The cycle time of any mold is largely influenced by the cooling cycle—how fast the resin can be sufficiently cooled so that the part can be ejected without permanent deformation. In any given mold, the areas that take longest to cool are those with the thickest wall section. […]
The importance of runner analysis on design and molding seems to have been long overlooked. When many flow analyses are carried out, the focus tends to be mainly on the part and cavity. […]
Once the mold is packed, you have to be sure that you have good cooling. Cooling is about 80 percent of the cycle, making challenging the mold cooling system very important. Checking each cooling channel to ensure that proper flow is achieved, in addition to developing a mold surface map of temperatures is key. [...]
It also is important during the time you are packing the mold, to observe whether or not the gate is sealed. This is an area that causes a lot of trouble with new tools. They are absolutely sure—based on the long hold time they have used in the process—that the gates are sealed, [...]
After filling you must pressurize the mold to get a good imprint of the cavity to minimize the effects of cooling. Short shots, sinks, voids and dimensional variations in parts are caused because of insufficient packing pressure in the mold cavities. […]
As part of a rigorous mold tryout, it is essential to instrument a mold to see what is going on inside the mold. […]
With the proper temperatures set, the mold must be filled as fast as consistently possible. This means that the mold should be able to be filled to at least 90 percent of the injection rate of the production molding machine without adverse effects. […]
It starts out with the temperatures of the plastic. The temperature of the plastic coming out of the molding machine should be right down the middle of the manufacturer’s spec. If you can run a mold here, […]
How do you get a ready-to-go mold? Obviously, it starts with good design with no broken rules. It must be cut properly. It must be assembled properly. Checks must be made to ensure that all items function as designed, clearances are proper and water lines are correct based on flow. […]
The unitized system offers considerable improvements in quality and addresses the cost of repair favorably. Since the integrated system is based upon using the unitized prewired design for installation in the mold, the chance for pinched or severed heater and thermocouple wires is eliminated during assembly. […]