Design subject: cold water pot cover injection mold design
Designer: Li Li
Specialty: mold design and manufacturing
Class: 2005 mold (3) class
Design time: 2007.12
Teaching and research department: mold teaching and research room
Instructor: Liu Quanxin
Department of Mechanical Engineering, Ezhou University
"Plastic molding process and mold design" course design task book
Subject design name: cold water pot cover injection mold design
Plastic drawing: (mold course design guidance) -(Plastic drawing compilation: page P68 legend 3-18)
Plastic name cold water bottle cover Material PE-HD Thickness 1 Workpiece accuracy 5
Design content:
1, the preparation of molding process regulations (that is, fill out the "plastic molding process card")
2, drawing plastic injection mold assembly diagram (A3 drawings 1 sheet)
3, drawing the mold convex mold, concave mold parts drawings of a set of (A3 drawings more)
4, to improve the preparation of the mold design manual (according to the A4 printing paper binding)
Table of Contents
I. Preparation of plastic molding process card .............................. .............................. ......4
II. Analysis and design of plastic molding process
1. Characteristics of plastic raw materials ............... .............................. ........................5
2. Plastic parts raw material molding performance .............................. .............................. ...5
3. Structure and dimensional accuracy of plastic parts, surface quality analysis .................. .....................5
4. Plastic parts molding method to determine ... .............................. .............................. ...6
3. Plastic part molding mold design
5. The number and arrangement of cavities .................. .............................. ..................6
6. Selection of injection molding machine model and its parameters ...... .............................. .....................6
7. Determine the parting surface... .............................. .............................. ............7
8. Selection and design of pouring system ............ .............................. .....................9
9. Design calculation of molded parts... .............................. .............................. 10
10. Lateral core extraction mechanism ........................ .............................. ..................10
11. Design of exhaust system ...... .............................. ............................. ..... ...11
12. Determination of mold frame and selection of standard parts (schematic) .............. ...........................11
13. Design of temperature regulation system ........................... ....................... ...............12
14. Push-out mechanism (mold release) ......... .............................. .............. ............12
15. Guide mechanism ............ .............................. .............................. .... .13
16. Mold design tips ........................ .............................. .......... .13
17. References ........................ .............................. ...................... .13
18. Mold assembly and part drawings ........................ .............................. ..... .13
Molding Process Card
Plastic Name HDPE Sketch
Material Brand PE-HD
Piece Weight 25.9g
Molding Equipment Model XS-ZY-1000
Number of Pieces per Mould 4
Molding Process Parameter
Material drying Drying equipment name Oven
Temperature /℃ 70~80
Time /h 1~2
Forming process Cylinder temperature Back section /℃ 140~160
Middle section /℃ 180~200
Front section /℃ 180~190
Nozzle /℃ 150~180 <
Mold Temperature /°C 30~60
Time Injection /s 0~5
Holding Pressure /s 15~60
Cooling /s 15~60
Pressure Injection /MPa 70~105
Holding Pressure /MPa
Post Process Temperature /°C _____
Time / min _____
< min _____
Compilation Date Review Date
Li Li 2007.12.4 Liu Quanxin 2007.12.15
Design Calculations and Explanations
I. Analysis and Design of Molding Processes for Plastic Parts
1. Properties of PE-HD (High Density Polyethylene)
(1) Chemical and Physical Properties
The high crystallinity of PE-HD results in high density, tensile strength, high twisting temperature, viscosity, and chemical stability.PE-HD is more resistant to permeation than PE-LD.PE-HD has lower impact strength.The properties of PH-HD are mainly controlled by density and molecular weight distribution. The molecular weight distribution of PE-HD suitable for injection molding is very narrow. With a density of 0.91- 0.925 g/cm3, the material has good flow characteristics with MFRs ranging from 0.1 to 28. The higher the molecular weight, the poorer the flow properties of PH-LD, but it has better impact strength.PE-LD is semi-crystalline and has a high shrinkage after molding, between 1.5% and 4%.PE-HD is susceptible to environmental stress cracking. Cracking can be mitigated by using materials with very low flow characteristics to reduce internal stress. PE-HD dissolves easily in hydrocarbon solvents when the temperature is higher than 60°C, but its resistance to dissolution is somewhat better than PE-LD.
(2) Typical applications
Refrigerator containers, storage containers, household kitchen utensils, sealing lids, and so on.
(3) PE-HD injection molding process conditions
Drying: No drying is required if stored properly.
Melting temperature: 220-260℃. For materials with large molecules, it is recommended that the melting temperature range is between 200-250°C. Mold temperature: 50-95 ℃. 6mm wall thickness of plastic parts should use a higher mold temperature, 6mm wall thickness of plastic parts use a lower mold temperature. The cooling temperature of the part should be uniform to minimize differences in shrinkage. For optimal cycle time, the cooling channel should be no less than 8mm in diameter and within 1.3d of the mold surface ("d" is the diameter of the cooling channel).
