소프트웨어 기술을 융합한 금형가공용 스마트머신 -...
TRANSCRIPT
한국정밀공학회지 제 35권 제 2호 pp. 121-128 February 2018 / 121
J. Korean Soc. Precis. Eng., Vol. 35, No. 2, pp. 121-128 https://doi.org/10.7736/KSPE.2018.35.2.121
ISSN 1225-9071 (Print) / 2287-8769 (Online)
• 특집 • 공작기계의 스마트화 기술
소프트웨어 기술을 융합한 금형가공용 스마트머신 개발
Software Technology Integrated Smart Machine Tool Development forMold Machining
박대유1, 엄규용1, 조현용2, 김두진2, 박재근3, 김수진4,#
De-Yu Park1, Kyu-Yeong Yum1, Hyun-Yeong Cho2, Du-Jin Kim2, Jae-Keun Park3, and Su-Jin Kim4,#
1 ㈜화천기공 기술연구소 (Research Center, Hwachoen Machinery Co., Ltd.)
2 ㈜엔씨비 기술연구소 (Research Center, NCB Co., Ltd.)
3 나이스솔루션 (Nice Solution Co., Ltd.)
4 경상대학교 기계항공공학부 (School of Mechanical and Aerospace Engineering, Gyeongsang National University)
# Corresponding Author / E-mail: [email protected], TEL: +82-55-772-1636
KEYWORDS: Computer aided manufacturing (CAD/CAM), Machining simulation (가공 시뮬레이션), Mold machining (금형 가공),
Smart machine tools (스마트 장비), Process planning (공정 설계), Graphite electrode (흑연 전극)
The mold manufacturing is one batch production that the same process does not repeat. The digital model in software is
processed with a real mold fabricated in high performance without error. In this study process planning, and machining
simulation software are integrated with a smart machine tool for the mold industry. It reduces the operational complexity to
four button clicks after dragging and dropping of 3d model data to fabricate multiple-numbers of graphite electrodes. The
smart machine tool fabricated 27 graphite electrodes with minimum interference of humans in 35 hours.
Manuscript received: November 24, 2017 / Revised: January 18, 2018 / Accepted: January 22, 2018
1. Introduction
Die and mold is a special tool used for the mass production of
same parts repeatedly. Mold manufacturing includes just about all
aspects of manufacturing: part design, mold design, process
planning, prototype production, advanced mechanical electrical
machining methods, and quality control.1 The mold machining is
single batch production that the same process does not repeated
again. The machine tools for mold industry should be smart
enough to fabricate the part of first and last in high performance
without error.
Experts with different skills are working for each of the mold
design, process planning, tool path generation, machine tool
operation and tool management. The separated process in which
the operator manually determines the machining process, tool and
machining pattern produce a long period of time and different
quality depending on their personal skill. The separated process
steps and interference of human are the reasons of fabrication
errors and process delays.
Therefore, there is a need for more researches on CNC machine
tools having an automatic machining function capable of
improving the quality of production process by minimizing the
frequency of manual selection and its effects on machining time.
