Enhancement of Machine Utilization by Using Digital ... · Enhancement of Machine Utilization by...

$: Enhancement of Machine Utilization by Using Digital ... · Enhancement of Machine Utilization by Using Digital ... 3D MODELING OF VIRTUAL KIT ... directory of UG NX, such as …..\NX$
International Journal of Engineering Trends and Technology (IJETT) – Volume 24 Number 5- June 2015

ISSN: 2231-5381 http://www.ijettjournal.org Page 237

Enhancement of Machine Utilization by Using Digital Manufacturing

Putta Priyanka¹ Dr. G. Amarendar Rao² Department of Mechanical Engineering VBIT, Hyderabad, Telangana, INDIA

ABSTRACT Digital manufacturing or virtual

machining Tool Kit will be a one stop solution right from operation creation, post process to NC validation with real time Machine simulation. Digital manufacturing is an off-line tool for detailed analysis and optimization of NC programs. Depending on the batch size (job-shop or large-volume), reduction of setup times or shortening of cycle times are two major benefits. Digital manufacturing enables the user to identify and realize potential savings in machining processes at an early stage. In Digital manufacturing any NC program can be validated and optimized according to the requirement. This optimization results in reduction of setup time, manufacturing cost, collision detection and finally increases machine utilization.

In this project to validate virtual machine, steering knuckle is taken as case study. In automotive suspension, a steering knuckle is that part which contains the wheel hub or spindle, and attaches to the suspension components.

Aim of the project is to develop virtual machine of DMG 5-axis using NX software and validate machine by taking steering knuckle component as case study.

Keywords: Digital Manufacturing, 5-axis milling machine, steering knuckle, Machine tool builder, UNIGRAPHICS.

I. INTRODUCTION

Manufacturing Process before Development of Digital Manufacturing:

In manufacturing environment before development of digital manufacturing operators used to generate NC program manually or by using postprocessors, this generated NC program is fed to machine directly or through DNC (direct numerical control) lines for CNC machines. The generated NC program using postprocessor or by manually result in dimensional error of component, collision of part and spindle, tool and work table or spindle and worktable. Collisions leads to breakage of component or tool sometimes results badly as damage to machine. The generated NC program will be edited manually to obtain component as customer required and trails are also done for modified NC program to find whether this modified NC program will produce the component as customer requirement. There are some collisions due to error in NC program or by considering wrong tools. Below images shows spindle-part collision due to length of the tool and tool-part collision. Tool breaks the part and damages due to error in NC program.

Fig1. collision of spindle and part

Fig 2. Breakage of work piece



To avoid this collisions digital manufacturing process is developed to check the generated NC program before fed to machine. The complete manufacturing process is examined in digital manufacturing process and collisions are detected and modifications in NC program are done. Finally modified NC program is given to machine these results in reduction of manufacturing errors.

II. METHODOLOGY

Virtual Machine Tool Kit will be a one stop solution right from operation creation, post process to NC validation with real time Machine simulation.

VIRTUAL KIT is an off-line tool for detailed analysis and optimization of NC programs. Depending on the batch size (job-shop or large-volume), reduction of setup times or shortening of cycle times are two major benefits. VIRTUAL KIT enables the user to identify and realize potential savings in machining processes at an early stage.

3D MODELING OF VIRTUAL KIT

My project deals with the virtual machining of 5-axis DMG milling machine

Fig.3 Final Assembly of DMG 5 axis CNC milling machine

PROCESS TO SET UP AN ISV SCENARIO RUNNING TOGETHER WITH

DMG_MILL_5AX

Building a directory for the machine tool resources NX has 2 places (directories) for storing the machine tool data: One for the resources (geometries, Post Processor files etc.) and another one for the ready-to-use machines including kinematics structure and other settings. We will build the machine model in the resources and will copy it later into the other directory. By default the resource directory is located in the installation directory of UG NX, such as …..\NX 7.5\MACH\resource\library\machine\installed_machines Create a new folder in the installed_machines library and name it DMG_mill_ 5ax Create a subdirectory called graphics and another subdirectory named postprocessor so that the structure looks like this:

Fig4. List of all geometry part file of the

DMG_mill_ 5ax The related cse_driver folder needs to be copied from one of the existing installed machine tools. Copy all geometry part files into the \graphics subdirectory



The location of the geometry files is assigned in the machine database later on. We will define a directory name which clearly identifies the machine tool (DMG_mill_ 5ax).

