IRJET- Design Automation of Cam Lobe Modeling in Creo using C#

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 09 | Sep 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 1570
DESIGN AUTOMATION OF CAM LOBE MODELING IN CREO USING C#
Harish Reddy M1, Dr. P. Srinivasa Rao2
1Student of M.Tech CAD/CAM, IARE, Telangana, India
2Professor, Dept. of Mechanical Engineering, IARE, Telangana, India
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Abstract - In mechanical engineering, the procedure of design requires additional time in view of its iterative and proficient
processes. For design, the availability of CAD packages in market, are so many which requires modeling skills. Many efforts had
been made in the area of design automation like integration of CAD software with different computerprogramminglanguages. In
between these CAD software and computer programminglanguage, intermediatesoftwareisresponsiblefortheinterfacebetween
them.
In this study, the Modeling of cam lobes has been done to validate the idea of Design Automation. Cam lobes are responsible for
opening and closing of valves in an engine cylinder, which are appeared on the camshaft. Cam lobes modeling process using CAD
software like Creo involves an integrated approach which is tedious. It will take minimum of 15-20 minutestomodelacamlobe. If
there are more lobes in an engine (say 20), then modeling all these lobes will take at least 3-4 hours and modeler should be very
much familiar with CAD software. The objective of this project is to develop an application using C# programming language to
automate cam lobe model. Using this application, we can design ‘n’ number of lobes in less than five minutes.
Key Words: Design Automation, Creo, GUI, Parametric modelling, C#
1. INTRODUCTION
1.1 Knowledge Based Engineering
It is closely related to the domain of manufacturing design and production. In KBE, theuseofKnowledgebasedtechnologyis
to support CAD and the knowledge based techniques can be applied to the entire product life cycle. KBE systems provide more
flexibility in the developmentof design automation. According to W.J.C. Verhagen et al. [1],KBEisalifecyclewithvariousstages
like identify, justify, capture, formalise, package and activate the design. In the process of design, use of KBE framework we can
save time and which makes a predominant role in the market [2]. It is quoted that in CAD without KBE, the creative design is of
20% and routine design is of 80%. Whereas with KBE, an additional time profit in the design process occurs. The conceptual
benefit of KBE is clearly shown in the below figure and also mentioned about the more time focused on creativity [3]. The
ultimate goal of KBE is to save the time and reduce the cost of design through automation.
1.2 Design Automation
In research field many efforts have been made in the area of design automation. According to Christian Johansson et al. [2],
“Design automation deals with automating design tasks which are normally carried out in manual fashion by engineers and
designers”. In simple, Design Automation creates shortcutstoquicklyaccomplishcommondesigntasks.Inorderto understand
design automation we have to go through with Knowledge Based Engineering. Benefits of KBE includetheautomationofparts
of a product life cycle. With use of DA, we can develop a Graphical User Interface (GUI) or tailor-made software in design
process with collaboration of computer programming language and CAD software. IndrajitSinh J. Jadeja et al. [4] discussed
about the methodology used having three phases; they are design phase, integration phase and Modelling phase. Till date we
have observed only the Modelling phase but not the analysis phase using GUI.
1.3 Parametric Modeling
In CAD/CAE, parametric Modeling plays a predominant role as it is used to change the shapeofmodel geometryassoonasthe
dimension value is modified. The important feature of parametric Modeling is to automatically change the attributes that are
interlinked with the model or component. The conceptual model of the research approachwithparametricdesignisdiscussed
by Marius Marian Cucos et al. [5]. These type of parametric Modeling is generally seen in advanced CAD software like CATIA,
SOLIDWORKS, CREO, etc. which saves Modeling time.

