(Đồ án hcmute) research and fabrication the effect of rough groove damping compliance on the surface roughness of straight milled part

HCMC UNIVERCITY OF TECHNOLOGY AND EDUCATION FACULTY FOR HIGH QUALITY TRAINING GRADUATION THESIS RESEARCH AND FABRICATION THE EFFECT OF ROUGH GROOVE DAMPING COMPLIANCE ON THE SURFACE R

MINISTRY OF EDUCATION AND TRAINING

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING

SKL 0 0 9 9 1 3

GRADUATION THESIS MECHANICAL ENGINEERING TECHONOLOGY

RESEARCH AND FABRICATION THE EFFECT

OF ROUGH GROOVE DAMPING COMPLIANCE

ON THE SURFACE ROUGHNE

SS OF STRAIGHT MILLED PART

ADVISOR: ME NGUYEN TRONG HIEU STUDENT: BUI ANH KHOA

HUYNH NGOC QUOC HUY

LE DUY NHAN

HCMC UNIVERCITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING

GRADUATION THESIS

RESEARCH AND FABRICATION THE EFFECT OF ROUGH GROOVE DAMPING COMPLIANCE ON THE SURFACE ROUGHNESS OF STRAIGHT

MILLED PART

Bui Anh Khoa – 18144029 Huynh Ngoc Quoc Huy – 18144021

Le Duy Nhan – 18144040 ADVISOR: ME Nguyen Trong Hieu

HCMC UNIVERCITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING

GRADUATION THESIS

RESEARCH AND FABRICATION THE EFFECT OF ROUGH GROOVE DAMPING COMPLIANCE ON THE SURFACE ROUGHNESS OF STRAIGHT

MILLED PART

Bui Anh Khoa – 18144029 Huynh Ngoc Quoc Huy – 18144021

Le Duy Nhan – 18144040 ADVISOR: ME Nguyen Trong Hieu

HCM City, February, 2023

TABLE OF CONTENTS

LIST OF FIGURES vi

PREFACE xviii

ABSTRACT xix

Chapter 1: OVERVIEW 1

The urgency of the topic 1

Published domestic and foreign research results 2

Goal of the topic 3

Tasks and range of the project 3

Tasks of the project 3

Range of the project 3

Research methods 4

Chapter 2: THEORETICAL BASIS 5

Theoretical foundations of metal cutting 5

Characteristics and role of metal cutting 5

The basic movements of tool when cutting 6

Feed movement and feed amount 7

Extra movement and depth of cut 7

Theoretical foundations of milling technology 7

Overview of milling processing methods 7

Type of milling tools 9

Milling technology capabilities 11

Surface roughness of machined parts 12

Concepts 12

Effect of surface roughness 13

Evaluation criteria 15

Symbols and callouts for surface roughness on drawings 19

Surface roughness selection 23

Method of evaluating surface roughness 24

Vibration during cutting 24

Overview of vibration in cutting 24

Types and causes of vibration 24

Solution to vibration reduction 27

Making built-in damping system for cutting tool 28

Introduction to damping cutting tool 28

Milling technology with dampers cutter handle 35

Milling technology with dampers cutter handle 37

Optimization method 45

Taguchi method 45

ANN_GA method 47

Chapter 3: EMPIRICAL STUDY OF THE EFFECT OF DAMPINGING CUTTER HANDLES ON DETAILED SURFACE GLOSS 49

Experiment conditions 49

Cutting conditions 49

Length of cutter 50

CNC machine VM750 51

Experiment procedure 51

Investigate the influence of L on the surface gloss of the workpiece: 51

Investigate the influence of l on the surface gloss of the workpiece: 52

Investigate the influence of ∅ on the surface gloss of the workpiece: 53 Investigate the influence of 𝐑 on the surface gloss of the workpiece: 54 Investigate the influence of 𝐝 on the surface gloss of the workpiece: 54

