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How to avoid the deviation load of a large injection molding machine?

2025/06/13 By Topstar

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Deviation loads are often encountered when operating large injection molding machines, where unexpected lateral forces cause the injection cylinder to deviate from its center. These loads can originate from uneven melt pressure in the injection molding machine, inconsistent clamping force, or slight wear of the guide components. When the molten plastic rushes into one side of the mold at slightly higher pressure, an unbalanced force is generated, trying to twist the injection unit. As a result, this lateral force or deviation load stresses the screw, causing uneven wear of the linear guides and reducing accuracy. In addition, the magnitude of these lateral forces gradually increases with increasing tonnage, so we avoid deviation loads to improve production consistency.

Key factors affecting deviation loads in large injection molding machine performance

Several factors influence deviation loads on large injection molding machines. First, melt viscosity is one reason. Suppose there are slight changes in the viscosity of the same batch of resin. In that case, it will also cause uneven flow into the mold cavity, thereby generating lateral forces on the injection cylinder. Second, fluctuations in barrel temperature or heating coil performance can exacerbate these viscosity differences, leading to higher deviation loads during startup or prolonged operation. In addition, mold design may also cause uneven flow channels.

In addition, mechanical wear from production with long cycle times can also exacerbate deviations. Guide bearing wear, seal degradation, and reduced cylinder parallelism can all lead to unbalanced loads. Therefore, engineers can review component wear through inspection, testing, and analysis. In addition, machine setup errors, such as slight misalignment of the injection unit with the clamping plate or incorrect sensor calibration, can also lead to repeatable deviation loads.

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Using a two-way synchronous injection cylinder structure on large injection molding machines

To alleviate deviation loads, we utilize a two-way synchronous injection cylinder structure in large injection molding machines. Unlike traditional single-rod cylinders, the two-way design supports the front and back of the piston rod simultaneously, thereby balancing the forces during injection and preventing bending moments. As a result, the injection cylinder maintains parallelism throughout the entire stroke, even at peak injection pressures. Additionally, the two-way synchronous design incorporates precision guide sleeves and adjustable preload bearings at both ends to ensure minimal radial clearance. As a result, the injection cylinder reacts evenly to the melt pressure, and the deviation load is negligible. By adopting a two-way synchronous injection cylinder structure, manufacturers can extend equipment life, reduce scrap rates, and maintain consistent mold quality during production.

How to prevent deviation loads from damaging the screw and linear guides？

The advantage of the bidirectional synchronous injection cylinder structure is its active correction ability. Any inherent misalignment or uneven resistance will generate a lateral force, and the synchronous injection cylinder will immediately apply an opposing force to counteract it. If the screw tries to deviate to the left, the right cylinder will automatically apply a slightly larger force, effectively counteracting the lateral thrust. At the same time, they ensure that the resultant force vector remains perfectly aligned with the screw center axis throughout the injection stroke.

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For linear guides, the lateral forces are neutralized, and the linear guides are no longer subject to substantial, uneven point loads. The carriage supporting the screw assembly moves smoothly and evenly along the guide rails, correctly distributing the load and minimizing friction and wear on these critical precision parts.

Reduce wear and extend the life of the injection molding machine.

The bidirectional synchronous injection cylinder structure eliminates deviation loads, extending the injection molding machine’s screw and barrel life. By avoiding continuous lateral grinding, it also significantly reduces wear on the screw and barrel. In addition, the smooth, aligned stroke produced prevents indentation and excessive wear on the linear guide and its bearings. This maintains the precision of the injection molding machines for a longer period, avoiding the need for expensive guide replacement or re-machining. The thrust bearing is responsible for bearing the massive axial injection force and for bearing uniform loads without the additional destructive bending moments caused by deviation loads.

The reduced wear of these key components directly translates into more consistent injection speed and pressure curves throughout the machine’s life, which in turn contributes to improved part quality consistency.

Get higher operational and quality results

The benefits of eliminating deviation loads on large injection molding machines go far beyond reducing maintenance costs and extending component life. It can improve part quality. The consistent linear injection force minimizes fluctuations in melt flow and pressure in the barrel. This enables the mold cavity to fill more evenly, thereby reducing defects such as insufficient material, flash in specific areas, or inconsistent dimensions.

It can also improve process stability. A large injection molding machine that is not affected by the instability of deviation loads can run more predictably and achieve and maintain reliability during each injection process, thereby simplifying process setup and optimization. In addition, eliminating the deviation load also reduces energy losses, lowering the operating energy consumption of large injection molding machines and extending their normal runtime.

Reduce deviation loads through a two-way synchronous injection cylinder structure

The two-way synchronous injection cylinder structure can directly solve the deviation load of the injection molding machine, thereby protecting the screw and linear guide from destructive lateral loads. By actively neutralizing the deviation load in each injection cycle, this technology provides better protection for the screw, barrel, and linear guide. The result is a significant extension of the life of large injection molding machines, reduced maintenance costs, and enhanced process stability.

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