CN111222083A - A method for calculating workpiece surface roughness during turning based on tool wear - Google Patents

A method for calculating workpiece surface roughness during turning based on tool wear Download PDF

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CN111222083A
CN111222083A CN202010165567.XA CN202010165567A CN111222083A CN 111222083 A CN111222083 A CN 111222083A CN 202010165567 A CN202010165567 A CN 202010165567A CN 111222083 A CN111222083 A CN 111222083A
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turning
workpiece
surface roughness
tool
wear
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赵国勇
李春霄
郑光明
孟建兵
周海安
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Shandong University of Technology
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Abstract

本发明提供一种基于刀具磨损的车削时工件表面粗糙度计算方法，采用以下步骤：1）根据车削参数与工件表面粗糙度的关系，并考虑刀具磨损状况对工件表面粗糙度的影响，建立车削时工件表面粗糙度计算模型；2）进行车削实验，借助粗糙度仪、金相显微镜测量并计算工件表面粗糙度计算模型中各待定系数；3）在刀具材料、工件材料、加工方式相同情况下，对于一个新的车削工艺方案，根据车削参数、车刀后刀面磨损量，计算车削时工件表面粗糙度。该方法优点是：综合考虑了车削参数、刀具磨损状况的影响来计算工件表面粗糙度，计算方法简单、精度高；有助于工艺参数选择以提高表面质量并减少废品率。

Figure 202010165567

The present invention provides a method for calculating workpiece surface roughness during turning based on tool wear. 2) Carry out turning experiments, measure and calculate the undetermined coefficients in the calculation model of workpiece surface roughness with the aid of roughness meter and metallographic microscope; 3) Under the same conditions of tool material, workpiece material and processing method , For a new turning process scheme, according to the turning parameters and the wear amount of the flank face of the turning tool, the surface roughness of the workpiece during turning is calculated. The advantages of this method are: comprehensively considering the influence of turning parameters and tool wear conditions to calculate the surface roughness of the workpiece, the calculation method is simple and high in accuracy; it is helpful for the selection of process parameters to improve the surface quality and reduce the scrap rate.