Investigate the influence of 𝐡 on the surface gloss of the workpiece: 55

Damping cutting tools and damping cores 56

Workpieces 58

Measuring instrument 59

Cases for experimentation 61

Optimization method 72

Chapter 4: CONCLUSION AND FURTHER RESEARCH DIRECTION 83

Conclusion 83

Further research direction 83

REFERENCES 84

LIST OF FIGURES

Figure 2.1: Technology system [7] 5

Figure 2.2: Basic movement of tool when milling [7] 7

Figure 2.3: Reverse milling [8] 8

Figure 2.4: Forward milling [8] 9

Figure 2.5: Cylindrical milling cutter [9] 10

Figure 2.6: Angle milling cutter [9] 10

Figure 2.7: Disc milling cutter [9] 10

Figure 2.8: End milling cutter [9] 11

Figure 2.9: Milling process capabilities [9] 12

Figure 2.10: Types of undulations on the detailed surface [10] 13

Figure 2.11: Effect on wear resistance [10] 14

Figure 2.12: Effect on fatigue strength of parts [10] 14

Figure 2.13: Effect on corrosion resistance [10] 15

Figure 2.14: Effect on corrosion resistance 15

Figure 2.15: Surface profile [10] 16

Figure 2.16: Surface profile [10] 17

Figure 2.17: Surface roughness note definitions (EN ISO 1302) [11] 19

Figure 2.18: How to read the requirements for surface texture [11] 20

Figure 2.19: Surface texturing on contour lines representing surfaces [11] 21

Figure 2.20: Feature-of-size dimension – surface texture requirement [11] 21

Figure 2.21: Geometrical tolerances indication [11] 22

Figure 2.22: Extensions lines of cyclindrical features [11] 22

Figure 2.23: Cyclindrical and prismatics surfaces [11] 23

Figure 2.24: Damping cutting tools [11] 28

Figure 2.25: Damping cutting tool structure 29

Figure 2.26: Vibration between normal cutter and damping cutter 29

Figure 2.27: Damping cutter [20] 31

Figure 2.28: The parameters of the damper cutter [20] 32

Figure 2.29: General technique [20] 32

Figure 2.30: Life force parts [20] 33

Figure 2.31: Aviation sector [20] 33

Figure 2.32: Oil and gas [20] 34

Figure 2.33: Auto parts [20] 34

Figure 2.34: Problems when machining [20] 35

Figure 2.35: Reduce vibrations when machined with damping cutter [20] 36

Figure 2.36: damping effect when using extensions chart [20] 36

Figure 3.3: CNC machine VM750 51

Figure 3.4: Definitions for parameters of damping compliance 52

Figure 3.5: Definitions for parameters of damping compliance 52

Figure 3.6: Definitions for parameters of damping compliance 53

Figure 3.7: Definitions for parameters of damping compliance 54

Figure 3.8: Definitions for parameters of damping compliance 54

Figure 3.9: Definitions for parameters of damping compliance 55

Figure 3.10: Damping cutting tool 56

Figure 3.11: Insert APMT1135PDER parameters 57

Figure 3.12: Damping compliance 58

Figure 3.13: Custom damping compliance holder 58

Figure 3.14: Damping cutting tool assembly 58

Figure 3.15: Experiment samples 59

Figure 3.16: Mitutoyo SJ-201 roughness meter 60

Figure 3.17: Mitutoyo SJ-201 roughness meter [19] 61

Figure 3.18: Definitions for parameters of damping compliance 62

Figure 3.19: Measuring Ra value 64

Figure 3.20: Results after measuring 65

Figure 3.21: Comparision of normal tool and damping compliance 1 to 4 67

Figure 3.22: Comparision of normal tool and damping compliance 5 to 8 68

Figure 3.23: Comparision of normal tool and damping compliance 9 to 12 69

Figure 3.24: Comparision of normal tool and damping compliance 9 to 12 70

Figure 3.25: Comparision of normal tool and damping compliance 17 to 20 71

Figure 3.26: Comparision of normal tool and damping compliance 21 to 25 72

Figure 3.27: Analyze Taguchi Design 72

Figure 3.28: Choosing factors 73

Figure 3.29: Choosing response data 74

Figure 3.30: Main effect for means 74

Figure 3.31: Input and target variables 75

Figure 3.32: Neural Network/Data Manager 76

Figure 3.33: Import Input Data 76

Figure 3.34: Import Target Data 77

Figure 3.35: Create new neural network 77

Figure 3.36: Prepare data and function for new neural network 78

Figure 3.37: Training network 79

Figure 3.38: Neural network training regression 80

Figure 3.39: Fitness function code 80

Figure 3.43: Comparison surface roughness of optimal damping tool and normal

tool 82

LIST OF TABLES

Table 2.1: Surface roughness parameter values (ISO 12085:1996) [10] 18

Table 2.2: Standard values of Ra and Rz [10] 19

Table 2.3: Surface roughness value according to the dimensional accuracy grade [10] 23

Table 3.1: Experiments conditions 49

Table 3.2: Parameters of damping compliance when changing L variable value 52 Table 3.3: Parameters of damping compliance when changing l variable value 53

