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Automated cutting tool selection and cutting tool sequenceoptimisation for rotational parts
Ali Orala，* M. Cemal Cakir
Mechanical Engineering Department, Uludag University, Bursa, Turkey
Abstract：
The aim of this work is to define computer-aided optimum operation and tool sequences that are to be used in Generative Process Planning System developed for rotational parts. The software developed for this purpose has a modular structure. Cutting tools are selected automatically using the machinability data, workpiece feature information, machine tool data, workholding method and the set-up number. An optimum tool sequence is characterised by a minimum number of tool changes and minimum tool travel time. Tool and operation sequence for minimum tool change are optimised with a developed optimisation method that is based on “Rank“Order Clustering’2003 Elsevier Ltd. All rights reserved.
Keywords:
Computer-aided process planning; Tool selection; Operation sequence; Tool sequence; Optimisation.
1. Introduction
The first step and one of the main objectives of a computer integrated manufacturing system is to integrate
the computer-aided design (CAD) and computeraided
manufacturing (CAM) components. The total integration of these two components into a common
environment CAD/CAM is still under development.
Many of the major developments have been uncoordinated
and there is a great deal of overlap in terms of their intended functions. For example, the present CAD/CAM systems have their strength in geometrical
definition, i.e., CAD component and CAM is mostly limited to CNC programming. Other important intermediate
elements such as process planning are not included. This is due to the fact that the numerical
information generated by a CAD system is not sufficient
for process planning. Computer-aided process planning
systems available in the market are incomplete and
limited when compared to the number of CAD and
CAM systems available [1].
Process planning is an activity, which determines
appropriate procedures to transform a raw material into
final product. In manufacturing industry, the task
of process planning mainly consists of determining
the usage of available resources, such as machine
tools, workholding devices, cutting tools, generation of
operation sequence, determining machining parameters
(i.e., cutting speed, feed rate, depth of cut) and selection
of auxiliary functions [2].
The production cost of a component depends upon
cost of the workpiece material, tooling cost and overhead
costs. Generally, these costs associated with
machining a part are fixed; thus the only scope to
reduce the overall cost of the part is to focus on the
tooling cost. Selection of optimal tooling directly affects
the part cost [1]. In the view of the significant reductions
in cost that can be obtained by selecting the correct
cutting tool and its associated optimum cutting conditions,
it is considered that any selection system that does
not take into account all of the relevant technological
parameters has several limitations [3]. Production time is
defined as the machining time plus non-machining time
to machine a component. Determination of optimal
sequence cutting tools on turret magazine of a CNC
machine tool is an important task for achievement of
optimal machining sequences for reducing total nonmachiningtime
[4].The aim of this work is to define computer-aided
optimum operation and tool sequencing to be used in
the generative process planning system developed for
rotational parts (GPPS-RotP).
2. State-of-art of cutting tool selection
The objectives of tool selection exercise are to select
the best tool holder(s) and insert(s) from available
cutting tools database. In the past, the operator would
select the best tool set according to his experience, which
cannot be converted into logic or algorithmic rules. This
method is called as manual approach, which commonly
results in errors and inconsistencies. Disadvantages of
manual approaches led to development of automated
approaches that aimed to reduce the probability of
errors and inconsistencies. The correct choice of cutting
tools is determined by the overall part configuration,
rather than by individual contour section or workpieces.
Computer-aided tool selection systems have been developedfor this purpose. Plummer and Hannam [5] took
workpiece material and profile geometry into account
but ignored selection of carbide grade, chipbreaker,
cutting edge length, and nose radius. Giusti et al. [6]
developed the expert tool selection module for turning
operations. This module depends heavily upon the
expertise of the operator for an efficient structuring of
the rule-based approach. Chen et al.[7] developed an
automatic tool selection system for rough turning on a
CNC lathe. Selection is made from appropriate tool
library employing a heuristic method in order to reduce
the search time. Tool selection procedure searches for
the best tool for a desired operation. Out of the various
potential tools, the only criterion for tool selection is
least cost. Chen and Hinduja [8] used a tool selection
process by checking collision between tool and workpiece
or machine tool for workpiece to be machined. In case of any collision, use of two or more tools formachining is considered.
Hinduja and Huang [2] carried out a study called OPPLAN
in which they assumed that single tool was used
for recess or groove machining. Domazet [9] used a
hybrid approach in that both algorithms and production
rules matrix method were used for tool selection; cutting
conditions were determined using tool manufacturer
data. Fernandes and Raja [1] carried out tool selection
process for external and internal turning, but they
considered only cylindrical and face turning operations.
Edalew et al. [10] developed a computer-based intelligent
system for automatic tool selection system. This
system was operated in a fully interactive mode and
information associated with a particular subject, such as
part status, feature ordering (up to 12 feature types
could be used to describe the component) and the
component materials were incorporated into system.
