[Dry Goods] Little Knowledge About Blister Packaging!

Blister is the process of heating, vacuum forming, cooling and other processes of PVC, PS, PET and other resin sheets in a blister forming machine to form them according to the shape of the mold, and then punching them into a single product with a knife die on a punching machine. Packaging products made by folding, punching and other processes. This packaging product has the characteristics of cheap materials, simple process, low investment and considerable profits. It is suitable for packaging small daily necessities, small electrical appliances, toys and other commodities. It is not suitable for packaging products with high cushioning requirements and heavy products.

 

01. The main production process of blister products

 

The main production processes of blister products include moulding, pulling, punching, hemming, punching, packaging, etc., which will be introduced separately below.

 

1) mold release

 

When the customer confirms the sample, the plaster mold used for proofing is used as the master mold, and after electroplating copper, the mold for production is made according to a certain number and position. There are three types of conventional molds: plaster mold, copper mold, and aluminum mold. Among them, the plaster mold is mainly used for proofing, and generally cannot be used for mass production, and its production time is generally 24 hours. The copper mold is plated with a layer of copper for the plaster mold, which has enhanced strength and wear resistance, and the cost is not high. For the production of commonly used molds, the general production cycle is 100 hours, at least 3 days, and the service life is about 100,000. When the number reaches more than 1 million, the aluminum mold can be made. The aluminum mold is made of pure aluminum, which is expensive and needs to be machined. The general mold making time is 3 days. Aluminum molds have good production quality, fast heat dissipation, high product precision and long service life. If customers have precise requirements for products, and copper molds cannot meet the accuracy requirements, aluminum molds must be made even if the quantity is small.

 

2) Pull tab

 

The blister machine automatically cuts the raw material coil into a predetermined size after heating, vacuum forming and cooling by the blister forming machine. This process is the main process of blister. The length of the pull tab is between 600 and 1170mm according to actual needs. Different materials and different thicknesses have different requirements for temperature adjustment, and the start-up personnel need to have considerable experience. The adjustment test of the pull tab is generally 3 pieces. The length of each feeding of the blister machine is called the length of the pull tab, which can be determined according to the length of the row of molds.

 

3) Punch

 

The pull tabs are generally multiple products (according to the number of die rows), which need to be punched into a single product on a punching machine with a knife die. This process is called a punching machine.

 

4) Hemming

 

For some products that need to fold the corners of two or more sides of the blister product to insert the paper card, this process is required. This process is completed by a folding machine.

 

5) Punching

 

If the customer has special requirements, this process should be added when perforating the blister.

 

6) Packaging

 

We must pay attention to the packaging of blister products, and determine the appropriate packaging method according to the strictness of customer requirements, the material and shape of the product, etc. If the customer has no special requirements, it can be packed in boxes and plastic bags. For white or brightly colored products that are prone to friction or cannot stick to dust and fingerprints, gloves are often worn during production.

 

02. Blister material

 

Commonly used plastic materials are PVC (about 50%, density is 1.36g/cm3), PS (about 30%, density is 1.06g/cm3), PET (about 10%, density is 1.39g/cm3) , PP (about 10%, the density is 0.92g/cm3).

 

Among them, the thickness of PVC is generally 0.8mm, and the thickness of PS is generally up to 1.2mm. Films exceeding this thickness are difficult to pull and easily cause damage to the equipment.

 

The color of the material is generally determined according to the customer's requirements. Generally, it is necessary to provide such as PANTON color code, color draft, color separation standard, etc., or the customer can specify the approximate color, and provide the customer with the color according to the product inventory. If the customer has no requirements, generally colorless and transparent materials that are easy to produce can be used. If you order colored sheets, generally need to reach more than 2t before you can order. Colored materials are denser than transparent materials. The flocking material is generally made of PS material with a lower density. If the density is high, it is easy to produce some lint-free surfaces after stretching.

