1 A. INTRODUCTION OF DISSERTATION 1. Dissertation title Optimization on determination of dressing parameters, lubricant conditions and exchanged grinding wheel diameter in internal cylindrical grinding process 2. Rationale of the study Nowadays, according to the great development of technologies, machining processes have to satisfy more and more requirements of mechanical products for quality as well as productivity. In reality, among machining processes, grinding is commonly used to obtain the high quality of surface finish. Especially, it predominates in machining annealed products with high hardness, high strength. It accounts for about 20-25% of the total expenditures for mechanical parts in industries. Because of these reasons, improvement of grinding performance and reduction of machining expenditure while remaining accuracy requirement have been interested in researchers. In comparison with other type of grinding, internal cylindrical grinding process is implemented in difficult conditions and tight spaces. For that reason, it is more difficult to study the process of internal grinding. Therefore, the research of the internal grinding process is less interested by scientists than studying external grinding or surface grinding. In order to improve the internal grinding performance, many solutions have been proposed such as using high standard grinding wheels (diamond or CBN wheel), high speed grinding and optimizing grinding process parameters (cutting, dressing and lubricant parameters). Among these solutions, optimization of grinding process parameters has been considered in many studies. 90CrSi is steel alloy with high mechanic strength and abrasion resistance. It is commonly applied to make molds, low speed cutting tools and machine parts required high durable and abrasion resistance. In medical factories in the North of Vietnam, this type of steel is often used for making tablet punches and dies. Although, internal grinding process has been used in finished step for making tablet dies, its quality and productivity are still low. Therefore, the
25
Embed
A. INTRODUCTION OF DISSERTATION 1. Dissertation title ...
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
A. INTRODUCTION OF DISSERTATION
1. Dissertation title
Optimization on determination of dressing parameters, lubricant
conditions and exchanged grinding wheel diameter in internal cylindrical
grinding process
2. Rationale of the study
Nowadays, according to the great development of technologies,
machining processes have to satisfy more and more requirements of
mechanical products for quality as well as productivity. In reality, among
machining processes, grinding is commonly used to obtain the high quality
of surface finish. Especially, it predominates in machining annealed
products with high hardness, high strength. It accounts for about 20-25% of
the total expenditures for mechanical parts in industries. Because of these
reasons, improvement of grinding performance and reduction of machining
expenditure while remaining accuracy requirement have been interested in
researchers.
In comparison with other type of grinding, internal cylindrical grinding
process is implemented in difficult conditions and tight spaces. For that
reason, it is more difficult to study the process of internal grinding.
Therefore, the research of the internal grinding process is less interested by
scientists than studying external grinding or surface grinding.
In order to improve the internal grinding performance, many solutions
have been proposed such as using high standard grinding wheels (diamond
or CBN wheel), high speed grinding and optimizing grinding process
parameters (cutting, dressing and lubricant parameters). Among these
solutions, optimization of grinding process parameters has been considered
in many studies.
90CrSi is steel alloy with high mechanic strength and abrasion
resistance. It is commonly applied to make molds, low speed cutting tools
and machine parts required high durable and abrasion resistance. In medical
factories in the North of Vietnam, this type of steel is often used for making
tablet punches and dies.
Although, internal grinding process has been used in finished step for
making tablet dies, its quality and productivity are still low. Therefore, the
2
results of this dissertation will provide suitable suggestions to improve the
efficiency of the internal grinding process when making these parts.
Based on previous studies, to increase the productivity and to reduce the
grinding cost, there are three proposed solutions including using optimum
lubricating-cooling condition, optimum dressing condition and using
optimum exchanged grinding wheel diameter.
3. Research objects
This study focuses on the internal grinding process for annealed 90CrSi
steel alloy.
4. Research aims and objectives
The aim of this study is to improve internal grinding process to reduce
grinding cost and surface roughness and increase productivity.
5. Research methodology
The proposed methodology is combined both theoretical and
experimental studies.
Theoretical study: internal grinding technologies and grinding cost
calculation are analyzed and synthesized.
Experimental study: the influence of lubricating-cooling parameters,
dressing parameters and exchanged grinding wheel diameter on the internal
grinding cost analyzed and optimized based in experiments.
6. Research contents
Overview of internal grinding technologies; Study on effect of
lubricating-cooling parameter, dressing parameter on surface roughness and
grinding productivity; Study on the calculation model of internal grinding
cost and the influences of grinding process on grinding cost; Determination
of optimal exchanged grinding wheel diameter.
7. New contributions
This study has analyzed the internal grinding cost and the influence of
grinding process parameters on the grinding cost.
Determining model to calculate the optimal exchanged grinding wheel
diameter (or optimum wheel lifetime) in internal grinding process and the
influence of grinding process parameters on the optimal exchanged wheel
diameter.
3
The lubricating-cooling parameters and dressing parameters have been
analyzed and optimized based on grinding experiments of 90CrSi steel
alloy.
