SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
UNIT SIX
MANUFACTURING PROCESSES
LESSON ONE MACHINING PROCESSES
process 过程
工艺规程,方法
The manufacturing (or production) process
of a factory,in a broad sense,is the sum total of
separate processes involved in the conversion of
raw materials or semi-finished products into final
products,As far as a factory is concerned,its
products can be blanks,fi ni shed parts,
mechanisms,units or end products,The raw
materials or semi-finished products used for
manufacturing the products are often produced
and supplied by other factories,Sometimes the
products of the factory need to be further
processed by other factories before they become
the end products.
in a sense
从某种意义上说
sum total 总数
as far as 至于
blank 空白的
毛坯，坯件
part 部分，零件
mechanism
机构，机理
unit 单位，部件
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
The manufacturing (production) process
includes not only processes acting directly upon
the manufactured objects,but also preparatory
processes (such as production planning,process
planning,production scheduling,tooling
preparation,etc.) and auxiliary processes (such as
equipment maintenance,inter-shop material and
workpiece handling,cutting tool sharpening,
quality inspection,production statistics,cost
accounting,etc.)
The processes,acting directly upon the
manufactured objects,change the shape,
dimensions and properties of raw materials or
semi-finished products,or assemble parts into
final products,These processes are manufacturing
(or production) processes in a narrow sense.
cost accounting
成本会计，
成本核算
narrow sense
狭义
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
There are various manufacturing processes
used for converting raw materials into finished
parts,These processes include casting,forging,
welding,punching,forming,machining,heat-
treatment,plating,coating,and so on,Among
them,the machining process plays an
important role in the manufacture of parts.
The machining process of a part may
include various machining operations,such as
turning,milling,drilling,grinding,broaching,
gear-cutting,etc,depending on the required
shape,dimensions,accuracy and surface
quality of the part,In order to ensure the
quality of a completed part,well-planned
processes documents are necessary.
casting 铸造
forging 锻造
welding 焊接
punching 冲压
forming 成形加工
heat-treatment热处理
machining 切削加工
plating 电镀
coating 油漆
operation 操作,工序
turning 车削
milling 铣削
drilling 钻削
grinding 磨削
broaching 拉削
etc.= et cetera
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
After a new product is designed,planning the processes for its
component parts is the first step of the preparatory work for
manufacturing,The planned process documents serve as the basis
and initial data for all other preparatory work,and the rules and
regulations for production operations,the quality of process plans
influences directly the degree of complexity of the preparatory
work for manufacturing,the time length of the preparatory stage,
the quality of parts and products manufactured,the degree of
complexity of production scheduling and operations sequencing,
the makespan of parts and products,and the production costs.
Hence process planning is of key importance to manufacturing.
制造时间
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
Often there exist alternatives of process plans for
manufacturing a part,The quality of a process plan should be
evaluated from a technological as well as an economical
standpoint,A good process plan not only ensures the required
quality of manufactured parts,but also reduces the production
cost,In process planning,a comprehensive analysis of part
structure,material and technical specifications,production
volume and manufacturing conditions must be made,so as to
properly make all the decisions related to the planning of the
process.
﹡ Many decisions should be made in machining process planning.
﹡ Selection of the blank and its manufacturing method.
﹡ Selection of machining methods for part surfaces.
﹡ Determination of operations sequence.
﹡ Determination of workpiece setting method for each operation.
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
﹡ Selection of machining equipment and tooling for operations.
﹡ Determination of operating procedure for each operation.
﹡ Determination of operational dimensions and tolerances for
machining operations.
﹡ Selection of machining conditions and determination of time
standards of each operation.
Composition of Machining Processes
A machining process is made up of a number of operations
through which raw materials or blanks are transformed into parts,
The basic components of machining processes are operations.
