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Contents
content 1
Preface 2
1. Analysis 3
1.1 Part action 3
1.2 Process analysis of parts 3
第2章 Process planning design 4
2.1 Determining the manufacturing form of blank 4
2.2 Datum plane selection 4
2.3 Working out the process route 4
2.4 Determination of machining allowance, process size and blank size 5
2.5 Determining cutting parameters and basic working hours 6
2.5.1 crude、Finish millingφ250 Front and rear end face 6
2.5.2 crude、Fine boring φ180H7 8
2.5.3Drilling reamingφ25 10
2.5.4 Milling slot 10mm 11
2.5.5 Drilling and expansion 6-φ13 12
第3 Fixture design for face milling 14
3.1 Workpiece degree of freedom analysis and location principle 14
3.3 Analysis of positioning error 15
3.4 Calculation of cutting force and clamping force 16
3.5 Brief description of fixture design and operation 18
Conclusion 19
Reference 20
Preface
The fixture of machine tools is now very widely used in the current metal cutting process, it can be said that basically all of the mechanical processing will be more or less applied to fixture. The fixture is mainly able to accurately determine the position of the work piece, and the work piece can be firmly fixed and clamped, so as to facilitate cutting tools to meet the needs of processing. In other words, the main function of fixture is to ensure the quality of the work piece, improve the efficiency of processing, reduce the intensity of labor, can give full play to the performance of machine tools, so fixture in the current machinery manufacturing occupies a very important position
With the great development of mechatronics, automation and artificial intelligence, the fixture used in the field of machinery has gradually evolved into a variety of forms, from the former manual fixture to the automatic assembly line fixture, and even to the present intelligent automatic fixture, the application of fixture is more and more people. With the development of industry, fixture will be improved and developed continuously to meet the needs of modern and diversified mechanical manufacturing production
From the actual development of machinery to the present, we learn the design of fixtures and mechanical manufacturing process knowledge, so that a good combination of the current mechanical manufacturing production, has a good learning effect, and can lay a certain foundation in the future development of mechanical manufacturing work, so familiar with the machine Machinery manufacturing technology and tooling and fixture design knowledge, for the future of mechanical manufacturing work has a great help, but also make their own step by step, gradually upgrade, for the motherland's mechanical manufacturing industry to contribute.
第1章 Part analysis
1.1 Part action
This part is a bearing seat, bearing seat is generally installed on a machine tool, the bearing seat and the corresponding connecting holes connected with the corresponding connecting screw or connecting shaft, the center hole and the corresponding shaft bearing with each other, with the rotation of the shaft, to ensure that the center hole and the shaft have a certain concentric effect.
1.2 Process analysis of parts
Some surfaces to be machined in this bearing seat part mainly include wide grooves on the upper end face and upper end face, wide grooves on the lower right end face and the lower right end face, opposite lower end face of wide grooves on the upper side, opposite end face of wide grooves on the right side, front and rear end face of 250, and so on. The front and rear end face of 250 is thick in these surface features. The roughness requirement is Ra6.3, and the width slot 50h11 requirement of the two parts is also Ra6.3. In addition, the surface roughness requirement of the other two parts is Ra12.5, and the surface roughness unmarked is not processed.
The characteristics of the misalignment hole include the large circular hole_180H7 on the center datum, the surface roughness requirement of this hole is Ra1.6, the surface roughness requirement of 2-_25 holes on the upper wide groove and the lower right wide groove is Ra12.5, and the requirement of 6-_13 through holes on the large end face is Ra12.5.
Form and position tolerance requires 0.12 mm perpendicularity between upper and lower right face, 0.008 mm roundness for center large round hole, 0.250 roundness for large end face, 0.4 mm positioning for center large round hole, 0.1 mm for front and rear large end face and 0.1 mm positioning for C reference center.
第2章 Process planning design
2.1 Determining the manufacturing form of blank
Correct selection of blank has a very important impact on the subsequent processing, for the blank materials and manufacturing methods, also includes the blank manufacturing accuracy on the quality of the workpiece has a significant impact on the subsequentSo it is very important to determine the manufacturing form of the blank. This bearing seat is considered for mass production. According to the shape of the parts, the blank is HT200. This material is gray cast iron. It needs to use casting to make the blank.