A lot of process planning, tool path generation, machining
simulation, computer numerical control, and process control have
been researched separately or coupled. The process planning
system coupled with machining simulation was proposed consists
of geometry feature recognition, cutting mode and tool selection,
Copyright © The Korean Society for Precision Engineering
This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/
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122 / February 2018 한국정밀공학회지 제 35권 제 2호
toolpath generation.2 The virtual machining process simulated
cutting mechanics along tool path and optimized NC data by
respecting the physical limits of the machine tool and cutting
operation.3 In order to enable process monitoring for single batch
production without a learning phase, a simulation based approach
should be researched for generating reference data to set process
limits.4 The tool wear and breakage monitoring for single
production of mold was possible based on the machining
simulation.5
Some researchers are trying to integrate computer aided
machining and simulation technology into machine tools. The
procedures to cut letters and patterns using the four-axis lettering
machine were implemented using a personal computer numerical
control system.6 Commercial CAD/CAM software was installed in
open architecture motion controller.7
A large number of EDM (Electric discharge machining)
electrodes are used in plastic injection mold manufacturing. Each
electrode, holder and working coordinate system are designed in
electrode boundaries identified by sharp corner uncut which can be
detected by calculating the surface angles at their common edges.8
Graphite has good thermal conductivity and machinability, is a
widely used tool in EDM electrode materials. Graphite machinability
tests were carried out, followed by an analysis of tool wear and
surface quality generated in down- and up-milling.9 The feed rate is
the most important machining factors affecting on the groove
width precision and the surface roughness average for the end-
milling of high-purity graphite under dry machining conditions.10
During the machining multiple graphite electrodes on a machine
table, a lot of human mistakes occur during stock positioning, work
coordinate setting, NC data handling, and tool setting. But, there is
no research on solving these problems with intelligent machining
process or machine tool.
In this research a smart machine tool for electrode machining in
mold industry is introduced. The process planning, tool path
generation, machining simulation, automatic graphite stock setting,
machining and tool management are integrated in windows
operation system of the open architecture controller of the machine
tool. When 3d models input in a CNC controller, the machining
sequence and tool are automatically selected and the tool path is
created. Afterward the workpiece will be machined based on the
data checked in machining simulation. During machining, the tool
length and spindle current are measured and the correction is made
when the value exceeds the control limit. Multiple numbers of 3d
models dragged and drooped form network folder to smart
machine tool are fabricated automatically to graphite electrodes
without interrupt of operators. The research did not stop at the
laboratory level experiment but commercialized to smart machine
tool in mold industry.
Three companies with a large share of the Korean market in
machine tool, simulation software and process planning for mold
processing started to develop smart machines that combined
equipment and software technology in 2010. The first smart
machine tool named Smart-UaX for graphite electrode machining
processing was launched in 2012 Seoul international machine tool
show. The machining center automatically fabricated dozens of
graphite electrodes together without interference of person after
input 3d models. It has been successfully sold into the market even
at the twice price of the general machining center. However, due to
the used of foreign commercial CNC controller and CAM
software, the problem of technology dependency still remain.
2. Software and Machine Tool for Mold Industry
A smart machine tool was developed using the software that the
authors have developed and used in the mold industry. The first
software is the machining process planning software N-CASS, the
second is the NC machining simulation and optimization software
NCBrain, and the third is the interface software running inside the
CNC controller.
2.1 CAPP and CAM
NC data are produced by a high-level technician manually
specifying the area, method, tool, and condition suitable for the 3d
model, so that there is a large difference in productivity and quality
depending on the person. It is necessary for CAPP (Computer aided
process planning) software to make the machining process. The
feature-based, knowledge-based, STEP-compliant, generic algorithm,
and neural network methods had been used in the majority of
computer aided process planning researches during the 2002-2013
period.11 The feature-based method extracts algorithmically
manufacturing features from 3d model.2,12,13
The feature recognition and knowledge based process planning
for automatic tool path generation system named N-CASS was
developed and had been used in the mold industry.14 The process
planning software controls existing functionality or customized
routines of commercial CAM software by applying OLE (object
linking and embedding) library with the Visual Basic programming
language. The system analyzes the 3d model and automatically
selects the appropriate process and generates the NC data, which
eliminates the difference caused by the skill of the person.
2.2 Simulation and Optimization
Stable and economic tool path is important in die and mold
한국정밀공학회지 제 35권 제 2호 February 2018 / 123
manufacturing because the first machining is the final opportunity
to increase productivity. NCBrain is a machining simulation and
optimization software stabilizes tool path and controls cutting
condition, liking the practical condition data proved in die and
mold industry.15 The geometric model, used to simulate material
removal process, is z-buffer which is the simplest and fastest
approach.3 The feed rate is regulated to control the instantaneous
maximum cutting forces computed by specific cutting energy and
the intersection of tool and workpiece.16-21 The simulation software
has been used by thousands die and mold manufacturing
companies to stabilize tool path and improve productivity.