Figure 202010165567

Description

Workpiece surface roughness calculation method during turning based on tool wear
Technical Field
The invention relates to a method for calculating the surface roughness of a workpiece, in particular to a method for calculating the surface roughness of the workpiece during turning based on tool abrasion.
Background
The turning process is to use a turning tool to cut excess metal from a rotating workpiece to form a machined surface. The surface roughness of the workpiece is an important parameter for representing the processing quality of the workpiece, and has a remarkable influence on the service performance of the workpiece. Generally, the rougher the surface of the workpiece, the more stress concentrations tend to occur, thereby affecting the fit accuracy and increasing wear caused by the mutual movement of the workpieces.
Many scholars have studied how to predict the surface roughness of a workpiece based on the cutting amount of the tool and the geometrical parameters of the tool. Zhang oas et al established a surface roughness multiple regression prediction model based on cutting speed, feed amount and cutting depth in a paper "application of response surface method in surface roughness prediction model and parameter optimization" published in academic journal Shanghai university of transportation journal (No. 4: P447-451 in 2016), aiming at the turning of titanium alloy TC11 which is a difficult-to-machine material. In a paper "surface roughness prediction for precision turning of lenses", published in academic journal, "journal of mechanical engineering (2013, 15 th: P192-198), Wang Xingsheng et al established a workpiece surface roughness prediction model based on the radius of a cutter arc, the feed per circle, the back bite, the spindle rotation speed and the discrete angle for precision turning of mirror surfaces. However, the above models do not take into account the influence of the wear condition of the tool on the surface roughness of the workpiece. The abrasion of the cutter is inevitable in the turning process, the abrasion of the cutter generally comprises three stages of initial abrasion, normal abrasion and rapid abrasion, and the cutter is generally operated in the initial abrasion and normal abrasion stages. The effect of tool wear conditions on workpiece surface roughness is very significant.
In conclusion, how to simply and accurately calculate the surface roughness of a workpiece during turning according to turning parameters and the abrasion condition of a cutter has important guiding significance for researching how to optimize process parameters to reduce the surface roughness of the workpiece and improve the surface quality, and becomes a technical problem which needs to be solved by technicians in the field.
Disclosure of Invention
The invention aims to provide a simple and accurate method for calculating the surface roughness of a workpiece during turning based on tool wear. The technical scheme is as follows: the method comprises the following steps: 1) establishing a workpiece surface roughness calculation model during turning, 2) measuring and calculating each undetermined coefficient in the workpiece surface roughness calculation model by means of a roughness meter and a metallographic microscope, and 3) calculating the workpiece surface roughness during turning according to turning parameters and the wear amount of a rear tool face of a turning tool under the condition that a tool material, a workpiece material and a processing mode are the same.
The method is characterized in that:
in the step 1), based on a metal cutting theory, according to the relation between the turning parameters and the surface roughness of the workpiece and considering the influence of the abrasion condition of the cutter on the surface roughness of the workpiece, establishing a calculation model of the surface roughness of the workpiece during turning:
Ra=k×ap a×fb×Vc×VBd(1)
wherein R isaIs the workpiece surface roughness; VB is the wear amount of the rear cutter face of the turning tool and is used as a characteristic value of the wear condition of the cutter; a ispThe amount of the back eating is the amount of the back eating; f is the feed amount; v is the cutting speed; k. a, b, c and d are undetermined coefficients.
In the step 2), each undetermined coefficient in a workpiece surface roughness calculation model during turning is measured and calculated by means of a coarseness meter and a metallographic microscope, and after a tool material, a workpiece material and a processing mode are determined, a turning experiment is carried out to cover the initial wear stage and the normal wear stage of a turning tool:
for each turning process, respectively measuring the wear loss of the rear tool face of the turning tool before and after the processing, and taking an average value as the wear loss VB of the rear tool face of the turning tool in the turning process;
after turning is finished each time, selecting two sections on the machined surface of the workpiece, measuring the surface roughness of the workpiece at intervals of 60 degrees on each section, and averaging 12 measured values to be used as the surface roughness R of the workpiece in the turninga。
Selecting more than 20 groups of turning parameters to carry out turning experiments, and enabling the wear VB and the back bite a of the rear tool face of the turning toolpFeed f, cutting speed V and workpiece surface roughness RaSubstituting the formula (1) to obtain an overdetermined equation set, and calculating coefficients k, a, b, c and d to be determined based on a least square method.
