1、欢迎进入MF世界,MF/FLOW 进阶训练课程,大綱說明,Model 修整 Mesh 必備條件 Meshing Modeling different types of gates 3D Runner balancing; preparation, analysis and interpretation of results Packing analysis,Topics Covered,Use of general attributes; setting, unsetting, checking Valve gates Overall interpretation of results New
2、 displaying techniques for results Analysis options in MFL How flow analysis effects other analysis types, such as cool and warp,Model Cleanup,Start with a good CAD model Suppress small features that are not wanted Blends Small radii fillets Best model is a fully connected solid model STL Patran IGE
3、S,Radius In MPG,Radius from STL model causes problems in MPG modelSuppress feature if possible,Model Cleanup,Start in Midplane Read in model Heal model Healing it several times in a row may continue to fix problem areas Squeeze model,Model Cleanup,Check for Mesh density Mesh size 1.5 times nominal w
4、all is a good place to start Generally the courser the mesh the better Midplane will work Experimenting with different mesh sizes may be useful Free edges Shown as yellow lines High aspect ratios Shown by red markers at the nodes on the element Create midplane,Free Edges,Free edges shown in yellowBe
5、fore translating, no free edges should existEditHeal Model may fix most problem areas,High Aspect Ratio Elements,High Aspect Ratio elements shown by RED markers on the nodes that form a high aspect ratio element.Before translating, EditRemesh Surfaces can be used to reduce the number of High aspect
6、ratio elements,Model Cleanup,Check for midplane errors Proper connectivity Intersections How Save model Read into MFVIEW Change all elements to 1 color ae red p v all Squeeze nodes and element to check for overlapping elements. They will be gray Read model into MPG and fix problem areas Mesh density
7、 Aspect ratios Thickness,Connectivity, Density Thickness,Zero Thickness on model,Thickness variation due to tapered wall and mesh density,Wide variation in mesh density, One row of elements across a major change in thickness,Ribs connected to rest of part,Model Cleanup,MFVIEW Check element thickness
8、 variation Average element thickness variation ag th 2.5 e th 2.4:2.6 Create surfaces MES CES Remesh if necessary,Element Thickness Variation,Zero Thickness wall,Thickness problems,Thickness Modified,The 0.65 mm and the 0.0 mm thickness elements changed to 2.8. This will make it easier to create sur
9、faces,Surfaces Created,QUESTIONS?,Mesh Requirements,Aspect ratio 6:1 Maximum 3:1 Average Checking Set Check AR Displaying,Mesh Requirements,Aspect Ratio Ratio of the longest side to the height perpendicular to that side.Maximum aspect ratio below 6:1, average 3:1,Average triangle aspect ratio = 1.97
10、 Maximum triangle aspect ratio = 27.79 at element 1754,Checking Aspect Ratio,Set command Quick menu Show SettingsQuick Menu Extensions Check model Display Aspect Ratios,Checking Aspect Ratio,Check Model Dialog,Output from check model dialog,Determining element Connectivity. Checking for overlapping
11、surfaces. Checking aspect ratios.Warning: aspect ratio = 5.23 at element 597Warning: aspect ratio = 5.90 at element 1029Warning: aspect ratio = 5.02 at element 1270Warning: aspect ratio = 5.02 at element 1371Warning: aspect ratio = 5.20 at element 1885Warning: aspect ratio = 5.20 at element 1886Warn
12、ing: aspect ratio = 5.40 at element 2011Average triangle aspect ratio = 1.97Maximum triangle aspect ratio = 5.90 at element 1029 Checking for geometric intersections .,Display Aspect Ratios,This result can be scaled from the ResultsContour Plots dialog,Mesh Requirements,At least 3 rows of elements a
13、cross a major change in thickness, to account for hesitation,1 row will not pick up the race track effect,Divisions set to produce 3 rows of elementsThis is easy, but creates a lot of elementsset div 180 s th 4.55,Created 3 surfaces across the thickness, them meshed to an aspect ratio of 6This may t
14、ake time to create the surfaces but will reduce the number of elements required. This is easiest to mesh as you dont need to remember to set a special no. of divisions.,Mesh Requirements,Density fine enough to pick up weld lines and transient effects Weld lines Gas traps Hesitation 3 rows across cha
15、nges in thickness,Weld Line Interpretation,Weld lines will always be formed around holes or when two flow fronts come together. If the mesh is too course, the weld lines may not be shown. The mesh may need to be refined locally around a hole or location of a weld line to accurately define the locati
16、on and severity.,Mesh Density Effects Weld Line,With the mesh refined locally, the weld line output is much better. The mesh has less effect on the result.The mesh was refined by the set div on the individual surfaces,Course Mesh Doesnt effect filling pattern, but does effect weld line description,G
