专业课程设计说明书
Specialty Course Design
Name
Mankani Mlungisi
Student ID 70077005
Batch
2020
Teacher
耿大喜
Table of Contents
Contents
Introduction ................................................................................................................................................. 1
I.
Design Content Description ................................................................... Error! Bookmark not defined.
II.
1.
2D Part Drawing ............................................................................. Error! Bookmark not defined.
2.
3D Model....................................................................................................................................... 3
Part Diagram Analysis ........................................................................................................................... 4
1.
Part Functional Analysis .................................................................................................................... 4
2.
Part Structure Analysis ...................................................................................................................... 5
Material ................................................................................................................................................. 5
Specific Technical Requirements .......................................................................................................... 6
III. Part Machining ......................................................................................................................................... 7
1. Process Routing Sheet Design ........................................................................................................... 7
2. Processing Cards Design.................................................................................................................. 12
V. Machine tools Used ................................................................................................................................ 13
Lathe .......................................................................................................... Error! Bookmark not defined.
Milling Machine ......................................................................................... Error! Bookmark not defined.
Drilling Machine ......................................................................................... Error! Bookmark not defined.
VI. Conclusion................................................................................................. Error! Bookmark not defined.
References ..................................................................................................... Error! Bookmark not defined.
Page. 1
Introduction
This is report about the design of machining process for a classical aeroengine part i.e., a lubricating oil pump shell. Proper lubrication is critical
to successful engine operation. Lubricating oil pumps are used to supply oil to lubrication points, e.g., for plain bearings. In the case of circulation
lubrication, the lubricating oil pump takes in an amount of oil from a reservoir, forces it through the lubrication points and then feeds it back to
the reservoir. The lubricating oil with a certain pressure will be continuously sent to the friction surface. For example, the oil film is formed at
main crankshaft bearing, connecting rod bearing and camshaft bearing, rocker arm and so on to ensure lubrication. The target part to be
designed is the pump shell of an external gear pump.
Fig 1. Pump shell
Design Content Description
2D Part Drawing
SolidWorks 2022 was used to create, iterate, and analyze the design of the pump shell prior to manufacturing. The design was scaled to the
actual dimensions. To accomplish this the SolidWorks 2022 used parametric modeling. After entering the SolidWorks workspace for a new part,
the preparation of a sketching plane was initiated. As mentioned before, SolidWorks uses parametric modeling. This means that parameters
were assigned to entities like lines and features of the sketch. As a result, it was necessary to assign the dimensions while the sketch was being
created. Afterwards the geometry of the sketch was refined. More dimensions were added to the sketch. The last step was to do the centering
and alignment of the drawing. Finally, the fully dimensioned 2D sketch had been created parameterizing the outline of the pump shell.
Page. 2
Fig 2. 2D drawing of the lubricating gear pump shell
Page. 3
Procedures for making the SolidWorks 2D Drawing of the lubricating gear pump shell.
1.
2.
3.
4.
5.
For making the 2D drawing, the 3D model of the target part (pump shell) was used.
The sheet format was selected and the drawing views from the view palettes were applied.
Manual dimensions, cross section views, detailed views, 3 standard views, dimensions with tolerances, basic, bilateral, symmetric,
geometric tolerances etc. were all applied.
Machining symbols and text were applied.
After creating the drawing, the sheet format was edited, applying material name, drawing name, title block, name of the student etc.
3D Model
There is no unique process and workflow, but these are general steps that were followed creating the 3D model with solid modeling techniques.
1.
2.
3.
4.
Defining the intent: The process of creating a solid model is by first establishing the intent of the design. To do this, the following questions were
considered:
a) What is the desired function of the object?
b) What will its physical form look like? What will it be made from? How will it react in its environment?
c) How will it operate in communication with other parts or objects?
Sketching the object: Once the design intent had been established, a rough plan of the object was completed. The sketch can be done manually
but, in this case, it was done using 2D CAD Software.
Converting the 2D sketch into a #D model: The 2D sketch is converted into a 3D model by using commands in solid modeling software such as:
a) Extrude
b) Revolve
c) Sweep
d) Loft
Refining the 3D model and adding textures: 3D model can be further enhanced by adding textures to it. Textures make the model seem more
lifelike and are crucial for designs that include repeating geometric features or patterns.
