DESIGN AND DEVELOPMENT OF A HYBRID MACHINE COMBINING RAPID PROTOTYPING AND CNC MILLING OPERATION
DESIGN AND DEVELOPMENT OF A HYBRID
MACHINE COMBINING RAPID PROTOTYPING
AND CNC MILLING OPERATION
Final Year B.Tech
Er. Nandhu S
DEPARTMENT OF MECHANICAL ENGINEERING
SAINTGITS COLLEGE OF ENGINEERING
Kottukulam Hills, Pathamuttom P .O, Kottayam 686532, Kerala.
Tel : +91-481-2436169, 0481-2436170, Fax : 0481-2430349
E-mail : email@example.com, Website : www.saintgits.org
DEPARTMENT OF MECHANICAL ENGINEERING
SAINTGITS COLLEGE OF ENGINEERING
Kottukulam Hills, Pathamuttom P .O, Kottayam 686532, Kerala. Tel
: +91-481-2436169, 0481-2436170, Fax : 0481-2430349
Website : www.saintgits.org
This is to certify that this Report entitled “Design and Development of a Hybrid
Machine combining Rapid Prototyping and CNC Milling Operation” is a bonafide
record of the Seminar work done by Shone John, Seventh semester bearing
Reg No: 14015040 towards the partial fulfillment of the requirements for the award of
B.Tech. Degree in Mechanical Engineering of Mahatma Gandhi University during the year
Asst. Prof Er. Nandhu S Dr. Jacob T Varghese
Seminar Guide Head of the Department
Dept. of Mechanical Engineering Dept. of Mechanical Engineering
First and foremost, I thankfully acknowledge our Principal Dr. M.C. Philipose for
giving me an opportunity to present this seminar.
The constant encouragement and timely support rendered by our Head of
Department, Dr. Jacob T Varghese is deeply remembered.
I express my heartfelt gratitude to my seminar guide, Er. Nandhu S, Assistant
Professor, Department of Mechanical Engineering, for his valuable guidance, support and
encouragement during the course of the seminar and in the preparation of the report. I have
greatly benefited from his experience and knowledge.
The help extended by all other staff members of the department are remembered with
I also remember with thanks to all our friends and well-wishers for their
encouragement and support.
Above all, I would like to express our profound gratitude to God Almighty for His
immense blessings upon me that led to the successful completion of this seminar.
Nowadays, two most important processes, namely rapid prototyping (RP) and CNC
machining are being used to produce prototypes. CNC machining (subtractive method) is
relatively more precise and accurate, but it is tough to create stuffs with complex features. RP
(additive method), by contrast, is able to form parts with sophisticated features. Combining
both subtractive and additive process on a single platform has significant advantages.
However, this has several challenges such as control system integration and maintaining
accuracy of alignment during the changeover process. This research attempts to assimilate
both of these processes and propose a new design of hybrid machine with the purpose of
overcoming the drawbacks related with different control panel and misalignment issues.
Fused deposition modelling (FDM) is considered as the RP process in this study. A CNC
cutting spindle and an FDM heat extruder has been designed to be placed respectively in
front of a rotary stage which will be used to overcome the misalignment with the help of IR
sensors. The proposed design allows CNC milling and FDM process in a single setup thus
attaining the benefit of decreasing expenses for additional actuators.
