Quality requirements of the hottest plastic prefab

The quality requirements of plastic prefabricated bags and the main inspection items during acceptance

Plastic prefabricated bags are one of the earliest packaging forms. They are favored by users for their convenience, wide range of uses, and no large-scale equipment investment. They are also widely used in detergent, food, cosmetics, drugs, clothing, chemical and other industries. Today's prefabricated plastic bags are more colorful in material selection, bag making form, structure and function, decoration and printing, variety and specification, etc. Take the prefabricated plastic bags used in detergent products as an example. From the structure, they can be divided into barrel bags and self-supporting bags. Among them, barrel bags are divided into side seal and back seal, with handle and without handle, etc; Self standing bags are divided into inserted edges and bottoms, with and without handles, and additional functions. Here, the author will introduce some quality requirements and main inspection items of plastic prefabricated bags in combination with our detergent products, hoping that the packaging suppliers will pay attention to them. Strengthen the corresponding quality control to obtain better economic benefits and higher product quality

material requirements

1. Material structure

the material structure selected for product packaging is determined after comprehensive consideration of product characteristics, packaging effect, storage conditions and other factors, and verified by storage stability test and transportation test. Generally, there is a specific description of the material structure in the packaging standard, and the standard samples confirmed by the supplier and the demander are provided as the basis for delivery acceptance. Any material change or misuse without verification and confirmation will be rejected

the physical properties of the corresponding material structure have specific indicators in the packaging standard, such as tensile strength, elongation at break, composite strength, puncture strength, oxygen/water vapor transmittance, etc. These are the specific items of material inspection

2. Unit weight

unit weight index is a simple and intuitive inspection item during the delivery and acceptance of plastic prefabricated bags. There are usually two inspection methods: one is to specify the unit weight of packaged products in the standard, and the sample with an area of 1ocm can be cut on the plastic prefabricated bag with a standard cutter for weighing during the acceptance. The unit weight expanded by the high-speed enlarger can be calculated; Another method is to specify the weight of each prefabricated plastic bag in the standard. During the inspection, the weight of each prefabricated plastic bag is directly weighed, and it is judged whether it is qualified or not

3. Thickness

most of the material thickness has clear requirements in the standard. The inspection of thickness has two aspects, one is the actual thickness of the material, and the other is the thickness deviation range

sealing quality

1. Heat sealing strength

heat sealing strength is a very important quality index of prefabricated bags. Poor heat sealing strength is one of the important reasons for package damage, so heat sealing strength is a necessary inspection item during delivery acceptance

heat sealing strength mainly depends on material structure and heat sealing process parameters, such as heat sealing temperature, heat sealing pressure and heat sealing time. Sometimes, due to the mismatch between the bag making equipment and the bag length, the heat sealing knife will overlap in some areas. At this time, if the heat sealing temperature is too high, the edge banding will be deformed, and if the heat sealing temperature is too low, the heat sealing strength in the area where the heat sealing knife is not superimposed will be low

the test method of heat sealing strength is usually to use a blunt (round) ruler to slide along the inner side of the edge sealing, and apply an appropriate amount of force to check whether there are weak areas or points at the edge sealing. Then, the heat sealing strength of prefabricated bags can be measured by tensile testing machine according to the standard

2. Edge banding width and appearance

edge banding width is generally clearly specified or marked in standards or technical drawings. Most of the reasons for unqualified edge banding width are caused by bag making and cutting errors. The appearance quality of edge banding drives the new growth of relevant industries, and the indirect economic benefits can reach us More than 50000 billion yuan directly affects the packaging quality and the shelf effect of goods. The appearance of edge banding shall be flat without deformation and shrinkage. The deformation and shrinkage of edge banding are mainly caused by high heat sealing temperature or insufficient cooling time

3. sealing position

the sealing position mainly includes two aspects: first, determine the opening edge of the prefabricated bag (such as the top or bottom of the bag), and the user can specify the opening edge of the prefabricated bag according to the filling process and sealing quality; The second is the stacking requirements of two-layer sealing film, mainly from the perspective of aesthetics. For example, the outer heat sealing film should cover the inner heat sealing film, and the heat sealing film on the front of the bag should cover the heat sealing film on the back. It is not allowed to have uneven two-layer heat sealing film

bag making requirements

1. Bag making size

bag making size should comply with the drawing, and the deviation should be controlled within the allowable range of the standard. The main bag making dimensions include the length, width, height, hem width, bottom width of the bag, and the structural modeling size of the handle. The common quality problem is that the size deviation is too large, beyond the allowable range