An operation is a complete portion of the machining process for
cutting,grinding,or otherwise treating,a workpiece (or several
workpieces simultaneously) at a single workplace,An operation
is accomplished by one or several operators (until they start to
repeat the same procedure for the next workpiece or next set of
workpieces in the batch),work piece 工件一批
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
The operation is characterized by the
unchanged equipment,unchanged workpiece,
and continuity,For example,a batch of
workpieces is machined first on a lathe,and
then on a milling machine,Obviously,two
operations are involved,Fig,6.l shows the
machining of the center hole and recess of a
flange,If a batch of the workpieces are
machined consecutively by drilling,boring
holes and boring recesses with three different
cutting tools at the same workplace (e.g,a
lathe),it is a single operation,If these holes
are drilled on a lathe and then bored on
another,the machining of the workpieces
will consist of two operations instead of one.
recess 退刀槽
flange 法兰盘
bore 镗孔
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
The contents of an operation include all activities directly
related to machining (or other treatment),as well as all necessary
handling and auxiliary motions,An operation is the basic unit of
a manufacturing process,An operation element is a component
of an operation,which is performed without changing the cutting
tool (or a group of simultaneously-used cutting tools),the
machined workpiece surface,and cutting speed and feed,If one
of them changes,it becomes a different operation element.
For example,the hole machining operation shown in Fig,6.l
consists of three operation elements which are first,drilling of
the hole; second,boring of the hole; and third,boring of the
recess,This is because,in each of the three operation elements,
either the changing of the cutting tool or the machined surface
occurs,If the hole is rough bored first and then,after changing
the cutting speed and feed,finish bored,the operation would
consist of four operation elements.
工
步
figure
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
In order to obtain higher machining efficiency,several
simple operation elements are sometimes combined into one
complex operation element,In a complex operation element,
several cutting tools are simultaneously used to machine
different workpiece surfaces,Fig.6.2 (a) shows the
machining of two plane surfaces using two milling cutters.
Fig.6.2 (b) illustrates the machining of a workpiece on a lathe
equipped with a turret,This has been commonly used in
many turret lathes,automatic lathes,and numerically
controlled turning centers for increased productivity,When it
is necessary to remove a thick layer of material from the
workpiece and it cannot be done in a single cut,an operation
element can be divided into several passes (or cuts),A pass,
or cut,is a single cutting motion of the cutting tool in the
direction of the feed along the machined surface,without
changing the set-up of the tool or the cutting speed or feed.
转
塔
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
As an example,if there is a big difference between the
diameters of the hole and the recess shown in Fig.6.1,the
boring of the recess must be accomplished in several passes,In
each pass,a layer of material is removed,However,all these
passes are part of the recess machining operation element,
since none of the cutting tool,machined surface,cutting speed,
or feed changes.
There are many elementary handling operations for the
operator to accomplish a given operation,an operation
element or a pass (for example,loading and unloading the
workpiece,changing the tool,starting the machine tool,
advancing the tool to approach the workpiece,measuring the
machined surface,etc.),Among them,the set-up of the
workpiece plays an important role.
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
A set-up consists of locating and clamping of a
workpiece,After locating,the workpiece is in a
correct position relative to the machine tool or
workholder,Clamping is used to fix the workpiece
at the located position,If an operation contains
only a single locating and clamping operation,it is
said that this operation is performed in a single
set-up as shown in Fig.6.2 (a) where two milling
cutters are used simultaneously to mill the two
sides of the workpiece.
Therefore,the term "set-up" has two different
meanings:
l,Setting up is to locate and clamp a workpiece on
a machine tool or workholder to obtain the correct
position relative to the machine tool.
locating 定位
clamping 夹紧
workholder
工作夹具
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
2,A set-up is part of an operation performed
without reclamping the workpiece,More set-ups
of the workpiece in an operation cause more
time and more set-up errors,For this reason,
when a workpiece must be machined at different
positions on a machine tool,a workholder often
is employed,This can change the position of the
workpiece without unclamping it,In this case,
there will be several different positions after a
single set-up.
reclamping
二次装夹
In the previous example,if an index base or
swivel-type fixture is used,which can change the
position of the workpiece without unclamping,
then the milling of the shoulders is accomplished
in two positions.
index 分度头
swivel 旋转
fixture 夹具
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
Similar to set-up,the term,position” also has two different
meanings,
l,A position refers to the position of a workpiece with respect
to the machine tool after the workpiece is clamped.
2,A position is part of an operation performed without changing
the position of the workpiece with respect to the machine tool.
Requirements for Process Planning
Process planning is a significant task linking product design
and product manufacturing,which greatly affects the quality of
products,production efficiency and costs,A reasonably good
process plan should satisfy the following requirements:
l,A process plan must ensure all the quality requirements of the
part defined in the part drawing.