LIST OF ABBREVIATIONS i
LIST OF FIGURES ii
1. INTRODUCTION 1
2. LITERATURE REVIEW 4
3. DESIGN OF THE HYBRID MACHINE
3.1 . MECHANICAL DESIGN PART OF THE HYBRID MACHINE 5
3.2. CONTROL SYSTEM FOR THE PROPOSED DESIGN 7
4. INVESTIGATION OF CHARACTERISTICS
4.1. CONTROL OF THE THREE AXIS 8
4.2. FIXING THE ALIGNMENT PROBLEM 9
4.3. TEMPERATURE CONTROL 9
5. CONCLUSION 11
INTERACTION AND DISCUSSION 13
LIST OF ABBREVIATIONS
LM Layered Manufacturing’
AM Additive Manufacturing’
CNC Computer Numerical Control
RP Rapid Prototyping
FDM Fused Deposition Modelling
CAD Computer Aided Design
LIST OF FIGURES
FIGURE NO TITLE PAGE NO
1 Illustration of FDM process 2
2 When the object (CNC spindle or FDM extruder) is
(a) in aligned position; (b) in misaligned position 6
3 Proposed design of the Hybrid machine with
(a) CNC milling spindle; (b) FDM extruder 6
4 Control Structure of the proposed system 7
5 The single GUI for both CNC milling and FDM operation 7
6 “IIUM” movement pattern 8
7 The difference of reflected IR signals as analog voltage when
the object is in (a) aligned and (b) mis-aligned position 9
8 Circuit diagram for temperature control 10
Rapid Prototyping (RP),as well known as „Layered Manufacturing‟ (LM) and „Additive
Manufacturing‟ (AM) is the “basic term for several technologies that allow components to be made
without the need to involve the services of expert model-manufacturers”. This technology has
pinched significant attention due to its capability to overcome many drawbacks of old-fashioned
manufacturing techniques. Its ability to form almost any geometric feature or shape is a great
advantage of AM. However, some new limitations have been introduced, which come out from its
manufacturing methodology. CNC (Computer Numerical Control) machining process is the perfect
way out to the downsides which occur in the RP process. Although high-precision, high-flexibility,
high-accuracy and high-speed and so on desired properties are offered by modern CNC technology,
the flexibility of the final products obtained from CNC machining is quiet pretty imperfect as
paralleled to the RP process. Among the vast area of RP, a number of methods are used:
Stereolithography (SLA), Fused Deposition Modelling (FDM), Laminated Object Manufacturing
(LOM), Selective Laser Sintering (SLS), Multi-jet Modelling or Solid Imaging (SI), Selective Laser
Cladding (SLC), 3D Printing (3DP) or Selective Binding, Laser Engineering Net Shaping (LENS)
.The basic technology of any RP system is LM technology that permits the production of three-
dimensional parts layer-by-layer . The principle of RP is that the original three-dimensional
geometrical part is firstly disintegrated into two-dimensional profile layers. After that material is
adjusted layer-by-layer until the completion of the final part of most RP systems whereas material is
removed in machining processes. Without the assistance of any tooling, RP process allows parts to
be manufactured directly from CAD descriptions . Based on using various forms of raw material the
Rapid Prototyping process is classified as solid base, powder base and liquid base. A light source is
used layer-by-layer in the liquid-based RP Process for solidifying the liquid polymer, till the product
is manufactured. The main difference between the powder-based RP process and liquid-based RP
process is that powder is used as a raw material instead of liquid, and a glue ejector takes the place
of the light sources. There is no need of support material in the powder based RP process for
manufacturing the overhang feature since the powder is able to act as the support material itself.
Among various solid-based RP processes FDM is extensively used . FDM has the outstanding
geometric capability as like as other RP processes and comparing to other RP processes it is quite
simple and has relatively higher accuracy, but it is not capable of handling any metallic product as
like as machining processes. In the FDM process, a plastic material (ABS or PLA) is extruded
through an extrusion nozzle layer-by-layer to buid a product. Usually, this material is supplied in the
form of a filament. Resistive heaters are contained by the nozzle that help to keep the temperature of
the plastic just above its melting point. So, the plastic can easily flow through the nozzle and create
the layer. After that, it hardens instantly and bonds to the previous layer. This procedure is continued
till the shape of the prototype is being created is shown in fig1 .
Fig. 1. Illustration of FDM process
The FDM can yield parts with complex features: nevertheless, for the reason of having residual
stresses and shrinkage which occurred during running the RP process, the precision and accuracy of
the produced product is usually low. Staircase effect causes poor surface quality that is another
limitation of FDM . The layer thickness was found out as the most important aspect for the finished
surface in FDM process . If we want to reduce the layer thickness, then we have to increase build
time that will create another issue. So, for the solution of the above problems we are influenced to
assimilate the CNC milling and FDM operation to attain a hybrid machining system. A hybrid
process was developed with the combination of three-axis milling and SLC where the milling
spindle and the laser head were mounted on two vertically isolated axes . In that research, SLC
process was applied to form a mold, followed by milling to the desired accuracy. Similar to this
another process was developed where CO2 laser welding was used as the RP process . Any type of
machinable material could be used for the fabrication of the product with that method but may not
be simply valid to products with a complex shape. However, The milling spindle and the laser head
were mounted on the similar side of the vertical axis in both of the methods, and therefore could
obstruct with each other throughout the process, hence restraining the traveling spaces of the X and
Y axes. Some other researches have been done where the only change in the implementing of RP
process for example gas metal arc welding (GMAW) and arc welding. Another type of hybrid
process was developed by using laser cladding (LC) technology and five-axis machining as RP
process and machining process respectively. In this system, the laser cladding nozzle was mounted
just afterward to the milling spindle. But the limitation of that machine was its complicated
mechanism . A different approach was adopted for the combination of conventional machining
process and RP process . In that research the product was divided into numerous portions,
machining was used to form each of those portions over the sheet material. Finally, the portions
were glued together. For the construction of the undercut feature, a mechanism was applied to
reverse the material. Any type of machinable material could be used for the fabrication of the
product with that method but may not be simply valid to products with a complex shape. This
drawback was solved by using multi-axis (5-axis) milling machine to construct the undercut feature,
lastly screws and pins were used to make the assembly. A more robust assembly was reported in
which ultrasonic welding was used to connect sheet material . Recently a hybrid RP system has been
developed with the combination of five-axis machining and FDM. The FDM extruder was installed
in a relation to the cutter spindle so that two modes could be interchangeable by 180º rotation of the
axis which prevented the interference between the cutter spindle and FDM extruder . One more
advantage of integrating both of the machining and FDM capabilities in one single platform is that it
lessens the errors and also time affected by refixing parts. But at the same time, this design was
bulky. In this study, the new design of the hybrid machine is suggested, which has achieved the
benefits of the singlesetup process of significant accuracy of CNC milling and FDM.