17、as Trap Interpretation,Gas traps may not be predicted if the mesh is not fine enough in the thin region.,Hesitation Prediction / Interpretation,When there are large changes in wall section thickness, there should be at least 3 rows of elements across each thickness region,3.0 mm,1.0 mm,2.0 mm,Meshin
18、g,Set Divisions Global Best to start out with global setting Look for problem areas Refine global setting Use with other techniques Command line, can set to any number, GUI limited to 30 (unix), 50 (PC) set div 25,Meshing,By surface, on the command line SET DIV no_of_div,DEF DEF set a default divisi
19、ons for surfaces not set yet SET DIV no_of_div,S,selection_list set div 100 s all red p v Excellent for meshing beam surfaces Gates Runners Any small area you want to control mesh size,Meshing,Aspect ratio Command line only ma ar 6 ms ar 6 not shell 1:500 Attempts to mesh all surfaces so element asp
20、ect ratio is below the number specified Sometimes fails due to sharp angle on surface Warning given for surfaces with problems,Meshing to an Aspect Ratio,From the command line, the part can be meshed to be below a specified aspect ratio MA AR 5 This will mesh the part maintaining an aspect ratio of
21、5 as a maximum,QUESTIONS?,Modeling Gates,What type of analysis to be done determines the level of detail For filling analysis, shear rate limit/sizing, or gate location, ONE element is OKIf gate freeze time is critical for PACKING then 3 elements across the thinnest section is required.,Gates Types,
22、Edge Gate,Normally modeled as a beam surface(s) Model as shell if width of gate is about same size as nominal distance between nodes on part. Model with 1 or 3 surfaces defining thinnest cross section Others can be used if gate tapers back to runner,Edge Gate,Use second (from left) cross-section, Th
23、e first is Shallow rectangle and is not supported for a flow analysis,Dimension 1 is the THICKNESS (the thinnest dimension of the cross-section) Dimension 2 is the widthRectangular shapes can NOT be tapered,Surface thickness thick_2 H.T.E. shape21 2.06 4.80 1.000 RECTANGLE32 2622 3.78 5.42 1.000 REC
24、TANGLE 33 3220 5.49 6.04 1.000 RECTANGLE31 33,Surfaces 21, 22, & 20 decreased in thickness and width modeling the taper from runner to gate land. Runner dia is 6.35 mm, Gate land is 1.125 mm x 4.5 mm. Each surface is the average thickness and width, for the length it represents.,Tunnel / Submarine G
25、ate,Surface thickness thick_2 H.T.E. shape block1 block2 Millimetres16 6.35 1.12 1.000 CIRCLE 0 027 28,Simple subgate model. One tapered surface, one end being the orifice dimension and the second being the diameter at the runner. The thickness is the side of the first point defining the gate,Tunnel
26、 / Submarine Gate,Surface thickness thick_2 H.T.E. shape Millimetres16 6.35 4.61 1.000 CIRCLE27 2917 4.61 2.87 1.000 CIRCLE29 3018 2.87 1.12 1.000 CIRCLE30 28,Subgate broken into 3 surfaces. This will ensure 3 elements in the gate. Each surface is tapered and is given the diameter at that point in t
27、he gate. The freeze time of the gate will be predicted to be longer than a straight element at the diameter of the orifice.,Tunnel / Submarine Gate,Surface thickness thick_2 H.T.E. shape block1 block2 Millimetres16 6.35 4.61 1.000 CIRCLE 0 027 2917 4.61 2.87 1.000 CIRCLE 0 029 3018 1.12 0.00 1.000 C
28、IRCLE 0 030 3119 1.12 0.00 1.000 CIRCLE 0 031 3220 1.12 0.00 1.000 CIRCLE 0 032 28,Subgate with the last tapered section changed to 3 straight surfaces. The diameter of the straight surfaces is the diameter of the orifice. This may over predict the pressure drop in some gates. This could be modified
29、 by making the length of the straight section shorter. The straight surfaces in this model represents 1/3 of the total gate length. It could be made to be 1/9 of the total length by making only surface 20 straight. To properly predict the freeze off, surface 20 should still have 3 elements, or be br
30、oken down into 3 separate surfaces.,Gate Freeze Times,Gate freeze in surface 20 with a straight section,Gate freeze in surface 18 with a tapered section,Pin Gate,Gate designed for 3 plate molds.Orifice must be very small normally well under 1 mm in diameter, as the part is de-gated by a tensile brak
31、e on the gate. The shear rate will be very high.The drop above is made by one tapered circular surface,Fan Gate,Unbalanced fan gate with a nominal wall of .120” (3.05 mm),Balanced fan gate with wall thickness from .118 (3.0 mm) on the out side to 0.098” (2.49 mm) in the middle and a 0.25” (6.35 mm)
32、runner down the back edgeThe walls were balanced in MFG,Fan Gate Balancing,The strip file was made by reading in the 3D Model into MFG, and using it to create points and surfaces down the middle of each surface in the gate. The cyan surfaces in the part represent the approximate volume of the part.
