What is Heavy Gauge Thermoforming?
Heavy Gauge Thermoforming is a thermoforming process of thick gauge plastic sheet.
The thickness used for heavy gauge thermoforming is usually more than 2mm. First spreading hard plastic sheet, heating and softening, then use of vacuum adsorption or air pressure difference, mechanical pressure, etc., so that it is closely attached to the mold surface, after cooling and curing after molding.
The material mainly includes various colors of ABS, acrylic, PETG, PVC, PC, PP, PE, PS, etc. and a variety of modified plastic light sheet, leather-like sheet, transparent plate.
Due to the thickness of the raw material exceeds the range of fully automatic vacuum molding machine can be processed, semi-automatic vacuum molding machine is used for heavy gauge vacuum forming processing.
Heavy Gauge Thermoforming Features:
- Low mold cost: Compared with injection molding, the mold cost of thick sheet is relatively low, especially suitable for small batch and multi-species products.
- Large product size: It can produce plastic parts with large area and height, such as automobile body jacket, large advertising light box, etc..
- Complex shapes: Can realize complex shape product design, for product appearance and functional design to provide greater flexibility.
- Higher production efficiency: The production process is relatively simple, fast molding speed, can produce a large number of products in a relatively short period of time, improve production efficiency.
Comparison of Heavy Gauge Thermoforming and Injection Molding
| Comparison Items | Thick Sheet Thermoforming | Injection Molding |
|---|---|---|
| Production Principle | Heat the flat plastic hard sheet with a thickness exceeding 2mm until it becomes soft, and then use vacuum adsorption, air pressure difference, mechanical pressure, etc. to make it closely adhere to the mold surface, and form after cooling and solidification. | Heat the thermoplastic or thermosetting plastic pellets until they melt, and then inject the molten plastic into the closed mold cavity under high pressure by an injection molding machine, and obtain the plastic product after cooling and solidification. |
| Molds | The cost is relatively low, the production cycle is short, and the mold structure is relatively simple. There are gypsum molds, electroplated copper molds, aluminum molds, etc. Among them, the gypsum mold has the lowest cost. | The cost is high, the production is complex and the cycle is long, but the mold has high precision and strong durability, and can realize the molding of complex structures and high-precision dimensions, which is suitable for large-scale production. |
| Material Selection | Mainly use various thermoplastic plastic sheets, such as ABS, acrylic, PETG, PVC, PC, PP, PE, PS, etc., and light plates, leather grain plates, transparent plates of various modified plastics, etc. The material thickness is generally thicker, usually more than 2mm. | Can use a variety of thermoplastic and thermosetting plastic pellets, with a wider range of material selection, including some engineering plastics and high-performance plastics, which can meet the requirements of different products for material properties such as strength, toughness, and heat resistance. The material thickness can be adjusted according to product design. |
| Product Characteristics | It can manufacture large-sized, thin-walled, and complex-shaped products, such as automobile body covers, large advertising light boxes, etc. However, the precision of the product is relatively low, the wall thickness uniformity is difficult to control, and the appearance quality may be affected by the quality of the sheet and the thermoforming process. | It can produce products with high precision, stable dimensions, and good surface quality. The product has good wall thickness uniformity and can realize complex structures and fine details, such as mobile phone cases, computer cases, etc. However, for the production of large products, the mold cost and equipment requirements are relatively high. |
| Production Efficiency | The production efficiency is relatively high, especially for the production of small batches and multiple varieties of products. Multiple molds can be used for thermoforming at the same time to produce multiple products at one time. However, for mass production, its efficiency may not be as high as that of injection molding. | Once the mold is debugged, continuous and rapid production can be achieved, and the production efficiency is high, which is suitable for large-scale and mass production. However, the mold replacement and debugging time is long, and the flexibility for the production of small batches and multiple varieties is poor. |
| Production Cost | The equipment investment cost is low, the mold cost is also relatively low, and the material utilization rate is high. Therefore, it has obvious cost advantages in the production of small batches and multiple varieties. | The equipment is expensive, the mold cost is high, and more waste may be generated during the production process. Therefore, the cost can be better shared and the cost-effectiveness can be reflected only in large-scale production. |