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
2,A process plan should bring about reasonably high production
efficiency in order to fulfill the production quota before its due
date.
3,A process plan should ensure low production costs,
4,A process plan should help improve the working conditions
and promote the uninterrupted development of manufacturing
technology.
定额，限额
Product quality,production efficiency,and production cost
are the main technological and economical considerations in
process planning,Of these,product quality is of primary
importance.
In process planning,the first important problem to be
resolved is how to achieve the required accuracy to meet design
specifications,When a process plan is implemented,it must
ensure all the quality requirements as much as possible without
relying upon the skills of the operator.
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
Other technological and economical problems should be
resolved as well,For example,is it appropriate to adopt
refined blanks (precision castings or forgings)? Is it suitable
to use newly developed machining methods,machine tools
or tooling (NC machine tools,machining centers,upper
precision machining methods,advanced tools,jigs and
fixtures,etc.),or unconventional machining methods
(ECM,EDM,supersonic or laser machining,etc.)? All these
questions have to be answered rationally in order to achieve
reasonable manufacturing efficiency and low-cost
production.
夹具
钻模
electro chemical machining 电解加工
electric discharge machining 电火花加工
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
Several alternatives of process plans or some of its operations
are evaluated and compared so that the best plan can be selected.
The best alternative is not necessarily the one which employs the
most advanced machine tools,nor the one which provides the
highest manufacturing efficiency,The evaluation of the alternatives
should be a synthetical analysis from the technological and
economical points of view,In most cases,the overall cost is the
basis for decision,But it is important that the alternatives meet the
requirements of quality and prompt production.
Basic Information for Process Planning
The planning of a machining process is based on the drawing
and specifications of the part to be manufactured,drawing of the
blank piece from which the part is made,planned volume of
production,available equipment and tooling for production,and
relevant engineering and economic standards and handbooks,They
provide the initial data for process planning.
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
Drawing and Specifications of a Workpiece
Part drawing and its technical specifications provide the
essential basis for process planning,The information comes
from a blueprint,a working drawing,or a CAD file,It should
be explicit to the most minor details,It includes:
l,Part configuration,This should consist of necessary and
sufficient projections,sections, cutaway views and
dimensions in order to illustrate the shape and size of the part.
2,Technical specifications,All necessary dimensions and shape
tolerances,the surfaces finish for all surfaces,and special
specifications (for instance,the weight check,the balance
check,the audio frequency check,etc.) should be clearly
indicated.
蓝
图
3,Material,The material of which the part is made should be
specified,including required heat-treatment,hardness of the
material,detection of defects,if any,and kind of blank
(casting,forging etc.).
局部剖视图
表面光洁度 Computer-Aided Design
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
All part information must be understood thoroughly by the
planner,It should be regarded as the starting point of process
planning,Incomplete,incorrect or indefinite part information
will result in bad technological decisions and ineffective
process plans.
A blank is designed according to the part drawing,taking
into consideration the mechanical property requirements and
cost of the part,It is necessary to know how the blank to be
manufactured,the shape,size and accuracy of the blank,These
factors determine the allowances of all part surfaces,which are
to be removed,and the locating and clamping methods of the
workpiece in the initial stage of a machining process.
Drawing of the Blankpiece
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
There are different kinds of blanks made by
different processes,for example,castings,smith
and die forgings,cermets (blanks pressworked
from sheet metal),welded blanks,and blanks cut
from rolled stock,etc.,One of the main trends in
the development of machining techniques is the
improvement in the accuracy and surface finish of
blanks,that is,to make the shape and size of the
blanks as close as possible to those of the parts.
This reduces the amount of machining and
material wasted during machining,However,the
selection of the blank manufacturing processes
depends also upon the type of production,since
the amount of blanks to be manufactured is the
decisive factor when determining the unit
production cost of the blanks.
smith 锻工
cermets
粉末冶金
die forging
热锻模
模锻件
rolled stock
轧制材
unit production
cost
单元生产成本
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
It is necessary to have a drawing of the blank as well as its
manufacturing specifications in process planning,Considering
these specifications,selection of the workpiece locating and
clamping methods can be properly performed,These
considerations are concerned with the design of the
workholders,and planning of operation elements in the initial
stages of the processes.