Injection pressure: 70-105MPa Injection speed: Use high speed injection. Runner and gate: runner diameter between 4 and 7.5mm, runner length should be as short as possible. Various types of gates can be used, the length of the gate should not exceed 0.75mm. polyethylene molding, in the flow direction and the vertical direction of the shrinkage of the larger differences in the injection direction of the contraction rate is greater than the vertical direction of the contraction rate, prone to deformation and make the gate around the part of the brittleness increased; molding shrinkage is larger, prone to shrinkage holes; the cooling rate is slow, it must be sufficiently cooled, and the cooling rate should be uniform; the texture of the soft and easy to It is easy to be demolded, and can be forced to be demolded when there is shallow side concavity. Especially suitable for hot runner molds.
2. plastic raw material molding performance
? Crystalline material, low hygroscopicity
? Excellent fluidity, overflow value of about 0.02mm, fluidity sensitive to pressure changes
? Melt rupture may occur, contact with organic solvents can occur cracking
? Decomposition and burns if heated for long periods of time
? Cooling is slow, so it must be sufficiently cooled, it is desirable to have a cold cavity, the mold should have a cooling system
? Shrinkage range, shrinkage value is large, the direction is obvious, easy to deformation, warping, crystallinity and mold cooling conditions have a great impact on the shrinkage rate, should control the mold temperature, to maintain uniform and stable cooling
? High-pressure injection is suitable, the material temperature is uniform, the filling speed should be fast, and the pressure is sufficient
? It is not suitable to use direct gating, easy to increase the internal stress, or produce uneven contraction, the direction of the obvious increase in deformation, should pay attention to the selection of the location of the inlet, to prevent shrinkage holes, deformation
? Soft and easy to demold, molded parts have shallow side grooves can be forced to demold
3. The structure and dimensional accuracy of the plastic parts, surface quality analysis
? Structural analysis: analysis from the parts diagram, the overall round side of this part has six 4mm × 22MM and rectangular holes, mold design must be set up lateral parting core extraction mechanism, the mouth of the part has a small table.
? Dimensional accuracy: the precision of the molded part is 7 level, the precision requirement is low.
? Surface quality analysis:
The requirements of the part of the surface without defects, burrs, because the cold water bottle cover is often in contact with the human hand more, so the surface is required to be smooth, the best natural formation of rounded corners.
4. plastic molding method to determine
In summary, the structure of the plastic parts is relatively simple, and wall thickness uniformity, molding process is good, can be produced by injection into the method.
Second, the mold design of plastic parts
5. The number of cavities and arrangement
The precision requirements of the plastic parts are not high, is a small plastic parts, and the shape is simple, but also for mass production, the initial set of four-cavity mold for a mold form, the arrangement of cavities using a well-balanced arrangement of the H-type, and its layout is shown in the following figure: In order to ensure that the quality of the surface of the part required, choose a point gate molding, the gate is good, and the surface quality is good, and the surface quality is good. In order to ensure the surface quality of the plastic part, we choose the point gate molding, the gate position is arranged in the top of the plastic part,
The mold is used for double parting surface injection mold (three-plate type).
6. Select the model of injection molding machine and its parameters
(1) Calculation of injection volume: through Pro/E modeling analysis, the volume of the molded part is 27,265 mm, the mass of the molded part: the volume of runner condensate is not known at this time, so it can be estimated according to the mass of the molded part of 0.6 times, so the injection volume is as follows:
(2) Calculation of clamping force: the projection of the runner condensate (including gate) on the parting surface of the parting surface is about 1.2 times of the surface of the molded part, so it is about 2.3 times the surface of the molded part. The projected area of the runner condensate (including the gate) on the parting surface is still unknown at this time, according to the empirical formula: ( for each molded part on the projected area of the parting surface), use to estimate:
?