2.3 Machine Tools for Mold
Machining is the main process of mold manufacturing and the
machine tool maker Hwachoen has the large customers in mold
industry.22 The process planning and machining simulation
companies suggested the machine tool maker to integrate their
software technology in the machine tool to make smart machine.
The developed process planning and machining simulation are
able to be installed in the Windows operating system of Fanuc 30i
CNC. The HMI (Human machine interface) is a dedicated personal
computer to easily customize into smart CNC.
3. Integration into a Smart Machine Tool
The commercial process planning and machining simulation
software developed by the authors of this paper were integrated
into the CNC controller to simplify the mold machining process.
The stock positioning method of several parts and HMI integrating
upper software is newly developed in this research.
3.1 Process Flow and HMI
The smart machine tool is consisting of workpiece setting,
process planning, tool path generation, machining simulation, real
machining, and process control as shown in Fig. 1. When the
power of the machine tool is turned on, the machining unit and the
delegating unit are ready, and the HMI, which is stored in the basic
database of the control unit, is executed and displayed on the
display unit of the interface apparatus.
The HMI inputs 3d models and positions stocks. When several
3d models are input, HMI shows the layout to place stocks on the
table and minimize the movement of tools. The N-CASS and
CAM generate tool path by analyzing the input modeling data and
automatically selecting the process of machining the workpiece
and the tool to be used from the database stored in the control
device. The NCBrain verifies and optimizes tool path. The
automatically generated tool path is verified by machining
simulation to eliminate the error and optimize it to the machining
condition database.
The CNC machine automatically measures the size and
coordinates of the workpiece and then the real machining
processes is started. It minimizes the manual selection frequency
and the quality error of the workpiece during the machining
process. The tool wear monitoring system measures tool length
before and after machining. If a tool breakage error detected during
the machining process, it would be replaced with same size one in
the automatic tool changer and the machining continues without
stopping.
3.2 Stock Positioning
Small workpieces such as electrodes are processed together by
placing several pieces on one table. There was a novel two-
dimensional nesting strategy suitable for sheet metal industries
employing laser cutting and profile blanking processes.23 But it is
different to the nesting that should be considered height and
interference in machining process.
In this research, stock positioning software is developed to place
many workpieces on single table. When several 3d models are
input, it analyzes the bounding box of each model to select a
suitable size of the workpiece, and shows the layout to place many
stocks on single table.
Fig. 1 Process flow chart of smart machine tool
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It places the workpieces on a grid-divided table according to the
stock size and the radius of the holder as shown in Fig. 2. The
material is arranged on the grid of the table from wide to small and
from high to low. The spacing of the workpieces should be at least
the distance between the holder radius and the tool radius as
written in Eq. (1), so that interference between neighboring
workpieces and tool does not occur during machining.
sw > rh + rt (1)
sw : space of workpieces
rh : holder radius
rt : tool radius
If the height difference between two neighboring workpieces is
larger than the space, the distance gap of them is enlarged as Eq.
(2).
sw > Δz (2)
Δz: height difference of workpieces
The completed batch status is displayed on the HMI as shown in
Fig. 2. An operator places the real stocks on a table based on the
stock position displayed on HMI. The OMM (On machine
measuring) measures the stock position and sets the working
coordinates in the memory of the CNC automatically. An alarm
message will be displayed when the measured size and position of
stock is different to the input model.
3.3 Process Planning and Tool Path Generation
The computer aided process planning is required for smart
machining. In this research the feature recognition and knowledge-
based methods were used for machining process planning.24 The
feature recognition step analyzes the 3d model to detect the size
and the special geometry. The features are used to select
automatically the machining pattern, cutting conditions and the
required tools prepared in the knowledge database. The recognized
features are the upper geometry, thickness of rib, the width of the
groove, concave fillet radius, and lower setting box.