2.2 base level selection processing.
（1）Rough benchmark selection
The basic roughness datum of the bearing seat parts can choose the shape of the workpiece. At the beginning, the front and back faces of the 250 large outer circles are used as the mutual roughness datum to process the front and back faces. Of course, the upper and lower ends of the parts can also be used as rough datum.
（2）Precise reference selection
The bearing seat parts of the choice of precision benchmark on the center of the large hole as a follow-up use of precision benchmark, such as the processing of its small hole and wide groove and so on can be used as a follow-up use of precision benchmark.
2.3 Working out the process route
In view of this bearing seat parts, this time to determine the formulation of two process routes, and to compare and select the best choice. as follows（1）工藝方案一
Process 1: casting blank
Process two: rough and fine milling 250 front end face.
Process three: rough and fine milling 250 100mm, ensure the size of the end Face.
process four: center hole for rough and fine boringφ180H7 In place
Process five: milling the upper end and the right side.
Process six: milling upper and lower ends and lower right sides to ensure two parts size 50mm
Process seven: milling the upper end and wide groove on the right side face to ensure the size 50mm
Process eight: drill and expand 2- 25 holes.
Process nine: drill 6- 13 holes.
Process ten: deburring chamfering
Process Eleven: Inspection and warehousing
(2) process plan two
Process 1: casting blank
Process 2: rough and fine lathe 250 front end face.
Process 3: rough and fine car, 250 rear end face to ensure size 100mm Process 4: rough and fine car center hole 180H7 in place.
Process 5: the upper and lower right ends of the upper part of the milling machine ensure the size 50mm.
Process 6: wide groove 50mm on upper and right ends of milling Process 7: drill and expand 2- 25 holes.
Process 8: drill the 6- 13 holes on the big end surface.
Process 9: deburring chamfering
Process 10: Inspection and warehousing
(3) comparative analysis of process plans
We will analyze and compare the two process plans mentioned above. In the second scheme, the lathe is used to process the large end face and the large center hole. The lathe can be used to process, but the volume of the part is larger. Because the part is not similar to the shape of the revolving surface, it is necessary to consider the use of tooling fixture. This part has a larger volume and is put on the lathe. It is necessary to choose both large lathe and large fixture for machine tool processing. The installation time and the cost of using the machine tool are greatly increased. So the second scheme is not adopted, and the final scheme is the final processing scheme.
2.4 determination of machining allowance, process size and blank size. According to the material of bearing block, HT200 grey cast iron blank is adopted to determine the processing.
Surface allowance, process dimension and blank size。
1、φ250Front and rear end face
Inquire about the planar machining allowance in Table 2-24 of "Guidance Course of Basic Course Design of Mechanical Manufacturing Technology". This bearing seaφ250The surface roughness of the front and rear faces is required to be Ra6.3, which is achieved by rough and semi-finish machining. The thickness ranges from 50 mm to 100 mm. It is known that the rough machining allowance is 2.5mm on one side and the semi-finish machining allowance is 1.5mm on one side. suchφ250 The blank size of the front and rear faces is 100+4+4=108mm.
2、hole（）
Inquiry Table 2-20 The maximum diameter of the bore of bearing seat center hole 180 before rough boring can be 170mm. Considering the use of a certain machining allowance, it is manufactured according to the blank size of 160 bore.
2.5 determine cutting parameters and basic working hours
2.5.1Rough, fine millingφ250 Front and rear end face
（1）Rough milling
Processed part material：HT200
Selection of machine tools：Vertical milling machineX53K
Tool selection：Sleeve end milling cutter，diameter φ100mm，Number of teeth Z=10
Milling depth ：
Feed per tooth ：According to "mechanical manufacturing technology basic course design guidance course" table 5-5，take
Milling speed: refer to table 5-11 of the course guide for mechanical manufacturing technology.