The analysis of the component included feature specificationand dimensions, which were entered by the user.
3. Tool selection parameters
Success in metal cutting depends on the selection
proper cutting tool both in respect to the tool and
material to be machined. The elements that influence the
tool selection decision are: (i) workpiece materials, i.e.,
chemical and metallurgical state, etc., (ii) part characteristic,
i.e., geometry, accuracy, finish and surface
integrity, etc. (iii) machine tools characteristics including
the workholder, tool number of the tool magazine and
tool holder dimension, (iv) cutting tools or insert
characteristics [11].
Cutting tools selection is a very important subtask
involved in process planning systems. Tool selection
module uses knowledge such as geometry for workpiece
(feature recognition), surface finish, shape, location and
direction tolerance, material of the workpiece, machinability
data such as speed, feed rate, depth of cut,
machine tool, set-up number, process type, workholding
device. GPPS-RotP has seven modules as shown in
Fig. 1.
3.1. Feature recognition
The first step in automatic process planning activities
is recognising the geometry of workpiece. Feature
recognition is a design interface for process planning
which is an automatic transfer of part description data
from CAD system to process planning system [12]. The
part-feature recognition system that is developed has got
similarities with syntactic pattern-recognition technique
developed by Fu [13]. Fu used 24 pattern primitives to
formalise the pattern-recognition process. In the present
work, 16 pattern primitives were defined as shown in
Fig. 2. They are basically different shapes of line and arc
segments with a start point, end point and a direction.
Turning surfaces can be defined an elements such as
diameter, taper, face, arc, chamfer, recess or grooving
with the aim of pattern primitive. For example,
a diameter can be represented by either the pattern
primitive “A” or “C”, a face can be represented by ”D”
or “B”.
In recognition, features are classified into two groups:
primary features and secondary features as shown in
Fig. 3. Primary form features are cylinder, taper and
arcs. Secondary form features are form features other
than cylinders, tapers and arcs often found on rotational
components. Giving only the upper half of the 2D
profile information, which is a series of lines and arc
segments, does the definition of the geometry of a
rotational part.
4. Cutting tool selection
Cutting tools that are considered consist of
two main components: the tool holder and indexable
insert. The objective of any tool selection is to
determine several parameters such as tool holder
(clamping system, type, point angle, hand of cut, size,
etc.), insert (shape, size, grade, nose radius, etc.),
cutting conditions (in this work insert size is
determined according to specified cutting data), type
of coolant (if required) and total cost of machining the
components [17].
The outline for selecting indexable turning tool
selection is first to select the tool holder system, followed
by the tool holder and finally the suiting insert. In the
present work, tool selection is feature based and fully
automatic. Required information for tool selection are:
machinability data, feature recognition for workpiece,
machine tool to be used, workholding device and initial
operation sequence.
Initial operation sequence consists of four basic steps:
machining of right-external zone (if workpiece consists
of two zones, right zone has machining precedence),
machining of right-internal zone, machining of leftexternal
zone, machining of left-internal zone. Initial
operation sequence is changed automatically according
to the clamping surface defined by clamping method
module.
The selection of tool holders is based on the basic
machining operations required to transform the
workpiece into desired shape. The first check is that
the tool holder is of a suitable overall type. Certain
critical dimensions of the cutter must also be
checked against the shape of the operation, such as
effective cutting edge length and gauge length. The
overall size of the tool must also fit into the machine
tool magazine [18].
4.1. Cutting tool selection for rough turning operations
The various geometrical parameters defining
indexable inserts for turning tools are included in ISO
code. Tool selection module not only takes the
parameters in the ISO codes into consideration, but
carbide grades and functions of tools as well. In the
present work, inserts with 95_ of approach angle
and 80_ of point angle are considered first
for rough turning operations. This enables them to
machine stepped profiles without any geometric
collision problem.
4.2. Tool selection for recess and groove turning
In comparison to tool selection criteria used for rough
turning, more comprehensive tool selection criteria
should be used for recessing and grooving.
The recess term used in this paper refers to a feature
that has a minimum width of 16mm and that can be
machined by one or two tools of opposite hands [2]. The
study reported herein adopts this definition. Yet it does
not use this definition as a sole criterion for cutting tool
selection for groove and recess. The width of a feature is
commonly used as a criterion for classifying it as a groove.
If no accessibility problem occurs during machining, then
another cutting tool other than grooving tool can be
selected. The characteristics of the features such as width,
depth, and concave, convex and taper parts should also be
considered in selecting appropriate cutting tools.
In tool selection process, it is necessary to analyse the
feature information through a series of IFyTHEN
structures. Thus, appropriate tool holder and insert are
automatically chosen from the tool library. Insert with
the largest point angle is the most preferred one in terms
of insert strength, therefore is the starting point. However,
large point angle may cause a problem in accessing to the
feature. Accessibility to the feature is then checked for the
tool with a smaller point angle. This control routine is
carried on until the most appropriate tool is found. If this
control routine cannot find any appropriate tool for
recessing, the accessibility of two tools to the feature is
tested via methods of geometric analyses.