The upper free geometry is finished with the ball end mill and
the lower setting box is finished with a flat end mill after the
roughing process. The diameter of the tool is selected from the size
of the bounding box, the width of the groove shape, and the
concave fillet radius as expressed in Eq. (3). The general condition
used to select the tool diameter is the volume and height of the
bounding box. The residual finishing and grooving tool diameter is
smaller than the width of the groove features.
dt = fk (vh, wg, rf) (3)
dt : Tool diameter
vh : Volume times height of bounding box
wg : Grove width
rf : Concave fillet radius
Fig. 3 and Table 1 show the machining process planning and
tool suggestion examples in case of (a) groove and (b) rib
Fig. 2 Automatic generation of initial stock position on HMI
Fig. 3 Process planning of N-CASS
Table 1 Process planning and tools for (a) groove and (b) rib
Process (a) Tool D(mm) Process (b) Tool D(mm)
Roughing Round D8 Roughing Round D10
Re-Rough Round D3 Re-Rough Ball D4
Finish Ball D3 Finish Ball D4
Re-Finish Ball D1 - -
Groove Flat D1 - -
Set box Flat D8 Set box Flat D8
한국정밀공학회지 제 35권 제 2호 February 2018 / 125
geometry. The basic machining process is the constant z-level
roughing and finishing of the upper geometry, and the flat end
milling of the lower setting box. The roughing, re-roughing and
finishing tool diameters of (b) are bigger than (a) because the
geometry is higher.
The thickness of the rib is calculated as the distance between
two parallel steep slopes.25 The roughing offset allowance is
increased and finishing z-step interval is decreased based on the
height per thickness ratio of rib feature to increase the bending
strength of the rib while finish machining.
The machining method, cutting tools, and cutting conditions
planned by CAPP is transferred to commercial CAM software to
generate tool paths without interference of an operator. The
software was installed in windows operation system of CNC and
run in the background automatically. Drag and drop of 3d models
into HMI is everything that a worker should do for tool path
generation.
3.4 Machining Simulation
The tool path generated in automatic process planning and
CAM software typically takes longer machining time than that of
high level engineer selecting the best process manually. The tool
paths automatically generated rarely includes error which includes
collision accident.
A machining simulation software NCBrain was used to verify
the collision error and optimize machining conditions to increase
productivity as shown in Fig. 4. It controlled in the background of
the controller by HMI to remove the error of NC data, delete
useless tool path, and optimize feed rates based on the knowledge
database.26 The optimized data saved in the directory of the
controller which is used by CNC machine tool for graphite
electrode machining.
3.5 Monitoring and Tool Replacement
The common collision accident happens because of the tool
length compensation value input error of operators. Automatic tool
setter measures each cutting tool before machining to compensate
tool length. The tool length is measured again after machining to
check the difference compared to the original tool length. If the
difference is large because the tool was broken during the
machining process the same tool will be searched in tool magazine.
The broken tool is replaced to the same one and the NC data is
automatically reloaded so that the machining continues again
automatically. The tool usage time is also calculated. If usage time
is longer than tool life, HMI will notice worker to change it to a
new one.
4. Smart Machining Experiment
4.1 Experiment Environments
The developed smart machine tool Smart-UaX27 shown in Fig. 5
was tested to fabricate graphite electrodes in a mold making
company.28 The machining time of conventional method calculated
by experts’ experience was compared with it of the smart machine
tool.