Kinematics to the Geometric Model

Now that we have built up the geometric structure of the model we have to define in which way the different components of the machine will move later on when we are going to simulate the machining process. Basically the kinematics definition procedure can be split in 4 areas:

Definition of kinematics components (k-components) which are placeholders for further kinematics information. K-components are nodes in the kinematics tree

Definition of junctions for the k-component. A junction or coordinate system defines the location and orientation of all components referring to that coordinate system. By way of example the junction of the fixture defines how the cam part is mounted.

Selection of axes for determining the moving direction of the k-component. Axes can be regarded as one of the properties of k-components. Axes are selected according to the respective junctions.

Classification of k-components. By assigning classes for the components a proper handling of the collision calculation and other information will be achieved later. Let’s build the kinematics for the current example:

Select menu Start → All Applications → Machine Tool Builder Open the Machine Tool Navigator, click twice on the item NONAME and change the name to "DMG_mill_ 5ax" Highlight this name and open the context menu by clicking with the right mouse button.

Select Insert → Machine Base Component In the Create K-component Dialog, press Add to add the geometry. Select the geometry of the machine (BED) directly in the graphics window. Use the Class selection dialog to apply the classification “MACHINE_BASE" Below image shows getting in to machine tool builder

Fig.5. Getting in to machine tool builder

Next step is to add a junction with a

specified name. This will be the basic junction for further handling of components in the machine model.

Select the item MACHINE_BASE, click the right mouse button and select →Junctions →Add.

Enter the designation “MACHINE_ZERO” as name.

Leave the dialog open and define a coordinate system. In the current case the zero coordinate system is located at the intersection of the vertical axis of the B_rotary table and the horizontal axis of the fixture (part holder). For the orientation it is a rule that the Z-axis is always pointing towards the tool. In principle the orientation of the X and Y axis are arbitrary but you should always contact the machine tool documentation for the exact definition for orientation and position of the machine zero.

Change the selection scope to “Entire Assembly” if not already done. This makes sure that you can select all components inside the graphics.



Measure the distance between the centre of the B_ROTARY component and the centre of the C-axis_Rotary (refer to the assembly navigator).

Activate the information window when the measurement is done. (Results Display→Show Information) Read the Delta in Z-direction which is 85 mm.

Place the coordinate system at the centre of the fixture, then make an adjustment of 85 mm in z-direction. Be sure that Z is pointing towards the tool (away from the fixture)

Select OK to complete the junction definition.

Below image shows creating junction to machine base component

Fig. 6. creating junction to machine base

component Below image shows display of the machine zero junction and classification of the machine zero junction

Fig7. Display of the machine zero junction and

Classification of the machine zero junction

With the Junction definition dialog still open highlight the item MACHINE_ZERO and click

“Classify”. Select “Machine Zero” as classification.

The next task is the definition of further k-components for building the kinematics chain. Be sure to keep in mind the two major rules for kinematics definition:

Every component or assembly that can move has to be a separate kinematics component

If the component or assembly which you are defining is itself mounted on another moveable component / assembly then the latter one has to precede the first one in the kinematics chain. If you click on the respective components in the assembly navigator you can identify the machine components. MACHINE CONFIGURATION MOVEMENT

AXIS LIMITS

1. X SPINDLE

2. Y SPINDLE

3. Z TABLE

4. B SPINDLE

5. C TABLE

X = 880 to -220

Y = 630 to 0

Z = 0 to -630

B = +30 to -120

C = 360deg

FINAL KINEMATIC MACHINE MODEL: This is the required CNC machine model with kinematics given to x-slide ,y-slide, table rotary and spindle.

