HL&S Consulting

Jay’s Simulation Tip of the Week – Review the Clamp Force, XY Result Comparing a Conventional and iMFLUX Analysis The Clamp Force, XY Result is an intermediate result that shows the clamp force at multiple times during the cycle. The clamp force is calculated by the projected area of each element to the XY plane and the pressure in each element. This result shows how the clamp force builds to its maximum value and then decays. It is critical that the part is modeled in tool position where the XY plane represents the parting line and the Z-direction represents the direction the mold opens for the clamp force to be correct. The first set of plots below shows two studies with the default scale for the axes. At first glance, you could assume that the study on the right has a higher clamp force, until you look at the Y-axis scale. Then you can see that the right study has a lower clamp force. Look at the second set of plots below. Here, the axis scales are the same. Now it is easy to see that the right study has a lower clamp force. The question now is why does the right study have a lower clamp force? The bottom graph is an XY graph that overlays the Pressure at the injection location XY plots (solid lines) and the Clamp Force XY plots (dashed lines) for both studies. The blue lines represent a conventional process. In this process, the pressure spikes during the filling phase to about 110 MPa. The packing pressure for the conventional analysis is 70 MPa. The maximum clamp force is just after V/P switchover, where the pressure is high, and the projected area is most or all the part. The green line represents an iMFLUX process. The Setpoint Pressure for iMFLUX is 75 MPa, which is higher than the conventional pack pressure. The clamp force is still much lower than the conventional because the iMFLUX pressure at maximum is 75 MPa while it is 110 MPa for the conventional. The clamp force spikes in the conventional analysis because of the timing of the V/P switchover. If the conventional process could switch over earlier than it does now, the clamp force could be reduced. Plotting pressure and clamp force on the same graph is the easiest way to see the relationship between pressure and clamp force. This graph was generated using an API script embedded in Excel. For more information, contact me, [email protected] #moldflow #imflux #simulation #autodesk #CAE?

Jay’s Simulation Tip of the Week – Review the Pressure, XY Result Comparing a Conventional and iMFLUX Analysis The Pressure result is an intermediate result that shows pressure distributions at multiple time steps during the cycle. The Pressure at V/P switchover is a pressure plot that shows the pressure distribution at an important time, when the process switches from velocity control to pressure control. This Pressure at V/P switchover result is typically viewed much more than the intermediate results-based Pressure plot. However, for iMFLUX, the V/P switchover is meaningless as it occurs very early. Look at the first set (1) of plots below. This shows the V/P pressure for a conventional and iMFLUX analysis. Notice how the iMFLUX result only has results in the top of the sprue. The pressure distribution when the part is 95% to 98% filled is still important, so the Pressure result must be set up to view the pressure at the desired time. The second set of plots (2) shows the Pressure plot for both the conventional and iMFLUX analyses. To produce these results several things were done. 1.?????The number of intermediate results was increased to ensure a small time step between results before the analysis was run. 2.?????The V/P pressure was plotted to determine the pressure and flow front position for the conventional analysis. 3.?????The pressure plot is displayed for the conventional analysis and the scale is set to per frame. 4.?????The pressure plot is animated one step at a time. With the scale set to per frame, the maximum pressure will change with every time step. The animation is stopped until the pressure is the same at the V/P pressure. The position of the flow front will also be the same as the V/P pressure. 5.?????The iMFLUX pressure plot is displayed with the scale set to per frame and is animated until the flow front is the same at the conventional plot. 6.?????The scale for both the conventional and iMFLUX plots are set to the same range so the colors on both plots represent the same value. The pressure on the iMFLUX part is about 30% lower than the conventional part. This setup of the Pressure result takes a little more work to plot but is the best way to compare the pressures between conventional and iMFLUX processes. The pressure distribution was compared at the V/P switchover time for the conventional analysis but the same thing can be done at any time or flow front position of interest. For more information, contact me, [email protected] #moldflow #imflux #simulation #autodesk #CAE?

