During the injection molding production process, the problem of glue leakage is extremely common and almost exists in various injection molding workshops. It is like an enemy hidden in the dark, constantly threatening the smooth progress of production.
1、 What is glue leakage?
Leakage of glue is the abnormal overflow of high-temperature molten plastic from the nozzle head and the connection between the nozzle and the material cylinder in injection molding production. It can not only cause product defects, but also damage equipment. This phenomenon usually occurs during the standby or glue stage before injection, manifested as the melt coming from the nozzle and
moldLeakage occurs at the contact surface of the sprue sleeve, the threaded connection of the nozzle, or the sealing part of the nozzle. Slight glue leakage can cause weight fluctuations and surface defects in the product; Severe glue leakage can lead to material shortage, shrinkage, and even burning of the heating coil, causing equipment failure.
2、 The hazards of glue leakage
Serious impact on product quality, resulting in appearance defects, dimensional deviations, and even product scrapping, increasing production costs. For example, if the product has problems such as insufficient filling and material waste, it will reduce the market competitiveness of the product.
Damage to equipment, such as the entry of adhesive into the interior, may result in component damage, electrical circuit burnout, shortened equipment lifespan, increased maintenance costs, and downtime.
On the early morning of June 21, 2024, the D12 Fanuc injection molding machine in a certain injection molding workshop in Dongguan suddenly sounded an alarm, and the sound echoed throughout the entire workshop. The equipment engineer found during inspection that the adhesive had wrapped the entire heating coil, causing temperature loss and burning of the heating coil. The equipment has tripped and stopped. After professional investigation by Fanuc service engineers, it was confirmed that the nozzle center deviation was about 0.3mm, causing the nozzle to leak glue. In addition, there was no supervision in the early morning, and the resin leakage slowly accumulated throughout the entire barrel. After the fact, the customer lost over 150 hours of production capacity and incurred high maintenance costs totaling over 240000 yuan.
3、 Common causes and solutions for glue leakage
Center deviation between nozzle and mold nozzle
When the mold operator is installing the mold, if the nozzle and the nozzle are not accurately aligned, resulting in deviation from the top, bottom, left, or right, it will cause the two to not fit tightly together, resulting in glue leakage.
Response plan: Adjustment of nozzle centrality
The centrality of the nozzle is the primary condition for preventing glue leakage. Based on the positioning hole, ensure that the nozzle is in the center position of the positioning hole. After adjustment, lock the seat mechanism and do not adjust it arbitrarily during production. And make regular checks for deviations before making adjustments.
Jizui deformation or nozzle wear
The mouthpiece and nozzle are prone to deformation or damage due to long-term high-pressure impact from the seat, and their contact surfaces may not fully match, leading to adhesive leakage.
Response plan: Physical repair or replacement
Perform spherical repair on the contact surface of the nozzle or spout, and confirm the R-angle matching, or replace it directly.
Jizui and nozzle do not match
The mismatch between the R angle and aperture of the mold nozzle and the material barrel nozzle may result in poor fit between the mold nozzle and the material pipe nozzle, leading to glue leakage.
Response plan: Mold nozzle and nozzle selection
The spherical radius of the nozzle must be slightly smaller (usually 1-2mm) than the spherical radius of the mold base nozzle surface to ensure that the contact surface can fit tightly and form an effective seal; The nozzle aperture must be slightly smaller than the mold nozzle.
Insufficient nozzle contact force
The nozzle contact force is insufficient, making it impossible to push the mold nozzle to death. During the high-pressure injection process, gaps are prone to occur between the nozzle and the nozzle, leading to glue leakage.
Response plan: nozzle contact force detection and adjustment
If the nozzle contact force is found to be insufficient, the cause should be immediately identified and repaired to avoid production with defects. Simultaneously develop a regular inspection plan for nozzle contact force and implement it for the long term.
The joint between the nozzle flange and the material cylinder is not tight
The joint between the flange and the material cylinder is not tight, and the joint between the nozzle and the flange is not tight or the screws are loose. During high-pressure glue injection, plastic will overflow from the gaps, causing glue leakage.
Response plan: Cleaning of joint surface
Clean all joint surfaces, confirm that there are no impurities or burrs on the fitting surfaces of the material cylinder end face, flange, and nozzle. Before heating up, tighten the screws diagonally and evenly in multiple times according to the standard torque. After heating up to the working temperature, tighten them diagonally again. After all are completed, a second confirmation is required!
The strength of the large mold horse is insufficient
In addition, for large molds, if the horse's strength is insufficient, the mold may sink during long-term production, causing the nozzle and mold nozzle to be misaligned, leading to glue leakage.
Response plan: Configure mold positioning ring
The configuration of the mold positioning ring is matched with the positioning hole of the injection molding machine to ensure that the mold does not slide down, and to keep the nozzle of the material cylinder aligned with the center of the mold nozzle, which can effectively prevent the occurrence of glue leakage.
4、 Establish a comprehensive daily operation and maintenance management system:
On the basis of ensuring equipment matching and normal parameters, it is also necessary to establish a sound daily operation and maintenance management system
Regularly inspect the machine and promptly handle and clean any glue leaks: It is recommended to inspect the machine every hour or every two hours. Once a glue leakage problem is discovered, even if the amount of glue leakage is not large, it should be cleaned immediately to ensure that production is not affected. Timely cleaning of glue leakage can prevent plastic accumulation and reduce damage to equipment and products.
It is recommended to conduct an annual inspection and include the above items in the inspection list. If there are any abnormalities, they should be adjusted in a timely manner.
Strengthen the training of operators to enhance their sensitivity and ability to handle glue leakage issues. Operators should understand the causes, hazards, prevention and treatment methods of glue leakage, and be able to promptly detect and solve problems during the production process.
Set parameter monitoring to enable, in case of unstable process parameters caused by glue leakage, alarm and check in advance.
At present, the causes and improvement methods of glue leakage in injection molding production are as described above. Although there is currently no automatic method for detecting glue leakage, daily inspections, strengthened management, and annual regular inspections of equipment can effectively prevent glue leakage, reduce equipment failure risks, and safeguard our equipment and products.