Comparison of Heavy Gauge Thermoforming and Thin Gauge Thermoforming
| Comparison Items | Heavy Gauge Thermoforming | Thin Gauge Thermoforming |
|---|---|---|
| Material Thickness | Generally, it uses sheets with a thickness ranging from 1 to 15MM. | Generally, it uses coils with a thickness ranging from 0.2 to 1MM. |
| Production Equipment | Mostly uses semi-automatic thermoforming machines, with a relatively slow production speed. | Adopts high-speed machines for production, which can achieve automated production such as automatic feeding, thermoforming, cutting, and stacking, resulting in high production efficiency. |
| Post-processing Methods | The cutting edges and holes are usually processed by CNC engraving machines, with high precision. It can produce products with complex shapes and sizes, but the processing time is relatively long. | Usually, die-cutting is used, which is fast and low-cost, suitable for products with simple shapes and small sizes, but the precision is relatively low. |
| Product Applications | Commonly used to manufacture products with high requirements for strength and stability, such as automotive interior parts, turnover partitions, refrigerator liners, trolley cases, electric vehicle door panels, medical device housings, and logistics turnover pallets. | Widely used in products that are more sensitive to weight and cost requirements, such as food and drug trays, cosmetic liners, lunch boxes and tableware, electronic component packaging, daily necessities packaging, fruit and vegetable packaging, and small mechanical parts packaging. |
| Product Precision | The product dimensional precision is relatively low. During the forming process, due to the thick sheet material, it is difficult to ensure the thickness uniformity and dimensional precision of each part. For some products with extremely high dimensional precision requirements, subsequent processing may be required to improve the precision. | It can achieve high dimensional precision and appearance quality, and can meet the high-precision packaging requirements of industries such as electronics and medicine. |
| Production Costs | The equipment investment is large, the mold cost is high, and the production efficiency is low, resulting in a relatively high unit product cost. However, for large and complex products, it has a certain cost advantage in mass production. | The equipment and mold costs are low, the production efficiency is high, and the material utilization rate is high, showing significant cost advantages in large-scale production. |
The advantages and disadvantages of heavy gauge thermoforming
Advantages
Wide range of application:
It can manufacture products of various shapes, including flat, three-dimensional, curved surfaces, etc., which can meet the diversified needs of different industries and fields, such as the manufacture of various parts, shells, containers and other products in automotive, industrial, construction, packaging and other industries.
Lower cost:
Compared with injection molding and extrusion molding process, thick sheet blister does not need high pressure injection molding machine or extruder and other expensive equipment, equipment investment cost is low. Moreover, the mold cost of thick sheet blister is smaller than that of injection molding, and the development cycle is short, which is suitable for small batch production and can effectively reduce the production cost.
High production efficiency:
Multiple products can be produced at the same time, the production cycle is short, to quickly meet market demand, especially for mass production of products, can effectively improve production efficiency and shorten the delivery time.
Variety of material selection:
We can use various plastic materials, such as ABS, PVC, PP, PE, PMMA, etc. According to the specific requirements of the products, such as strength, transparency, corrosion resistance, etc., we can select the appropriate material for blister molding processing to meet the different use of the environment and performance requirements.
Good product performance:
High strength: the manufactured products have enough thickness, more solid, can withstand certain external forces, reduce the risk of distortion and deformation, more stable and safe in use, such as automobile body parts.
Beautiful appearance: the product surface is smooth, no obvious surface lines or special traces, can draw different patterns and identifiers, and the plastic material is not easy to scratch and abrasion, without additional protective layer, has a better decorative.
Strong weather resistance:
Can withstand a variety of harsh climatic conditions, such as extreme cold, high temperature and humidity, ultraviolet rays, etc., has a long durability, can be used outdoors and other harsh environments for a long time.