Fig.8. Final Kinematic Machine Model

Adding the Machine To Machine Database: Machine data base file is located in …\ProgramFiles\UGS\NX7.5\MACH\



resource\library\machine\ascii\ machine_database.dat

Fig.9. machine data base file

III. POST PROCESSOR: For every CNC machine there will be a specified post processor to generate NC program. Postprocessor is created using post builder application. Process to open post builder Start all programs UGS NX7.5 manufacturing tools post builder File new postprocessor specify name of the processor going to create and specify all required data.

Fig.10. creating new postprocessor

The below image shows generated Post processor of DMG_mill_5ax. Specify all required machine specifications to generated postprocessor for virtual kit DMG_mill_5ax.

Fig.11. postprocessor input window

3 Post processor files will be generated as def, tcl, pui DMG_mill_5ax.PUI: Post User Interface file (.pui) used by post builder to edit the event handler (.tcl) and definition files (.def).This file contains static information on how to write out the .tcl file. DMG_mill_5ax.TCL: Tool Command Language or Event handler (.tcl) contains a set of instructions dictating how each event type is to be processed. Post also uses this file at run time to generate NC code. DMG_mill_5ax.DEF: Definition file (.def) This file defines all the static information for the postprocessor. This includes formats, address and NC blocks. This file is used by Post to postprocess the tool path and generate NC code. DMG_mill_5ax.CDL: User defined events and machine control events are how NX sends messages to the postprocessor that are outside of the normal tool path messages. this would be a message to turn on high pressure coolant or unclamp a rotary axis. These events are added to a program using the User Defined Events. The below image shows Post processor files of DMG_mill_5ax.

Fig.12. Post processor files of DMG_mill_5ax



This generated file should be pasted in DMG_mill_5ax postprocessor which is located in C folder installed machines. Along these 3files another .cdl file is generated, paste .cdl file in user_def_event. The below image shows installed machine folder.

Fig.13. installed machine folder

The below image shows user_def_event folder. Along these 3files another .cdl file is generated, paste .cdl file in user_def_event.

Fig.14. user_def_event folder

This post process files helps virtual machine to run according to generated NC program and shows exact simulation of machine. Errors and collisions can be detected while simulation of virtual machine is going on, NC program will be edited to remove collisions and errors according to the simulation of tools and part.

3d Model of Steering Knuckle

Fig.15 final 3D model of Steering Knuckle

COMPUTER AIDED MANUFACTURING

(CAM)

The generation of tool path on 3D model of Steering knuckle will be done using NX-CAM software. By generating tool path NC program will be generated. This NC program is given input to the CNC machine to run operations.

The main objective of the project is to obtain to reduce machining errors and collision of tools and rotary table by developing virtual kit.

Methodology of manufacturing Steering knuckle

Identify suitable machine. Selecting suitable tools for

manufacturing Steering knuckle component.

Selection of fixture. Listing down the Sequence of

operation performed on Steering knuckle component.

Generating tool path at specified cutting speed.

Retrieving virtual machine in NX-CAM and simulating machine.

Verification of machining process in virtual machine simulation.

Generating NC program using NX-CAM software.