Table 3.4: Parameters of compliance when changing Ø variable value 53

Table 3.5: Parameters of compliance when changing R variable value 54

Table 3.6: Parameters of compliance when changing d variable value 55

Table 3.7: Parameters of compliance when changing h variable value 55

Table 3.8: Basic component of high-speed steel [18] 56

Table 3.9: High-speed steel heat treatment [18] 56

Table 3.10: Chemical compositions and mechanical properties of SS400 steel 59

Table 3.11: All damping cases dimensions 63

Table 3.12: Surface roughness for each cases 65

Table 3.13: Average surface roughness of normal cuttin tool 66

Table 3.14: Parameters and surface roughness of compliance 1 to 4 66

Table 3.15: Parameters and surface roughness of compliance 5 to 8 67

Table 3.16: Parameters and surface roughness of compliance 9 to 12 68

Table 3.17: Parameters and surface roughness of compliance 13 to 16 69

Table 3.18: Parameters and surface roughness of compliance 13 to 16 70

Table 3.19: Parameters and surface roughness of compliance 13 to 16 71

Table 3.20: Parameters of optimized damping cutting tool 82

Table 3.21: Surface roughness of optimized damping tool and normal tool 82

TRƯỜNG ĐẠI HỌC SƯ PHẠM KỸ THUẬT TP HCM CỘNG HOÀ XÃ HỘI CHỦ NGHĨA VIỆT NAM

Độc lập - Tự do – Hạnh phúc

KHOA ĐÀO TẠO CHẤT LƯỢNG CAO

NHIỆM VỤ ĐỒ ÁN TỐT NGHIỆP Giảng viên hướng dẫn: TS NGUYỄN TRỌNG HIẾU

Sinh viên thực hiện: BÙI ANH KHOA MSSV: 18144029 ĐThoại:

2 Các số liệu, tài liệu ban đầu:

- Sử dụng phần mềm MATLAB cho tối ưu hóa;

- Sử dụng dụng cụ đo độ nhám bề mặt;

- Sử dụng cán dao BAP300R C20-20-160-2T;

- Vật liệu phôi: SS400;

3 Nội dung chính của đồ án:

- Tổng quan về cơ cấu giảm chấn;

- Mô hình cơ cấu giảm chấn 1 khớp mềm;

TRƯỞNG KHOA TRƯỞNG NGÀNH GIẢNG VIÊN HƯỚNG DẪN

(Ký, ghi rõ họ tên) (Ký, ghi rõ họ tên) (Ký, ghi rõ họ tên)

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY OF MECHANICAL ENGINEERING

CAPSTONE PROJECT EVALUATION FORM

(FOR ADVISOR USE ONLY)

Title of thesis:

RESEARCH AND FABRICATION THE EFFECT OF ROUGH GROOVE DAMPING COMPLIANCE ON THE SURFACE ROUGHNESS OF STRAIGHT MILLED PART

Major: Mechanical Engineering Technology Committee number Student’ s name 01 (SN 01):

Bùi Anh Khoa

Student’s ID: 18144029

Student’ s name 01 (SN 02):

Huynh Ngoc Quoc Huy

Student’s ID: 18144021

Student’ s name 01 (SN 03):

Le Duy Nhan

Student’s ID: 18144040

Student’ s name 01 (SN 04): Student’s ID:

Reviewer: Academic Position:

Name of Institute:

COMMENTS

1 Structure of the capstone project

2 Main contents

4 Capstone strengths and weaknesses

5 Questions and Suggestions

6 EVALUATION

POINT

ACHIEVED POINT

1 Structure of the capstone project 30

Student follows exactly the format for

The motivation of the project is clearly

The NEED of project is clearly showed in

2 Main contents (demonstration that

students have ability to): 50

Apply knowledge of math, engineering,

(Signature and Name)

Design and manufacturing the system,

Use the software and technical tool to

3 Real-life applications of capstone project 10

4 Products of capstone project 10

v

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY OF MECHANICAL ENGINEERING

CAPSTONE PROJECT EVALUATION FORM

(FOR REVIEWER USE ONLY)

Title of thesis:

RESEARCH AND FABRICATION THE EFFECT OF ROUGH GROOVE DAMPING COMPLIANCE ON THE SURFACE ROUGHNESS OF STRAIGHT MILLED PART

Major: Mechanical Engineering Technology Committee number Student’ s name 01 (SN 01):

Bùi Anh Khoa

Student’s ID: 18144029

Student’ s name 01 (SN 02):

Huynh Ngoc Quoc Huy

Student’s ID: 18144021

Student’ s name 01 (SN 03):

Le Duy Nhan

Student’s ID: 18144040

Student’ s name 01 (SN 04): Student’s ID:

Reviewer: Đỗ Thành Trung Academic Position:

Assoc Prof Name of Institute:

COMMENTS

1 Structure of the capstone project

2 Main contents

vi

3 Results of capstone project

4 Capstone strengths and weaknesses

5 Questions and Suggestions

6 EVALUATION

POINT

ACHIEVED POINT

5 Structure of the capstone project 30

Student follows exactly the format for

capstone project given by FME

10

The motivation of the project is clearly

provided in the thesis

10

x vi

(Signature and Name)