Better environmental protection:
The production process generally does not produce waste water, waste gas, waste residue and other pollutants, in line with environmental requirements. In addition, some manufacturers also use biodegradable and environmentally friendly raw materials, and recycling corners, to further reduce the impact on the environment.
Light weight:
The weight of thick sheet blister products is usually lighter than other packages or products of the same size, which can save a lot of transportation costs for goods that need to be transported over long distances, as well as facilitating handling and installation.
High plasticity:
It can be precisely cut and processed according to the shape and size of the goods, which can be better adapted to the packaging or usage needs of the goods, and realize personalized customization.
Disadvantages
Limited dimensional accuracy
The dimensional accuracy of blister molding is relatively poor, the relative error of the size of its products is generally more than one percent, for some of the products that require very high dimensional accuracy, may not be able to meet the demand, such as parts of some precision instruments.
Thickness uniformity is not good:
Blister molding can only produce products with uniform wall thickness, generally thin at the chamfer, it is difficult to produce plastic products with different wall thicknesses, which may affect some of the performance or appearance of the product.
Only single-side:
In the blister molding process, only one surface of the sheet is in contact with the mold, so only one surface is consistent with the geometry of the mold, and the contour of the other surface of the product needs to be obtained through drafting, which may lead to differences in the shape and dimensional accuracy of the two sides of the product.
Limitations on shapes:
Although thick sheet blister molding is capable of producing a wide range of shapes, for some overly complex or special shapes, it may not be possible to achieve the desired molding results, or it may require a higher level of technology and cost to achieve.
Problems of appearance defects:
During the production process, appearance defects such as bubbles, crystal dots, water ripples, pull lines, scratches, etc. may appear, affecting the transparency and aesthetics of the product, especially for products used in high-grade packaging or products with high quality requirements for appearance, these defects may lead to the product becoming inferior.
Material cost is relatively high:
The sheet used for thick sheet blister processing is a semi-finished product made of granule or powder, compared with injection molding, the raw material for blister molding will increase the extra cost.
The main materials used and their properties for heavy gauge thermoforming molding
ABS
Performance: high strength, good toughness, excellent impact resistance and machinability, easy to process molding, good dimensional stability, high surface hardness, good gloss, general chemical resistance.
Applications: Widely used in automotive interior and exterior parts, such as automotive instrument panels, door panels, etc.; electronic and electrical products shell, such as computer chassis, TV shells, etc.; mechanical parts and other fields.
Acrylic (PMMA)
Performance: excellent transparency, light transmittance of up to 92% or more, similar to glass but only half the weight of glass, impact resistance is 7-18 times higher than ordinary glass, high mechanical strength, good processing performance, good weather resistance, long-term exposure to outdoor environments are not easy to change color, aging.
Applications: Commonly used in the manufacture of display racks, advertising light boxes, sanitary products, optical lenses, instrument panels, such as shopping malls to display cosmetic display racks, large advertising light boxes on the street.
PETG
Performance: excellent transparency and finish, good display effect; excellent surface decorative properties, can be printed without surface treatment, easy to press patterns, easy metal processing; good mechanical strength; good barrier properties to oxygen and water vapor; good chemical resistance, can withstand a variety of chemical substances; non-toxic, reliable hygiene performance, in line with the requirements of food, drugs and medical equipment packaging, and recyclable! It is non-toxic, reliable hygiene performance, meets the requirements of food, medicine and medical equipment packaging, and can be recycled.
Application: Mainly used in electronics, food, toys, color box window, collar tray, footwear packaging and other fields.
PVC
Performance: high toughness, not easy to burn, combustion will produce chlorine gas, a certain impact on the environment, with good transparency, surface gloss, less crystal points, small water lines, strong impact resistance, easy to mold, good mechanical strength, chemical stability in general.
Application: Commonly used in toys, food, electronic products, medicine, electrical appliances, gifts, cosmetics, stationery and other products, such as toys, blister packaging, food trays, etc..