Spindle speed of machine tool ：
Feed rate ：
Worktable feed per minute ：
According to the basic milling time calculation in Table 5-47 of "Guidance Course of Basic Course Design of Mechanical Manufacturing Technology", this is a nested face milling cutter. The basic milling time calculation formula is as follows
式中
工件的銑削長度
刀具切入長度：
In the form of
For the nominal width of milling, query table 5-11 shows that the width of the face milling cutter diameter 100mm is 48mm
：Diameter of milling cutter is 100mm
After substituting the above formula
，Obtain
Cutting length of cutting tool ：取，This choice 3mm
：Horizontal feed of worktable
The number of steps is 1
Maneuver time
（2）Finish millingφ250 end face
Machined part material: HT200
Machine tool selection: vertical milling machine X53K
Selection of tools: sleeve end mill, diameter 100mm, tooth number Z=10 Milling depth ：
Feed per tooth: according to table 5-5 of course guide for mechanical manufacturing technology,
Milling speed: refer to table 5-11 of the course guide for mechanical manufacturing technology.
Spindle speed of machine tool ：
Feed rate: ：
Worktable feed per minute ：
According to the basic milling time calculation in Table 5-47 of "Guidance Course of Basic Course Design of Mechanical Manufacturing Technology", this is a nested face milling cutter. The basic milling time calculation formula is as follows
In the form of
Milling length of workpiece
Tool cut in length ：
In the form of
Nominal width for milling，Query table 5-11 shows that the width of the face milling cutter diameter 100mm is 48mm
The milling cutter diameter is 100mm
After substituting the above formula，Obtain
Cutting length of cutting tool ：取，This choice 3mm
：Horizontal feed of worktable
The number of steps is 1
Maneuver time
2.5.2 Rough and precise boring φ 180H7
(1) rough boring to φ 179
Selection of high speed steel boring cutter
The choice of rough machining is
Feed rate reference refer to "mechanical manufacturing technology basic course design guidance course" table 5-36, take
Referring to Table 5-1, cutting speed is obtained.
Spindle speed of machine tool ：
The cutting time is calculated according to the following formula.
In the form of
L: the length of cutting is 179mm.
The actual length of the workpiece is 179mm
：Rough machining is selected as 2mm
Main deflection angle ，that
，This selection 4mm
The number of times of feed is
（2）Fine boring
Feed inquiry refer to "mechanical manufacturing technology basic course design guidance course" table. 5-1，take
Reference table for cutting speed 5-1，have to
Spindle speed of machine tool ：
The cutting time is calculated according to the following formula.
In the form of
L: the length of cutting is 180mm.
The actual length of the workpiece is 180mm
Main deflection angle ，that
，This selection 4mm
The number of times of feed is
2.5.3Drilling reaming φ25
（1）Drilling toφ20
Feed rate: according to "mechanical manufacturing technology basic course design guide course" table 5-22，take
cutting speed ：Refer to "mechanical manufacturing technology basic course design guidance course" table 5-22，take
Spindle speed of machine tool ：，
The cutting time of drilling is calculated according to the following formula.
In the form of
The length of the cutting layer is ：according to the cutting depth,
Tool cut in length ：
：Front corner of taper shank twist drill，Generally 118 degree，This calculation is based on 120 degrees.
Cutting length of cutting tool ：，This is drilling through hole, according to 3mm.
The number of times of walking is 1.
Maneuver time ：
（2）Reaming φ25
Feed rate ：According to "mechanical manufacturing technology basic course design guidance course" table 5-25，take
cutting speed ：Refer to "mechanical manufacturing technology basic course design guidance course" table 5-26，take
Spindle speed of machine tool ：，
The cutting time of reaming is calculated according to the following formula.
In the form of
Length of cutting layer ：According to the cutting depth,
Tool cut in length ：
：Front corner of taper shank twist drill，Usually 118 degrees.，This calculation is based on 120 degrees.
Cutting length of cutting tool ：，This is through hole.，According to 3mm
The number of times of walking is 1.
Maneuver time ：
2.5.4 Milling slot 10mm
Machine tool: milling machine X53K
Tool: high speed steel keyway milling cutter Tooth number
Feed rate ：According to "mechanical manufacturing technology basic course design guidance course" table 5-15，take
cutting speed ：Refer to "mechanical manufacturing technology basic course design guidance course" table
5-15，take
Spindle speed of machine tool ：，
The method of milling keyway is used to calculate the basic working hours of milling.