Table 2 is the features of the Smart-UaX. The controller H-
SMART is a dedicated operating system for smart machine tools
that allows anyone to complete easily the entire process; analysis
of machining shape, creation of machining data, setting of tool and
workpiece, and machining. The maximum travel distance is 1,300
mm in the X direction and 750 mm in the Y direction so that many
workpieces can be placed together on one table. The rapid traverse
Fig. 4 Machining simulation and optimization of NCBrain
Fig. 5 Smart machine tool named Smart-UaX
Table 2 Features of Smart-UaX
Features Unit Smart-UaX
Controller - H-SMART
Table size mm 1,200/720
Travel(X/Y/Z) mm 1,300/750/420
Rapid feedrate mm/min 20,000
Max. spindle rpm 12,000
ATC storage ea 50
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speed is 20,000 mm/min and the maximum spindle speed is 12000
rpm to meet the high speed machining conditions of graphite. With
50 tools in the tool storage magazine and the tool management
system of the controller, the operator only needs to replace the
worn tool.
The workpieces are 27 graphite electrodes of a commercial
mold maker. The actual electrode designs to be used for electric
discharge machining in the mold company are fabricated in the
smart machine tool without intervention of processing experts. In
the results, all graphite electrodes are fabricated in the smart
machine tool successfully as shown in Fig. 6.
4.2 Process Time
The conventional method analyzes the shape of each part before
machining, selects machining conditions and tools, outputs a large
number of NC files with CAM software, assigns the work
coordinate of the parts in the files, sorts the machining sequence,
edits NC file into one. It transfers the file to CNC controller, fixes
the workpieces in the table, sets the workpiece coordinate system,
and sets the cutting tools. If one part takes 10 min for CAM and
3 min for workpiece positioning and setting based on the expert’s
experience, it took more than 5 hours 51 min to prepare before
machining in the conventional method as shown in Table 3. If
machining time is same, the total fabrication time will be 39 hours
48 min in the conventional method.
The smart machine tool was possible to finish the preparation in
20 min with four clicks after input 27 3d design files and to run
machining process simultaneously with CAM operation as shown
in Fig. 6. The CAM and VM time which is run in background
simultaneously with stock positioning and machining process is
not included to total machining time in case of smart machine tool.
So the 4 hours 51 min preparation time is saved compared to
experts’ conventional method. An operator fixed electrodes on the
table based on the stock position report displayed on the HMI after
designs were input. The sizes and positions are measured with
OMM in the machine, and working coordinate is automatically set
in CNC. The roughing NC data were prepared while the operator
was setting stocks, and the machining started without waiting time.
Because of limited space of the table, stock positioning and
machining process were repeated 3 times. The total fabrication
time, including stock fixing, process planning, tool path generation,
simulation, and machining was 34 hours 57 min as shown in Table 3.
4.3 Operation Complexity
The automatic machining using a smart machine tool is easy to
operate and saves time for machining preparation comparing to
conventional machining method of graphite electrode. A trained
CAM engineer creates the machining path and the NC operator
prepares tools, workpieces, and organizes the order of execution
sequence of the numerous NC files to execute the machining. The
operation complexity of the experts’ conventional method is about
344 steps as shown in Table 4. Both experienced engineers have a
long preparation time and can make mistakes in complex
processes.
The smart machine tool reduced the operational complexity to 4
button clicks in HMI after drag and drop of 3d model data. 1st
AUTO button starts the smart process, 2nd OK button confirms
your models, 3rd JIG Ready button confirms after stocks are set on
Fig. 6 27 graphite electrodes fabricated by smart machine tool
Table 3 Comparison of process time
ProcessTime (hour:min)
Experts Smart-UaX
CAM Sim 4:30 (2:27)
Stock position 1:21 1:00
Machining 33:57 33:57
Total time 39:48 34:57
Table 4 Comparison of operation complexity
Experts Complexity Smart-UaX Complexity
Process plan 27 AUTO 1
CAM 27 × 5 OK 1
Stock set 27 JIG Ready 1
Simulation 27 × 5 Auto RUN 1
Tool set 20
Total 344 Total 4 click
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the smart jig, and 4th Auto RUN button starts machining if NC
data of first model is generated as shown in Fig. 1 and Table 4. All
software processes are run in background to prepare machining
during an operator setups workpieces. It is able to automatically
find and replace alternate tools without human operation when the
tool is broken during the machining process. Thereby, the
productivity and quality are only depending on the knowledge of
the smart machine tool without considering the skill of the operator.