 

Generally, materials with brighter colors are easier to produce, and the requirements for packaging are not high. Light-colored materials are easy to see scratches, and the packaging requirements are strict. Generally, the flocking material needs to be prevented from scratches and indentations. When the products are put together, the tight contact area is prone to friction and whitening. In such places, special attention should be paid to the packaging. If the requirements are strict, the use of plastic bags, copy paper and other methods should be considered for protection. Flocking materials are generally ordered according to length (meters).

 

The properties of the material are generally antistatic. Anti-static materials are prepared by soaking or adding anti-static components, and the latter method has long-lasting anti-static properties. The electrostatic value of anti-static materials can generally reach 106 ~ 1012Ω. In addition, there is environmental protection, among which APET is more environmentally friendly and PVC is recyclable. Generally speaking, the thicker the material, the longer the heating time, and the slower the production speed; the thinner the material, the faster the production speed, but the longer the length of a roll.

 

03. Blister mold

 

Blister molds can be divided into lower molds, upper molds, and knife molds, which will be introduced separately below.

 

1) Lower die

 

The lower mold is an indispensable mold in the plastic production. According to the different production process and materials, it can be divided into plaster mold, copper mold and aluminum mold. When customers provide samples, drawings or real objects, they need to make plaster molds for adding samples. The gypsum mold is made of gypsum powder and water, and then set to a certain shape, and then hardened to make a mold after dehydration. Materials and tools such as gypsum powder, drills, emery cloths, boards, etc. are required. Because it is hand-made, there will be a deviation of about 2mm for the drawing. After the plaster is molded, it can be directly proofed, which is not suitable for mass production.

 

Gypsum molds can be modified after forming, and it is generally easier to make smaller than larger ones. After the customer confirms the sample, the proofing plaster model can be used as the seed model (master model), and multiple child models can be discharged according to the needs of production. The difference between the size of the sub-mold and the seed mold is not very large, generally around 0.5mm. After the lower molding is made, it needs to be fixed on a five-plywood with a thickness of about 8mm, and it can be installed on the mold basin when it is produced. When the heated sheet passes through the mold, it is sucked by the vacuum pump and attached to the lower mold to make a product with the same shape as the lower mold.

 

2) Upper die

 

Sometimes vacuum suction alone is not enough to shape the product, and a certain external force is required to make the upper mold. The upper mold is not necessary for all products, but depends on the needs of production. When testing the machine, if the blister forming is not good and the upper mold is needed, the boot master will make the upper mold according to the shape. The material of the upper mold is generally iron or wood, and the surface in contact with the product needs to be covered with a softer sponge or flannel.

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3) Knife die

 

Generally, multiple blister molds are opened in one mold. After forming, they need to be cut into finished products according to the size and shape of the products. The process of cutting into finished products is a punch, and the mold used is a knife die. Die can be divided into three types according to the material and production process: iron knife, wood-like knife and laser knife die. Among them, the iron knife is thicker, and can generally be made into a knife mold with a relatively regular shape, such as a rectangle, an ellipse, etc., and is not suitable for a shape that is too curved.

 

The blade used in the wooden sample knife is the beer machine knife mold used in the color box, which needs to be superimposed a certain number of layers according to the height of the product, and sometimes it needs to be placed under the cushion. For knife molds that require high precision, laser knife molds can be made, which are similar to wood-like knives. After the knife mold is made, the product that needs to be positioned generally needs to fix a finished product in the knife mold, which is convenient for positioning when punching the product. Products that do not require positioning, such as boundless blister products, generally use an iron knife as a knife mold.

 

04. Dimensions and tolerances

 

The size of the blister can be divided into three types: copying according to customer samples (mold-making is called complex mold), making molds according to drawings, and designing according to real objects. Because the shape of the blister is generally customized according to the physical object, the shape is often irregular, and many dimensions are inaccurate or cannot be marked when the drawing is made, so there is a large deviation when the drawing is made. For the sake of accuracy, it must be matched with a physical trial. According to the product made by the sample remolding, the dimensional deviation is not large.