UNIT SIX
MANUFACTURING PROCESSES
LESSON ONE MACHINING PROCESSES
process 过程
工艺规程,方法
The manufacturing (or production) process
of a factory,in a broad sense,is the sum total of
separate processes involved in the conversion of
raw materials or semi-finished products into final
products,As far as a factory is concerned,its
products can be blanks,fi ni shed parts,
mechanisms,units or end products,The raw
materials or semi-finished products used for
manufacturing the products are often produced
and supplied by other factories,Sometimes the
products of the factory need to be further
processed by other factories before they become
the end products.
in a sense
从某种意义上说
sum total 总数
as far as 至于
blank 空白的
毛坯，坯件
part 部分，零件
mechanism
机构，机理
unit 单位，部件
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
The manufacturing (production) process
includes not only processes acting directly upon
the manufactured objects,but also preparatory
processes (such as production planning,process
planning,production scheduling,tooling
preparation,etc.) and auxiliary processes (such as
equipment maintenance,inter-shop material and
workpiece handling,cutting tool sharpening,
quality inspection,production statistics,cost
accounting,etc.)
The processes,acting directly upon the
manufactured objects,change the shape,
dimensions and properties of raw materials or
semi-finished products,or assemble parts into
final products,These processes are manufacturing
(or production) processes in a narrow sense.
cost accounting
成本会计，
成本核算
narrow sense
狭义
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
There are various manufacturing processes
used for converting raw materials into finished
parts,These processes include casting,forging,
welding,punching,forming,machining,heat-
treatment,plating,coating,and so on,Among
them,the machining process plays an
important role in the manufacture of parts.
The machining process of a part may
include various machining operations,such as
turning,milling,drilling,grinding,broaching,
gear-cutting,etc,depending on the required
shape,dimensions,accuracy and surface
quality of the part,In order to ensure the
quality of a completed part,well-planned
processes documents are necessary.
casting 铸造
forging 锻造
welding 焊接
punching 冲压
forming 成形加工
heat-treatment热处理
machining 切削加工
plating 电镀
coating 油漆
operation 操作,工序
turning 车削
milling 铣削
drilling 钻削
grinding 磨削
broaching 拉削
etc.= et cetera
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
After a new product is designed,planning the processes for its
component parts is the first step of the preparatory work for
manufacturing,The planned process documents serve as the basis
and initial data for all other preparatory work,and the rules and
regulations for production operations,the quality of process plans
influences directly the degree of complexity of the preparatory
work for manufacturing,the time length of the preparatory stage,
the quality of parts and products manufactured,the degree of
complexity of production scheduling and operations sequencing,
the makespan of parts and products,and the production costs.
Hence process planning is of key importance to manufacturing.
制造时间
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
Often there exist alternatives of process plans for
manufacturing a part,The quality of a process plan should be
evaluated from a technological as well as an economical
standpoint,A good process plan not only ensures the required
quality of manufactured parts,but also reduces the production
cost,In process planning,a comprehensive analysis of part
structure,material and technical specifications,production
volume and manufacturing conditions must be made,so as to
properly make all the decisions related to the planning of the
process.
﹡ Many decisions should be made in machining process planning.
﹡ Selection of the blank and its manufacturing method.
﹡ Selection of machining methods for part surfaces.
﹡ Determination of operations sequence.
﹡ Determination of workpiece setting method for each operation.
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
﹡ Selection of machining equipment and tooling for operations.
﹡ Determination of operating procedure for each operation.
﹡ Determination of operational dimensions and tolerances for
machining operations.
﹡ Selection of machining conditions and determination of time
standards of each operation.
Composition of Machining Processes
A machining process is made up of a number of operations
through which raw materials or blanks are transformed into parts,
The basic components of machining processes are operations.