SEQUENCE OF OPERATIONS PERFORMED ON STEERING KNUKCLE

Setup_1

Face milling

Planar milling

Fixed contour

Spot drilling

Drilling

Setup_2

Face milling

Planar milling

Spot drilling

Drilling

Fig.16 Final cam part

TOOLING LIST

DRILLING TOOLS

TOOL

NAME

DESCRIPT

ION

DIAME

TER

TIP

ANG

FLUT

E

LEN

SPOTDRILLI

NG_TOOL

Drilling

Tool 2.0000

120.0

000

35.00

00

DRILLING_

TOOL

Drilling

Tool 7.5000

118.0

000

35.00

00

DRILLING_

TOOL_D

Drilling

Tool 3.0000

118.0

000

35.00

00

DRILLING_

TOOL_D3.58

Drilling

Tool 3.5800

118.0

000

35.00

00

DRILLING_

TOOL_D2

Drilling

Tool 2.0000

118.0

000

35.00

00

DRILLING_

TOOL_D2.1

Drilling

Tool 2.1200

118.0

000

35.00

00

DRILLING_

TOOL_D1.22

Drilling

Tool 1.2200

118.0

000

35.00

00

DRILLING_

TOOL_D3

Drilling

Tool 3.0000

118.0

000

35.00

00

DRILLING_

TOOL_1

Drilling

Tool 7.5000

118.0

000

35.00

00

DRILLING_

TOOL_2

Drilling

Tool 3.0000

118.0

000

35.00

00

MILLING TOOLS

TOOL

NAME

DESCRIP

TION DIAMETER

COR

RAD

FLUTE

LEN

MILL Milling

Tool 20.0000 0.0000 50.0000

MILL_1 Milling

Tool 20.0000 0.0000 50.0000

MILL_2 Milling

Tool 3.6000 0.0000 50.0000



BALL_

MILL

Milling

Tool-Ball

Mill

3.4000 1.7000 50.0000

MILL_3 Milling

Tool 4.0000 0.0000 50.0000

MILL_4 Milling

Tool 3.0000 0.0000 50.0000

MILL_5 Milling

Tool 12.0000 0.0000 50.0000

MILL_6 Milling

Tool 10.0000 0.0000 50.0000

MILL_7 Milling

Tool 3.0000 0.0000 50.0000

MILL_8 Milling

Tool 8.0000 0.0000 50.0000

MILL_9 Milling

Tool 5.0000 0.0000 50.0000

MILL_10 Milling

Tool 2.4000 0.0000 50.0000

MILL_11 Milling

Tool 4.0000 0.0000 50.0000

MILL_12 Milling

Tool 6.0000 0.0000 50.0000

MILL_D4 Milling

Tool 4.0000 0.0000 50.0000

MILL_13 Milling

Tool 10.0000 0.0000 50.0000

MILL_14 Milling 2.0000 0.0000 50.0000

Tool

MILL_15 Milling

Tool 3.0000 0.0000 50.0000

MILL_16 Milling

Tool 2.4000 0.0000 50.0000

MILL_17 Milling

Tool 4.0000 0.0000 50.0000

Integrated Simulation Verification process

Fig 17. Dialog to load objects like machine tool, tool or devices from the library

Creating the machining scenario For building a complete simulation scenario where the machine is simulated it is expected that a CAM part which already has some operations defined so that the tool path can be generated. Furthermore this method requires that the machine is a member of the machine tool library, this is true for our sample. Open the CAM sample part in NX. It is called cam_sample.prt and has some common parts in a subdirectory.



Time taken to manufacture steering knuckle

Below image shows only machining time of steering knuckle with defined speed and feed



Simulation verification

Fig. 18 Simulation verification to check the errors

developed while machining the component

Collision of spindle and fixture when spindle is tilted to 90 deg for milling operation

Fig.19 Simulation verification

Remedy for collision is to increase tool length.

Flute length and total length of the tool is increased to overcome collision of spindle and fixture

Tool used before collision

Tool used after collision detection

Again the same operation is verified to check whether collision is occurs with new tool.

Fig.20. No collision observed with new tool



Collision occurred between spindle house and rotating work table while doing fixed contour operation.

Fig.21 Collision occurred between spindle house and rotating work table

Remedy to overcome from this collision is to increase the fixture height.