Page. 4
Fig 3. 3D model of the lubricating gear pump shell
Page. 5
Procedures for making the SolidWorks 3D Model of the lubricating gear pump shell.
1.
2.
3.
4.
5.
The front plane was selected and a sketch of a circle with a diameter of 72mm was made.
Using the Boss-Extrude command a cylinder of diameter 72mm and height 24mm was created.
4 identical circles of diameter 7mm and 49 degrees from the Y axis and 29 mm from the origin were drawn on the end face of the cylinder.
Using the Cut-Extrude command four through all holes of diameter 7mm were created.
Using Mirror Entities command 2 circles of diameter 12mm and 16mm with the centre line along the X axis being the mirror line, their
centres 14.44mm from the mirror line.
6. Using the Cut-Extrude command 2 through all holes were made of diameter 12 mm and 16mm.
7. Using Cut-Extrude command 2 blind holes of 34.3 mm and length of 18mm concentric to the previous 2 through holes were made starting
from the surface of the end face of the cylinder to the specified length of 18mm.
8. Using the Cut-Extrude command straight oil groove, inclining oil groove and a two 45-degree chamfers were created.
9. Two fillets (as shown on 3D model) of radius 4mm were created.
10. Using Cut-Sweep command a ring of diameter of 2mm was created inside the 12mm and 16mm through all holes.
11. A ring of diameter of 2mm was extruded around the cylinder.
12. Two blind holes of 2mm diameter were extruded according to the specified lengths for each hole as shown in the 2D drawing and the two
holes intersect in the origin and one whole was extruded on the straight oil groove as shown on the 2D drawing.
Part Diagram Analysis
Part Functional Analysis
Fig 4. Lubricating gear pump
Page. 6
The working Principle of the lubricating gear pump
Basic Concept:
The basic concept of a gear is very simple. Its most basic form is that two gears of the same size mesh and rotate with each other in a closefitting shell. The inside of the shell is like the “8” shape, and two gears are installed inside. The outer diameter and both sides of the gear are
closely matched with the housing. The material from the extruder enters the middle of the two gears at the suction port, and fills the space,
moves along the housing with the rotation of the teeth, and is final discharged when the two teeth mesh.
A gear pump is also called a positive displacement device, which is like a piston in a cylinder. When one tooth enters the fluid space of another
tooth, because the liquid is incompressible, the liquid and the tooth cannot be at the same time and occupy the same space, so the liquid is
mechanically squeezed out. Due to the continuous meshing of the teeth, this phenomenon occurs continuously, so a continuous discharge
amount is provided at the outlet of the pump, and the discharge amount is the same for every revolution of the pump. With the uninterrupted
rotation of the drive shaft, the pump continuously discharges fluid. The flow of the pump is directly related to the speed of the pump.
In fact, there is a small amount of fluid loss in the pump, because these fluids are used to lubricate the bearings and both sides of the gears, and
the pump body can never fit without clearance, so the fluid cannot be discharged from the outlet 100%, so a small amount of fluid loss is
inevitable, which prevents the pump’s operating system from reaching 100%. However, the pump can still run well, and for most extruded
materials, it can still reach an efficiency of 93% to 98%.
For fluids whose viscosity or density changes during the process, this pump will not be affected too much. If there is a damper, such as a strainer
or a restrictor on the side of the discharge port, the pump will push the fluid through them. If this damper changes during operation, that is, if
the filter screen becomes dirty, clogged, or the back pressure of the limiter increases, the pump will maintain a constant flow rate until the
mechanical limit of the weakest component in the device is reached.
There is a limit to the speed of a pump, which mainly depends on the process fluid. If the oil is conveyed, the pump can rotate at a high speed,
but when the fluid is a high-viscosity polymer melt this restriction will be greatly increased during physical activity.
It is very important to push the high-viscosity fluid into the two-tooth space on the side of the suction port. If this space is not filled, the pump
will not be filled, the pump will not be able to discharge the accurate flow rate, so the PV value is also another limiting factor and a process
variable. Due to this limitation, gear pump manufactures will provide a series of products, namely different specification, and displacement.