2. Cutting position

unqualified prefabricated bag products also occur from time to time due to incorrect cutting position, mainly including the following problems

(1) the position of the cutting reserved edge is wrong. Some design patterns are not connected without trace after making up, so the position of the cutting point and residual edge (at the bottom or top of the prefabricated bag) must be confirmed with the user before making the bag

(2) the margin of edge banding is too large. Edge banding allowance refers to the distance from the edge banding outer line at the top/bottom of the prefabricated bag to the edge line of the finished bag. Generally, the edge banding allowance is required to be less than 3mm. When making bags, if the cutting line is far away from the edge banding of the bag, and the edge banding allowance is too large, it will affect the volume and aesthetics of the finished bag

(3) the position of the cutting line is wrong. If the bag making equipment is not adjusted properly, and the cutting line is just at the edge sealing part of the top/bottom of the prefabricated bag, there will be no opening of the prefabricated bag (that is, there are hot edges at the top and bottom of the prefabricated bag), so that users cannot use it

3. Exhaust pinhole

when making bags, it is necessary to confirm whether users have requirements for punching exhaust pinholes in prefabricated bags. If there is such a requirement, it must be carried out in accordance with the number, size, position, arrangement, etc. of pinholes specified in the standard. Common pinhole quality problems include missing pinholes, pinholes and even the performance of the driver's personality. The diameter of pinholes is too large, the position of pinholes is improper, pinholes are torn, etc

4. Handle

prefabricated bags with handles are mostly large-size packaging bags, so handle strength is the main item of handle inspection. There are many inspection methods for handle strength. Some companies use tensile testing machine to measure, and some companies use simulation test to evaluate. The main reason for the unqualified strength of the lifting handle is the punching defects of the lifting hole, such as burrs and notches on the edge of the lifting hole

other defects of the handle include excessive position deviation, deformation of the lifting hole, no lifting L or incomplete lifting hole, etc

5. Other functions

other functions of prefabricated bags are increasing, such as self-supporting bags with additional functions such as zippers/self sealing, spiral nozzles, diversion pipe spill prevention ports, and special-shaped structures. They are more and more widely used in the field of liquid product packaging

printing quality

printing quality is very important for product packaging, involving printing schemes, quality requirements, inspection items, inspection methods, common quality defects and many other aspects. In view of the content in this regard, there are many discussions and relevant articles in the industry, so I won't repeat them here

use performance

1. Drop performance

the drop performance of prefabricated bags must meet the standard requirements to ensure the safety of packaged products. The drop test method is usually to fill the prefabricated bag with the actual content or similar content of the nominal weight. After heat sealing, make it fall freely from the height of 1.2 ~ 1.5m, repeat it for three times, and check whether the bag has cracks or leakage. Of course, the inspection methods of Beijia company are different and need to be inspected according to the corresponding standards

2. Easy opening and no adhesion

prefabricated bags are mostly used for manual packaging and semi-automatic packaging. Engineers strictly control the quality of each experimental machine, which has a direct impact on workers' operation and production efficiency. Therefore, it is required that the opening performance of prefabricated bags is good, and there is no adhesion between bags

the adhesion between bags will not only affect the operation, but also easily cause quality problems such as ink transfer and falling off for surface printed prefabricated bags, and even the whole prefabricated bags are bonded together and cannot be used

3. No damage, leakage of bags

the prefabricated bags are not allowed to have scratches, tears, notches, holes and other damage

4. No pollution

the prefabricated bag is not allowed to have equipment oil, dust, foreign matters and other pollution

delivery quality

1. product label

the prefabricated bag should have a clear and complete product label, and the main contents should include: product name, specification, packaging quantity, order number, production date, quality and supplier information. The main purpose of providing this information is to meet the needs of delivery acceptance, storage and delivery, production and use, quality tracking, etc

2. Put an end to wrong delivery

put an end to wrong products, wrong labels, wrong packaging and other phenomena

3. avoid transportation damage

the delivery process of prefabricated bags should be controlled to avoid damage (such as scratches, tears, holes, etc.) or pollution of prefabricated bags due to damaged outer packaging (damage, watering, pollution, etc.)

reprinted from: Printing Technology