? The formula
? Check the injection pressure required for plastic parts 70-105Mpa, and the average pressure of the cavity is 30% -65% of the injection pressure, because the plastic parts for thin-walled plastic parts, and the gate for the point gate, the pressure loss is relatively large, so take a larger, then
(3) Selection of injection molding machine: According to the above calculation of the amount of injection and clamping force, you can choose the domestic XS-ZY-1000 screw injection molding machine The relevant parameters are as follows:
Nominal injection volume/
1000 Maximum thickness of the mold plate/mm 700
Screw diameter/mm 55 Minimum thickness of the mold plate/mm 300
Clamping force/N
Size of the mold plate 690×790
Injection pressure /MPa 121 Tie rod space/mm 650×550
Injection stroke/mm 280 Clamping method Hydraulic machinery
Screw speed/(r/mm) 0~47 Motor power/KW 22
Maximum stroke of stencil/mm 700 Positioning ring size/mm 150
Nozzle ball radius/mm 18 Nozzle hole diameter/mm 7.5
Injection method Screw Max. Mode of injection Screw type Maximum molding area/
1800
Positioning ring size/mm 150 Injection time/s 4
(4) Calibration of parameters of the injection machine
? Calibration of the number of cavities
Calibration of the number of cavities in the mold from the rated injection volume of the injection machine:
The number of cavities passed the calibration
where Vj is the volume of the injection system required for the condensation and fringe
Vz is the volume of each part
Vg is the rated injection volume of the injection machine
? Calibration of injection pressure
The injection pressure calibration is qualified
where K is the safety factor of injection pressure generally 1.25-1.4
? Clamping force calibration
Clamping force calibration is qualified
K is the safety factor of clamping force, generally 1.1-1.2
Other dimensions of the calibration can only be carried out after the mold frame is selected and the structure size is determined.
7. Determine the parting surface
The part requires smooth outer surface and no trace of gate at the lower edge. According to the principle of selecting the parting surface, the parting surface of the part should be selected as shown in the following A-A position, so that the concave model cavity is molded as a whole, and the outer surface of the part is smooth and easy to demold.
8. Pouring system selection and design
(1) Main runner design
? Main runner size
Small end diameter of main runner: ;
Spherical radius of main runner: ;
Main runner cone angle: take ; Main runner length: take L=70mm;
Big end diameter of main runner:
? The form of main runner bushing
As the entrance of main runner is in contact with injection machine nozzle repeatedly, it is very easy to be damaged, and the requirement of material is relatively high, therefore, the main runner is designed as a sprue bushing, adopting T10A, heat-treated to 50HRC-55HRC as shown in the above figure:
The structure of the locating ring which is matched with it is as shown in the following figure:
(2) Design of manifold
? Arrangement of manifold: In order to make the manifold to be able to meet the good pressure transfer and maintain the ideal filling state, so that the condensate melt as soon as possible to distribute to the cavities, therefore, the balance of the manifold structure as shown in the following figure:
? Shape and cross-section size of manifold:
Because of the good fluidity of polyethylene, semi-circular manifold with better processing performance is chosen, and the table shows that d=10㎜
? Surface roughness of runner:
The surface roughness of runner is not required to be very low, generally 0.8-1.6, take 1.6, as shown in the above figure
(3) Design of gate
Because the surface quality of the molded part is required to be relatively high, and there should be no obvious burnout marks, therefore, a point gate is used, and its dimensions are shown in the right figure:
This is because of the high surface quality requirement of molded part, and there should be no obvious burnout marks, so we use point gate. Its dimension is shown in the right figure:
(4) Calibration of injection stroke
Check the injection stroke of XS-ZY-1000 injection is 280, the length of the pouring system:
, is established.
9. Mold molding parts design calculation
Analysis of the structure of the plastic part can be known according to the dimensional tolerance can be known: plastic parts in the radial direction of the tolerance level of MT7 level (GB4458.5-84), for this plastic this precision is medium. Analysis of the structure of the plastic part can be seen in the moving part of the mold if the overall structure will not be able to process, so the use of a combination of core structure.
? Cylindrical core
It adopts the form of shoulder fixation, and its lower bottom surface is pressed by mold nut.
Dimensional calculation. Check its dimensional tolerance:
Since the dimensional accuracy is medium, the manufacturing deviation is taken as 1/3 of the dimensional tolerance and wear deviation is taken as 1/6 of the dimensional tolerance
respectively, i.e. .
The plastic shrinkage range is 1.5-2.0%, the average shrinkage is:
.
Therefore, the cavity core size is: (design dimensions refer to the parts drawing)
? Dynamic mold core cavity
Dynamic mold core adopts a combination of screws to fix it on the dynamic template, check its size tolerance:
Cavity size:
(design dimensions refer to the parts drawings)
? Fixed mold cavity
Fixed mold core is a combination of screws fixed on the moving template to check the dimensional tolerances: Cavity dimensions:
(design dimensions refer to the parts drawing)
? Slider core
The design of the slider core for the integral structure, the total **** 4, the corresponding side hole size:
10. 9, lateral core extraction mechanism
? Selection of lateral core pulling mechanism
There are 6 square holes in the side wall of the plastic part, all of which are perpendicular to the direction of demolding, preventing the molded part from coming out of the mold after molding. Therefore, the molding must be set up lateral parting core extraction mechanism, after analysis of the mold using oblique guide column core extraction mechanism.
Determine the core pulling distance: the side hole depth of this part is 1mm, then S=h+(2-3)=4mm
Determine the inclination angle of the inclined guide column: because the core pulling distance of this mold is relatively short, so the inclination angle can be taken a little smaller, taken as 12°.