These pumps will be matched with the specific application process to optimize the system capacity and price.
The gear and shaft of the PEP-II pump are integrated, and the whole-body hardening process is adopted to obtain a longer working life. The "D"
type bearing incorporates a forced lubrication mechanism, allowing the polymer to pass through the bearing surface and return to the inlet side
Page. 7
of the pump to ensure effective lubrication of the rotating shaft. This feature reduces the possibility of polymer retention and degradation. The
precision-machined pump body can accurately match the "D" type bearing with the gear shaft to ensure that the gear shaft is not eccentric to
prevent gear wear. Parkwood seal structure and PTFE lip seal together constitute a water-cooled seal. This kind of seal does not actually touch
the surface of the shaft. Its sealing principle is to cool the polymer to a semi-molten state to form a self-sealing. Rheo seal can also be used,
which has reverse spiral grooves on the inner surface of the shaft seal, so that the polymer can be back pressured back to the inlet. To facilitate
installation, the manufacturer has designed a ring bolt mounting surface to match the flange mounting of other equipment, which makes the
manufacture of cylindrical flanges easier.
The PEP-II gear pump has heating elements that match the specifications of the pump, which can be selected by users, which can ensure rapid
heating and heat control. Different from the heating method in the pump body, the damage of these components is limited to one board and
has nothing to do with the entire pump.
Drive device:
The gear pump is driven by an independent motor, which can effectively block upstream pressure pulsation and flow fluctuations. The pressure
pulsation at the outlet of the gear pump can be controlled within 1%. Using a gear pump on the extrusion line can increase the flow rate and
reduce the shear and residence time of the material in the extruder.
The external gear pump is the most widely used gear pump, and generally refers to the external gear pump. Its structure is shown in Figure 1,
mainly composed of driving gear, driven gear, pump body, pump cover, and safety valve. The sealed space formed by the pump body, pump
cover, and gear is the working room of the gear pump. The axles of the two gears are respectively installed in the bearing holes on the two pump
covers, and the driving gear shaft extends out of the pump body and is driven to rotate by the motor. The external gear pump has a simple
structure, light weight, low cost, reliable operation, and wide application range.
When the gear pump works, the driving wheel rotates with the motor and drives the driven wheel to rotate. When the meshing teeth on one
side of the suction chamber are gradually separated, the volume of the suction chamber increases and the pressure decreases, and the liquid in
the suction pipe is sucked into the pump; the suction liquid is pushed into the discharge chamber by the gear in the tooth groove in two ways.
After the liquid enters the discharge chamber, the gear teeth of the two gears continuously mesh, so that the liquid is squeezed from the
discharge chamber into the discharge pipe. The driving gear and the driven gear rotate continuously, and the pump can continuously suck and
discharge liquid.
The pump body is equipped with a safety valve. When the discharge pressure exceeds the specified pressure, the conveying liquid can
automatically open the safety valve to return the high-pressure liquid to the suction pipe.
Page. 8
The internal gear pump is composed of a pair of internal gears meshing with each other, crescent-shaped pieces, pump casings, etc. between
them. The role of the crescent-shaped piece is to separate the suction chamber from the discharge chamber. When the driving gear rotates, a
partial vacuum is formed where the gear disengages and the liquid is sucked into the pump to fill the teeth of the suction chamber, and then
enter the discharge chamber in two ways along the inner and outer sides of the crescent-shaped piece. Where the gear teeth enter the mesh,
the liquid existing between the teeth is squeezed and sent into the discharge pipe.
In addition to the characteristics of self-priming capacity, flow and discharge pressure, the gear pump has no suction valve and discharge valve
on the pump casing. It has the characteristics of simple structure, uniform flow, reliable operation, but low efficiency, high noise and vibration,
and easy to wear. It is mainly used to transport various oils that are non-corrosive, non-solid particles and have lubricating ability, and the
temperature generally does not exceed 70 ℃, such as lubricating oil and edible vegetable oil. The general flow range is 0.045-30ms/h, the
pressure range is 0.7-20MPa, and the working speed is 1200-4000r/min.
