Plastic absorption process of building film

Plastic absorption process of building film

The plastic absorption of building film is to form PVC, PS, PET and other resin sheets according to the shape of the mold through heating, vacuum forming, cooling and other processes in the plastic absorption molding machine, and then press them into a single product with a knife die on the press, and finally make packaging products through folding, punching and other processes, mainly including building film, PVC film, PS plastic absorption sheet, PET film.

This packaging product has the characteristics of cheap materials, simple technology, low investment and considerable profits. It is suitable for packaging small daily necessities, small appliances, toys and other commodities, and is not suitable for packaging products with high cushioning requirements and heavy products.

Main production process of blister products

The main production processes of blister products include mold lifting, sheet pulling, punching machine, folding, punching, packaging, etc., which are described below.

1. Demoulding

After the customer confirms the sample, the gypsum mold used for proofing is used as the master mold, and after copper plating, the mold used for production is made according to a certain number and position, which is called stripping.

There are three types of conventional molds: gypsum mold, copper mold and aluminum mold. Gypsum mold is mainly used for proofing, and generally cannot be used for mass production. Its production time is generally 24 hours.

The copper mold is a gypsum mold plated with a layer of copper, which has high strength and wear resistance and low cost. It is the most commonly used mold for production. The general production cycle is 100 hours, at least 3 days, and the service life is about 100000.

When the quantity reaches more than 1 million, the aluminum mold can be made. The aluminum mold is made of pure aluminum, which has high cost and needs to be machined. Generally, the mold making time is 3 days. The aluminum mold has good production quality, fast heat dissipation, high product accuracy and long service life. If the customer requires accurate products and the copper mold cannot meet the accuracy requirements, the aluminum mold must be made even if the quantity is small.

2. Pull tab

The blister machine automatically cuts the raw material coil into the set size after heating, vacuum blister forming and cooling by the blister forming machine. This process is the most important process of blister.

The length of the tab is between 600 and 1170mm according to the actual needs. Different materials and thicknesses have different requirements for temperature regulation, which requires the start-up personnel to have considerable experience. Generally, the machine adjustment test of the pulling piece is 3 pieces. The length of each feeding of the blister machine is called the pulling length, which can be determined according to the length of the die.

3. Punch press

Generally, the products pulled out are multiple products (according to the number of die rows), which need to be punched into a single product with a knife die on a punch. This process is called a punch.

4. Hem

For some products that need to fold both sides or multilateral corners of the blister products to insert paper cards, this process needs to be added. This process is completed by the folding machine.

5. Punching

If the customer has special requirements, this process should be added when piercing the blist

6. Packaging

Attention must be paid to the packaging of blister products, and the appropriate packaging method shall be determined according to the severity of customer requirements, product materials, shape, etc. If the customer has no special requirements, the method of packing and plastic bags can be used. For white or brightly-colored products that are easy to wear or can not stick dust or fingerprints, gloves are often worn during production.

Blister material

The commonly used plastic absorbing materials include PVC (about 50%, density 1.36g/cm3), PS (about 30%, density 1.06g/cm3), PET (about 10%, density 1.39g/cm3), PP (about 10%, density 0.92g/cm3).

The maximum thickness of PVC is generally 0.8mm, and PS is generally up to 1.2mm. The film exceeding this thickness is difficult to pull, which is easy to cause equipment damage.

The color of the material is generally determined according to the customer's requirements. Generally, it is required to provide PANTON color code, color draft, color removal 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, the colorless, transparent and most easily produced materials can generally be used.

If the color sheet is ordered, it can be ordered only after it reaches more than 2t. Colored materials have a higher density than transparent materials. Flocking materials generally use PS materials with low density. If the density is large, part of the surface will be free of lint after stretching.

Generally, materials with bright colors are easier to produce and have low requirements for packaging. It is easy to see scratches on light-colored materials, and the packaging requirements are strict.

Generally, flocking materials should be protected from scratches and indentations. When the products are put together, the tightly contacted parts are prone to friction and whitening. For places like this, special attention should be paid to packaging. If the requirements are strict, the methods such as plastic bags and paper separation should be considered for protection. Flocking materials are generally ordered according to the length (meters).

The characteristics of materials generally include anti-static property. Anti-static materials are prepared by soaking or adding anti-static components. The latter method has long-lasting anti-static performance. The static value of anti-static materials can generally reach 106~1012 Ω. In addition, there is environmental protection, among which APET is the most environmentally friendly and PVC can be recycled. 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.

Blister mold

The blister mold and building film can be divided into lower mold, upper mold and knife mold, which are introduced below.

1. Lower mold

The lower mold is an indispensable mold in blister production. According to different manufacturing processes and materials, it can be divided into gypsum mold, copper mold and aluminum mold.

When the customer provides samples, drawings or real objects, it is necessary to make gypsum molds with samples. Gypsum mold is made of gypsum powder and water to form a certain shape, which is hardened after dehydration. Materials and tools such as gypsum powder, drill bit, emery cloth and wood board are required. Because it is made by hand, there will be a deviation of about 2mm for the drawing. Gypsum can be directly proofing after molding, which is not suitable for mass production. Gypsum mold can be modified after forming. Generally, it is easier to change smaller than larger.

After the customer confirms the sample, the prototype gypsum mold can be used as the seed mold (master mold), and multiple sub-molds can be discharged according to the production needs. The deviation between the size of the sub-mold and the seed mold is not very large, generally about 0.5mm. After the lower mold is made, it needs to be fixed on the plywood with a thickness of about 8 mm, and it can be placed on the mold basin when it is produced. When the heated sheet passes through the mold, it is sucked by the vacuum pump and pasted on the lower mold to make the product consistent with the shape of the lower mold.

2. Upper mold

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

3. Knife die

Generally, there are multiple the first mock examination for blistering. After forming, the finished product needs to be cut according to the size and shape of the product. The process of cutting the finished product is a punch, and the mold used is a knife mold.

The knife mold can be divided into three types according to the different materials and manufacturing processes: iron knife, wood sample knife, and laser knife mold. The iron knife is thick, and can be made into regular knife molds, such as rectangular and oval shapes, which are not suitable for making too curved shapes. The blade used for the wood sample knife is the beer machine knife mold used for the color box. It needs to be stacked with a certain number of layers according to the height of the product, and sometimes it needs to be padded. For the knife mould that requires high precision, laser knife mould can be made, which is similar to wood sample knife.

After the knife mold is made, the products that need to be positioned usually need to fix a finished product in the knife mold to facilitate positioning when punching products. Products that do not need positioning, such as rimless blister products, are generally made of iron knives.

Dimensions and tolerances

The size of blister can be divided into three types: copy according to the customer's sample (mold making is called duplicate mold), mold making according to the drawing, and self-design according to the real object.

Because the shape of the blister is generally customized according to the real object, the shape is often irregular, and many dimensions are inaccurate or cannot be marked when making drawings, so there is a large deviation when making according to the drawings. For the sake of accuracy, it is necessary to match the actual trial assembly. The size deviation of the product made according to the sample replica is small.

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

1. Deviation caused by manual stripping. This deviation is generally less than 2mm.

2. The deviation generated when the seed mold copies the sub-mold. 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 pulled, the thinner the thickness of this 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 dimensional tolerance. However, because the mold can be modified and corrected, the deviation of blister can be controlled within 2mm generally.

It should be noted that the thickness of the material is two marks smaller than the thickness of the finished product (0.05mm). Although there are phenomena 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, generally speaking, the difference is 0.05mm. Blister is a very clear "tailored" product. If you want to fit it properly, you must take the real object to try it out.