School of Engineering

 

Engineering Science

System Modelling
Control

(1SMC)

Control System of an
Engraving Machine

 

 

 SMC Assignment Report

AY 2017/2018, October
Semester

 

Date of Submission: 4 June 2017

 

Report By:

Aaron Oon Wei Yan

Student Number:

S10166387G

Supervisors:

Mr Lee Yong Him

Tutorial Group:

P3C2

Diploma:

Engineering Science Year 3

 

 

Introduction

 

Engraving is the act of incising a design onto a solid, typically flat
surface by cutting grooves into them. When materials like silver, gold, or
steel are engraved, the result may be a decorated object. It may also act as an
intaglio printing plate when copper or another metal is used.

 

Engraving has been a historically important methodology for producing
images on paper for artistic and mapmaking purposes, and for commercial usage
and illustrations for books and magazines. However, this traditional method has
long been replaced by various photographic processes in its commercial
applications. This is partly due to the difficulty and intricacy of the
technique.

 

Burin engraving, or engraving with the use of machines, continues to be
practiced by multiple professions such as goldsmiths, glass engravers, gunsmiths and many others. In contrast, modern design-incising
techniques such as photoengraving and laser engraving
are continuously improved in terms of accuracy, affordability and portability
with systems such as the control system. In this report, we will be going
in-depth about the position control system of an engraving machine, more
specifically, a laser engraving machine.   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Methods of Engraving

 

When it comes to engraving equipment, consumers have 2
choices – rotary engraving machines or laser engraving machines. The preferred
method  depends on the desired result,
durability, and the materials to be engraved. The durability and depth of the
design are the most important factors for consideration  For metals or plastic materials, or for
oddly-shaped items and objects requiring permanent engravement, rotary
engraving machines make better engraving equipment solutions. The reasons are
elaborated below

If the material is metal, rotary engraving machines will
provide a greater depth  that is not
achievable with a laser. Additionally, if the material is plastic, a rotary
engraving machine can easily cut the material. Lasers are economically
disadvantageous because they are required to have multiple filters to eliminate
toxic fumes. The shape of the item is also another factor for consideration.
Rotary engraving machines can produce excellent results on uneven surfaces
while lasers only perform well on flat surfaces. Last but not least, if the
durability of the component to be engraved is important to the buyer, the
rotary system is preferred. The rotary engraving process provides a more
durable and permanent finished product.

Rotary Engraving
Machines

Rotary engraving machines etch the surface of the material
with tools that are fixated in a rotating spindle. The cutting tool eliminates
the material from the surface to create the engravement

Rotary engraving is overall cheaper and requires less
maintenance. This is because of its simplicity as compared to its
technologically advanced laser counterparts, which require specialized
knowledge to operate and maintain the equipment.

 

 

 

 

 

 

 

 

 

 

 

 

Laser Engraving Machines

 

Laser engraving is a
subset of laser marking. It is the act of employing lasers
to engrave
an object. The technique does not need inks, nor does it involve mechanical
engraving instruments that will wear over time. Laser engraving has its advantages because of its
ability to engrave a wider variety of materials as compared to rotary
engraving. The laser provides an extremely high quality engravement in
materials such as wood and trophy plaques and is also able to generate
photographic images of a number of materials. Laser engraving equipment employs
laser power focused through multiple mirrors and lenses to etch parts.

 

Here are some other
advantages of laser engraving:

?    
It is a permanent identification method
that cannot be modified

?    
It does not require consumables which
reduces cost

?    
It is environment-friendly with fewer
emissions

 

This report focuses on the modeling and analysis of
the laser engraving machines.

 

Laser Engraving
Machines

 

Physical Arrangement

The laser engraving machine can be broken down into
three main parts: a laser, a controller, and a surface. The laser emits the
beam which removes matter from the object, allowing the controller to etch the
intended design on the object. The direction, intensity, speed and laser beam
spread is controlled by the controller. The surface is picked to match what the
laser can act on. The figure below shows a laser engraving machine

Figure 1: Laser engraving machine

 

 

Control

 

Figure 2: Control schematic of laser
engraving machine 1

 

Applications

Laser engraving is one of the most
vastly employed processes in the manufacturing world. It can be found across
various industries such as the aerospace, automotive, electronics, semiconductor and medical sectors. It is evident that 
it’s clear that the possibilities for laser cutting is endless.

Listed below are some applications
for laser engraving:

?     Laptop engravement

?     Glass engravement

?     Textile engravement

?     And many more

 

However, with its many advantages comes along many
disadvantages as well.  It is limited to the
two-dimensional plane of the x-y direction scan. Metals with high hardness and
low ignition point cannot be used as the material to be engraved. For example:
ceramic, glass, wood, iron, and copper.

 

 

 

 

Analysis of Laser
Engraving Machine Control System

The movement of a laser engraving machine is operated
using a closed loop control. The transfer function of a typical laser engraving
machine is as follows:

With these estimated parameter values, the transfer function of the laser
engraving machine is as follows:

 

Analysis

COMSOL was employed to simulate a dynamic thermal ray
over different materials. With interaction modeling of various materials with
the laser beam, the temperature distribution was produced. The temperature is
the main parameter to finding out the geometry of an engravement. As the laser
heats up the material and the temperature passes the vaporization temperature
at high power intensity, the density of the material would take up the density
of air to form the engravement.

 

(a) Sensitivity of
closed-loop system to changes in the actuator constant ? 2

COMSOL was used to generate the output responses
(above figure) for ? = 0.2 (red curve) and ? = 0.5 (green curve) and ? = 0.8 (blue curve)
respectively. From the response curves it can be concluded that with increase
in ?,
the output tracks the input more closely. However, the response oscillates
more. By introducing derivative control action, the system damping can be
improved.

 

Conclusion

 

1. This report introduces both modern forms of engraving machines. We
compared the differences, advantages and disadvantages of the rotary engraving
machine and the laser engraving machine.

 

2. The focus of the study is on the modeling and evaluation of the
closed-loop laser engraving machine control system. The analysis was carried
out and the results are produced using COMSOL.

 3. Given the analysis and
simulation results, it can be concluded that as the actuator gain ? increases, the system becomes
more responsive to the input commands and the disturbance rejection improves.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

References

 

1 Dongyun, W., & Xinpiao, Y.
(2014, March 18). An Embedded Laser Marking Controller Based on ARM and FPGA
Processors. Retrieved January 22, 2018, from https://www.hindawi.com/journals/tswj/2014/716046/

 

2 Karbasi, H. (n.d.). COMSOL
Assisted Simulation of Laser Engraving . Retrieved January 23, 2018, from https://www.comsol.com/paper/download/62352/karbasi_paper.pdf