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MECH XXXXXXXXXX
Assignment 1 (25% in Total)
Part A - CNC Code (12.5%)
Due Friday 11:59pm 24th of March (Week 5)
The first assignment in MECH XXXXXXXXXXis made up of two separate parts. Part A is worth
12.5% and Part B is also worth 12.5% of the assessment for this Unit of Study. Part A concentrates on
writing the CNC code for the outside surface of the Gear-box Cover that you were given as a Tutorial in
Week 1 for machining on the Mori Seiki NV4000.
Some Guidelines:
1. Adjust your SolidWorks model (or in your CAD system of choice) to ignore minor details such as any
fillets, chamfers, or tapped holes.
2. You only need to write the CNC code for the mi
or image of the outside surface of the Gear-box
Cover detailed in the Engineering Drawing in Figure 2.0. Do NOT write the CNC code for the inner
surface of the Gear-box Cover drawing.
Figure 1.0
Gear-box Cover
(Courtesy of Mr. Benedict Wilson - Tutor)
3. Select from the Mori Seiki Header the most appropriate tool to ca
y out the task.
4. Your CNC code should be optimised so that a minimum of time is spent by the tool moving in free air.
5. The bores with Ø16 mm and Ø32 mm are to have a better surface finish than the rest of the Gear-box
Cover.
6. You are writing an initial CNC code to produce a prototype Gear-box Cover, not the final product.
7. The stock material size that the Gear-box Cover is to be manufactured from is; 250mm long * 200 mm
high * 60mm thick.
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Additional Requirements:
1. No tool changing is allowed.
2. When writing the CNC code, NO consideration for fixtures is required.
3. The CNC program MUST be combined into the Mori Seiki Template.
4. No traversing across the XZ or YZ axis is allowed.
5. All dimensions must have a decimal point with no more than three decimal places.
6. All major steps must be fully documented with comments.
6. Assume all machining operations only require one cut, not multiple cuts increasing in depth.
7. Appropriate feed rates are to be used in your CNC program.
10. Your CNC program must be in an ASCII text format i.e.
Do not submit a Microsoft Word document or a SolidWorks model.
When you have completed your CNC program, name your file as per the example below using a .txt
extension;
e.g. XXXXXXXXXX XXXXXXXXXXtxt
NOT XXXXXXXXXXnc
and submit it into the folder located in CANVAS, Assignment 1 Part A.
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Figure 2.0
“Gear-box Cover”
From Engineering Drawing A.W Bound 3rd Ed., p152
PART A OF THIS ASSIGNMENT SHOULD TAKE A STUDENT APPROXIMATELY 8 HOURS
TO COMPLETE.
Paul Briozzo
10/03/2023
MECH XXXXXXXXXX
Assignment 1 (25% in Total)
Part A - CNC Code (12.5%)
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MECH XXXXXXXXXX
Manufacturing Engineering
Compiled by Paul Briozzo
School of Aerospace, Mechanical & Mechatronic Engineering
University of Sydney
2023
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Contents
CNC Machining / Manufacturing Processes:
Chapter 1 – CNC Machining: Writing CNC code
Chapter 2 – Forces in Machining
References
Preface
The MECH XXXXXXXXXXstudents of 2022 are thanked for their enthusiasm for the subject
and their support during the transition to online teaching due to the effects of COVID-19.
The year 2023
ings with it new challenges and opportunities as we slowly move out of the enforced
COVID-19 teaching paradigm. The year 2023 will introduce some additional CNC machining
software to the undergraduate program.
Paul Briozzo
Fe
uary 2023
Sydney,
Australia
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Chapter 1 - CNC Machining – Writing CNC code
Introduction
The numerical control part of MECH XXXXXXXXXX, Manufacturing Engineering, is a Unit of
Study (UOS) designed to give a basic but realistic overview of the general area of CNC machine
tools. In 2023, this component is roughly five weeks in duration. It incorporates a number of lectures
and tutorials covering the definition and usage of CNC commands and the use of a computer package
to view machining simulations.
Aims
The aim of the CNC machining part of MECH XXXXXXXXXXis to give students a basic
introduction into numerically controlled machine tools such as the Mori Seiki NV4000 mill that are
used in practice for producing real products. If each student gains some understanding and feel (and
perhaps some enthusiasm!) for this area of manufacturing then the main aim of this component has
een largely achieved.