2. LITERATURE SURVEY
IndrajitSinh J. Jadeja et al. [4] discussed about the research work carried out on Flange Coupling using GUI based design
software. Considered a step by step methodology i.e.,
 Design Phase
 Integration Phase
 Modelling Phase
In design phase, selection of programming language anda component took placealongwithdesignvariableandprogramme
structure. Integration phase uses export valuesfromdesignphaseandusedtoimportthevaluestomodellingphase.Inthiswork
[4], the programminglanguage used in Design phase is VisualBasicwithinputvariablesofFlangecoupling,Integrationphaseby
MS Excel and the CAD software used in Modelling Phase is CREO. With input variables in Visual Basic, the output variables with
design equationsare obtained and these variablesare exported to MS Excel sheet.ThesolidmodelcreatedinCREOisintegrated
with MS Excel sheet to regenerate the model and updateddimensions are obtainedas perthesheetvalues.Asthisworkreduces
the design time and increases the production efficiency with this type of GUI or Tailor-made software.
Ramakrishnan BalajiIyer et al. [6] discussed about the design optimization of CAD model using Creo simulation result and
computation in MathCad as an integrated approach. In this work researcher links the Creo simulation result as the input in the
MathCadand output of this program is again directed to Creo Parametric, then using this output result CAD modelisoptimized.
The step by step procedure carried in this work, primarily the design of the model in Creo and defining the design parameter
which is to be optimized. Then the analysis of the model is carried in the Creo Simulation and these results are integrated with
the MathCad to optimize the design, which is later validated with theoretical values.
The research work by Chanwoo Park et al. [7], discussed about the design optimization of an Aircraft Wing using
Multidisciplinary Design Optimization (MDO) via, Parametric Modeling. A fully automatic computational capability in a MDO
system was developed and parametric Modeling was used for analysis. MDO framework structure made up of two groups. The
first one is an automated analysis, consisting of an interface module, a parametric Modeling module, an aerodynamic analysis
module, a load transfer module and a structure analysis module. And the second one is an optimization group consisting of a
response surface module andan optimization module. Dhaval B. Shah [8] discussed about the FlangeCouplingmodelcreatedin
Autodesk Inventor which was integrated with Excel spreadsheet to reduce the cycle time of design modeling. The dimensions
required for modeling was calculated in Excel sheet using empirical formulas and exported to Inventor design software. Initial
input dataare physically entered in Excel sheet and later output data areobtained.The3DmodelofFlangecouplingwascreated
in Inventor and using the parameter feature, model was dimensionally allotted with specific characters. Then the Inventor
software is linked with Excel sheet using parameter feature. After successful linking of Excel sheet, the model in Inventor is
regenerated with the obtained values from the sheet.
Yogesh H.Sawant et al. [9] discussed about the Design automation of a Screw Conveyor Components in CATIA using Visual
Basic for Application (VBA) and Excel sheet. In this work, the dimensional calculations are done in Excel sheet using Loop
function feature. The input parameters of Screw conveyorcomponents was entered in the functionandoutputdimensionsdata
obtained automatically, which was later integrated with CATIA. VBA which was inbuilt in CATIA, helped in generation of
components automatically. The screw conveyor model having different components and sub-components are automatically
generated by VBA code according to input parameters. The work concludes the scope of programming language in design and
time in modeling a component is reduced.
Umesh A. Bedse et al. [10] developed Graphical User Interface (GUI) based designsoftware using Visual Basicprogramming
language integrated with Creo CAD softwareforthedesignandModelingofCIengine.DiscussedabouttheDesignAutomationby
developing GUI in Visual Basic and then output data was transferred to Excel sheet. After that, integration of Excel sheet with
Creo took place for simulation of CI engine model. Initially in Visual Basic, the CI engine components are coded to calculate the
dimensional values of each component with someinput data. The output dimensionalvaluesobtainedinGUIwastransferredto
Excel sheet and later it was integrated with Creo software to regenerate the model with latest dimensional values of CI engine
components.