PC
Performance: colorless and transparent, glossy and beautiful, non-toxic, no odor, prevent ultraviolet transmission performance and moisture preservation performance is good, wide range of temperature resistance, in – 180 ℃ does not brittle crack, in the 130 ℃ environment can be used for long periods of time, but prone to stress cracking, the need for strict control of the processing conditions in the production or the use of modified resins to improve the anti-stress cracking properties.
Application: It is an ideal food packaging material, can be manufactured into bottles, cans and various forms of containers for packaging beverages, alcohol, milk and other fluid substances, but also commonly used in the manufacture of medical equipment, optical lenses, electronic and electrical products shells and so on.
PP
Performance: non-toxic, tasteless, hygienic, high mechanical strength, good barrier, good heat resistance and low temperature resistance, can be used in a wide range of temperatures, but low dimensional accuracy, rigidity is not enough, poor weathering, easy to produce “copper damage”, with the phenomenon of post-shrinkage, easy to age after demolding, brittle, easy to deform.
Application: It can be used for packaging in industry, agriculture, fruit and other industries, such as making pallet box, turnover box, etc. It is also a common material for packaging of high cold-resistant frozen food, such as ice cream box, dumpling box, soup dumpling box, etc..
PE
Performance: including high-density polyethylene (HDPE) and low-density polyethylene (LDPE), etc., with good flexibility, impact resistance and low temperature resistance, good chemical stability, not easy to react with acids, alkalis and other substances, non-toxic, odorless, harmless to the human body, but the surface hardness is lower, the transparency is general.
Application: Widely used in food packaging, daily necessities packaging, chemical packaging and other fields, such as food preservation film, plastic film, plastic bags, plastic drums.
HIPS
Performance: high impact polystyrene, with high impact strength, strength and toughness, easy to process molding, relatively low cost, but lower transparency, not resistant to organic solvents.
Application: Commonly used in the manufacture of some of the appearance requirements are not high, but need a certain degree of strength and toughness of the product, such as electrical accessories, toy parts, stationery, etc..
Main issues needed attention during material selection for heavy gauge thermoforming
Material selection:
According to the product performance needs to choose material: different application scenarios on the product performance requirements are different, need to choose the right plastic material accordingly. Such as automotive interior parts, often choose ABS material, because it has good strength, toughness and impact resistance; food packaging field, the use of PET material, it meets food safety standards, and high transparency, can visually display the food.
Consider the compatibility of materials: If the product needs to be subsequently processed or used in conjunction with other components, make sure that the selected material is compatible with other materials. For example, in the case of electronic equipment, if you want to paste labels or paint on the blister casing, you need to choose a material whose surface can be well combined with glues and paints.
Thickness considerations:
According to the product size and structure to determine the thickness: product size is large or complex structure, need to appropriately increase the thickness of the material to ensure the strength and stability of the product. Such as large outdoor advertising light boxes, in order to withstand the wind and sun and its own weight, often using thicker acrylic (PMMA) or PC board.
Attention to thickness uniformity: uneven thickness of the material will lead to inconsistent stretching of the sheet in the blister process, affecting product quality, local thinning, rupture and other issues. Therefore, we should choose the material with good thickness uniformity, or test and screen the material before processing.
Quality control:
Check the appearance quality: the surface of the material should be smooth, flat, without obvious scratches, bubbles, impurities and other defects. For transparent or high appearance requirement products, these defects will seriously affect the aesthetics and quality grade of the product.
Testing of physical properties: The tensile strength, bending strength, impact strength and other physical properties of the material are tested to ensure that it meets the requirements for the use of the product. For example, the materials used to manufacture protective covers for mechanical parts need to have high strength and rigidity in order to provide good protective performance.
Concerned about the stability of the material: the material should have good thermal and chemical stability, in the high temperature environment of the blister process does not decompose, do not deform, in the use of the process is not easy to be affected by environmental factors and aging, deterioration. For example, in the outdoor use of blister products, need to choose a good weather resistance of the material, in order to ensure the service life of the product.