Structural features
⑴ Simple structure and cheap price;
⑵ Low work requirements and wide application;
⑶ The end caps and the inter-tooth grooves of the gear form many fixed sealed working chambers, which can only be used as a quantitative
pump.
The gear adopts the new technology of the international advanced level in the 1990s-double arcsine curve tooth profile arc. Compared with
involute gears, its most prominent advantage is that there is no relative sliding on the tooth profile surface during the gear meshing process, so
the tooth surface has no wear, running balance, no liquid trapping, low noise, long life, and high efficiency. The pump gets rid of the shackles of
traditional design, making the gear pump enter a new field in design, production, and use.
Pump Classification
As far as the core component gears are concerned, they are mainly composed of common normal gear pumps and arc gear pumps. Common
normal gear pumps are more durable than circular arc gear pumps when transporting impurity media, and circular arc gear pumps have a special
structure, transport clean media, low noise, and long life. Each has its own advantages.
Page. 9
Part Structural Analysis
23To seal up the cavity for the oil pump shell. The following points are the emphasis during process routing design.
Fig 5. Part Analysis
Page. 10
⚫
⚫
The surface (K and T) should be close fitted with the end cover, so the parallelism is controlled small.
The holes A and B should have high coaxial degree to both holes H.
Fig 6. Part Analysis
Page. 11
⚫
To make the twin gears’ meshing well, the distance between holes A and B should have high precision, i.e., narrow tolerance.
Material
Fig 7. Magnesium Alloy
Magnesium alloy (brand MB2) was chosen because of its very low density (1.74g/cm3 compared to 2.7g/cm3 for aluminium alloys). Magnesium
alloys also have a higher strength to weight ratio compared to aluminium alloys. They have exceptional machinability and low cost. They suffer
however from brittleness and poor formability at room temperature. Their formability increases with increasing temperature, but that requires
high energy. Furthermore, studies have shown that formability can be enhanced at the expense of strength, by weakening the basal structure of
the Mg alloys. They have a relatively low Young’s Modulus (42 GPa) compared to other common alloys such as aluminium or steel alloys.
Alloying, heat treatment and plastic deformation are the most effective and inexpensive methods to modify the mechanical properties and
corrosion behaviour of Mg-based alloys according to former research.
Page. 12
Structure and Composition of Magnesium Alloy (MB2)
The composition of Magnesium Alloy MB2 typically includes aluminium (Al), zinc (Zn), and manganese (Mn). Aluminium is added to improve the
strength and hardness of the alloy, while zinc enhances its corrosion resistance. Manganese is used to improve the alloy's workability and
formability. The specific composition of Magnesium Alloy MB2 can vary depending on the desired properties and application requirements.
However, a typical composition may consist of approximately 90% magnesium, 2% aluminium, 0.5% zinc, and 0.2% manganese. These
percentages may vary slightly depending on the manufacturer and specific alloy grade.
The structure of Magnesium Alloy MB2 is characterized by a hexagonal close-packed (HCP) crystal structure. This crystal structure provides the
alloy with its lightweight properties and contributes to its excellent strength-to-weight ratio. The HCP structure also affects the mechanical
properties of the alloy, such as its ductility and deformation behaviour.
In terms of processing, Magnesium Alloy MB2 can be cast, forged, or extruded into various shapes and forms. The alloy's composition and
structure contribute to its excellent machinability and weldability, making it suitable for a wide range of manufacturing processes.
Overall, Magnesium Alloy MB2 is a versatile material with a specific composition and structure that provides it with desirable properties such as
lightweight, high strength, corrosion resistance, and good formability. These characteristics made it a preferred choice.
Recommended cutting parameters for magnesium alloy:
Cutting speed: 300-700 m/min
Feed rate: 0.2-1.0 mm/r
Depth of cut: 1.0-4.0 mm
Finish machining: decrease all the values.
Specific Technical Requirements
1.The connecting radius of plane M to H is not more than R0.1
2.Making 0.3X45° chamfer in the circular hole
3.Sharp edged round R0.2
4.Check the paint plane M on A and B Tight lock should be 100%
Page. 13
5.Check the K and T plane coloring evenly in the whole plane continuous density is 80%
Part Machining
Machining is the most important means and method to obtain qualified machine parts. Machining process is the process of gradually changing
the shape, size, relative position, and surface properties, until it becomes qualified parts.