Jay’s Simulation Tip of the Week – Review the Pressure at Injection Location, XY Result Comparing a Conventional and iMFLUX Analysis Pressure at injection location:XY plot is an important plot to review. For the conventional process, the filling phase is controlled by velocity, so the pressure is an output. The pressure builds through the filling phase and typically spikes before the V/P switchover. After switchover, the pressure is an input from the packing profile and typically lowers to the packing pressure from switchover. iMFLUX is a pressure-controlled process, so the pressure at injection location shows the input pressure profile. A conventional analysis is often used to determine the iMFLUX pressure profile. The first pair of plots below has the Default Scale. The conventional process on the left and iMFLUX process on the right. Without careful inspection, you would think that the iMFLUX pressure is higher than the conventional packing pressure. Upon closer inspection, you can see that the Y-axis scales are not the same. The second pair of plots scales the X and Y-axes to the same range. Here, it is easier to see that the iMFLUX pressure is lower than the conventional packing pressure. You may also notice that the time it takes for the iMFLUX pressure to get to the setpoint pressure is faster than the conventional pressure takes to get to that same pressure. This requires careful inspection. Changing the X-axis scale to a smaller value, say 2s, would make the time to Setpoint Pressure, easier to interpret. The third plot shows the results being plotted on the same graph. The XY results were exported and plotted in Excel. Now it is easier to see how the iMFLUX reaches its Setpoint Pressure of 74 MPa before the conventional analysis reaches 74 MPa. To set up the iMFLUX pressure profile, the Setpoint Pressure and the time to Setpoint Pressure are needed. Typically, the initial Setpoint Pressure is about 60% of the peak pressure from the conventional analysis. The iMFLUX analysis shown here was not the first iteration. This pressure is 74 MPa or about 65% of the peak conventional pressure. To find the time to Setpoint Pressure, examine the conventional Pressure XY graph at the desired Setpoint Pressure, in this case 74 MPa. The time is 0.95s. The iMFLUX time to Setpoint Pressure is typically shorter than the conventional process to reach the Setpoint Pressure. In this case, the time to Setpoint Pressure is 0.60 s, well under the time the conventional analysis gets to 74 MPa. The Excel plot was quickly created using an API script built into an Excel file. If you would like a copy of the Excel file contact me at the e-mail address below. For more information, contact me, [email protected] #moldflow #imflux #simulation #autodesk #CAE?

Jay’s Simulation Tip of the Week – Review the Flow Rate on Beams, XY Result Comparing a Conventional and iMFLUX Analysis The flow rate, Beams:XY result is not a default plot, but it is very useful to create and use. Normally when simulating iMFLUX, a runner system is included as part of the model. By using the first beam element, (at the injection location) the graph has a similar shape as the screw speed that is plotted on the iMFLUX controller and most molding machine controllers. The units will be cm3/s, or in3/s rather than mm/s or in/s. The shape of the XY plot comparing a conventional analysis vs an iMFLUX analysis shows nicely the differences between the two processes. The shape of the flow rate graph is also an indicator of the quality of the iMFLUX process as well. Look at the series of plots below. The first pair of plots with the Default Scale shows the conventional process on the left and iMFLUX process on the right. You can see that the conventional process has a mostly uniform flow rate during the filling phase while the iMFLUX process does not. The second pair of plots scales the X and Y-axis to the same range, making the two studies easier to compare. With the Y-axis at the same range, you can see that the iMFLUX process has a higher maximum flow rate and decays slowly towards a low post filling (packing) flow rate. This slow decay is what results in many of the benefits of the iMFLUX process. Conversely, the conventional process suddenly drops in flow rate. Rapid reductions in flow rate resulting from going into the packing phase quickly often contribute to visual defects in the part. The X-axis was scaled to concentrate on the filling phase to easily see the changes during this part of the cycle. The disadvantage of these plots is that it is difficult to see when changes are happening relative to each other. The third plot shows the results being plotted on the same graph. The XY results were exported and plotted in Excel. Now it is easier to see when the iMFLUX flow rate spikes relative to the conventional analysis and how long the flow rate decay is. Finally, the last plot shows both Pressure and Flow Rate on the same graph. Here you can confirm the rapid drop in flow rate for the conventional process and how the maximum flow rate for the iMFLUX analysis occurs after the Setpoint Pressure is reached. The flow rate changes in the iMFLUX process are a result of the pressure profile and the part geometry as the polymer is filling the part. The two excel plots were quickly created using an API script built into an Excel file. If you would like a copy of the Excel file contact me at the e-mail address below. For more information, contact me, [email protected] #moldflow #imflux #simulation #autodesk #CAE?