The NEED of project is clearly showed in

the thesis

10

6 Main contents (demonstration that

students have ability to):

50

Apply knowledge of math, engineering,

and science

5

Design and manufacturing the system,

component or process to meet needs

15

Use the software and technical tool to

solve the problem

5

7 Real-life applications of capstone project 10

8 Products of capstone project 10

Total 100

PREFACE

Since the beginning of time, our ancestors have urged us to "drink water, recall the source," which is a reminder to always reflect on the conception and upbringing of our parents from conception to adulthood good for the family and the community I'd want to start by expressing my gratitude to my parents for giving me life and nurturing me so that I could become the person I am today

No one can succeed in this world without the support of others around them Without the assistance of professors who are committed to instructing and disseminating beneficial knowledge, I would not have been equipped with the necessary knowledge

to complete my studies good thesis for graduation after four years of studies

With this appreciation, our team would like to extend our sincere gratitude to Mr Nguyen Trong Hieu for his leadership, assistance, and protection When I faced challenges during the research process, he did not hesitate to take the time to edit and offer suggestions so that I could complete this project as effectively as possible Next, we would like to extend our profound gratitude to Mr Tran Minh The Uyen and Mr Nguyen Trong Hieu for giving the tools necessary for me to complete the experiment successfully

In order to complete the machining and testing procedure, our team would like to extend its heartfelt gratitude to Mr Nguyen Van Minh in the Vocational Practice workshop for supplying the equipment

It would be hard to discuss this project without mentioning the faculty office instructors who set up the ideal environment for us to complete it

Finally, we would like to extend our sincere gratitude to the companies who sponsored this project—VPIC Company and G.A Consultants Company

Finally, I wish you good health, happiness, and continued youth so you can pass on your knowledge and help the next generation become contributing members of your family and society

Bui Anh Khoa

Le Duy Nhan Huynh Ngoc Quoc Huy

ABSTRACT

The group concentrates on designing the damping tool structure, providing the parameters, and producing the damper within the parameters of this topic Then, the damper is measured and the experimental findings are analyzed using statistical software

to provide a set of data optimum tool selection and computation of real-world and hypothetical error

Design objective: Reduce manufacturing costs while maintaining sufficient design information to provide a tool holder that can reduce roughness while milling with a damper tool

The group's graduation project is: " RESEARCH AND FABRICATION THE

EFFECT OF ROUGH GROOVE DAMPING COMPLIANCE ON THE SURFACE ROUGHNESS OF STRAIGHT MILLED PART " using a damping tool

during machining and then comparing the results with a normal tool, under the guidance

of ME Nguyen Trong Hieu

Project work:

- Structural design of damping mechanism and milling cutter

- Provide a set of structural parameters by statistical model

- Crafting and experimenting

- Measure and analyze results

- Test for error

The team's knowledge of surface tolerances, material theory, applying mathematics to engineering models, improving knowledge of fundamental subjects and machine building technology, knowing more about engineering mechanics, and practicing effective teamwork are all things that have been accomplished as a result of putting this project into practice This information will considerably aid each team member's future job and make them feel more confident when they enter the workplace

Chapter 1: OVERVIEW The urgency of the topic

Entering the 4.0 era, with the great development of science and technology, the precision mechanical processing industry increasingly requires more and more stringent requirements for accuracy while still ensuring high productivity and quality for products Products Therefore, the precision machining process is facing great challenges If in the machining process to ensure productivity, machining with high speed is required, the depth of each cut has a relatively large thickness, such machining means creating a lot

of vibration and noise, the first is easy damage to the cutting tool and the second is the difficulty of guaranteeing the surface quality

When mechanical processing in general and milling machining in particular, it always creates great vibration and noise Mostly to reduce this vibration and noise, the machine operator often chooses the method of reducing the machining process parameters n: spindle speed (rpm), Vc: cutting speed (m/min), fz: tooth feed amount (mm/tooth), t: depth of cut (mm) Such reduction of process parameters negatively affects machining productivity Therefore, this research paper will help to provide solutions to overcome vibration while ensuring process parameters and maintain productivity by applying damping tools to the mechanical processing process [1]

In addition, processing with end mills can easily meet the technical requirements of Insert shape as well as gloss, roughness of the product and the requirements for cutting tools as well as parameters of the cutting process too high, because when machining according to the outer profile, it is not necessary to have a large tool shank length, but in order to process the outer profile, the axis of the CNC machine will take care of the movement, how long the machining profile is, depends on the displacement limit of the machine shaft With milling cutters with long shanks, it is very difficult to achieve high gloss because the longer the shank is mounted, the rigidity also decreases and from there the vibration and noise are also generated and directly affect the gloss, the quality of the machined surface, as well as the product shape

Stemming from the above reasons, our group has deeply researched, researched and

implemented the topic: “RESEARCH AND FABRICATION THE EFFECT OF

ROUGH GROOVE DAMPING COMPLIANCE ON THESURFACE ROUGHNESS OF STRAIGHT MILLED PART " for graduation project

Published domestic and foreign research results.

