Injection Molding Machine Mold Closing and Locking Parameter Adjustment Standards and Key Points of Low-Pressure Protection
Mold closing and locking are core basic processes in injection molding production. Rationality of parameter settings directly determines mold accuracy, equipment wear, product quality, and production costs. Most mold damage, excessive product burrs, decreased equipment accuracy problems stem from improper adjustment of low-pressure protection parameters during mold closing. Following will standardize adjustment specifications, parameter standards, and common misconceptions for three processes of initial mold closing, low-pressure mold closing, and high-pressure mold locking, providing a reference for stable mass production.

 

Initial mold closing is initial stage of moving mold platen's start-up operation. Core adjustment principles are: low-pressure speed control, steady start-up, reducing hard wear on equipment.
1. Initial Mold Closing Pressure
Basic reference setting value is 25. During production debugging, if mold closing speed is slow or cycle time is not up to standard at a pressure of 25, adjust gradually by increasing pressure by only 5 units at a time, and avoid increasing pressure significantly at once.
Parameter Taboos and Impacts: Initial mold closing pressure should not be too high. Excessive pressure will cause stationary moving mold plate to receive high-pressure thrust instantly, rapidly starting its movement and generating high-intensity hard friction between moving mold plate hole and tie rod. Long-term high-pressure startup will accelerate wear of tie rod and mold plate hole, directly reducing smoothness and positioning accuracy of moving mold plate. For high-precision mold production, this can easily lead to quality problems such as mold closing misalignment and forming deviations.
2. Initial Mold Closing Speed: Speed should be flexibly adapted according to mold specifications and equipment conditions. Core requirement is smooth operation without any jamming or interruption.
Optimal Debugging Logic: High-speed setting, low-pressure speed control. By limiting actual operating speed by lowering pressure value, mold closing action is ensured to be smooth, avoiding obvious pauses in segmented movements, while also preventing impact on mold and equipment caused by excessively fast initial startup speed, ensuring smooth operation throughout mold closing process.

Low-pressure mold closing is core safety feature of the entire mold closing process. Its function is to operate at low speed and low pressure before mold is fully closed. If there are hard obstacles such as ejector pins not resetting, product residue, or foreign matter between mold cavity and mold plates, it can trigger a timely protective shutdown, preventing mold crushing and collision accidents.
Low-Pressure Mold Closing Operating Range: From starting position of mold safety protection until mold is fully closed.
1. Low-Pressure Mold Closing Speed
Core Principle of Debugging: Slower is better. Even with low-pressure parameters set, excessively high operating speeds will generate huge inertial impact forces, still causing ejector pin breakage, slider misalignment, and mold cavity damage.
Standard Debugging Method: Initially set speed to a low value (usually tens of units) and keep it fixed. Prioritize lowering pressure for testing, relying on pressure to precisely control actual operating speed, then gradually fine-tune pressure to match low-speed protection state suitable for production.
2. Low-Pressure Mold Closing Pressure
Adopt "high-speed, low-pressure start, gradual pressure adjustment" method:
During initial adjustment, speed can be increased while pressure is reduced to a very low value (reference value 5); Since pressure is core of mold closing power, even if speed parameter is high under low pressure, actual operating speed will be limited; Increase pressure slightly from 5 until a critical value is reached that allows for smooth mold closing while maximizing mold anti-collision protection, always adhering to principle of minimum effective pressure adjustment.
3. Low-Pressure Mold Closing Starting Position
This parameter has no fixed value, is entirely adjusted based on mold size and structure type. Standard range is 5-20cm before mold is fully closed.
Frequently Used Misconception in Industry (Important): Many operators set starting position too close, only activating low-pressure protection when mold is about to close. In this state, high-pressure, high-speed impact force of initial mold closing has already acted on mold. If there are foreign objects or protruding ejector pins inside mold at this time, low-pressure protection will activate late, completely losing its protective function and directly causing mold collisions, slider misalignment, ejector pin breakage, and other malfunctions.
4. Low-Pressure Mold Closure Termination Position (High-Pressure Mold Locking Start Point)
Definition: Position where mold is fully closed and moving mold plate reaches its limit end point is critical dividing point between end of low-pressure protection and start of high-pressure mold locking.
Standardized Debugging Procedure:
First, adjust pressure and speed parameters for low-pressure mold closure; Reset termination position parameter to zero, manually close mold, and record precise value of complete mold closure (e.g., measured value 2.2); Leave a tolerance margin, adding 0.1-0.3 units to measured value (e.g., adjust to 2.4).
Parameter Tolerance Principle: This value will fluctuate slightly due to factors such as accuracy of electronic ruler, mold tightness, mold closure pressure, impurities on mold surface, and equipment wear. Directly using measured value can easily lead to out-of-tolerance mold closure position, causing low-pressure program to fail to end normally and equipment to be unable to switch to high-pressure mold locking.
Fatal Industry Misconception: In many production settings, low-pressure protection is prematurely terminated, with mold still having several centimeters of gap before fully closing, leading to premature high-pressure mold locking and complete failure of low-pressure protection. When residual semi-finished products or foreign objects are trapped in mold cavity during production, high pressure will directly compact mold, causing mold cavity deformation, tearing, and scrapping.