In step 3), in the knifeUnder the condition that the material, the workpiece material and the processing mode are the same, for a group of new process parameters, according to the turning parameters and the wear amount of the rear cutter face of the turning tool, the surface roughness calculation model of the workpiece during turning obtained in the step 1) and the step 2) is used for calculating the surface roughness R of the workpiecea。
Compared with the prior art, the invention has the advantages that: the influence of turning parameters and the abrasion condition of the cutter is comprehensively considered to calculate the surface roughness of the workpiece during turning, and the calculation method is simple and high in precision; process parameter selection is facilitated to improve surface quality and reduce scrap rate.
Drawings
Fig. 1 is a flowchart of the present invention for calculating the surface roughness of a workpiece during turning based on tool wear.
FIG. 2 is a flow chart of calculation of undetermined coefficients in a tool wear-based turning workpiece surface roughness calculation model.
Detailed Description
The invention is described in further detail below with reference to fig. 1 and 2.
In the step 1), based on a metal cutting theory, according to the relation between the turning parameters and the surface roughness of the workpiece and considering the influence of the abrasion condition of the cutter on the surface roughness of the workpiece, establishing a calculation model of the surface roughness of the workpiece during turning:
Ra=k×ap a×fb×Vc×VBd(1)
wherein R isaIs the workpiece surface roughness; VB is the wear amount of the rear cutter face of the turning tool and is used as a characteristic value of the wear condition of the cutter; a ispThe amount of the back eating is the amount of the back eating; f is the feed amount; v is the cutting speed; k. a, b, c and d are undetermined coefficients.
In the step 2), each undetermined coefficient in a workpiece surface roughness calculation model during turning is measured and calculated by means of a coarseness meter and a metallographic microscope, and after a tool material, a workpiece material and a processing mode are determined, a turning experiment is carried out to cover the initial wear stage and the normal wear stage of a turning tool:
for each turning process, respectively measuring the wear loss of the rear tool face of the turning tool before and after the processing, and taking an average value as the wear loss VB of the rear tool face of the turning tool in the turning process;
after turning is finished each time, selecting two sections on the machined surface of the workpiece, measuring the surface roughness of the workpiece at intervals of 60 degrees on each section, and averaging 12 measured values to be used as the surface roughness R of the workpiece in the turninga。
Selecting more than 20 groups of turning parameters to carry out turning experiments, and enabling the wear VB and the back bite a of the rear tool face of the turning toolpFeed f, cutting speed V and workpiece surface roughness RaSubstituting the formula (1) to obtain an overdetermined equation set, and calculating coefficients k, a, b, c and d to be determined based on a least square method.
In the step 3), under the condition that the cutter material, the workpiece material and the processing mode are the same, for a group of new process parameters, the surface roughness R of the workpiece is calculated by applying the workpiece surface roughness calculation model obtained in the step 1) and the step 2) during turning according to the turning parameters and the wear amount of the rear cutter face of the turning toola。
The invention is realized in a CKJ6163 numerical control lathe. The turning workpiece is a 304 stainless steel bar, and 25 times of excircle turning orthogonal experiments are carried out by adopting a CNMG120408 hard alloy blade, an Axio-lab-A metallographic microscope and an RTP-120 multifunctional roughness meter. The turning parameters, tool wear and workpiece surface roughness in the experiment are shown in table 1.
TABLE 1 turning test and actually measured tool wear and workpiece surface roughness
Figure 339574DEST_PATH_IMAGE001
Substituting 25 groups of data in the table 1 into the formula (1) to obtain an overdetermined equation set, and solving a coefficient to be determined based on a least square method, wherein the coefficient to be determined is as follows: k =20.29835, a = -0.03476, b =1.66432, c =0.03534, d = 0.02909. The calculation model of the surface roughness of the workpiece during turning is
Ra=20.29835×ap -0.03476×f1.66432×V0.03534×VB0.02909(2)
The mean square error of the calculated model of the workpiece surface roughness is 0.0102. Under the condition that the cutter material, the workpiece material and the processing mode are the same, a new set of process parameters is used for verifying the effectiveness of the workpiece surface roughness calculation method during turning, and the effectiveness is shown in table 2. The wear amount of the rear tool face of the used turning tool is 0.1097mm, the surface roughness of the workpiece during turning is 3.2634um calculated by the formula (2), the actually measured surface roughness of the workpiece is 3.3075um, and the calculation precision is 98.6%.
TABLE 2 verification test of the established method for calculating the surface roughness of a workpiece during turning
Figure 325329DEST_PATH_IMAGE002
The method comprehensively considers the influence of the turning parameters and the abrasion condition of the cutter to calculate the surface roughness of the workpiece during turning, and has simple calculation method and high precision. The invention is beneficial to selecting technological parameters during turning, improving the surface quality and reducing the rejection rate.