The preparation of machining process procedures is divided into the following four stages:
(1) Work preparation stage. This stage includes the collection of raw data and basic data, process analysis of the parts, calculation of production
program, and determination of production type and blank type.
(2) Process route drafting stage. This stage is to determine the whole process route, which is the main working stage of the process procedures
preparation. This stage needs to consider the influence of many factors and requires considerable experience in process design. Generally, this
phase can be roughly divided into the following three steps:
① Determine the machining method and acquisition steps of each machining surface on the part according to the specified technical
requirements and the selection of the positioning reference.
② All the required processing steps are determined in order according to certain principles to form an orderly step arrangement.
③ The several steps in the step sequence are combined to form a process of the process. The preliminary design of this processing process
forms the machining process route of the parts.
Process Routing Sheet
Total pages: 1
Beihang University
Student ID
70077005
Process routing
Material:
MB2
Name: Mlungisi Mankani
Page:1
Blank type: Cake
shaped
Machine Tool
Procedure
No.
Procedure Name
0
Page. 14
Part Name:
Blanking
Type
Model
Fixture
Page. 15
5
Rough turning the end faces and cylindrical Face
Lathe
CA6140
Three jaw chuck
10
Drilling and reaming the holes 4XΦ7,1XΦ12 and 1XΦ15
Drilling machine
ZSK4132×1
Drilling/Reaming
fixture
15
Rough boring holes 2×Φ34.4
Boring Machine
tool
TX68
Boring Machine Tool
20
Milling straight oil groove, inclining oil groove, two
45°chamfers
Milling machine
Xk299A
Milling machine
25
Heat Treatment
30
Milling unloading groove
Milling machine
Xk300A
Milling machine
35
Drilling two blind holes Φ2 and one Φ3 hole
Drilling machine
ZSK4132×3
Drilling/Reaming
fixture
40
Turning ring groove
Lathe
CA6140
Three jaw chuck
45
Boring ring groove
Boring Machine
tool
TX68
Boring Machine Tool
50
Finish turning the end faces and cylindrical face
Lathe
CA6142
Three jaw chuck
55
Benchwork
60
Final Dimension Check
65
Surface Oxidation
The commonly used machining technologies:
1.
Turning can be used for turning the outer circle, end face, groove, cutting and hole processing, and can also be used for turning thread,
taper surface and revolving body forming surface.
Fig 8. Turning.
Rough turning: used to remove materials.
Finishing turning: the dimension accuracy is generally IT7 ~ IT8. The surface roughness is Ra 0.4μm ~ 0.6μm.
Fig 9. Three jaw chuck
Page. 16
The three-jaw chuck is a self centering clamping device driven by bevel gear, which is suitable for clamping small and medium sized regular parts
in mass production.
2.
Drilling is a method of drilling holes on solid materials with a drill bit. The drilling accuracy is low, and the dimension accuracy is generally
IT10 ~ IT11. The surface roughness is Ra 50μm ~ 12.5μm.
Fig 10. Drilling
3.
Reaming is carried out based on drilling or semi precision boring, which is one of the most common methods of hole finishing (through
hole). The dimension accuracy is generally IT6 ~ IT8. The surface roughness is Ra 0.2μm ~ 0.8μm.
Fig 11. Reaming
Page. 17
Guidance of drill bit
Part
Fig12.Drilling or Reaming fixture
Page. 18
4.
Milling is mainly used for machining plane (including horizontal plane, vertical plane and inclined plane), groove, forming surface and
cutting off, etc. The machining accuracy is generally up to IT8 - IT7, and the surface roughness Ra is 1.6-6.3μm.
Fig13.Milling
5.
Boring: For the existing hole processing: the larger diameter (d > 80mm), boring is the only suitable processing method. Machining large
through holes or blind holes. The machining accuracy is generally up to IT8 - IT7, and the surface roughness Ra is 1.6-6.3μm.
Fig 14. Boring
Page. 19
6.