 Detailed working of rapid prototyping technologies.
 Principles behind Additive manufacturing
 State that CNC machines and rapid prototyping machine follows same concept of working
 Combining both subtractive and additive process on a single platform has significant
advantages However, this has several challenges such as control system integration and
maintaining accuracy of alignment during the changeover process
 Concept of Integration of subtractive manufacturing in 3D printer
 Designing and development of five axis milling machine
 The FDM can yield parts with complex features: nevertheless precisionand accuracy of the
produced product is usually low.
DESIGN OF THE HYBRID MACHINE
Firstly, the mechanical design of the hybrid machine is described in this section. Finally, the
outline of the control system of the hybrid machine is discussed.
3.1. Mechanical Design part of the Hybrid Machine:
One of the major issues with respect to designing this hybrid machine was determining how
to incorporate the cutting tool spindle and the FDM extruder together without unnecessary upsurges
in the complexity of mechanism. The main issue for this one was the alignment. The advanced
design idea was using a rotary stage on which to incorporate the CNC cutting spindle and heat
extruder of FDM separately. For maintaining the alignment, a rotary stage and two IR sensors have
been used. In front of the rotary stage, there is an attachment where the CNC Milling Spindle and
FDM multi-nozzle extruder is attached respectively just parallel to the rotary stage. The rotary stage
can be operated both manually and automatically. The IR sensors are attached to another
attachment that is perpendicular to the rotary stage. The sensors will be used to omit the problems
of misalignment during exchanging the equipment of CNC milling and FDM process. The
misalignment problem is overcome by the differences of the analog signal coming from the IR
sensors. The rotary stage is moved according to the signal from the IR sensors. When the two
reflected IR signals come from at the same distance then there is no difference between the signals
that means voltage difference is zero which indicates that the object (CNC spindle or FDM heat
extruder) is at the correct position. Similarly, if the signals come from different distances then there
will be voltage difference which indicates that the object is not at the correct position. This
principle is shown in fig 1(a) and 1(b).
Fig. 2. When the object (CNC spindle or FDM extruder) is (a) in aligned position; (b)
in misaligned position
After that, we will implement the CNC spindle for doing the milling operation. After doing
the milling operation, we will go for the Rapid Prototyping (FDM) process The FDM system will
be developed using two materials known as modelling material and support material where
modelling material constitutes finished object and supporting material act to support the object. We
will use multi-nozzle heat extruder form FDM process. Fig. 3(a) and 3(b) shows the proposed
design for the Hybrid machine with CNC spindle and FDM extruder respectively.
Fig. 3. Proposed design of the Hybrid machine with (a) CNC milling spindle; (b) FDM
One more benefit of having the CNC machining and FDM capabilities in single platform is
that it lessens the time and errors affected by re-fixing the stuffs. Deprived of this proposed hybrid
machine, still people can use an FDM system to form FDM item and then take it to a machine tool
for subsequent machining. However, it is tough or time-consuming to line up the milling spindle
with the reference of the FDM object because of inexact dimensions or lack of references of the
FDM parts. The proposed design of the hybrid machine will eliminate this problem.
3.2. Control system for the proposed design
The total control system for the proposed design was PC-based. The whole control unit for
the machine was developed using separate controller, circuitry to handle the CNC milling and FDM
process. For our research purpose, we have used Lab VIEW 2014 for programming. The total
control structure of the proposed hybrid system is shown in Fig.4.