Below image shows the fixture used before collision

Fig.22. 2D input and 3D model of fixture

Below image shows the fixture used after collision detection to avoid the collision between spindle house and work table

Fig.23. 2D input and 3D model of new fixture

Fig.24. Remedy to overcome from this

collision is to increase the fixture height

Machine vice is fixed on the work table along with fixture and raw material of steering knuckle to increase the height of fixture.



Manufacturing time of steering knuckle after virtual simulation verification



IV. RESULTS

Product cost reduction, Reduction of setup times

Manufacturing component on CNC machine without virtual simulation

The component directly machined on the CNC machine with trial and error and after each operation machine will be stopped and inspection will be done this increases manufacturing time of the part and as well as increases cost and reduces machine utilization.

Time and cost calculation for manufacturing steering knuckle as shown below including setup time and manual modification of NC program on CNC machine.

Manufacturing time taken by single component= 4hrs 42min

Machining cost per hour for milling operations = 1000rs

Machining cost per hour for drilling operations = 800rs

Machining cost per piece for milling operations (machining cost per min x machining time in min) = 1000/60*279 min= 4650 rs

Machining cost per piece for drilling operations (machining cost per min x machining time in min) = 800/60*3 min= 40 rs

Total machining cost per piece= milling + drilling= 4650 + 40 = 4690 rs

Table 1: time and machining cost of operation without VMS

Manufacturing component on CNC machine with virtual simulation

There is no time waste for trial and error operations on machine and time consumption will be less because every operation is virtually verified and modification will be done in software itself. Speed and feed is increased along depth of cut to reduce machining time. Increased parameters are verified using virtual simulation. This reduces setup time and product cost. Manufacturing time taken by single component= 3hrs 9min

Machining cost per hour for milling operations = 1000rs

Machining cost per hour for drilling operations = 800rs

Machining cost per piece for milling operations (machining cost per min x machining time in min) = 1000/60* 186min= 3100 rs

Machining cost per piece for drilling operations (machining cost per min x machining time in min) = 800/60* 3min= 40 rs

Total machining cost per piece= milling + drilling= 3100+40 = 3140 rs

SET UP

Milling&drilling operations

TIME REQUIR

ED IN MINS.

MACHINING COST

PER HOUR

MACHINING COST/PIECE

Milling 279 RS.1000/HR RS.4650

Drilling 3 RS.800/HR RS.40

TOTAL 282 RS.4690



Table 2: time and machining cost of operation with VMS

SET UP

Milling&drilling operations

TIME REQUIRED IN MINS.

MACHINING COST

MACHINING COST/PIECE

Milling 186 RS.1000/HR

RS.3100

Drilling 3 RS.800/HR

RS.40

TOTAL 189 RS. 3140

282 189

4690

3140

0

1000

2000

30004000

5000

without virtual simulation

with virtual simulation

TIME (min) COST (rs)

GRAPH Optimization of cycle times Cycle time (hrs) without VMS= no.of parts x manufacturing time taken by single part in hrs.

Manufacturing time taken by single part in mins = 282mins

Cycle time (hrs) with VMS= no.of parts x manufacturing time taken by single part in hrs.

Manufacturing time taken by single part in mins = 189mins

Cycle time is optimized by using virtual simulation. In virtual simulation complete manufacturing process can be checked and verified in offline if any modification in NC program will be edited in software itself

which reduces machine idle time and increases machine utilization.