An operation is a complete portion of the machining process for
cutting,grinding,or otherwise treating,a workpiece (or several
workpieces simultaneously) at a single workplace,An operation
is accomplished by one or several operators (until they start to
repeat the same procedure for the next workpiece or next set of
workpieces in the batch),work piece 工件一批
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
The operation is characterized by the
unchanged equipment,unchanged workpiece,
and continuity,For example,a batch of
workpieces is machined first on a lathe,and
then on a milling machine,Obviously,two
operations are involved,Fig,6.l shows the
machining of the center hole and recess of a
flange,If a batch of the workpieces are
machined consecutively by drilling,boring
holes and boring recesses with three different
cutting tools at the same workplace (e.g,a
lathe),it is a single operation,If these holes
are drilled on a lathe and then bored on
another,the machining of the workpieces
will consist of two operations instead of one.
recess 退刀槽
flange 法兰盘
bore 镗孔
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
The contents of an operation include all activities directly
related to machining (or other treatment),as well as all necessary
handling and auxiliary motions,An operation is the basic unit of
a manufacturing process,An operation element is a component
of an operation,which is performed without changing the cutting
tool (or a group of simultaneously-used cutting tools),the
machined workpiece surface,and cutting speed and feed,If one
of them changes,it becomes a different operation element.
For example,the hole machining operation shown in Fig,6.l
consists of three operation elements which are first,drilling of
the hole; second,boring of the hole; and third,boring of the
recess,This is because,in each of the three operation elements,
either the changing of the cutting tool or the machined surface
occurs,If the hole is rough bored first and then,after changing
the cutting speed and feed,finish bored,the operation would
consist of four operation elements.
工
步
figure
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
In order to obtain higher machining efficiency,several
simple operation elements are sometimes combined into one
complex operation element,In a complex operation element,
several cutting tools are simultaneously used to machine
different workpiece surfaces,Fig.6.2 (a) shows the
machining of two plane surfaces using two milling cutters.
Fig.6.2 (b) illustrates the machining of a workpiece on a lathe
equipped with a turret,This has been commonly used in
many turret lathes,automatic lathes,and numerically
controlled turning centers for increased productivity,When it
is necessary to remove a thick layer of material from the
workpiece and it cannot be done in a single cut,an operation
element can be divided into several passes (or cuts),A pass,
or cut,is a single cutting motion of the cutting tool in the
direction of the feed along the machined surface,without
changing the set-up of the tool or the cutting speed or feed.
转
塔
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
As an example,if there is a big difference between the
diameters of the hole and the recess shown in Fig.6.1,the
boring of the recess must be accomplished in several passes,In
each pass,a layer of material is removed,However,all these
passes are part of the recess machining operation element,
since none of the cutting tool,machined surface,cutting speed,
or feed changes.
There are many elementary handling operations for the
operator to accomplish a given operation,an operation
element or a pass (for example,loading and unloading the
workpiece,changing the tool,starting the machine tool,
advancing the tool to approach the workpiece,measuring the
machined surface,etc.),Among them,the set-up of the
workpiece plays an important role.
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
A set-up consists of locating and clamping of a
workpiece,After locating,the workpiece is in a
correct position relative to the machine tool or
workholder,Clamping is used to fix the workpiece
at the located position,If an operation contains
only a single locating and clamping operation,it is
said that this operation is performed in a single
set-up as shown in Fig.6.2 (a) where two milling
cutters are used simultaneously to mill the two
sides of the workpiece.
Therefore,the term "set-up" has two different
meanings:
l,Setting up is to locate and clamp a workpiece on
a machine tool or workholder to obtain the correct
position relative to the machine tool.
locating 定位
clamping 夹紧
workholder
工作夹具
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
2,A set-up is part of an operation performed
without reclamping the workpiece,More set-ups
of the workpiece in an operation cause more
time and more set-up errors,For this reason,
when a workpiece must be machined at different
positions on a machine tool,a workholder often
is employed,This can change the position of the
workpiece without unclamping it,In this case,
there will be several different positions after a
single set-up.
reclamping
二次装夹
In the previous example,if an index base or
swivel-type fixture is used,which can change the
position of the workpiece without unclamping,
then the milling of the shoulders is accomplished
in two positions.
index 分度头
swivel 旋转
fixture 夹具
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
Similar to set-up,the term,position” also has two different
meanings,
l,A position refers to the position of a workpiece with respect
to the machine tool after the workpiece is clamped.
2,A position is part of an operation performed without changing
the position of the workpiece with respect to the machine tool.
Requirements for Process Planning
Process planning is a significant task linking product design
and product manufacturing,which greatly affects the quality of
products,production efficiency and costs,A reasonably good
process plan should satisfy the following requirements:
l,A process plan must ensure all the quality requirements of the
part defined in the part drawing.