式中
Cutting length of workpiece
Tool cut in length ：，according to 25mmCalculation
Cutting length of cutting tool ：take ，This choice 2mm
：Horizontal feed of worktable
Maneuver time
2.5.5鉆擴6-φ13
（1）Drilling to φ10
Feed rate ：According to the guidance course of mechanical manufacturing technology basic course design, table 5-22,
cutting speed ：Refer to "mechanical manufacturing technology basic course design guidance course" table 5-22，
take
The cutting time of drilling is calculated according to the following formula.
Spindle speed of machine tool ：，
In the form of
Length of cutting layer ：According to the cutting depth,
Tool cut in length ：
：The front angle of a taper shank twist drill is usually 118 degrees, which is calculated at 120 degrees.
Cutting length of cutting tool ：，This is drilling through hole, according to 3mm.
The number of times of walking is 1. Maneuver time ：
（2）Reaming φ13
Feed rate ：According to the guidance course of mechanical manufacturing technology basic course design, table 5-25,
cutting speed ：Refer to table 5-26 of course guidance for mechanical manufacturing technology.
Spindle speed of machine tool ：，
The cutting time of reaming is calculated according to the following formula.
In the form of
Length of cutting layer ：According to the cutting depth,
Tool cut in length ：
：Front corner of taper shank twist drill，It is generally 118 degrees, and this is calculated according to 120 degrees.
Report errors
Cutting length of cutting tool ：，This is through hole.，According to 3mm
The number of times of walking is 1.
Maneuver time ：
. 3.1 milling fixture design.
workpiece freedom analysis and positioning principle When milling the large front and rear end face of bearing base, the main positioning datum is the bottom face of the large end face. The main positioning datum based on the bottom face can select three degrees of freedom of the workpiece. The upper end face or the right end face can limit two degrees of freedom. The upper end face or the right end face can also be selected. It can limit the degree of freedom of its movement. The whole positioning principle follows the principle of six point positioning, and the following is a reference map.
Fig. 3-1 six point positioning principle
Locate the bottom three points by supporting pins to determine three degrees of freedom restricting X-direction rotation, Y-direction rotation and Z-direction movement, two points on the side to restrict X-direction movement and Z-direction rotation, and one point on the side of the vertical plane to restrict one degree of freedom restricting Y-direction movement, totally restricting six degrees of freedom.。
圖3-2六點定位
In the six-point positioning principle of supporting plate positioning, the two supporting plates on the bottom can limit three degrees of freedom of X-direction rotation, Y-direction rotation and Z-direction movement, while the supporting plates on the side can limit two degrees of freedom of X-direction movement and Z-direction rotation. The method adopted in this paper is basically in accordance with Figure 3-2. The difference is that when the large end face of_250 is considered as the positioning datum, four supporting nails are selected.，Among them, three supporting nails play the role of locating and restricting degrees of freedom, while the other supporting nails only play the role of strengthening strength. The upper end of one side uses a fixed supporting screw as positioning element, while the right end uses a movable handle to tighten the head of the screw to contact its surface, which limits a degree of freedom of its movement.
3.3 positioning error analysis
One of the positioning methods of this time is that the right end and the lower end are two perpendicular planes. The positioning errors can be analyzed as follows
Error reporting Bilingual contrast
Fig. 3-1 two vertical plane positioning
Through two vertical plane positioning tolerance analysis, the following formula is calculated.
This time Choose for 90 degree，Two dimensions of the side. and They were 30 and 35 respectively.，After substituting this formula
Positioning error accounts for machining tolerances. ，Can ensure processing requirements.
The positioning scheme can meet the accuracy requirement of machining.，The positioning scheme is reasonable.
3.4 Calculation of cutting force and clamping force
(1) calculation of cutting force
The milling end is adopted, and the milling force is calculated according to the following formula.
The milling cutter is cylindrical milling cutter, vertical milling cutter, disc milling cutter, saw blade milling cutter, angle milling cutter, semicircle shaped milling cutter.
式中
：cutting force
：When milling with hi