3. EXPERIMENTAL STUDY
3.1. Conventional modeling in Creo 2.0
The process involves an integrated approach which seems lengthy. This process takes time if one has to modify previously
modeled camshafts as this process takes into account the featurebased Modeling practice fromverybeginninginordertomake
it easy for future changes.
To demonstratethe process,I assume that other features(ex:journal,dowelholeandkeyslotetc.)arealreadycreatedbefore
lobes. That gives us a reference for our lobes modelingprocess.Itisveryimportanttokeepstandardreferenceplanesandaxisas
our reference when we need to create subsequent feature like lobes.
Fig-1: Camshaft model without Lobe
3.1.1. Creation of a Standard View
First step is to create a view which is standard for all lobes from where we can see lobes oriented at different angles with
respect to single point of reference. This single reference can be either dowel holeorkeyslot.Forinstance,givethisviewaname
as “LOBE_ORIENTATION”.
It is very important to pay enoughattention while creatingthis view as weare goingtousethisviewinprocessofcreatingall
lobes and drawing items.
Key Points for Creating LOBE_ORIENTATION view:
 It should face to front of the screen at the end from where we see all orientation angles.
 As shown above, LOBE_ORIENTATION view must adjust such a way that dowel hole comes at the top. The reason
behind this is, we always measure lobe orientation angles with respect to dowel hole in counter clock direction.
3.1.2. Points File Data to Creo
This is a compilation of data generated from Dynasty (Dynamic Analysis Simulation Software). ".pts" file can be opened
using WordPad. We are going to use these data in our Creo model at the first place after creating a standard view.
Process of Importing Points Data
Insert--->Model Datum---> Graph
We have to give a standard name which defines its significance. Here, weconsider eachlobe with unique number generated
from CamDesign software. Now, prefer to use that number as graph name. In this reference model wehaveimported4different
points file forcreating different lobes. Theyare 783,784,785 and 786lobes. Once wenameitasperlobenumber,asketchscreen
opens with a grid. We have to import our data to this sketch screen as a graph with specific details as discussed below.
 Create a coordinate axis for graph
 Creating lines that represents 360 degree
 Creation of Lobe Profile Points in the Graph

3.1.3. Creation of Lobe
3.1.3.1 Creating Plane for Lobe Start Location
For First Lobe - Inlet Number 10 - the distance from datum was 67.3 mm. Name this plane such a way that, it can signify
its type, number and its purpose. As shown below, it is named as "IN10_DISTANCE" which describes that it is inlet lobe for
cylinder 10 and the plane itself is the starting point of the lobe surface, distance measured from datum.
3.1.3.2 Creating Plane for Lobe Orientation
 Bring your view on the screen to standard "LOBE_ORIENTATION" view which can showthedowel holeintop position
and a pane passing through hit. Always select center axis A that passes through the entire camshaft for reference
whenever it is necessary to choose an axis as a reference from model tree.
 Select axis A as your first reference and "ORIENTATION_DOWEL" plane as your second reference for creating your
orientation plane for Inlet-10lobe.
 Enter the value of orientation angle required for this lobe. Recall the list of items required to make a lobe had this
value. Then take the value from the following information table provided.
So now, we have created a plane passing from axis A and oriented at 312.49 degree counter clock direction with respect to
"ORIENTATION_DOWEL" plane. Such an orientation plane for each lobe signifies the maximum lift point of the lobe.
3.1.3.3 Creating a sketch of trajectory of center of roller which rolls on the lobe profile
Here, wewill first create the path of roller which rolls on camshaft lobe and then wewillcreateanoffsetpathbyrollerradius
to actually create the lobe profile. In order to create this roller trajectory, we will have to create a sketch which is shown in next
step. This process is common for all lobes creation.
 Select plane "IN10_DISTANCE" as our sketching plane.
 Make sure that we have right sketch setup to create our sketch. For this we need to follow following steps: i) after
selecting a sketch plane, see in which direction your sketch setup orients. If it does not become as our standard view
"LOBE_ORIENTATION" then bring it to that view by applying following settings.
 Select sketch references:
i) Axis A (Always)
ii) Orientation Plane for the lobe, in this caseIN10_ORIENTATION.
 Sketch a circle with
Radius= (Cam Follower/Roller Radius + Base Circle radius)
We are creating a path of roller/cam follower center's trajectory. We will use our points file to describe its lift from nominal
position. But in closed condition, the roller/cam follower follows on the circle with above diameter.
 Now recall the list of items discussed from excel sheet. For 783 lobe, these values are 27.5 and 33.125. So now we will
sketch a circle with radius 27.5+33.125 = 60.625 (i.e., diameter 121.250) placing center at axis A reference point.
 Now, we actually do not need entire circle. We need to consider only part of it which falls between the angles of
OPENING (-65) and CLOSING (+80). So let's trim the remaining lines by creating a boundary of these angles.
Now here, it is important to understand which side we put our opening angle and which side we put our closing angle. We
know that orientation angle is 312.49 for Inlet-10 lobe andhence wecan make surehere that it stays in4thquadrant.Sowewill
dimension our angles from that reference which is in 4th quadrant.

