Will your molding machine have enough pressure to inject the plastic into the mold?
When the amount of filling pressure it takes to fill a mold exceeds the capacity of the molding machine, it results in a situation commonly referred to as “pressure limitation.” First, let’s look at the machine itself. The maximum pressure capability of a molding machine can be calculated by multiplying the machine’s maximum hydraulic pressure by the intensification ratio. The intensification ratio (Ir) is the surface area of the hydraulic injection cylinder divided by the surface area of the screw. This ratio is typically from 8.5 to 18.0, depending on the machine manufacturer. So if the maximum hydraulic pressure is 2150 and the Ir is 15.7, the maximum plastic pressure is 33,755 ppsi. If the injection filling pressure reaches this max pressure, the molding machine then becomes too sensitive to viscosity changes in the melted plastic. As discussed in the last post, also leads to short shots.
The Solution – SOLIDWORKS Plastics Filling Simulation.
By using simulation you can accurately predict what the injection pressure will be during the filling phase, then compare that to the targeted molding machine. If the filling pressure comes within 80% of the max pressure of the machine, then a decision must be made either to modify the mold, modify the machine, or select another machine to run the mold in. At the very core, this is information you would want to know BEFORE you put the mold in the machine only then to find out that the mold and machine combination will not work.
How The Solution Helps
This issue is typical for injection molders… putting a mold into a machine and hoping for the best. SOLIDWORKS Plastics can be used to save time and money by preventing this issue from occurring in the first place. By predicting during the part or mold design phase, changes can be made up front to alleviate these issues that are preventable. Changing the part design or mold design up front saves the headaches of finding out after the fact. Timelines are not getting longer with customers less tolerant of delays. Using simulation can prevent the delays and give you more confidence going into the launch phase of the mold.
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