Different criteria to be used to machine a recess with a
single tool and appropriate tool parameters are given in
Table 3. Different recessing methods and tools are
sketched in Fig. 11. Recesses that can be machined with
a single tool or two tools are shown in Fig. 11a and c,
respectively. For any problem in accessing to the feature
with all available tools, accessibility of the feature using
two tools is checked through methods of geometric
analyses. Geometric analyses are applied to check any
collision between workpiece and tool that prevents
accessibility to the feature. If there is any collision, the
geometry of workpiece is temporarily modified as shown
in Fig. 11b. For the un-machined region on the recess/
groove, another tool with an opposite feed direction is
chosen (Fig. 11c). For the temporarily modified geometry,
there should be no collision between workpiece and tool to
be able to machine the recess/groove. If no collision is
detected, two tools are assigned for the operation.
Geometric analysis in tool selection module ATOS (Automatic
Tool Selection Module) is carried out as follows:
1. During the last pass of the first tool that does the
machining, first contact point K of tool on the groove
base is determined.
2. Groove contact point L of the second tool that
finishes the machining is determined。
6. Conclusion
In this work, cutting tool selection was carried out by
taking the geometry of workpiece, surface roughness,
chip breaking area of the cutting tools, machinability
data, machine tools information, workholding methods
and number of set-ups into consideration. Tools are
chosen and operation sequence is then optimised with a
developed optimisation method that is based on “Rank
Order Clustering“.
More than 500 practical rules and years of experience
are used in the determination of machinability data,
machine tool, workholding method and cutting tools;
and the application of the software into practical life
shows that the system developed is capable of providing
fast and successful process plans for complex workpieces.
。
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自動化的切割工具選擇和切割工具序列優(yōu)化為旋轉的零件
阿里, *, M. Cemal Cakir
機械工程部門, Uludag 大學, 伯薩, 土耳其
摘要：
這工作的目標將定義將被使用在生產(chǎn)過程的計算機輔助的最宜的操作和工具序列規(guī)劃系統(tǒng)顯現(xiàn)了出為旋轉的零件。軟件被開發(fā)為這個目的有一個模件結構。切割工具是自動地選擇使用可切削性數(shù)據(jù), 制件特點信息, 機械工具數(shù)據(jù)的方法和設定數(shù)字。一個最適宜的工具序列為工具變動和極小的工具旅行時間的一個最小數(shù)字描繪。工具和操作序列為極小的工具變動被優(yōu)選以根據(jù)"等級的一個被開發(fā)的優(yōu)化方法命令成群“。 2003 年Elsevier 有限公司。版權所有。
主題詞:
計算機輔助的過程計劃; 工具選擇; 操作序列; 工具序列; 優(yōu)化。