? Determine the size of the inclined guide pillar:
, check the table to get d=18mm
After calculation, check the table to get the standard inclined guide pillar length is 100mm.
11. Determination of mold frame and selection of standard parts.
From the front of the cavity layout and mutual position size, and then according to the size of molding parts combined with the mold standard frame, the choice of structural form for the P4-type, mold frame size of 500 × 560 of the standard mold frame, can meet the requirements.
Calibration of parameters related to cavity parts
? Calibration of the distance between the edge of the type
Calibration of qualified
For the permissible application of the cavity material, the permissible stress of Cr12MoV is 245MPa
P is the average pressure of the cavity
? Cavity bottom plate thickness of the calibration
, calibration qualified
? The closing height of the mold. Calibration
Calculate the closing height of the mold as:
Check XS-ZY-1000 to get, that is, the mold meets
the installation requirements.
? Calibration of the shape of the mold:
The size of the shape of the mold is: check XS-ZY-1000 injection machine template of the maximum installation size for , so it can meet the requirements of the mold installation
? Mold opening stroke checking:
The stroke of the mold for the XS-ZY-1000 maximum mold opening stroke of 700mm>183mm, which can meet the mold opening requirements of the injection molding machine.
12. exhaust system design
This part is a small reverse part, can use the push rod, movable core and the gap between the template exhaust, the gap is .
13. 11, temperature regulation system design
Check the table to get the polyethylene molding mold temperature required for 30-60 ℃, this set the temperature of the mold for 40 ℃.
? Volume flow rate of cooling water
? Cooling water pipe diameter
In order to make the water in a turbulent state, check the table in .
? Cooling water flow rate in the pipe
By the formula
is greater than the minimum flow rate of 1.10m/s, to achieve a turbulent state, so the pipe diameter selection is reasonable.
? Cooling pipe hole wall and cooling water between the heat transfer film coefficient
Check the table to f = 7.22 (water temperature of 30 ℃), so
? Total heat transfer area of the cooling pipe:
? Number of cooling water holes to be opened in the mold:
14. Push-out mechanism (mold release)
? The form of the push-out mechanism to determine:
This plastic part is launched using the top bar, push rod design in the plastic part of the step, each plastic part is launched by 8 push rods, in the step of the round evenly distributed, **** 32. Its structure is shown in the assembly diagram.
? Calculation of demolding force:
Coefficient of demolding force Linear expansion coefficient of plastic
Tensile modulus of elasticity of plastic at the demolding temperature Softening temperature of plastic
Temperature of plastic part at the time of demolding Thickness of plastic part
Height of core demolding direction
? Checking of demolding force
The ejector force of XS-ZY-1000 can meet the requirement of injection molding machine.
15. guide mechanism
The guide column is selected from the specifications of the mold frame itself, but its length is related to the mold opening stroke, it must be designed and selected separately. Calculated from the table to take the standard to get the length of the long guide column for, the length of the guide column for
The relevant coordination is shown in the assembly diagram, and the corresponding guide sleeve selection mold with its own specifications.
16. References
1. Wu Xianming et al. Plastic mold design guide? Beijing: National Defense Industry Press, 2006?5
2. Yu Dongrong, Cheng Shengwen? Plastic molding process and mold design? Beijing: Science Publishing House, 2005
3. Chinese Mechanical Engineering Society, China Mold Design Dictionary Editorial Committee. China mold design dictionary. Nanchang: Jiangxi Science and Technology Publishing House, 1998
17. Mold design experience
Through the mold design, make my professional knowledge more systematic and complete. In the design, I mastered the relevant technical standards and norms, and learned how to learn and make good use of the valuable design experience and information accumulated by the predecessors. I also exercised my ability to consider the structure, technology, economy and standardization, and consolidated the knowledge of the professional courses I learned in the past. I have grasped the basic process of injection mold design, and also exercised my hands-on ability and the rigor of engineering technology. In short, through this mold design to make my professional level to a higher level.
18. mold assembly and parts drawings: (attached engineering drawings) results
The molding process of this plastic part is better
The use of a four-cavity gate casting three-platen structure
The use of XS-ZY-1000 screw injection molding
The manifold adopts a semi-circular, D = 10
mm
The use of a combination of core design and injection molding.
Adopt combined core structure
The specification of oblique guide pillar is
The inclination angle is 12°
The size of the mold frame is 500×560 and the standard mold frame of P4 type is used
The calibration of the cavity parts is qualified
The calibration of the mold closing height is qualified
The calibration of the mold appearance is qualified
The calibration of the mold stroke is qualified
The calibration of the mold opening stroke is qualified
The calibration of the mold opening stroke is qualified
The mold opening stroke is qualified
The diameter of cold water pipe:
The number of holes is 2
Adopting pusher to push out the mechanism
The mold release force is qualified
The mold is qualified.