8. Dissertation structure
The dissertation includes the following parts: Introduction, 5 chapters,
conclusions and appendix.
Chapter 1: Overview of internal grinding process.
Chapter 2: The model of efficiency improvement of internal grinding
process and experimental system.
Chapter 3: Experimental study on influence of lubricating-cooling
parameter in internal grinding process
Chapter 4: Experimental study on influence of dressing parameter in
internal grinding process
Chapter5: Determination of optimal exchanged grinding wheel diameter.
9. Significances
Science significances
This dissertation has studied the influence of lubricating-cooling
parameters and dressing parameters on the surface roughness as well as the
grinding productivity when internal grinding 90CrSi steel alloy. The model
of grinding cost has been developed relating to the proposed formula of the
optimal exchanged grinding wheel diameter. This research has provided a
significant contribution in the reduction of grinding cost that is one of
interested research directions in internal grinding process.
Reality significances
This study has determined solutions to improve the internal grinding
efficiency to increase the grinding productivity and the reduction of the
grinding cost when grinding 90CrSi tool steel. The results of this study can
be applied for internal grinding tablet dies.
4
B. DISSERATION OUTLINES
CHAPTER 1. OVERVIEW OF INTERNAL GRINDING PROCESSS
1.1. Internal grinding process: grinding schema, grinding shaft, position
and role of internal grinding in machining process.
1.2. Properties of internal grinding process.
- The properties of internal grinding process are grinding chord length lk,
grinding depth az, equivalent grinding wheel diameter Dtd, shaving removal
process of grinding grains, grinding productivity, grinding forces.
- Wear of grinding wheel.
- Grinding wheel life and method to determine it.
- Surface roughness.
- Topography of grinding wheel and method to measure Topography
1.3. Literature of internal grinding process.
This section focuses on researches relating to the influences of
lubricating-cooling, grinding and dressing parameter on the ground surface
in the internal grinding process. In addition, the models to determine
grinding cost such as Tarasow – Shaw, Field and Ebbrells – Rowe are
reviewed and analyzed.
1.4. Proposal solution to improve grinding efficiency
- Determination of appropriate lubricating-cooling conditions;
- Determination of optimal dressing parameters;
- Determination of optimal grinding wheel life (optimal exchanged
grinding wheel diameter).
CHAPTER 2. MODEL TO IMPROVE THE EFFICIENCY OF
INTERNAL GRINDING PROCESS AND DEVELOPMENT OF
EXPERIMENTAL SYSTEM
2.1. Model to improve the efficiency of internal grinding process
Normally, researches focus on the technical efficiency of the grinding
process to improve the accuracy and the ground surface quality; reduce
force, heat, vibration or increase productivity. In order to solve both
directions, the dissertation develops a model to improve the efficiency of
the internal cylindrical grinding process. This model has been proposed
5
including three parts to increase accuracy and machining surface quality and
reduce grinding cost in internal cylindrical grinding process.
Part 1: Input parameters.
Internal grinding process is complex under the influences of many input
parameters. These input parameters can be classified into five groups
including: grinding machines and cutting parameters; workpieces; grinding
wheels; dressing technologies and lubricating-cooling technologies. Among
these five input groups, some significant groups can be chosen to be
studied.
Figure 1. Model to improve the efficiency of internal grinding process
Part 2: Solutions to improve the efficiency of internal grinding process
Three solutions to improve the efficiency of internal grinding process
including finding optimal lubricating-cooling parameters to reduce surface
roughness and increase the grinding wheel life; finding optimal the dressing
parameters to increase the grinding wheel life and the grinding productivity;
finding the optimal grinding wheel life to reduce the grinding cost. These
models will be presents in next chapter respectively.
Part 3: The quality of the grinding process is increased and technical
requirements are ensured, productivity is increased and grinding cost is
decreased. All of the input lubricating-cooling parameters and dressing
parameters affect the surface roughness.
6
Based on these arguments, it can provide a model to improve the
efficiency of the internal grinding process as shown in Figure 1.
Three solutions are proposed for studying to improve the efficiency of
the process when internal cylindrical grinding small holes. Among these
solutions, the application of the optimal grinding wheel life (exchanged
grinding wheel diameter) has not been considered in previous researches.
Figure 2 presents the relationship between the grinding wheel life (L),
grinding cost (Cgw,p) and cost of machine, labor and management (Cmt,p) in
internal grinding process for one product.
Figure 2. The relationship between the grinding wheel life and grinding
cost
The longer the grinding wheel life, the lower the cost of grinding wheel
is. In contrast, the cost for machines, labors and management linearly
increases with the machining time. The total machining cost for a part
includes the expenditures of grinding wheel, machines, labors and
management ... In Figure 2, a certain optimal grinding wheel life always
exists.
2.2. Experimental system
Experimental system includes technical system and measurement
devices
2.3. Conclusion of chapter 2.
1. The input and output parameters have been analyzed and determined