4.4 Quality
Fig. 6 shows 27 graphite electrodes fabricated automatically by
the knowledge of smart machine tool. The quality is related to tool
path pattern, tool geometry and cutting condition. The tool path
pattern, step interval and tool diameter are selected at CAPP step
and the spindle speed and federate condition are regulated in
virtual machining step. Experts in the experimented mold company
checked the quality of 27 electrodes and decided the quality is
same to the parts fabricated by their conventional method except a
thin long rib shape.
A lack of knowledge of the smart machine tool can lead to
defects in unconsidered geometry. Smart machining for thin and
long rib shapes caused poor surface roughness due to tool shaking.
In order to improve the machining completeness of the thin and
long rib shape, knowledge data were improved to recognize thin
and long rib features and to apply different machining processes
and machining conditions.
5. Conclusion
As the virtual machining of the digital world is synchronized
with the actual machining, the machine tool will become smart to
simplify and reduce human mistakes in the complex processes.
A smart machine tool that fabricates graphite electrodes with
only 3d model input was developed by the cooperation of process
planning, machining simulation, and machine tool making
companies. The stock positioning method and HMI integrating
software technology is developed in this research.
It reduces the operational complexity to 4 button click after drag
and drop of 3d model data to fabricate multiple-number of graphite
electrodes. The smart machine tool fabricated 27 graphite
electrodes with minimum interference of human in 35 hours.
REFERENCES
1. Altan, T., Lilly, B., Kruth, J.-P., König, W., Tönshoff, H., et al.,
“Advanced Techniques for Die and Mold Manufacturing,” CIRP
Annals-Manufacturing Technology, Vol. 42, No. 2, pp. 707-716,
1993.
2. Yamazaki, K., Kawahara, Y., Jeng, J.-C., and Aoyama, H.,
“Autonomous Process Planning with Real-Time Machining for
Productive Sculptured Surface Manufacturing Based on
Automatic Recognition of Geometric Features,” CIRP Annals-
Manufacturing Technology, Vol. 44, No. 1, pp. 439-444, 1995.
3. Altintas, Y., Kersting, P., Biermann, D., Budak, E., Denkena, B.,
et al., “Virtual Process Systems for Part Machining Operations,”
CIRP Annals-Manufacturing Technology, Vol. 63, No. 2, pp.
585-605, 2014.
4. Denkena, B. and Koeller, M., “Simulation Based Parameterization
for Process Monitoring of Machining Operations,” Procedia
CIRP, Vol. 12, pp. 79-84, 2013.
5. Kim, S., “Integration of Pre-Simulation and Sensorless
Monitoring for Smart Mould Machining,” International Journal
of Simulation Modelling, Vol. 15, No. 4, pp. 623-636, 2016.
6. Lee, C.-S., “Tool Path Generation for a Four-Axis Machine to
Engrave Letters on Tire Sidewall Molds,” Int. J. Precis. Eng.
Manuf., Vol. 10, No. 3, pp. 75-82, 2009.
7. Ramesh, R., Jyothirmai, S., and Lavanya, K., “Intelligent
Automation of Design and Manufacturing in Machine Tools
Using an Open Architecture Motion Controller,” Journal of
Manufacturing Systems, Vol. 32, No. 1, pp. 248-259, 2013.
8. Ding, X., Fuh, J., Lee, K., Zhang, Y., and Nee, A., “A
Computer-Aided EDM Electrode Design System for Mold
Manufacturing,” International Journal of Production Research,
Vol. 38, No. 13, pp. 3079-3092, 2000.
9. Schroeter, R. B., Kratochvil, R., and de Oliveira Gomes, J.,
“High-Speed Finishing Milling of Industrial Graphite
Electrodes,” Journal of Materials Processing Technology, Vol.
179, Nos. 1-3, pp. 128-132, 2006.