 After placing correct angles on correct side of reference plane (orientation plane), we will trim extra lines as shown
below. After trimming extra lines, oursketchlookslikeshownbelow.Pleasenotethattheboundariescreatedbyplacing
two lines from center axis are just construction lines and not part of the sketch.
 Now using this sketch our next step is to create the trajectory of roller center.
 Select the sketch and click on Variable Section Sweep tool.
The yellow arrow shows the starting point of our profile curve for roller trajectory (which is not at correct location by
default). Now to be clear, profile curve (i.e., 783) in the model tree is read from -65 to +80. That means,itisalwaysreadfrom-ve
to +ve direction of angles.
Now we will setup the relation to read all points from 783 graph to create the trajectory.
1) Dimension the distance between PTN20 and the point beyond PTN 20 as 107.1
2) Go to Tools--> Relationsand type following relation asshownbelow forthe dimension just placed betweenPTN20andthe
point beyond PTN 20. There are 5 important things to understand about this relations shown below
Fig-2: Trajectory of roller or cam follower
The relation is:
sd4 = evalgraph("783", trajpar*145-65)
This has to be typed same as shown. The arguments inside this relation change, when we change the lobe.
1. sd4 is the dimension that we had placed between PTN20 and the point beyond PTN 20 and we are driving this
dimension using the relation expressed after " = " to sign.
2. evalgraph is the function which will evaluate this function by reading the argument inside this function.
3. "783" is the graph name we had given from which all points data will be read starting from -65 to +80
4. trajpar - function decides to make trajectory using the extracted points from 783graph
5. Angle Value - 145: This is very important. This value is the total included angle between opening and closing. That
means in our case it is 65+80 = 145. Trajpar function acts for total of 145degree
6. angle value -65 This decides the start point fortrajpar function to act so if wethisargument as 65 then trajpar function
will extract points from 783 graph starting at -65 to total of 145 degree in increasing direction.
Click on Variable Section Sweep in model tree (i.e., keep it selected)andagainclickonVariableSectionSweeptool.Selectthe
trajectory of roller/cam follower if not selected already and do not changeany set up on this one. Here we just need tocreatean
offset path of the same trajectory by amount of roller radius in internal direction. After having this,clickonsketchtoolshownin

the same panel. It will orient in some orientation for sketch purpose. Do not bother about orientation here as we just need to
create an offset path.
Draw the line starting from the point shown below and inthe internal direction.Changethedimensiontorollerradiusthatis
27.5 mm taken from the excel sheet. It should create an offset profile. Please note that this offset profile itself is our lobe profile.
Now you should have another section sweep in the model tree which is your lobe profile. The only step remaining now is to
extrude this up to appropriate lobe width.
3.1.3.4 Create an extrude using the offset profile just created.
1) Select a sketch plane (always choose the plane we created for lobe distance, here it is IN10_DISTANCE) because that is
the starting point of the lobe surface.
2) Select extrude tool -->go to placement and select Define
It will orient at some random orientation but we have to make sure that we have right orientation. Always choose your
base standard view as your orientation ("LOBE_ORIENTATION" view). And then Sketch by selecting sketch reference as Axis
A and Select Use Tool from Tool bar. Then capture the offset trajectory created in previous process
And now, create an arc passing from center axis A and completing the trajectory. If you would not have selected the
"tangency" relation in the 783 graph, you will never be able to complete this sketch by connecting with an arc like this. Then
select an appropriate direction for extrusion. (Make it opposite here). And then enter the lobe width = 26.9 here.
Fig-3: Cam lobe model in Creo
3.2 Modeling with C# application
3.2.1 Design Phase
In order to develop the GUI for camshaft and cam lobe, we have to follow some program structure that the main window
displays. It mainly comprises of input data that has to be given for the changes in the model. The program that has to be
designed is written in programming language, C#. After successful execution of program, the window displaces with some
buttons. The Design interface of the cam lobe model is createdusinginputvariablesiflobeinprogramminglanguage.Theinput
variables that are considered for cam lobe are
 Opening angle of valve: at which the valve starts opening, at the angle of crankshaft rotation before the intake valve.
 Closing angle of valve: at which the valve comes to closing position, the angle of crankshaft rotation after the intake
valve.
 Valve timing: the duration of valves in the opened and closed state, whichcanbedeterminedfromValvetimediagram.
 Valve Lift: the distance between the valves during fully opened and closed state.
 Engine RPM: the crankshaft rotational speed is considered for calculations of valve.