Jay’s Simulation Tip of the Week – Review the Fill Time Result Comparing a Conventional and iMFLUX Analysis The fill time result is often the first graphical result we review when looking at an analysis result. There are a couple of things that are different with an iMFLUX process compared to a conventional process. The first is the time required to fill the part. In most cases, the time required to fill a part with iMFLUX is longer than the fill time for a conventional analysis. A good rule of thumb is 1.5 to 2.5 times longer. There are good iMFLUX processes that are faster and slower than the rule of thumb range, but many will be within that range. The farther outside this range, the more the results should be investigated to determine if it is an acceptable process or not. The second characteristic of an iMFLUX fill time result is that the velocity of the flow front is not as uniform as a conventional process. Most conventional processes have a constant volumetric flow rate, so we are used to seeing the progression of the flow front to be dictated mostly by the size of the flow front. If the flow front is not getting longer, the flow front velocity is uniform, and the color gradient of the fill time result is uniform. iMFLUX does not have a constant volumetric flow rate, so the filling progression is more varied. In the figure below, look at the shaded images of the fill time result. These plots are with the default plot settings. You can see that the conventional part fills in about 1.6 seconds and the distribution of the colors from blue to red is what we would expect. Note the cold runners are not displayed. With the iMFLUX result, the fill time is about 2.7 seconds. You see more blue and green and less red, indicating most of the part volume is filled in less than half the total fill time. The second fill time result in the figure below, uses contour lines with the results scaled to the same range. Using contour lines, you can better see the velocity differences between the two studies. Location 1 on the conventional and iMFLUX parts mark the same time of 0.75 seconds of fill. The iMFLUX part’s flow front is farther in the part and the contour lines are more widely spaced indicating a faster flow front. However, the conventional analysis fills first because the volumetric flow rate is uniform. For the iMFLUX process, the flow rate drops significantly, as shown by the very narrow spacing of the contours at the end of fill (point 2). As shown in this example, I rarely look at a single study in isolation. I normally look at two or more studies at the same time, including multiple results, to decide which study I like best. More about other results in later posts. For more information, contact me, [email protected] #moldflow #imflux #simulation #autodesk #CAE?

Jay’s Simulation Tip of the Week – Review the Packing Log of an iMFLUX Analysis ? When simulating an iMFLUX process, the Packing analysis log is the second thing you should look at after the Filling analysis log, even when the analysis is still running. Look to ensure that the inputs are correct and for results that suggest another analysis is required with different inputs. The figure below shows the Filling and Packing phase tables of a log file for two studies. The difference between the studies is the PFA Pressure. The study on the left has a PFA of 0 (42 MPa) and the one on the right has a PFA of -0.5 (35 MPa). Look at these two studies. First, look at the end of the filling phase. For the study on the left with a PFA of 0 (point 1), the pressure does not change and the highest clamp force during filling is at the last time step of the filling phase. For the study on the right with a PFA of -0.5 (point 2), the pressure and clamp force are starting to drop. Next, find the highest clamp force for the study with a PFA of 0, (point 3). This clamp force is about 77 tonnes, or about 44% higher than the clamp force at fill. The study with a PFA of -0.5 has a maximum clamp force of about 55 tonnes (point 4), about 5% higher than the clamp force at fill. Also notice that the targeted PFA pressure of 35 MPa is reached 0.25 seconds after the pressure started reducing. Now, look at the time pressure is released, (points 5 and 6). Ensure this is the time you expected based on the packing profile you entered. If there is a high clamp force at this time, the end of packing may be too short. If the clamp force is equal to zero well before this time, the packing time may be too long. Additional investigation is warranted with the Time to reach ejection temperature result. Finally, review the last time step, (points 7 and 8). The difference between this time and when the pressure is released is the cooling time. Ensure this time is long enough to plasticate the material for the next shot. You may not be able to know plastication time early in the design cycle, but a reasonable time should be used to help estimate a reasonable cycle time. It is possible that the packing time is longer than necessary and cooling shorter than it should be. Consider shortening the packing time and increasing the cooling time to make the values more reasonable on a subsequent analysis. By carefully reviewing the log files, you can learn a great deal about the iMFLUX process and what should be changed in a subsequent analysis. The packing log may help you identify results to review in more detail depending on project objectives such as cycle time reduction or clamp force reduction. For more information, contact me, [email protected] #moldflow #imflux #simulation #autodesk #CAE?