1. 介紹第一步和a 的當中一個主要宗旨計算機集成制造系統(tǒng)將集成計算機輔助設計(CAD) 并且計算機輔助制造的(CAM) 組分。共計這兩個組分的綜合化入共同性環(huán)境CAD/CAM 仍然是在發(fā)展中。許多主要發(fā)展不協(xié)調并且有很多交疊根據(jù)他們的意欲的作用。例如, 禮物 CAD/CAM 系統(tǒng)有他們的力量在幾何定義, 即, CAD 組分和CAM 主要是對CNC 編程限制。其它重要中間體元素譬如處理計劃不是包括。這歸結于數(shù)字的事實信息由計算機輔助設計系統(tǒng)引起不是充足的為處理計劃。計算機輔助的過程計劃系統(tǒng)可利用在市場上是殘缺不全的和有限當與CAD 的數(shù)字比較和 CAM 系統(tǒng)可利用[ 1 ] 。處理計劃是活動, 確定合適規(guī)程變換原材料成最終產(chǎn)品。在制造工業(yè), 任務處理計劃主要包括確定可利用的資源用法, 譬如機器工具, 工件夾緊的設備, 切割工具, 世代操作序列, 確定用機器制造的參量 (即, 切開的速度, 供給率, 裁減的深度) 并且選擇輔助函數(shù)[ 2 ] 。組分的生產(chǎn)成本依靠制件材料的費用, 用工具加工的費用和天花板費用。通常, 這些費用與交往用機器制造零件是固定的; 因而唯一的范圍減少零件的整體費用是集中于鑿出的裝飾費用。優(yōu)選的鑿出的裝飾直接影響的選擇零件費用[ 1 ] 。根據(jù)重大減少在可能由選擇獲得正確的費用切割工具和它伴生的最宜的切口情況, 它被考慮的任一個選擇系統(tǒng)不考慮到所有相關技術參量有幾限制[ 3 ] 。生產(chǎn)時間是定義如同機時加上非用機器制造的時間用機器制造組分。決心優(yōu)選程序化切割工具在CNC 的塔樓雜志機械工具是一項重要任務為成就優(yōu)選的用機器制造的序列為減少總nonmachining 時間[ 4 ] 。這工作的目標將定義計算機輔助最宜的操作和工具程序化被使用生產(chǎn)處理規(guī)劃系統(tǒng)顯現(xiàn)了出為旋轉的零件(GPPS-RotP) 。
2. 切割工具選擇狀態(tài)藝術工具選擇鍛煉宗旨將選擇最佳的工具holder(s) 和insert(s) 從可利用切割工具數(shù)據(jù)庫。從前, 操作員會選擇最佳的工具箱根據(jù)他的經(jīng)驗, 不能被轉換成邏輯或算法規(guī)則。這方法叫作為手工方法, 共同地結果在錯誤和不一致。不利指南方法導致發(fā)展自動化接近那打算減少可能性錯誤和不一致。切口正確選擇工具由整體部份配置確定, 而不是由各自的等高部分或制件。計算機輔助的工具選擇系統(tǒng)被開發(fā)了為這個目的。Plummer 和Hannam [ 5 ] 采取了制件材料和外形幾何但碳化物等級, chipbreaker 的被忽略的選擇, 先鋒長度, 和鼻子半徑。Giusti 等[ 6 ] 發(fā)展了專家的工具選擇模塊為轉動操作。這個模塊沉重取決于操作員的專門技術為一高效率構造基于規(guī)則的方法。陳?等。
[ 7 ] 開發(fā)了自動工具選擇系統(tǒng)為概略轉動在a CNC 車床。選擇由適當?shù)墓ぞ弑蛔鰣D書館使用一個啟發(fā)式方法為了減少查尋時間。工具選擇做法查尋為為渴望的操作的最佳的工具。在各種各樣外面潛在的工具, 唯一的標準為工具選擇是最少費用。陳和Hinduja [ 8 ] 使用了一種工具選擇過程由檢查碰撞在工具和制件之間或為制件的機械工具用機器制造。在任何碰撞案件, 對二個或更多工具的用途為用機器制造被考慮。Hinduja 和黃[ 2 ] 執(zhí)行了研究稱OPPLAN 在哪些他們假設, 唯一工具被使用了為凹進處或凹線用機器制造。Domazet [ 9 ] 使用了a 雜種方法算法和生產(chǎn)規(guī)則矩陣方法被使用了為工具選擇; 切口情況是堅定的使用工具制造商數(shù)據(jù)。Fernandes 和Raja [ 1 ] 執(zhí)行了工具選擇過程為外在和內部轉動, 但他們認為只圓柱形和面孔轉動的操作。 Edalew 等[ 10 ] 開發(fā)了一計算機為主聰明系統(tǒng)為自動工具選擇系統(tǒng)。這系統(tǒng)被管理在一種充分地對話方式下和信息聯(lián)系了一個特殊主題, 譬如部份狀態(tài), 特點定貨(12 以型為特色能被使用描述組分) 和組分材料被合并了系統(tǒng)。對組分包括的特點規(guī)格的分析并且維度, 由用戶輸入。
3. 工具選擇參量成功在金屬切口取決于選擇適當?shù)那懈罟ぞ哧P于工具和材料用機器制造。影響的元素工具選擇決定是: (i) 制件材料, 即, 化工和冶金狀態(tài), 等, (ii) 部份特征, 即, 幾何、準確性、結束和表面正直, 等(iii) 機械工具特征包括 workholder, 工具雜志的工具數(shù)字和工具囤戶維度, (iv) 切割工具或插入物特征[ 11 ] 。切割工具選擇是一個非常重要子任務介入在處理規(guī)劃系統(tǒng)。工具選擇模塊使用知識譬如幾何為制件 (特點認識), 表面結束, 形狀, 地點和方向容忍, 制件的材料, 可切削性數(shù)據(jù)譬如速度, 供給率, 裁減的深度, 機械工具, 被設定的數(shù)字, 處理類型, workholding 設備。GPPS-RotP 有七個模塊依照被顯示圖1.
3.1. 特點認識第一步在自動處理計劃活動認可制件幾何。特點認識是一個設計接口為處理計劃哪些是部份描述數(shù)據(jù)自動調動從計算機輔助設計系統(tǒng)到處理規(guī)劃系統(tǒng)[ 12] 。部份特點被開發(fā)的識別系統(tǒng)相似性以語法pattern-recognition 技術由Fu [ 13 ] 顯現(xiàn)出。Fu 使用了24 樣式原始形式化pattern-recognition 過程。在禮物依照被顯示工作, 16 樣式原始被