Table 3: cycle time with and without VMS

NO.OF PARTS

cycle time(hrs) without VMS

cycle time(hrs) with VMS

50 235 157.5

100 470 315

150 705 472.5

200 940 630

250 1175 787.5

300 1410 945

350 1645 1102.5

400 1880 1260

VMS = virtual machining simulation

0

200

400

600

800

1000

1200

1400

1600

1800

2000

50 150 250 350

cycl

e ti

me

in h

rs

no.of parts

Optimization of cycle times

cycle time(hrs) with out VMS

cycle time(hrs) with VMS



Increase in machine utilization The values are directly taken when component is manufacturing on the machine without virtual simulation. First component on CNC machine is run in block mode, means component is inspected after every operation by stopping machine. At that time machine is idle which decreases machine utilization. Table 4: machine utilization with and without VMS Single part

manufacturing

time

Machine

utilization

without VMS

(min)

Machine

utilization with

VMS (min)

Total time 4hrs 42min 3hrs 9min

Machine cutting

time

3hrs 28min 2hrs 48min

Machine idle time 1hr 14min 21min

Total manufacturing time is reduced by 33%

Machine idle time and machine utilization time are inversely proportional. When idle time is reduces then machine utilization time will increases.

Machine utilization is increased by 71%

V. CONCLUSION

By developing virtual machine, spindle house and work table collision is detected, spindle and fixture collision is detected. Remedy for this collisions is done in software itself by increasing tool length and changing fixture. Manufacturing time taken for steering knuckle without virtual simulation verification and with virtual simulation verification is shown in results by plotting graphs as well as optimization of cycle time and machine utilization also shown in results. Finally concluding using virtual simulation process will benefits small scale and large scale

industries investment for this process is very less and results in more profits for industries.

REFERENCES

1. Development of Virtual Machine Tool for Simulation and Evaluation Volume 8 Number 6 Pages 849-858, DOI: 10.3722/cadaps.2011.849-858.

2. Research of Virtual Machine Based on UG and VERICUT, Applied Mechanics & Materials;2014, Issue 644-650, p782

3. Fredin J., Wall J., Jönsson A. & Broman G., A robust motor and servo drive model for real-time machine tool simulation, in: Proceedings of the 19th European Modeling and Simulation Symposium (EMSS 2007),Bergeggi, 4-6 October, 2007

4. Damien Chablat, Peer-Oliver Woelk VIRTUAL MANUFACTURING Tools for improving Design and Production.

5. P. Depinc ´ e, E. Noel, P.O. Woelk 2004 THE VIRTUAL MANUFACTURING CONCEPT: SCOPE, SOCIO-ECONOMIC ASPECTS AND FUTURE TRENDS. ASME 2004 Design Engineering Technical Conferences and Computers and Information in Engineering Conference September 28-October 2, 2004, Salt Lake City, Utah, USA.

6. E. Raj Kumar, K.Annamalai AN OVERVIEW OF VIRTUAL MANUFACTURING WITH CASE STUDIES International Journal of Engineering Science and Technology Vol. 3 Apr 2011.

7. Marinov V., What Virtual Manufacturing is? Part I: Definition, 13 October 2000, <bosphorus.eng.emu.edu.tr/vmarinov/VM/VMdef.htm>

8. Marinov V., What Virtual Manufacturing is? Part II: The Space of Virtual Manufacturing: October 2000, <bosphorus.eng.emu.edu.tr/vmarinov/VM/VMspace.htm>

9. Iwata K., Onosato M., Teramoto K., Osaki S. A., Modeling and Simulation Architecture for Virtual Manufacturing System, Annals CIRP, 44, 1995, pp. 399-402

10. Lee D.E., Hahn H.T., Generic Modular Operations for Virtual Manufacturing Process, Proceedings of DETC’97, ASME Design EngineeringTechnical Conferences, 1997.

11. BowyerA., Bayliss G., Taylor R., Willis P., A virtual factory, International Journal of Shape Modeling, 2, N°4, 1996, pp215-226.

12. Lin E., Minis I., Nau D.S., Regli W.C., The institute for System Research, CIM Lab, 25 March 1997, www.isr.umd.edu/Labs/CIM/vm/ vmproject.html

Enhancement of Machine Utilization by Using Digital ... · Enhancement of Machine Utilization by...

Documents

Transcript of Enhancement of Machine Utilization by Using Digital ... · Enhancement of Machine Utilization by...