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
2,A process plan should bring about reasonably high production
efficiency in order to fulfill the production quota before its due
date.
3,A process plan should ensure low production costs,
4,A process plan should help improve the working conditions
and promote the uninterrupted development of manufacturing
technology.
定额，限额
Product quality,production efficiency,and production cost
are the main technological and economical considerations in
process planning,Of these,product quality is of primary
importance.
In process planning,the first important problem to be
resolved is how to achieve the required accuracy to meet design
specifications,When a process plan is implemented,it must
ensure all the quality requirements as much as possible without
relying upon the skills of the operator.
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
Other technological and economical problems should be
resolved as well,For example,is it appropriate to adopt
refined blanks (precision castings or forgings)? Is it suitable
to use newly developed machining methods,machine tools
or tooling (NC machine tools,machining centers,upper
precision machining methods,advanced tools,jigs and
fixtures,etc.),or unconventional machining methods
(ECM,EDM,supersonic or laser machining,etc.)? All these
questions have to be answered rationally in order to achieve
reasonable manufacturing efficiency and low-cost
production.
夹具
钻模
electro chemical machining 电解加工
electric discharge machining 电火花加工
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
Several alternatives of process plans or some of its operations
are evaluated and compared so that the best plan can be selected.
The best alternative is not necessarily the one which employs the
most advanced machine tools,nor the one which provides the
highest manufacturing efficiency,The evaluation of the alternatives
should be a synthetical analysis from the technological and
economical points of view,In most cases,the overall cost is the
basis for decision,But it is important that the alternatives meet the
requirements of quality and prompt production.
Basic Information for Process Planning
The planning of a machining process is based on the drawing
and specifications of the part to be manufactured,drawing of the
blank piece from which the part is made,planned volume of
production,available equipment and tooling for production,and
relevant engineering and economic standards and handbooks,They
provide the initial data for process planning.
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
Drawing and Specifications of a Workpiece
Part drawing and its technical specifications provide the
essential basis for process planning,The information comes
from a blueprint,a working drawing,or a CAD file,It should
be explicit to the most minor details,It includes:
l,Part configuration,This should consist of necessary and
sufficient projections,sections, cutaway views and
dimensions in order to illustrate the shape and size of the part.
2,Technical specifications,All necessary dimensions and shape
tolerances,the surfaces finish for all surfaces,and special
specifications (for instance,the weight check,the balance
check,the audio frequency check,etc.) should be clearly
indicated.
蓝
图
3,Material,The material of which the part is made should be
specified,including required heat-treatment,hardness of the
material,detection of defects,if any,and kind of blank
(casting,forging etc.).
局部剖视图
表面光洁度 Computer-Aided Design
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
All part information must be understood thoroughly by the
planner,It should be regarded as the starting point of process
planning,Incomplete,incorrect or indefinite part information
will result in bad technological decisions and ineffective
process plans.
A blank is designed according to the part drawing,taking
into consideration the mechanical property requirements and
cost of the part,It is necessary to know how the blank to be
manufactured,the shape,size and accuracy of the blank,These
factors determine the allowances of all part surfaces,which are
to be removed,and the locating and clamping methods of the
workpiece in the initial stage of a machining process.
Drawing of the Blankpiece
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
There are different kinds of blanks made by
different processes,for example,castings,smith
and die forgings,cermets (blanks pressworked
from sheet metal),welded blanks,and blanks cut
from rolled stock,etc.,One of the main trends in
the development of machining techniques is the
improvement in the accuracy and surface finish of
blanks,that is,to make the shape and size of the
blanks as close as possible to those of the parts.
This reduces the amount of machining and
material wasted during machining,However,the
selection of the blank manufacturing processes
depends also upon the type of production,since
the amount of blanks to be manufactured is the
decisive factor when determining the unit
production cost of the blanks.
smith 锻工
cermets
粉末冶金
die forging
热锻模
模锻件
rolled stock
轧制材
unit production
cost
单元生产成本
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING
It is necessary to have a drawing of the blank as well as its
manufacturing specifications in process planning,Considering
these specifications,selection of the workpiece locating and
clamping methods can be properly performed,These
considerations are concerned with the design of the
workholders,and planning of operation elements in the initial
stages of the processes.