Jay’s Simulation Tip of the Week – Review the Filling Log of an iMFLUX Analysis When simulating an iMFLUX process, the Filling analysis log is the first thing you should look at. Look to ensure that the inputs are correct and for results that suggest another analysis is required with different inputs. The figure below shows the Filling table of a log file for two studies. The difference between the studies is the Setpoint Pressure. The study on the left has a Setpoint Pressure of 40 MPa and the one on the right is 42 MPa. Look at these two studies. First, look at the time at Switchover (points 1 and 2). The time is 0.011 sec. The switchover set in the Process Settings was 0.01 sec. We want to confirm our input is correct. Typically, the actual switchover will be slightly longer than the value set in the process settings. This will have an influence you will see later. Next, find the time when the pressure reaches the Setpoint Pressure (points 3 and 4). The time is roughly 0.5 sec. The first time step that is exactly the Setpoint Pressure is at 0.625 sec. because the V/P time is not exactly 0.01 seconds. The pressure at 0.5 sec. is just below the Setpoint Pressure. We look at this mostly to confirm our input is correct. Now, look at the flow rate at 0.5 sec., (points 5 and 6). This is the maximum flow rate during the cycle. Consider if this flow rate is too high relative to the machine’s flow rate capacity. Typically, the maximum flow rate required by iMFLUX is higher than a conventional analysis and you need to determine if the required flow rate is too high. If the flow rate is too high, then the time to Setpoint Pressure must be increased. Finally, at the time when the part fills, (points 7 and 8). For the study with a Setpoint Pressure of 40 MPa, the part short shots at about 98% filled, indicating that the Setpoint Pressure is too low. By increasing the Setpoint Pressure to 42 MPa, the part fills at about 4 seconds rather than shorting at about 8 sec. Another observation is that the time to the Setpoint Pressure is 0.5 sec., relative to the fill time of the second study of about 4 sec. The typical time to Setpoint Pressure is 20% to 50% of the time to fill. The second study’s time to Setpoint Pressure is about 13% of the fill time, indicating the time to Setpoint Pressure is too fast. The next analysis should have a longer time to Setpoint Pressure. By increasing the time to Setpoint Pressure, the maximum flow rate will go down. However, the Setpoint Pressure may need to increase to prevent a short shot. By carefully reviewing the log files, you can learn a great deal about the iMFLUX process and how good it is or what should be changed on a subsequent analysis. In the case of this example, there is no need to review results further before starting another analysis, saving you valuable time. For more information, contact me, [email protected] #moldflow #imflux #simulation #autodesk #CAE?

Jay’s Simulation Tip of the Week – Determine iMFLUX’s PFA Value ? With iMFLUX technology, PFA is the pressure used in post filling. With conventional molding it is called packing. With the iMFLUX controller, PFA is a factor ranging from -3 to 5. With simulation, pressure values are used. In this weeks’ tip, we will discuss how to determine what the PFA should be. The PFA value used is often dictated by part requirements or project objectives. These can include: -???????Clamp force reduction requirements -???????Part weight reduction objectives -???????Dimensional tolerances -???????Visual aesthetics The Pressure and Clamp Force graph in the figure below, shows five studies with PFA’s of 1.0 (56 MPa), 0.5 (49 MPa), 0.0 (42 MPa), -0.5 (35 MPa) and -1.0 (28 MPa). The study i113, has a PFA of 0.0 so the pressure remains constant throughout the cycle and is the nominal process. The maximum clamp force is with a PFA of 1.0 is about 125 tonnes, or about 61% higher than the nominal process. Study i115 has a PFA of -1 and has a clamp force of about 52 tonnes, or 32% below the nominal process. When trying to reduce clamp forces, PFA’s are typically lowered. The Pressure and Part Weight graph below shows the same five studies. The part weight increases from the nominal value by 1.37% with a PFA of 1 and decreases by 2.42% with the PFA of -1. Today with company’s sustainability goals, saving part weight helps achieve these goals while saving money. Clamp force and weight reductions may be primary goals when simulating a process or molding the parts but are not likely going to define the final process used. Achieving critical dimensions must be achieved with a process. The Length vs PFA Factor graph below shows how the length dimension changed with different PFA values. The nominal dimension is 394.0 mm with a tolerance of +/- 0.8mm or ~0.2% of the nominal dimension.?All five of the processes produce parts within the specified tolerance, indicating that the lower PFA processes that also save clamp force and part weight, will achieve the tolerance desired. Visual aesthetics such as sink marks, and blush may be the final criterion that define the final process. Simulation cannot quantify these effects but iMFLUX has a wide processing window that will produce an acceptable process while meeting critical objectives. For more information, contact me, [email protected] #moldflow #imflux #simulation #autodesk #CAE?