Introduction
Automotive manufacturers are one of the world’s largest consumers of plastic, using the material in everything from exterior body panels to interior parts and internal mechanics. The industry’s demand for plastics is also expanding rapidly. According to Global Market Insights, the worldwide automotive plastics market is projected to grow from its $18 billion mark in 2020 to $35 billion in 2027, with a healthy average annual growth rate of 11%.[1]
Auto manufacturers seeking to improve their profit margin and market share in a turbulent economy are continually on the lookout for ways to reduce costs while enhancing product quality. Essential techniques in conventional molding, such as sequential valve gating (SVG) are critical to molding many larger automotive parts, like door panels and bumpers/fascias, but they can be costly and suffer from significant quality issues, leaving room for optimization.
This article is the fourth in a series investigating how iMFLUX’s low-constant-pressure injection molding technology can help create new solutions and opportunities across the transport and automotive industries. Below, we’ll discuss how low-constant-pressure injection molding for automotive parts can help manufacturers through sequential valve gate reduction.
What Is Sequential Valve Gating?
In plastic injection molding, a “gate” is a small opening in the mold cavity through which the molten plastic is injected into the mold cavity. Inside this cavity, the plastic cools and solidifies, forming the final product.
As a standard injection molding technique, SVG uses a series of gates that open and close at specific intervals, providing a high degree of control. Valve gates have a pin or valve that determines the timing at which the plastic can enter the mold. Manufacturers must carefully configure the shape, position, and structure of the gates so that they can produce the highest-quality results, and program each one to account for the different pressure and temperature levels in the plastic that reaches that gate.[2]
This process does have its drawbacks. SVG can lead to defects such as weld lines (or “knit lines”), which appear when the molten plastic from separate flow fronts join. Another common quality issue is “tiger striping,” which often occurs on larger automotive parts such as dashboards, panels, and bumpers. This flaw presents as large streaks or wavy lines on the plastic’s surface, like a tiger’s stripes.
SVG can also result in greater complexity and cost when making plastic injection-molded parts and products. For one, the molds are significantly more expensive. And the more gates there are, the more difficult the process is to control — and the more expensive it is in terms of capital, implementation, and operator oversight. Any innovation that can effectively decrease the number of gates in the plastics molding process while maintaining or improving product quality would be a welcome advantage to automobile manufacturers.
Reducing Sequential Valve Gating with Low-Constant-Pressure Injection Molding
Due to variation in the amount of control the conventional injection molding process can manage for long flow lengths, it can be challenging to fill molds evenly with conventional techniques. Conventional molding processes typically experience significant pressure drops and spikes relative to the gates sequencing, which directly impacts the parting line life of your mold, resulting in frequent repairs.
iMFLUX has introduced a new approach: low-constant-pressure injection molding, which responds to the unique flow characteristics of each shot and/or gate sequence. The iMFLUX Process senses the changes in pressure either caused by part geometry or in the case of larger automotive components, sequentially valve-gated molds. iMFLUX offers the unique ability to self-profile the screw movement to compensate for the changes in pressure, seen in these unique tools, creating harmony between your machine injection phase and valve-gate sequencing that has not existed until now. This monitoring of flow pressure at sequential gates ensures that each cavity is accurately filled and packed as the flow moves through channels.
By using fewer gates, manufacturers help address the all-too-common challenges of conventional molding, such as seams and other defects. Although this approach has a range of automotive industry applications, it is especially beneficial for the most prominent parts, such as dashboards and car doors.
Users of iMFLUX technology can achieve lower costs through sequential valve gate reduction in several ways:
- Fewer moving parts means less steel and less complexity in the physical building of a mold, resulting in less capital — for example, manufacturers may be able to create a mold with eight gates instead of 18 gates.
- The ability of the iMFLUX process to pack while it fills simplifies scenarios where a gate may need to sequence both in filling and during pack/hold. iMFLUX eliminates this need to “re-sequence” the gate because the plastic is already pressurized during filling.
- Less manual effort required on the part of molders, thanks to automated process control based on a sensor reading pressure changes every millisecond. This results in lower operating costs. Changes to valve gate sequencing can also be done in a safe manner. The iMFLUX controller will not allow the injection pressure to exceed the controlled value, meaning changes to gate sequencing wouldn’t result in an over-pressurized mold and flashed part.
- Cycles up to 10 to 15 percent faster, allowing manufacturers to achieve more output in the same amount of time, for faster fixed cost recovery.[3]
Conclusion
Sequential valve gating is an integral part of the automotive plastics manufacturing process. However, by using iMFLUX technology to reduce SVG, automobile manufacturers can cut capital, operating costs and produce better products, dramatically improving the automotive plastics manufacturing ROI.
Do you want to learn more about the advantages of low-constant-pressure injection technology for your business? Get in touch with our team today for a chat about your needs and objectives. You can also follow our blog for all the latest news and updates about this revolutionary technology.
Keep an eye out for our next article in this series, exploring how to simplify the automotive supply chain with PCR-optimizing injection molding processes.
External Resources
[3] Low-Pressure Injection Molding Technology Boasts Faster Cycles, Better Parts