Claims (1)

1.一种基于刀具磨损的车削时工件表面粗糙度计算方法，采用以下步骤：1）建立车削时工件表面粗糙度计算模型，2）借助粗糙度仪、金相显微镜测量并计算工件表面粗糙度计算模型中各待定系数，3）在刀具材料、工件材料、加工方式相同情况下，根据车削参数、车刀后刀面磨损量，计算车削时工件表面粗糙度，其特征在于：1. A method for calculating the surface roughness of a workpiece during turning based on tool wear, using the following steps: 1) establishing a calculation model for the surface roughness of the workpiece during turning, 2) measuring and calculating the surface roughness of the workpiece with the aid of a roughness meter and a metallographic microscope Calculate the undetermined coefficients in the model, 3) In the case of the same tool material, workpiece material and processing method, according to the turning parameters and the wear amount of the flank face of the turning tool, calculate the surface roughness of the workpiece during turning, which is characterized by: 步骤1）中，根据车削参数与工件表面粗糙度的关系，并考虑刀具磨损状况对工件表面粗糙度的影响，建立车削时工件表面粗糙度计算模型：In step 1), according to the relationship between the turning parameters and the surface roughness of the workpiece, and considering the influence of the tool wear condition on the surface roughness of the workpiece, a calculation model for the surface roughness of the workpiece during turning is established: Ra=k×ap a×fb×Vc×VBd (1)R a =k×a p a ×f b ×V c ×VB d (1) 其中，Ra是工件表面粗糙度；VB是车刀后刀面磨损量，作为刀具磨损状况的特征值；ap是背吃刀量；f是进给量；V是切削速度；k、a、b、c和d是待定系数；Among them, Ra is the surface roughness of the workpiece; VB is the wear amount of the flank face of the turning tool, which is used as a characteristic value of the tool wear condition; a p is the amount of back cutting tool; f is the feed rate; V is the cutting speed; k, a , b, c and d are undetermined coefficients; 步骤2）中，借助粗糙度仪、金相显微镜测量并计算车削时工件表面粗糙度计算模型中各待定系数，在刀具材料、工件材料、加工方式确定后，进行车削实验，要涵盖车刀的初期磨损和正常磨损阶段：In step 2), use the roughness meter and metallographic microscope to measure and calculate the undetermined coefficients in the workpiece surface roughness calculation model during turning. After the tool material, workpiece material, and processing method are determined, the turning experiment is carried out, covering the turning tool. Initial wear and normal wear stages: 对于每次车削加工，在加工前和加工后分别测量车刀后刀面磨损量，取平均值作为该次车削加工中车刀后刀面磨损量VB；For each turning process, measure the flank wear amount of the turning tool before and after machining, and take the average value as the flank wear amount VB of the turning tool in this turning process; 每次车削加工完成后，在工件已加工表面选取两个截面，在每个截面上每隔60º取一个点测量工件表面粗糙度，对12个测量值取平均值作为该次车削加工中工件表面粗糙度Ra；After each turning process is completed, two sections are selected on the machined surface of the workpiece, and a point is taken every 60º on each section to measure the surface roughness of the workpiece, and the average of 12 measured values is taken as the workpiece surface in this turning process. roughness R a ; 选取20组以上车削参数进行车削实验，将车刀后刀面磨损量VB、背吃刀量ap、进给量f、切削速度V以及工件表面粗糙度Ra，代入公式（1）得到一个超定方程组，基于最小二乘法计算待定系数k、a、b、c和d；Select more than 20 sets of turning parameters for turning experiments, and substitute the flank wear amount VB of the turning tool, the amount of back engagement a p , the feed amount f, the cutting speed V and the surface roughness R a of the workpiece into formula (1) to obtain a Overdetermined equation system, calculate undetermined coefficients k, a, b, c and d based on the least squares method; 步骤3）中，在刀具材料、工件材料、加工方式相同情况下，对于一组新的工艺参数，根据车削参数、车刀后刀面磨损量，运用步骤1）步骤2）得到的车削时工件表面粗糙度计算模型，计算工件表面粗糙度Ra。In step 3), when the tool material, workpiece material, and processing method are the same, for a new set of process parameters, according to the turning parameters and the wear amount of the flank face of the turning tool, the workpiece during turning obtained in step 1) and step 2) is used. Surface roughness calculation model, calculate the workpiece surface roughness Ra .
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111753433A (en) * 2020-07-03 2020-10-09 中国工程物理研究院机械制造工艺研究所 Construction method of moving model of tool rear tool face abrasion area in curved surface turning process

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008082856A (en) * 2006-09-27 2008-04-10 Nagaoka Univ Of Technology Surface roughness evaluation method and evaluation apparatus
CN105269402A (en) * 2015-10-13 2016-01-27 南京航空航天大学 Method for predicating surface roughness of titanium alloy material based on milling
CN107186547A (en) * 2017-05-25 2017-09-22 重庆大学 Numerical control turning batch machining tool wear on-line monitoring method based on cutting power
CN109277883A (en) * 2018-08-17 2019-01-29 中国航发北京航空材料研究院 Roughness prediction method of ultra-high strength titanium alloy based on weight of cutting parameters

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008082856A (en) * 2006-09-27 2008-04-10 Nagaoka Univ Of Technology Surface roughness evaluation method and evaluation apparatus
CN105269402A (en) * 2015-10-13 2016-01-27 南京航空航天大学 Method for predicating surface roughness of titanium alloy material based on milling
CN107186547A (en) * 2017-05-25 2017-09-22 重庆大学 Numerical control turning batch machining tool wear on-line monitoring method based on cutting power
CN109277883A (en) * 2018-08-17 2019-01-29 中国航发北京航空材料研究院 Roughness prediction method of ultra-high strength titanium alloy based on weight of cutting parameters

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111753433A (en) * 2020-07-03 2020-10-09 中国工程物理研究院机械制造工艺研究所 Construction method of moving model of tool rear tool face abrasion area in curved surface turning process
CN111753433B (en) * 2020-07-03 2022-06-24 中国工程物理研究院机械制造工艺研究所 Construction method of moving model of tool rear tool face abrasion area in curved surface turning process

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