Environmental requirements:
Conform to environmental standards: With the improvement of environmental awareness, many products have strict requirements on the environmental protection of materials. We should choose materials that comply with the relevant environmental standards, such as the EU RoHS Directive, REACH regulations, etc., to avoid the use of materials containing harmful substances to the environment and the human body.
Considering the recyclability of materials: choosing recyclable materials is conducive to reducing the pollution of waste to the environment and reducing the waste of resources. For example, PET, PP and other materials have good recyclability, and can be prioritized in product design and material selection.
Cost factor:
Comparison of the cost of different materials: there are differences in the price of different materials, different brands of materials, under the premise of meeting the performance and quality requirements of the product, the comparison of the choice of cost-effective materials, in order to reduce production costs. However, the price should not be the only measure, but also need to consider the quality of the material, processing performance and other factors.
Accounting for material utilization: the shape and size of the material will affect its utilization in the blister processing. Reasonable choice of material specifications, optimize the layout and cutting methods, improve material utilization, is also an important part of cost reduction.
Heavy gauge thermoforming molds types:
According to the shape of the mold :
Convex mold:
The advantages are easy to reduce the size of the mold, the B surface is smooth and clean, suitable for automotive dashboards and other requirements of the B surface exposed to the outside of the parts. The disadvantage is that the thickness of the material is thicker than the concave molding, material stretching, A surface roughness, and freezer refrigerator liner, bathtubs and other requirements of the A surface of the product is not very suitable for smooth.
Concave mold:
The inner surface (A-side) is not in contact with the mold, so the surface is smooth and clean, and it is suitable for parts that use the inner surface as the use surface, such as refrigerator and freezer liners. In addition, under the premise of ensuring the size of the inner surface, the thickness of the plate can be reduced, thus saving material and making molding relatively easy. However, its mold size parameters are not easy to grasp, the internal size of the mold is easy to expand, difficult to reduce, vacuum molding also need to configure auxiliary molding tooling.
According to the mold material points :
Gypsum mold:
The production cost is low, is in the state of gypsum half-wet carving molding, and then drying that is into the mold. Its hardness is small, plasticity is strong, easy to modify, but the precision is not high enough, the surface is not smooth and fragile and not durable, often used for sampling, to do electroplating copper mold mold species or some of the requirements are not high for small batch production of blister molds.
Electroplated copper mold:
Plating a layer of copper shell on the basis of the sample made of plaster mold is electroplated copper mold. Its production cost is higher than the plaster mold, but cheaper than the aluminum mold, with the advantages of surface finish and durability, is a commonly used vacuum mold.
Aluminum mold:
The use of aluminum ingots through mechanical processing, relatively high precision, smooth surface. Aluminum mold is good, but expensive, generally used in high precision requirements, copper molds can not reach the blister products.
Case Study: Heavy Gauge Thermoforming Applied in Auto Industry
Case Background
Automotive interior parts have an important impact on the comfort, aesthetics and functionality of the car. With the development of the automotive industry, consumers have higher and higher requirements for the quality and personalization of automotive interiors, and thick sheet blister technology is increasingly widely used in the manufacture of interiors because it can meet these diversified needs.
Product design and mold making
Product design:
Automotive interior parts, such as instrument panels, door panels, etc., usually have complex shapes and structures, and need to consider ergonomics, functionality, and coordination with the interior style of the entire car.
Take the instrument panel of a certain sedan as an example, its design should not only meet the driver’s convenience in operating the instrument and control equipment, but also take into account the overall aesthetics and comfort, so it adopts a streamlined design, and some textures and decorative lines are designed on the surface to enhance the texture of the interior.
Mould making:
According to the product design, aluminum mould is chosen. Aluminum mold has the advantages of high precision, smooth surface and strong durability, which can ensure the molding quality and dimensional accuracy of the interior parts.
