State-of-the-art low-pressure plastic structural foam multi-nozzle molding machines allow us to mold very large plastic parts or run multiple molds on a single machine at the same time. This capability is driven by low-pressure injection molding multi-nozzle technology.
What Is Multi-Nozzle Structural Foam Molding?
Multi-nozzle molding, also called sequential injection molding, is used for more complex designs and parts that can’t be filled from a single nozzle. The large press platens contain hundreds of inlet holes where multiple injection nozzles can be precisely located so the plastic will fill the hard-to-reach extremes of the tool. Multi-nozzle plastic injection offers a key advantage when producing very large or complex parts. The technique is used because it can greatly improve the cosmetic finish of a part.
Multi-nozzles eliminates the need for a hot runner system which saves on costs. Multiple tools with multiple cavities can be run at the same time using multi-nozzles and the large platen presses. This can be done on the same machine that would be used to mold a single large plastic part. Multiple materials or colors can be molded simultaneously.
Much like traditional high-pressure injection molding, structural foam multi-nozzle injection molding machines use a reciprocating screw and barrel to inject heated plastic into a tool. This however is where the similarities end. The most obvious difference is the size of the machines themselves. Structural foam multi-nozzle machines are large, so are the parts, and the design opportunities they provide to mechanical engineers. Unlike injection molding, plastic structural foam molding uses low pressure, gas-assist, and other unique methods to mold components or full assemblies up to 400 lbs. in one machine cycle.
With multi-nozzle molding the optimum number of injection nozzles can be located throughout the platen surface. Each is independently controlled producing the perfect fill and better finished product.
Shot size, sequence, open & close time, gas-assist and more is digitally controlled at each individual nozzle. This saves material and time and produces a higher quality product.
What are the benefits of low-pressure plastic structural foam multi-nozzle injection molding?
Inherently you will get the same benefits from structural foam molding but the greatest advantages of multi-nozzle molding include the ability to make larger parts on smaller injection molding machines & being able to mold multiple parts from the same or separate aluminum molds at once.
Take for example, making a large truck bed liner. In a traditional high-pressure injection molding process, this part would require an extremely large tonnage injection mold machine, steel mold, & hot-runner system. Both the capital investment & machine rate in this process would be greater than the smaller structural foam machine, aluminum mold, & multi-nozzle rods & barrels needed.
An alternative use for structural foam multi-nozzle molding is making entire assemblies from multiple molds & cavities. Using a large deck box as an example, multi-nozzle molding allows for a separate mold to be built for each part, then put onto one machine. In turn, one part from each mold is made during the machine cycle so that every two and a half minutes, all six parts are molded. Since the parts can then be kitted into their box for distribution & shipping as soon as they are done being molded, this is much more effective than molding each part on a separate machine & kitting in a different manufacturing cell.
Another benefit includes the ability to mitigate risk & ramp up if demand requires. Since demand for some products is difficult to gauge when first releasing to a market, a single cavity structural foam multi-nozzle mold can be built. A second multi-nozzle mold can be built can also be built if demand increases above what a single cavity mold can support. Often, both molds can run in the same machine which can decrease a per part cost.
Multi-Nozzles Mean Multi-Options
Instead of a single nozzle, multi-nozzle structural foam presses have multiple injection locations. Using sequential injection molding, we have complete control over shot size, sequence, open & close time, gas-assist, and more through each individual nozzle.
One tool and cavity
A single large-sized part may be molded using four or the optimum number of injection nozzles. Each nozzle is individually controlled.
Multiple tools and cavities
The same press used to produce a single large part can also be run with numerous tools and cavities using many nozzles.
Structural foam molding and multi-nozzle produce a perfect fill for large parts or multi-part runs. Molds can be switch out or changed for future productions to give ever more flexibility.
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Multi-Nozzles Give Complete Control
Instead of a single nozzle, a structural foam molding press has multiple injection locations, eliminating the requirement for a hot runner manifold system
Shot size, sequence, open & close time, gas-assist, and more are digitally controlled at each individual nozzle via sequential injection molding technology. This saves material and time and produces a higher quality product.
The nozzle inlet holes are spaced 6 inches apart. This allows precise positioning of every nozzle that is being used.
When to build a multi-cavity tool instead of multiple tools for a multi-component assembly.
Assume your program is an outdoor garden bin. Your product has 2 sides, a front, back, base & lid for a total of 6 parts. Once molded, the cabinet will be placed in a single package for shipping for the end-user to assemble.
This program could use 5 separate tools: 1 tool for the sides, 1 tool for the front, 1 for the back, 1 tool for the base, and another for the lid. Each tool would need to be running on a separate machine and would require a separate cell for final assembly and/or packaging. Since each piece will be running on a different machine, the color could have some variation between the 6 separate pieces.
This tooling strategy could be used in a multi-nozzle process; however, a larger machine would be needed to make up for the size in multiple tools. Unless the tool for the sides was a 2 cavity mold, it would also require more tool cycles to make a complete unit since the production ratio would be off. The material color would be uniform and the product could be packaged after molding.
Using the multi-nozzle process, you can fit each one of these parts in a single tool with 6 cavities. Or 6 separate tools all running at the same time in the same machine with the same mold cycle. The material color would also be uniform across all parts.