǎn)品質(zhì)量、生產(chǎn)率與經(jīng)濟性三個方面有時會相互矛盾，所以，合理的工藝規(guī)程應(yīng)當處理好這些矛盾，體現(xiàn)這三者的統(tǒng)一。
三、機械加工產(chǎn)生的誤差及其原因
1、機床的誤差
加工中刀具相對于工件的成形運動一般都是通過機床完成的，因此，工件的加工精度在很大程度上取決于機床的精度。機床制造誤差對工件加工精度影響較大的有：（1）主軸回轉(zhuǎn)誤差；（2）導(dǎo)軌誤差；（3）傳動鏈誤差。
2、刀具的幾何誤差
刀具誤差對加工精度的影響隨刀具種類的不同而不同。采用定尺寸刀具成形刀具展成刀具加工時，刀具的制造誤差會直接影響工件的加工精度；而對一般刀具，其制造誤差對工件加工精度無直接影響。
3、工藝系統(tǒng)受力變形產(chǎn)生的誤差
（1）工件剛度。工藝系統(tǒng)中如果工件剛度相對于機床、刀具、夾具來說比較低，在切削力的作用下，工件由于剛度不足而引起的變形對加工精度的影響就比較大。（3）刀具剛度。外圓車刀在加工表面法線（y）方向上的剛度很大，其變形可以忽略不計。鏜直徑較小的內(nèi)孔，刀桿剛度很差，刀桿受力變形對孔加工精度就有很大影響。（3）機床部件剛度。機床部件由許多零件組成，機床部件剛度迄今尚無合適的簡易計算方法，目前主要還是用實驗方法來測定機床部件剛度。變形與載荷不成線性關(guān)系，加載曲線和卸載曲線不重合，卸載曲線滯后于加載曲線。兩曲線線間所包容的面積就是載加載和卸載循環(huán)中所損耗的能量，它消耗于摩擦力所做的功和接觸變形功；第一次卸載后，變形恢復(fù)不到第一次加載的起點，這說明有殘余變形存在，經(jīng)多次加載卸載后，加載曲線起點才和卸載曲線終點重合，殘余變形才逐漸減小到零。
4、工藝系統(tǒng)受熱變形引起的誤差
工藝系統(tǒng)熱變形對加工精度的影響比較大，特別是在精密加工和大件加工中，由熱變形所引起的加工誤差有時可占工件總誤差的50%。
四、改進誤差的工藝措施
通過對誤差的分析，在機加過程中不可避免的存在加工誤差，但是仍可以通過各種方式盡量減小加工誤差。下面對改進加工誤差提出了幾點措施。
1、 減少原始誤差。由于機床加工是一個復(fù)雜的系統(tǒng)，存在很多影響因素，夾具、量具及刀具本身的精度，工件在加工中受力、受熱，刀具磨損等均屬于原始誤差，為了避免原始誤差積累影響加工精度。需要在加工過程中對其進行檢驗，根據(jù)不同的誤差原因采用相應(yīng)的解決措施，減小原始誤差。
2、轉(zhuǎn)移原始誤差法：
誤差敏感方向是指通過刀刃的加工表面的法線方向也就是產(chǎn)生加工誤差最大的那個方向，切線方向為誤差非敏感方向，誤差非敏感方向，影響小。轉(zhuǎn)移原始誤差法實質(zhì)是將誤差轉(zhuǎn)移到從敏感方向轉(zhuǎn)移到非敏感方向上。所以在加工過程中應(yīng)設(shè)法將加工誤差轉(zhuǎn)移到非敏感方向，提高加工精度。
3、 誤差補償法。對于某些無法減小的原誤差，可采用人為施加與原誤差大小相等方向相反的誤差，通過這種方式抵消原誤差，采取誤差補償?shù)姆椒ㄒ钥刂破鋵α慵庸ふ`差的影響。
（1）誤差補償法：該方法是人為地造出一種新的原始誤差，從而補償或抵消原來工藝系統(tǒng)中固有的原始誤差，達到減少加工誤差，提高加工精度的目的。
（2）誤差抵消法：利用原有的一種原始誤差去部分或全部地抵消原有原始誤差或另一種原始誤差
4、分化或均化原始誤差
（1）分化原始誤差（分組）法：分化原始誤差法的思想就是化整為零。對于復(fù)雜的工件，如果在機加過程中，不對誤差進行相應(yīng)的處理，則誤差在每一道工序中累積疊加，誤差會不斷地擴大，直接影響到加工件的精度。所以應(yīng)采取相應(yīng)的手段，將毛坯或工件尺寸經(jīng)分割為n組，每組工件的尺寸范圍就縮減為原來的1/n。誤差范圍也相應(yīng)的縮小到原來的1/n。然后在小范圍內(nèi)，調(diào)整刀具相對工件的準確位置，最大限度地減少了原始誤差對加工件影響。
（2）均化原始誤差法：對于配合精度要求很高的軸或孔，研具在與加工件相對運動，通過表面的摩擦和磨損，對加工件進行微量削切，誤差不斷減少。均化誤差法就是通過有工件與工具表面的相互比較和檢查，從中找出它們之間的差異，然后再進行相互修正加工或基準加工。
五、機械加工工藝的發(fā)展
機械加工工藝將沿著自動化的趨勢發(fā)展，對未來的社會起到很大的決定性作用，而國民經(jīng)濟發(fā)展主力在于機械工藝的動力所在。但是在現(xiàn)實的狀況下，機械加工所需要資源日漸變少，這就成為了機械工藝向著自動化方向發(fā)展的絆腳石。然而，隨著新世紀的到來，計算機的普及與應(yīng)用，將靈活的運用在機械工藝自動化的研發(fā)中。當計算機逐步代替人力的時候，這在某一程度上也緩解了資源不足這個問題。
同時，實現(xiàn)機械加工工藝生態(tài)化發(fā)展也是一個不錯的方向，既可以推動社會的可持續(xù)發(fā)展，又可以使得發(fā)展更加的綠色化，無污染化。如今機械加工的技術(shù)已經(jīng)越來越來成熟，基本上已經(jīng)有了自己一套完整的體系。在我國有已經(jīng)有許多企業(yè)單位對衛(wèi)星機械加工技術(shù)進行了多方面的研究，并且自己摸索出了新的技巧，也為以后微型機械的發(fā)展奠定了基礎(chǔ)。
結(jié)語
本文通過分析機械加工誤差的成因，有針對性的給出了若干具體的提高機械加工精度的方法和措施。對于廣大機械加工技術(shù)人員而言，如何降低機械加工誤差，首先必須要明確影響機械加工誤差的若干途徑和因素，因此，本文對于機械加工誤差的探討是有一定實際應(yīng)用價值的，對于機械加工誤差的控制具有較好的指導(dǎo)借鑒意義。這也為了以后機械加工工藝的發(fā)展奠定了良好的基礎(chǔ)。