10. Yang, Y.-K., Shie, J.-R., and Huang, C.-H., “Optimization of Dry
Machining Parameters for High-Purity Graphite in End-Milling
Process,” Materials and Manufacturing Processes, Vol. 21, No. 8,
pp. 832-837, 2006.
11. Yusof, Y. and Latif, K., “Survey on Computer-Aided Process
Planning,” International Journal of Advanced Manufacturing
Technology, Vol. 75, Nos. 1-4, pp. 77-89, 2014.
12. Deja, M. and Siemiatkowski, M. S., “Feature-Based Generation
of Machining Process Plans for Optimised Parts Manufacture,”
Journal of Intelligent Manufacturing, Vol. 24, No. 4, pp. 831-
846, 2013.
13. Wang, L., Wang, W., and Liu, D., “Dynamic Feature Based
Adaptive Process Planning for Energy-Efficient NC Machining,”
CIRP Annals-Manufacturing Technology, Vol. 66, No. 1, pp.
441-444, 2017.
14. Nice Solution Co., Ltd., http://www.ncass.co.kr (Accessed 24
JAN 2018)
128 / February 2018 한국정밀공학회지 제 35권 제 2호
15. NCB Co., Ltd., http://www.ncbrain.com (Accessed 24 JAN
2018)
16. Fussell, B., Jerard, R., and Hemmett, J., “Robust Feedrate
Selection for 3-Axis NC Machining Using Discrete Models,”
Journal of Manufacturing Science and Engineering, Vol. 123, No.
2, pp. 214-224, 2001.
17. Fussell, B. K., Jerard, R. B., and Hemmett, J. G., “Modeling of
Cutting Geometry and Forces for 5-Axis Sculptured Surface
Machining,” Computer-Aided Design, Vol. 35, No. 4, pp. 333-
346, 2003.
18. Altintas, Y., Spence, A., and Tlusty, J., “End Milling Force
Algorithms for CAD Systems,” CIRP Annals-Manufacturing
Technology, Vol. 40, No. 1, pp. 31-34, 1991.
19. Ko, J. H., “Plunge Milling Force Model Using Instantaneous
Cutting Force Coefficients,” Int. J. Precis. Eng. Manuf., Vol. 7
No. 3, pp. 8-13, 2006.
20. Yun, W.-S. and Cho, D.-W., “Accurate 3-D Cutting Force
Prediction Using Cutting Condition Independent Coefficients in
End Milling,” International Journal of Machine Tools and
Manufacture, Vol. 41, No. 4, pp. 463-478, 2001.
21. Weinert, K., Enselmann, A., and Friedhoff, J., “Milling
Simulation for Process Optimization in the Field of Die and
Mould Manufacturing,” CIRP Annals-Manufacturing Technology,
Vol. 46, No. 1, pp. 325-328, 1997.
22. Hwacheon Machinery Co., Ltd., http://www.hwacheon.com
(Accessed 24 JAN 2018)
23. Anand, K. V. and Babu, A. R., “Heuristic and Genetic Approach
for Nesting of Two-Dimensional Rectangular Shaped Parts with
Common Cutting Edge Concept for Laser Cutting and Profile
Blanking Processes,” Computers & Industrial Engineering, Vol.
80, pp. 111-124, 2015.
24. Park J. G., “CAM Automatic Standard System,” KOR Patent,
100985514 B1, 2010.
25. Park J. G., “Rib and a Solid Distinction Automated Method
Using the Program,” KOR Patent, 101567529, 2015.
26. Kim, D. J. and Kim, S. J., “Method for Regulating a Path of an
Instrument,” NCB Co., Ltd., No. 100872394, 2008.
27. Yum, K. Y., Park, J. Y., and Park, D. Y., “Intelligent CNC
Machine Tool with Automatic Processing Function and Control
Method Thereof,” KOR Patent, 101257275 B1, 2013.
28. Kunnung Co., Ltd., http://www.kumnung.co.kr (Accessed 24
JAN 2018)