 Pitch curve: it defines the function of curve in uniform velocity, uniform acceleration, and simple harmonic motion of
valve during the opening and closing state.
After successful input variables, the Graphical User Interface is developed as shown in the figure. The window has two input
options initially, i.e., number of cylinders and number of lobes. After entering the data, additional options of inlet, exhaust and
injector buttons with extract files and angle of opening for respective buttons appear. Then after, the distances between the
lobes, bearings, etc., has to be modified. Later we can generate the model with new values.
Fig-4: GUI window design
3.2.2 Integration phase
In this phase of experimentation, the Creo model is integrated with GUI to achieve Design automation. The process of
integration can be done using Creo API’s (Application Programming Interface). Visual Studio is the API used in this study. It is
the software that allows two applications to interface each other. The output variables from the design phase are the input
variables of Visual studio. And the values in this frame work are the inputs to the CAD software.
Visual Basic API for Creo Parametric is an asynchronous application. For the application to communicate with Creo
Parametric, you must set the PRO_COMM_MSG_EXE
1. Click on Start > Settings > Control Panel.
2. Click on System. The System Properties windows open.
3. In the Advanced tab, click the Environment Variables button.
4. Add PRO_COMM_MSG_EXE to System variables.
After successful integration with Visual Studio, the model gets updated when the values in the GUI are changed, which can be
seen in the upcoming chapter.
4. RESULTS & DISCUSSIONS
As discussed in previous chapter, interfacing the Creo Model with VB API, the model is ready for automation. In order to
change dimensions of the model, just enter the values in the GUI and Click Generate Model. The Model gets generated
automatically with given values in the GUI.
After completion and debugging, the program was able to carry out as planned. By providing the necessaryuserinputs,the
program is able to return the planned outputs. The end result of the project, an interactive software tool that assists the user

within the answer of the primary encountered problems when modelling a camshaft, was carried out as initially planned. It
does simplify the task and saves the modelling time.
Step-by step model gets generated as per the input parameters in the user interface. The change in the model, before and
after the model generation is shown in the fig.5.
Fig-5: Before and after generation of model through GUI
In this project, we can clearly see the time difference in creating a model through conventional modeling and through
programming language interfacing with CAD software. The modeling time difference can be shown through the flow chart as
shown in the fig.6.
Fig-6: Flow chart of design process compared with conventional modeling and modeling using C#

From the flow chart we can easily observe the time taking through conventional modeling for each lobe, whereas, in GUI
using programming language the time taking for modeling is too less. It can save the modeling time by more than 70% for the
modeler. From the generated model, dimensions can becrosscheckedwiththemodel fromgiveninputasshowninfig.asoneof
the example, which gives the same valve that we have entered in GUI.
Fig-7: Exact dimensions obtained from GUI to Creo model
5. CONCLUSIONS AND FUTURE SCOPE OF STUDY
According to the experimental study on design automation, following conclusions can be made
 Scope of programming languages in the mechanical design and modeling processes is for effectivework intheindustries.
 Use of programming languages helps in saving the time in design phase and decreases the time gap between designing
and modeling.
 Parametric Modeling in CAD software useful for faster regeneration of models during the simulation with new
dimensional values of a component.
 Integration of programming languages and CAD software helps the industries in this fast growing competitive world.
 Further, the integration of analysis phase in Automation, in future has a decent extension.
REFERENCES
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[6] Ramakrishnan Balaji Iyer, Vijay Kumar Jattia, Yeshpal Yadavb, Anurag Vermab, Jaimin Desaib, C.P. Dewanb. “Design
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