 

Function of high-pressure mold locking: After mold is fully closed, high-pressure thrust opens machine hinge, allowing mold to be fully locked and compacted, offsetting injection pressure and preventing burrs and mold expansion in product.
Core Prerequisite: High-pressure mold locking must be activated only after mold is fully closed. High pressure must not be applied before mold is fully closed; otherwise, low-pressure protection will be ineffective.
1. High-Pressure Mold Locking Pressure
Basic reference setting is 60. If locking force is insufficient, or slight mold expansion or burrs occur during production, adjust by increasing pressure by 10 units each time. Blindly increasing locking pressure is prohibited; excessive pressure will significantly increase equipment load, accelerate machine hinge wear, shorten equipment lifespan, and provide no production benefit.
2. High-Pressure Mold Locking Speed
Basic reference setting is 25. If locking force is insufficient, adjust pressure first, and then fine-tune speed last. If a speed increase is necessary, increment by 10 units each time.
Key points regarding equipment wear and tear: High-pressure mold clamping is a rigid mechanical locking process. Even a slight doubling of speed will exponentially increase frictional wear on hinges, mold plates, and tie rods. A high-quality mold clamping condition in production is characterized by no abnormal noise, a tightly locked mold, and no impact or vibration.

Over 90% of mold closure failures stem from excessively late low-pressure start-up and premature end-of-pressure settings. Incorrect parameter settings in these two stages result in an excessively short low-pressure protection range. Mold suffers initial high-speed, high-pressure impact during mold closure and subsequent high-pressure clamping, losing protection in both directions and triggering a series of chain reactions:
Irreversible Degradation of Mold Precision: After impacts from foreign objects and high-pressure compression, positioning accuracy and fit of mold cavity decrease, rendering previously mature injection molding process parameters ineffective and significantly increasing difficulty of process debugging;
Continuous Deterioration of Product Quality: Poor mold fit leads to increased burrs and roughness in products, resulting in frequent appearance defects and a continuous decline in yield;
Significantly Increased Labor Costs: Excessive burrs require manual secondary trimming and polishing, increasing labor intensity of operators and reducing production efficiency. Reduced efficiency; simultaneously, increased manpower workload easily leads to employee fatigue and increased staff turnover, requiring additional staff when necessary, further increasing production costs;
Production downtime and maintenance costs: Severe mold collisions and pressing failures directly lead to mold shutdown and scrapping, requiring disassembly for repair, welding repairs, and cavity grinding, not only incurring high repair costs but also delaying production delivery;
Damaged product quality and reputation: Mold cavity scratches and repairs leave permanent marks, resulting in flaws on finished product's appearance, failing to meet high-quality delivery standards and reducing product market competitiveness;
Shortened mold lifespan: Repeated impacts and high-pressure extrusion accelerate aging of mold components and reduce precision. The more repairs, the worse mold structure stability, ultimately leading to premature scrapping, significantly increasing mold procurement and iteration costs.

 

Mold Closure ≠ Mold Locking: Mold closure is process of moving platen driving mold to close; mold locking is high-pressure locking process after mold closes. These processes must not be confused or switched prematurely.
Low-pressure protection is the first line of defense for mold. The key is to extend low-pressure stroke and reserve sufficient protection range to prevent damage to mold from impact forces from preceding and following processes.
All parameter debugging follows principle of "from low to high, small-scale fine-tuning, and fault-tolerant adaptation," avoiding blindly pursuing high speed and high pressure. Core standards are equipment stability, mold integrity, and high-quality products.