In general, there have been many studies on the influence of technological factors on the quality of details, but specifically here in the topic that the group is working on is the influence of the tool on the surface gloss such as:

- Subject: Clarence W de Silva, Vibration Damping, Control, and Design, April

5, 2007 [2]

- Application of Taguchi method in optimization of end milling parameters by

J.A Ghani, I.A Choudhury, H.H Hassan – University Malaysia [3]

- Subject: "Study on the effect of cutting mode on surface roughness when

machining on CNC milling machines" by Truong Thi Ngoc Thu - University of

Da Nang [4]

Advantages: Determine the effect of cutting mode on surface roughness with

independent variables (S,t)

State the influence relationship of cutting mode (S,t) to surface roughness

Disdvantages: Research results are determined only under certain experimental

conditions, specifically not taking into account other influencing factors such as tool wear, different processing materials, rigidity of the technological system

- Thesis "Experimental study on the properties of self-excited vibration and the

influence of feed rate on its growth during metal cutting with the help of computer" by Ngo Duc Hanh - University Thai Nguyen Industrial Engineering [5]

Advantages: Identify types of vibration and causes of vibration on machine tools Disdvantages: There is no optimal method to minimize the vibrations that occur when

machining on machine tools

- Subject: "Research to improve the surface quality of machine parts when

finishing milling" by Hoang Trong Hieu - University of Da Nang [6]

Advantages: There is a sufficient theoretical basis for the phenomena occurring during

Walter these tests are mostly being carried out on standard materials and under perfectly machined conditions so the obtained results are quite ideal and of course these studies also serve their commercial purposes and parameters It is easy to see in manufacturers' catalogs, in trade fairs demonstrating their technology

However, there are no published studies on the effect of damping tool holders on the surface gloss of facet milled parts

Goal of the topic

- An overview study of damping technology in metalworking

- Fabrication and experimentation of milling cutter shank with integrated damping system on detail surface gloss when changing internal parameters of damper shank on C45 steel material in Vietnam and comparing with normal cutting tool

- Comment on which parameters optimize surface quality when using a damper shank with a built-in damping system

Tasks and range of the project

Tasks of the project

Starting from the title of the topic and the above purpose, the research direction includes the following tasks:

- Theoretical system of metal cutting related, machined surface quality and factors affecting machined surface quality

- Theory of vibration in machining includes what causes vibration, how vibration affects machining quality, and suggested solutions to reduce vibration

- Design and manufacture of milling cutter shank with integrated damping system

- Set up the experimental procedure

- Experiment:

 Prepare workpieces, 2 types of shank (regular and damping) and inserts

 Prepare machines, tools and test cutting to check whether the technology system is ok, is the cutter well mounted?

 Conduct the experiment with the same cutting conditions for 2 different types of shank (normal handle and damper shank)

 Process data, make graph and compare, analyze and evaluate the results

Range of the project

Due to limited time and equipment, the scope of the study is as follows:

- The sample was milled in the mechanical workshop using CNC milling machine

Doosan VM750

- The test was conducted on only one end mill cutter BAP 300R C20-20-2L160-

1135 19E13 and BAP 300R C20-20-2L150- 1135 19E13 from Mitsubishi

- Use insert: APMT1135PDER-HT from DESKAR

- Only conduct the test on SS400 steel material

- Solely focus on the studying the effect when changing the internal design parameters of the damping core to the surface gloss with the same cutting parameters proposed by the manufacturer

Where: fz = feed rate = 0.15mm/tooth

Vc = cutting speed = 200mm/min

t = depth of cut = 0.75mm

Research methods

- Manufacturing, experimental comparison

- Milling and measuring gloss on the surface of SS400 steel material

- Use damping end mill (BAP 300R C20-20- 2L160-1135 19E13) and a normal end mill (BAP 300R C20-20-2L150-1135 19E13) with diameter of Dc = 20 mm

- Experiment on CNC milling machine Doosan VM750 in the mechanical workshop

- Utilizing Mathlab and Minitab to optimized damping compliance parameters using Taguchi and ANN_GA method

- Measure surface roughness with Mitutoyo SJ-201 handheld roughness meter

- Make a table of the results and draw graph then comparing the roughness between surface milled by a normal cutting tool and a damping cutting tool when milling with the same cutting conditions

- Comments and conclusion

Chapter 2: THEORETICAL BASIS Theoretical foundations of metal cutting

Characteristics and role of metal cutting

Currently, there are many methods for metal cutting: Casting, forging, rolling, welding but these methods are basically creating billets or rudimentary products, often with low precision and gloss