33、The pressure used to balance was the pressure to fill flow 1.,Fan Gate Land,Part,Gate Land,Gate Body,The gate land is 0.045” (1.14 mm) wide and 0.040” (1.02 mm) thick. The gate body was the part balanced,The gate land was meshed with a divisions of 80 for this part, and the gate body was meshed to a
34、 divisions of 40. The whole part was meshed to an aspect ratio of 6.,Flash Gate,The flash gate is NOT a good design. This is the “land” of the fan gate with the cold runner down the back side. With some adjustment the flow front could be made flatter, but this type of gate is prone to hesitation and
35、 can significantly limit the molding window. This type of gate is NOT recommended. If it must be used, make sure there are 3 rows of elements across the flash land, and the aspect ratios are below 6:1,Hot Drop Tips,The tips geometry for a hot drop needs to closely follow the geometry of the drop. Ma
36、ny different tip styles are available. Consult with the hot drop supplier. The orifice itself should be a cold round flow with 3 surfaces. The use of the general attribute TOPTEMP can be used to set a mold temperature higher so it will be close to the melt temperature as it would be in the drop.,Gat
37、e Sizing,Gates should be sized using shear rate as a guide Shear rate guidelines in MATSEL are based on the fast algorithm Multi Laminate results may have higher values and must be evaluated,Gate Sizing,Keep the gate shear rate below the material limit If the gate geometry allows, reduce the shear r
38、ate further, to about 20,000 1/sec. Large gates this is easy; edge, fan, flash Difficult for sub gates and hot drops Impossible for pin gates,Gate Shear Rates,Shear rate profile of an element in the gate at 90% full,Shear rate plot from a multi-laminate analysis showing the maximum shear rate in any
39、 laminate at any time during the fill time,Shear rate plot from a fast analysis showing a cross-section averaged shear rate at any time during the fill time. This result is what the guidelines are based on.,QUESTIONS?,3D Runner Balancing,Preparation Occurrence numbers Reduces the number of elements
40、and/or increases mesh density Lowers number of iterations to solve Cant use if going on to cooling or warpage,Model with occurrence numbers,Full model,Assigning Occurrence numbers,Assign occurrence 4 to all surfaces ag oc 4 s all Assign occurrence 2 to main runners, pick with a mouse Assign occurren
41、ce 1 to sprue, pick with mouse,Red surfaces are the model. The gray is being represented by occurrence numbers,3D Runner Balancing,Preparation Regions Define components of the model for a runner balance Moldcavity (the plastic part, not to be confused with modeltype cavity) Gate Runner Sprue The bal
42、ance will size BEAMS not assigned and runners,Assigning Regions,Assign moldcavity to all surfaces (vast majority of surfaces in the model form the plastic parts) ag moldc s all Assign runner by shape circle If beams are used in the part, use circle and color or region ag run s circle,Assigning Regio
43、ns,Assign gate by shape and/or thickness If the gate is a rectangular beam assign by shape (normally only gates use a rectangle shape) If the gate is circle, assign by thickness and if necessary circle (many times the gates have a unique thickness in the model, or for circles) If the gates have a un
44、ique color, this can be used ag gate s rect ag gate s circle th .060,Assigning Regions,Assign sprue with the mouse Normally the sprue is only one to three surfaces It is easiest to assign by the mouse ag sprue s,Checking Assignments,Region assignments can be checked, or the selection list used to as
45、sign regions can be checked with the DS command dc;ds circle (make sure surfaces for your part are not displayed.) dc;ds run dc;ds circle th .060 (this should display only gates. If it does, it can be used to assign region gate to the gates.) dc;ds th .060:.090 (this could be used to assign all surf
46、aces within this range to region gate),3D Runner Balancing,Preparation Balance pressure Balance pressure determines the size of runner Run a regular flow analysis first Look at the pressure to fill and time series trace of the injection node. The fill pressure gives a place to start. If the time ser
47、ies trace shows a big pressure spike, the balance pressure may need to be lower A higher balance pressure will reduce volume, but may make the runners too small,3D Runner Balancing Analysis,Numerical parameters Balance iteration limit The number of flow analyses run Balance time tolerance Difference
48、 in time between the time the first to last cavity fills Balance pressure tolerance Difference between target pressure and solution pressure Max section imbalance Difference between the set tolerance and solution pressure drop,Setting Numerical Parameters,Reducing the Max Section Imbalance will norm
49、ally result in a pressure distribution that is balanced. The net result is the runners in the flow closest to the sprue normally get smaller.,3D Runner Balancing Analysis,Reviewing results Pressure balance Is the pressure even between the cavities? If not, is it OK anyway? Time balance Is the time t
50、o fill the cavities close enough. Is 5% OK, or should it be tighter? Runner sizes Are the runner sizes good, Too small or big? Can they be averaged or rounded to close standard sizes? Cooling times Do the cooling times suggest packing problems Is the minimum cooling time in a runner 80% or more of the cooling time of the part?,