Grinding: The grinding machine used in grinding has higher precision, better rigidity, and stability than general cutting machine tools. The
machining accuracy is generally up to IT6 - IT7, and the surface roughness Ra is 0.01-0.8μm.
Fig13.Grinding
Page. 20
Tolerance and surface roughness for hole machining methods
Methods
Condition
Tolerance（IT）
Surface roughness Ra（μm）
<φ15mm
11～13
5～80
>φ15mm
10～12
20～80
半精铰(semi-finish reaming)
8～9
1.25～10
精铰(finish reaming)
6～7
0.32～5
粗 拉
9～10
1.25～5
一次拉孔（铸孔或冲孔）
10～11
0.32～2.5
精 拉
7～9
0.16～0.63
粗 镗
12～13
5～20
半精镗
10～11
2.5～10
精镗
7～9
0.63～5
粗 磨
9～11
1.25～10
半精磨
9～10
0.32～1.25
精 磨
7～8
0.08～0.63
钻/drilling
铰/Reaming
拉/Broaching
镗/Boring
内 磨/Hole-Grinding
Page. 21
Technical Process Cards Design
For a given machining procedure, give simple sketch, select the machine tool, positioning datum, fixture, cutting tools and parameters,
measuring tools, etc.
Fill the cutting parameters according to the recommended cutting parameters for magnesium alloy.
Cutting speed =Spindle rotation speed * 2*π*Diameter of rotation (in unit m)
Example of a process routing sheet.
Page. 22
Machine tools used.
1.
Lathe:
Lathes generally are the oldest machine tools. Although woodworking lathes originally were developed during the period from 1000 to 1 BC,
metalworking lathes, with lead screws, were not built until the late 1700s. The most common lathe originally was called an engine lathe because
it was powered with overhead pulleys and belts from a nearby engine on the factory floor. Lathes became equipped with individual electric
motors starting in the late 19th century.
The maximum spindle speed of lathes typically is around 4000 rpm but may be only about 200 rpm for large lathes. For special applications,
speeds may range from 10,000 to 40,000 rpm, or higher for very high-speed machining (see Section 25.5). The cost of lathes ranges from about
$2000 for bench types to over $100,000 for larger units.
Lathe Specifications.
• Its swing, the maximum diameter of the workpiece that can be accommodated this may be as much as 2 m (78 in.)
• The maximum distance between the headstock and tailstock centers
• The length of the bed
Fig 14. Lathe
Page. 23
2.
Milling and Milling Machines
Fig 15. Milling and Milling Machines
Page. 24
3.
Drilling Machine
Drills typically have high length-to-diameter ratios hence they can produce relatively deep holes. However, high ratios make drills somewhat
flexible and prone to fracture or producing inaccurate holes; moreover, the chips produced within the hole present significant difficulties in their
disposal and ensuring cutting-fluid effectiveness.
The diameter of a hole produced by drilling is slightly larger than the drill diameter (oversize), as one can note by observing that a drill can easily
be removed from the hole it has just produced. The amount of oversize depends on the quality of the drill, the equipment used, and on the
machining practices employed. Furthermore, depending on their thermal properties, some metals and nonmetallic materials expand significantly
due to the heat produced during drilling, thus the final hole diameter could be smaller than the drill diameter when the part cools down.
Fig 16. Various types of drilling and reaming operations.
Page. 25
Conclusion
This was a good and essential training course for me. I learned extensive basic theoretical knowledge of mechanical manufacturing process. I learnt
about the machining process procedures which are the process cards that stipulate the machining process and operation methods of products or
parts, and they are the disciplinary documents that all relevant production personnel should strictly implement and conscientiously implement.
Therefore, the machining process procedure design is an important and serious work.
References
[1] Trang, T. T. T. et al. (2018) Designing a magnesium alloy with high strength and high formability, Nature Communications 9, 2522
[2] National Research Council. (1975) Properties of Magnesium and Magnesium Alloys. In Trends in Usage of Magnesium. (pp. 37-42)
[3] Machining-eBook-Turning and Hole Making (CODE 119)
[4] Machining-ebook-Milling. (CODE 119)
[5] Specialty Course Design— Machining PPT
[6] https://www.harsle.com/The-working-principle-of-gear-pump-id3890111.html
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