In order to improve the gloss and precision of the parts according to the technical requirements, it is necessary to conduct machining by metal cutting

Metal cutting is a technological process that creates mechanical products with the shape and size of surface gloss according to the technical requirements from an original workpiece by cutting off the metal layer in the form of chips

Machining is performed at normal ambient temperature (both before and after the heat treatment operation) It gives a higher gloss and precision than welding, casting, forging, hot stamping…

Basic metal cutting methods: turning, milling, planning, drilling, boring, boring, broaching, grinding

Machining by cutting accounts for 30% of mechanical machining workloads and may

be more in the future

The system of equipment used to complete the cutting task is called a technology system, including: Machine - Fixture – Cutting Tool - Workpiece

Figure 2.1: Technology system [7]

The machine is responsible for providing the necessary energy for the cutting process The jigsaw is responsible for determining and keeping the exact relative position between the tool, the machine and the work piece during the part machining process The tool is responsible for directly cutting the "excess metal" layer from the part thanks

Machine Cutting tool Fixture Workpiece

to the energy of the machine provided through relative movements

The work piece is the object of the cutting process All results of the cutting process are reflected on the work piece

The basic movements of tool when cutting

Each type of metal cutting machine has a different trajectory of relative motion between tool and the part There are three types of motion:

Main motion: (main cutting motion) The basic movement of the cutter performed through the cutting tool or work piece It can be rotation, round-trip translation or in a combination…

Example: When turning, the main movement is the rotation of the workpiece on the

chuck When milling, drilling and grinding, the main movement is the circular motion

of the milling cutter, drill and grinding wheel; and when planning and cutting is the reciprocating and up-and-down reciprocating motion of the tool

Tool motion: Is the movement of the tool or work piece it is associated with the main movement that makes up the cutting process

The feed movement can be continuous or intermittent This movement is usually done

in a trend perpendicular to the main movement, specifically:

- When turning, the feed movement is the horizontal - vertical movement of the

tool table when cutting

- When milling is the horizontal-vertical-vertical movement of the table carrying

the workpiece

- When grinding is the horizontal (vertical) movement of the table and the up and

down movement of the tool head

- When grinding is the transverse (vertical) reciprocating motion of the table or the

axis of the grinding wheel

- When drilling is the downward movement of the drill bit

Extra motion: It is the movement that does not directly generate the chip such as the forward and backward movement (without cutting into the workpiece)

Figure 2.2: Basic movement of tool when milling [7]

To characterize the main motion, we use two quantities:

- The relative displacement between the cutting edge and the workpiece per unit

time (or the relative displacement of a point on the workpiece surface and the cutting edge per unit time)

- Number of revolution n (or number of double strokes) in time unit

Feed movement and feed amount

It is the relative distance of the cutting edge relative to the part in the direction of the tool feed movement after a unit time, after one revolution of the workpiece or after a double stroke The feed rate can be the circular feed rate, the minute feed rate, etc When turning, the feed rates is the amount of tool displacement in the toolpath along the work surface per revolution of the workpiece (mm/round)

When planning and cutting the feed amount s is the amount of displacement of the tool

or table after a double stroke of the table (or tool) – mm/double stroke

For multi-blade tools such as milling cutters, it is possible to calculate the feed rate after one tooth (mm/tooth), the feed rate after one revolution of the tool (mm/rotation), the feed rate after one minute of tool operation (mm/min)

Extra movement and depth of cut

The depth of metal removed after a cut (or the distance between two adjacent machinable and unmachined surfaces measured perpendicular to the toolpath)

 The set of factors such as cutting speed V, depth of cut t, feed rate S is called the cutting mode

Theoretical foundations of milling technology

Overview of milling processing methods

Milling is a metalworking method that uses a cutter with multiple cutting edges The

main movement is the circular motion of the tool, the feed movement is the horizontal, vertical and vertical movement performed by the table

The cutting speed when milling is calculated by the formula:

The amount of feed in milling is determined by one of three factors:

- The tooth feed amount (Sz) is the displacement of the part during the time one tooth (1 cutting edge) of the milling cutter enters the metal, the unit is mm/teeth

- The feed rate (Sv) is the displacement of the part when the milling cutter rotates one revolution, denoted by Sv and has the unit of mm/rev

- The minute feed rate (Sm) is the displacement of the part after a time of one minute, denoted by Sm and the unit is mm/min

Thus, the relationship between the above feed rates is as follows:

Sm = Sv.n = Sz.Z.n [mm/min] [7]

Where:

- Z: number of teeth (number of blades) of milling tool

- n: number of revolutions of tool in one minute

When milling can be done in two methods:

- Forward milling is when the forward direction of the workpiece coincides with

the direction of the tool rotation

- Reverse milling is the direction of motion of the workpiece against the rotation of

the tool

Figure 2.4: Forward milling [8]

During forward milling, the thickness of the cutting part varies from amax to zero The milling cutter exerts pressure on the workpiece to the machine table Does not cause slippage when feeding, so the surface gloss is better than reverse milling The collision between the cutter and the large part Suitable for finishing When back-milling, the cutting process is less prone to impact, less machine and tool damage, suitable for rough milling

The advantage of reverse milling is that the cutting length increases from amin = 0 to

amax, so the cutting force increases slowly, avoiding impact, the force acting in the forward direction has the effect of stimulating between the nut and the lead screw of the machine table, does not produce vibration does not cause vibration

The disadvantage of reverse milling is that at the beginning when the new tooth is

cut, the cutting thickness amin = 0, so there is a sliding phenomenon between the cutting edge and the machined surface, making the surface smoothness poor and making the tool worse fast wear Therefore, reverse milling is only used for roughing

The advantage of forward milling is that there is no slippage when the new cutting

edge enters the break, and the blade thickness varies from amax to amin Therefore, the tool has less wear and the tool life is increased, the surface smoothness is high

The disadvantage of forward milling is that when cutting, there is a collision, the cutter

is fragile, and the vibration is large…The cutting force in the feed direction makes the engagement between the lead screw and the nut on the table discontinuous…

If we cut with small cutting thickness, the small impact force affects the vibration insignificant

Type of milling tools

Unlike turning tools, milling cutters have many cutting edges, these cutting edges can

be built into the tool body, which can be manufactured separately called chamfer teeth The cutting edge is arranged on the cylinder face, the end face or both the cylinder face and the end face Depending on the insert shape, blade position and structure, milling cutters are divided into the following types:

Figure 2.5: Cylindrical milling cutter [9]

Figure 2.6: Angle milling cutter [9]

Figure 2.7: Disc milling cutter [9]

Figure 2.8: End milling cutter [9]

Cylindrical milling cutters are cutters where the cutting edge is arranged on the cylindrical face of the tool There are two types of cylindrical milling cutters, straight tooth milling cutters and inclined tooth milling cutters Straight tooth milling cutters are milling cutters where the direction of the main cutting edge is parallel to the tool axis Inclined tooth milling cutters have a main cutting edge that is made with the tool axis at

a certain angle

- Face end mills are milling cutters whose cutting edge is arranged on the face of

the tool The end face milling cutter can be either solid teeth or joined teeth

- End mills can have from 2 to 8 cutting edges

- Disc milling cutter

- Angle milling cutter

In addition, there are Inserts-defined milling cutters, keyway milling cutters, and modular tooth roller milling cutters for gear processing

Milling cutters should have a back angle α from 10 to 200 and a cutting angle from 60

to 900 When milling soft materials, it is recommended to choose a large α angle and a smaller cutting angle δ

Milling technology capabilities

Milling can machine many different types of surfaces, but below we will only study two types of surfaces: flat and keyed surfaces Only gear milling will be studied in the next chapter (gear machining chapter)

The machined planes on the milling machine are the horizontal planes, the vertical planes and the inclined planes When machining these types of planes, cylindrical Inserts mills, end mills, end mills or disc mills can be used In large series production, end mills are used more than cylindrical Inserts milling cutters for the following reasons:

Figure 2.9: Milling process capabilities [9]

- Allows the use of large-diameter cutters, which can cut a large width plane, so the

productivity is high

- The tool mandrel does not need to be long, so the rigidity of the tool shaft is better,

allowing to improve the cutting mode

- Multiple cutting edges are in contact with the workpiece, so the cutting process is

smoother

- Allows the use of multiple tools to machine multiple surfaces at once

- It is easy to manufacture all kinds of chiseled cutters

- Sharpen cutters more easily

Grooved or small tread surfaces are usually machined with disc or end mills

Keyway and keyshaft often require high machining accuracy to ensure the fitting properties of keyed or keyed joints

Depending on the key type, the keyway can be machined with a three-sided disc milling cutter or using an end mill

When milling a keyshaft, a three-sided disc milling cutter can be used by milling the two sides with two disc milling cutters, then using a key cylinder milling cutter Key hubs are also commonly machined with profile milling cutters

Surface roughness of machined parts

Concepts

The surface of the part after machining is often not ideally flat but has undulations There are different types of undulations on the surface Observing a magnified part of the surface, the following types of undulations can be seen:

The undulation with height h1 is aberration in the form of a large optical inserts

An undulation of height h3 is the surface roughness These are microscopic undulations

on the surface within a very small standard length l

To distinguish between wave and surface roughness, the following relative ratio between step pi and height hi can be used:

Roughness: 𝑷𝒊

𝒉 𝒊 = 0 ÷ 50 ; Wavelength: 𝑷𝒊

𝒉 𝒊 = 50 ÷ 100

Figure 2.10: Types of undulations on the detailed surface [10]

Effect of surface roughness

Effect on wear resistance: when working, the surfaces of the part are in contact with each other at some undulating peaks, so the actual contact area is only a part of the calculated area Therefore, the pressure at those contact points is very large, which disrupts the laminar flow of the lubricating oil, pushing the oil to the contact area, making the contact surface wear quickly The higher the gloss, the better the wear resistance

Profile

Lubricating oil

Figure 2.11: Effect on wear resistance [10]

Effect on fatigue strength of the part: Surface roughness has a great influence on the fatigue strength of the part, especially when the part is subjected to cyclical loads, dynamic loads The larger the surface undulations, the easier it is to concentrate stress at the bottom of the undulations, making the part more prone to cracking and fracture

Figure 2.12: Effect on fatigue strength of parts [10]

Affects Corrosion Resistance: The depressions of surface undulations are prone to contain acids, salts and other impurities that have a corrosive effect on the surface The

Lubricating oil

higher the gloss, the better the corrosion resistance.

Figure 2.13: Effect on corrosion resistance [10]

Effect on the accuracy of the joint: For a gap fitting, the surface undulations wear out very quickly in the initial time, making the mounting gap

Figure 2.14: Effect on corrosion resistance

The coupling increases and the docking accuracy is destroyed For joints with redundancy, when two parts are pressed together, the surface undulations will be flattened, reducing the redundancy in the joint and affecting the strength of the joint

length l The reference length is the length of a surface interval used to measure the microscopic undulation of the surface, without taking into account other undulations of larger steps The value of the specified reference length depends on the surface texture Arithmetic mean deviation of profiling 𝑅𝑎: is the mean of the distances from points on the undulating line to the mean OO' taken as absolute value within the standard length l

(Figure 3.23)

𝑅𝑎 =1

𝐿∫(|𝑦|𝑑𝑥 →

𝐿 0

Figure 2.15: Surface profile [10]

Average height of profiling in 10 points Rz: is the average value of the 5 distances from the 5 highest peaks to the 5 lowest troughs of the profile in the standard length range l

∑ ℎ𝑖𝑚𝑖𝑛

5 𝑖=1

) Average line

Figure 2.16: Surface profile [10]

From level 6 ÷ 12, mainly use Ra, while for levels 1 ÷ 5 and 13 ÷ 14 use Rz when

recorded on the drawing the gloss is shown as Figure 2.16 In actual production,

depending on different processing methods, we have different levels of gloss

Average line

Table 2.1: Surface roughness parameter values (ISO 12085:1996) [10]

Ra Rz

1 320 -

160 8

Rough turning, sawing, filing, drilling

Non-contact, critical surfaces: stand, tripod, etc

Static, dynamic contact surface, screw, gear

5 20 - 10 2.5

6 2.5 -

1.25 2.5

Drilling, grinding, polishing…

Dynamic contact surface: tooth face, piston face, cylinder, latch, etc

Suction surfaces, valves, balls, rollers, measuring tools, sample alignment, etc

14 0.05 –

0.025 0.08

Table 2.2: Standard values of Ra and Rz [10]

R a(μm) R z(μm) 0.008 0.125 1.25 12.5 125 1250 0.010 0.160 1.6 16 160 1600 0.012 0.125 1.25 12.5 125 0.20 2.0 20 200

Symbols and callouts for surface roughness on drawings

One of the following symbols may be indicated on the drawing:

- Basic symbol

- For surfaces that require machining

- For surfaces where the machining method is not permitted

Figure 2.17: Surface roughness note definitions (EN ISO 1302) [11]

Where:

- a: Single surface texture requirements

- b: Other surface requirements

- c: Manufacturing method (e.g turning, grinding, chrome plating)

- d: Surface lay and orientation

- e: Machining allowance (in mm)

- x: Letter for simplified reference if space is limited

Types of surface undulation and their symbols:

- Parallel undulation direction: symbol =

- Perpendicular undulation direction: symbol ┴

- Cross undulation direction: symbol ×

- Multi-directional: symbol M

- Direction of swirling undulations: symbol C

- Radial swirl undulation direction: symbol R

- Lay is particulate, non-directional or protuberant: symbol P

Position and orientation of graphical symbol and its annotation

 General

According to ISO 129-1, the general guideline is that the graphical sign and the supplementary information must be positioned so that they are readable from the bottom

or right side of the artwork

Figure 2.18: How to read the requirements for surface texture [11]

 On outline or by reference line and leader line

A reference/leader line with an arrowhead at the end must touch the surface or connect the surface texture requirement (graphical symbol) to it