 

The general thickness tolerance is 0.1mm, and the product deviation is ±2mm. The main reasons for the tolerance are:

 

1) Deviation caused by manual mold release. This deviation is generally less than 2mm.

 

2) The deviation generated when the seed model replicates the child model. This deviation is small, generally less than 0.5mm.

 

3) Thickness deviation of the same mold due to different materials and blister temperatures. This deviation is small, generally less than 0.1mm.

 

4) The thickness tolerance depends on the specific situation. The larger the same area is drawn, the thinner the thickness of the block becomes. Different operators and different temperatures will also make the thickness of the same part different.

 

Among the above reasons, the first is the main reason for the dimensional tolerance, but because the mold can be modified and corrected, the deviation of the blister can generally be controlled within 2mm.

 

It should be noted that the thickness of the material is two numbers (0.05mm) smaller than the thickness of the finished product. Although there is a phenomenon that when the surface area of the finished product is much larger than the surface area of the material, the thickness of the finished product will be much smaller than the thickness of the material, the surface area of the finished product will be much larger than the surface area of the material, and the thickness of the finished product will be much smaller than the thickness of the material. In general, the gap is 0.05mm. Blister is a very clear "tailor-made" product. If you want the right size, you must take the real object to try it on.

 

05. Draft angle

 

All products that are formed by die stamping need to be designed with a draft angle, and the same is true for blister. Generally, the draft angle of blister is 3°. The draft angle will cause the size of the upper surface to be smaller than the size of the lower surface. If the blister is placed in a box, there will be a gap between the upper surface and the box wall. When the draft angle is the same, the size of the gap is related to the height, and the calculation formula is:

 

d=h×tgθ

 

in the formula

 

d - the size of the gap on each side;

 

h——the height of the blister;

 

θ——Draft angle, generally 3°.

 

2d can represent the gap difference between the upper surface and the lower surface. When the draft angle is 3°, Table 2-1 is a quick calculation table of height and clearance:

 

06. Die layout and material setting

 

Die arrangement refers to arranging the die on the die plate and fixing it. The distance between die and die depends on the height of the product. Conventionally, the distance between the mold and the mold is equal to the height of the mold, and the distance between the mold and the four sides of the mold plate is equal to the height of the mold divided by 2. The high point of the die refers to the highest point of the die.

 

The height of the product refers to the highest dimension of the product, as shown in Figure 2-1, h1 and h2 are not the height of the product, the larger h is the height of the product.

 

Product high point and draft angle

 

When arranging the mold, the width must be arranged to the side, and the length can be more or less, but not more than 1120mm, at least not less than 600mm, between 600 and 1120mm, the longer the better. The number of rows of APET materials should not be too many, between 600 and 800.

 

The width of the die plate plus 50mm is equal to the width of the material, and the length of the row of molds plus 50mm is equal to the length of the pull tab. See Figure 2-2.

 

Example: The size of a blister is 297mm×210mm×32mm (length×width×height), please determine the number of rows and materials used.

 

Schematic diagram of layout

 

1) Analyze the optional die width and material width: the product can be divided into horizontal placement and vertical placement. Divide the four die widths of 510mm, 560mm, 610mm and 660mm by the sum of the length and height of the product to obtain the savings. The width of the die plate and the layout plan of the material. A good solution is to use a 660mm die plate to arrange 2 horizontally, then the width of the material used is 710mm.

 

2) Determine the length of the pull tab: divide the length of the 1120mm large pull tab by the sum of the width and height, and the obtained value is taken as an integer, which is the maximum number 4 that can be arranged, and the maximum number that can be arranged × (width + height) + 50mm=1020mm, 1020mm is the length of the pull tab.

 

3) Calculate the number of rows of moulds: 2 horizontally and 4 vertically, so the number of rows of moulds for this product is 8. Through the above calculation, it can be seen that the mold arrangement method of this blister is: use a 660mm×1120mm mold plate, use a 710mm film, and the pull-piece length is 1020mm, which can arrange 8 products. Table 2-2 is an example of row pattern selection.