Fig. 4. Control Structure of the proposed system
For controlling the whole process we are using NI PCI-7344, UMI-7764 and USB 6211. It
was suggested to use three servo motors, one stepper motor one rotary stage and two IR sensors
which are desired to be controlled: three motors for the X, Y and Z axis, and the other one is for the
FDM heat extruder. NI PCI 7344-four-axis motion was suggested to use for controlling the four
motors. This controller is able to achieve simultaneous three-axis motion trajectories through linear,
spherical, circular or helical interpolation, which will placate all our requirements for concurrent
three-axis machining and also for the FDM operation. The full control panel was in the same
Graphical User Interface (GUI) which had given a unique position for our proposed Hybrid
Machine is shown in the following fig.5.
Fig. 5. The single GUI for both CNC milling and FDM operation
INVESTIGATION OF THE CHARACTERISTICS
Some cases were studied to demonstrate the capability and the features of the proposed
design of the hybrid machine. Firstly, the JOG operation and three axes movement operation is
done with the control panel. Then, experiment was done to check the alignment using IR sensors
on that same control panel. The next case was to control the temperature at a fixed point which is
necessary for the FDM extruder and also for the heat bed. All these features were done in the
same control panel which is one of the most important objectives of this research.
4.1. Control of the three axis:
To perform the CNC milling operation and FDM extrusion operation we need to move the
Cartesean robot into 3 axis. To do this operation we made a program in LabVIEW 2014. In this
case we have successfully done the JOG operation and also have done the linear and circular
interpolation which are useful for performing CNC milling and FDM extrusion operation. A
sample operation is shown as writing “IIUM” shown in fig.6 with the program where both linear
and circular interpolation operation were included.
Fig.6. “IIUM” movement pattern
4.2. Fixing the alignment problem
One important issue design was to overcome the misalignment of the position of the object.
We have used two IR sensors for this purpose. From the sensors the Analogue signal goes to the
NI USB 6211. According to the signal we could aligned the position of the CNC spindle and FDM
extruder. Fig 7(a) and 7(b) shows the reflected IR signals when the object is in aligned and mis-
aligned position respectively
Fig. 7. The difference of reflected IR signals as analog voltage when the object is in (a) aligned
and (b) mis-aligned position
The white and red signal is coming from the upper and lower IR sensor respectively as shown in fig
3(a) and 3(b). In fig 7(a) the two signals are overlapped with each other which means there is no
voltage difference. It indicates that the object (CNC spindle or FDM heat extruder) is in aligned
position. In fig 7(b) there is a voltage difference between the two signals which implies that the
object is not in the aligned position. Getting information from this voltage difference we rotate the
rotary stage accordingly to overcome the misalignment issue. In both of the figures 7(a) and 7(b),
there are some spikes in the signal which is only for some unwanted noises. It will not affect
significantly on the alignment issue.
4.3. Temperature control:
For FDM extrusion process the main important part is to control the temperature of the heater
and heat bed. To do this observation, we have used the 12V-40W heater and one 100k NTC
thermistor. Thermistor is one kind of resistor which resistance varies with the changing of
temperature. The data acquisition device measures voltage instead of resistance. So, we had to
construct a voltage divider circuit to measure the resistance. Fig.8 shows the schematic for the total
temperature control circuit.
Fig.8. Circuit diagram for temperature control
Here Vi is a fixed voltage from the data acquisition device Then we measured the temperature of the
thermistor as a function of voltage using data acquisition device.
After reading the temperature it was necessary to keep the temperature at a fixed point. To do so we
needed to make a circuit with MOSFET which is regulated by the PWM signal from the data
acquisition device. We have created an on-off control using PWM signal to control the temperature
of the heater. When the current temperature is upper than the set temperature, the PWM duty cycle
goes to 0% and the heater is off. Similarly, when the current temperature is below the set-value, the
PWM duty cycle rises to 100% and the heater is on. As the temperature crosses the set-value to
interchange the output condition, the process temperature will be cycling repetitively, going from
above set-point to below, and back above. In this way, we were able to keep the temperature at a
constant value for the FDM operation.
The design for hybrid system, consisting of CNC milling and FDM, was proposed in this
study. the design consist of installing the CNC cutting spindle and the heat extruder of FDM
on a rotary stage and using the IR sensors which makes the mechanism simple and
overcomes the problem with misalignment issue. The other feature of this research was the
single control panel for both CNC milling and FDM operation.
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INTERACTION AND DISCUSSION
1. What is additive manufacturing and subtractive manufacturing process?
In subtractive manufacturing the material is removed from the work piece while in
additive manufacturing material is added one above the other for making of a
2. How material is melted inside the Heat extruder?
Resistive heaters are used inside extruder for the melting of filament.