Overview
MECH XXXXXXXXXX, will have a weekly focus on either an important part of CNC machining
or a manufacturing process that is being considered. During the semester, there will be lectures and
tutorials that will concentrate on providing you with the information and time that you will need to
produce CNC code for the manufacture of some of the features of the parts we will consider for
manufacture.
Some emphasis will also be placed on material removal rates and the forces generated during the
machining process. Some basic coverage of rapid prototyping and the kinematics of CNC machines
will also be presented as well as an appreciation of the precision, accuracy, and repeatability of CNC
machines.
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Programming the NV4000 mill
The CNC part of this course is intended to introduce the topic of numerically controlled machines
and machining, by
ief descriptions of the construction and operation of such machines and
comparing their function to manual processes. In addition, sample tool-path programs for simple
illustrative examples are included in these notes. The software package CIMCO is available in the
Undergraduate Computer rooms S345, S322, S329 and N216. This package allows editing, graphical
simulation, and verification of the CNC code before it is run on the milling machine.
The example programs included in these notes for the Mori Seiki NV4000 mill have every line fully
described. These programs may be used as a starting point for writing and checking your own
programs for your own needs. Students are encouraged to read each program included in these notes
and to ensure that they understand what each function does and how it in turn influences the tool’s
motion.
The Mori Seiki NV4000 mill (Figure 1.0) is a standalone industrial 3-axis machine. The instructions
are in a systematic CNC machine code form consisting of the so-called G & M codes. The main or
more commonly used G & M codes will be covered in the lectures and will be demonstrated via
examples. It is these codes that most students will use to produce their designs. Other less commonly
used codes will still be included in these notes for reference purposes.
Figure 1.0
Mori Seiki NV4000 mill System Specifications (Basic-Mechanical)
Table size:………………………………………..700.0mm x 450.0mm
Travel (X Axis):………………………………….600.0mm
Travel (Y Axis):………………………………….400.0mm
Travel (Z Axis):………………………………….400.0mm
Feed rates:………………………………………..1.0mm to 6000.0mm/min
Accuracy:………………………………………...+/- 0.001mm
Spindle speed range:……………………………..1 to 12,000 RPM
Hold down provision:…………..………………..Pneumatic air vice and conventional T-Slots
Motor - Spindle:…………………………………11kW (continuous)
Motor - Feed:…………………………………….X:1.6kW x 2, Y:1.6kW x 2, Z:3.0kW x 2
Power requirements……………………………...27.4kVA
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Writing a Program
A part-program consists of lines of code, each comprising one block and each representing the next
location of the tool centre point along the tool path.
Traditionally, a line of code begins with a block number, N, followed by a G-code, indicating a
geometric motion by the tool, or an M-code, representing a machine function such as turning the
spindle on. The Mori Seiki mill does not require block numbers except when you need to reference
ack to a particular point on the program.
Each line of a program has a standard form with variations according to the particular motion required
for the tool and the co
esponding machine codes used. Refe
ing to Figure 1.1 and the sample code
is included below;
Figure 1.1
Sample code Comments
N0 M03 (set spindle on)
N1 G90 (in absolute co-ordinates)
N2 G00 X17.1 Y18.0 Z1.0 (move rapid to next position XXXXXXXXXX))
N3 G01 Z-5.0 F70.0 (move tool down (-Z) 5mm at a feed rate of 70mm/min)
N4 G01X82.9 Y32.0 F170.0 (move tool to position XXXXXXXXXXat a feed rate of 170mm/min)
N5 G00 Z XXXXXXXXXXrapid feed the tool up (+Z) 50.0mm)
N6 M05 (spindle motor off)
N7 M02 (end of program)
Feed rates, shown by an F-code, will appear in conjunction with a G01, G02 or G03 code. Most G-
codes are followed immediately by X, Y and Z values to show the next physical position of the tool
centre.
There is in every program an a
itrary point, called the "program zero", chosen by the part-
programmer, to which all co-ordinates are refe
ed, whether absolute or incremental values. This
point is not refe
ed to in the program, but is implied by the co-ordinates of the tool path. The location
of this zero point has to be communicated to the machine operator using a drawing of the part and of
the blank as it appears before any machining is done.
N.B. For ease of setting up, and checking that the program does not send the tool into the machine
table, the "program zero" should always be
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IN THE MIDDLE & AT THE TOP SURFACE OF THE BLANK
If a program is already stored on a USB stick, it may be read into the memory of the controller and
un. In every case, the program