In the process of mold making, CNC machining center is used to carve and process the aluminum ingot accurately to ensure that every detail of the mold meets the design requirements. At the same time, special treatment is carried out on the surface of the mold to improve its demolding performance and prevent the plastic parts from being damaged or deformed during demolding.
Material Selection
ABS plastic is usually chosen as the main material for plastic injection molding, which has good mechanical properties, heat resistance, cold resistance and chemical stability, and can meet the requirements of automotive interior parts in different environmental conditions.
Its surface hardness is high, not easy to be scratched and abraded, and can maintain the aesthetics of the interior parts. In addition, ABS plastic also has good processability and painting performance, through a variety of surface treatment processes, such as painting, plating, etc., to achieve different colors and decorative effects, to further enhance the quality and personalization of the interior parts.
Production process of thick sheet blister molding
Heating and softening: Put the cut ABS plastic sheet into the heating device of the blister machine and heat it up to a suitable temperature to make it become soft and moldable. Generally the heating temperature is between 150℃-200℃, the specific temperature is adjusted according to the thickness and material of the plastic sheet.
Forming: The heated plastic sheet is quickly transferred to the top of the mold, and by means of vacuum or air pressure, the sheet is tightly adhered to the surface of the mold, forming the same shape as the mold. During this process, precise control of the air pressure or vacuum level, as well as the molding time, is required to ensure the quality of the molded plastic part.
Cooling and Curing: After molding, the plastic part is cooled naturally in the mold or quickly cooled by a cooling device to cure and set the shape. The length of cooling time will also affect the performance and dimensional accuracy of the plastic parts, which need to be reasonably adjusted according to the specific situation.
Demolding and post-processing: The cooled plastic parts are taken out from the molds, after cutting, trimming, drilling and other post-processing procedures, to remove excess corners and burrs, and to carry out the necessary assembly hole processing. Then, the surface of the interior parts will be sanded, polished, painted, etc., so as to meet the final quality requirements and appearance.
Advantages
Design Flexibility: Thick-sheet blister technology is capable of molding complex shapes and structures in one piece to meet the diverse design needs of automotive interior parts. For example, in the case of the instrument panel above, smooth lines and curved surfaces can be produced through the blister molding process, providing more creative space for automotive interior design.
Cost-effectiveness: Compared with the traditional injection molding process, the mold cost of thick-sheet blister is lower and the production cycle is shorter. For small-lot, multi-variety production of automotive interior parts, it can effectively reduce production costs and development cycles, and improve production efficiency.
Quality and performance: The interior parts made of thick sheet blister have good dimensional accuracy and surface quality, which can ensure the precise assembly with other parts. At the same time, the performance advantages of ABS plastic make it outstanding in the durability and comfort of interior parts, such as good heat resistance to prevent deformation at high temperatures, and cold resistance to ensure that it will not become brittle and fragile at low temperatures.
Lightweight: Plastic interior parts are lighter in weight than traditional metal or wood interior parts, which contributes to the lightweight design of automobiles and reduces fuel consumption and exhaust emissions, in line with the development trend of environmental protection and energy saving in the automotive industry.
Disadvantages and countermeasures
Material performance limitations: Although ABS plastic has a variety of excellent performance, but in some special performance may not be as good as other materials, such as fire performance. To address this issue, the material can be modified by adding flame retardants and other ways to improve its fire performance to meet the relevant safety standards for automotive interior parts.
Dimensional stability: In some extreme temperature or humidity conditions, plastic interior parts may have dimensional changes. In order to improve dimensional stability, some stabilizers can be added to the material formulation, while optimizing the production process parameters, such as controlling the heating and cooling speeds, to reduce the impact of dimensional changes.
Surface quality problems: Surface defects, such as bubbles, wrinkles, etc., may occur during the thick sheet blister molding process. By optimizing the mold design, adjusting the molding process parameters, strengthening the quality control of raw materials and other measures, you can effectively reduce the probability of surface quality problems, and improve the yield rate of the product.