1. Hot compression moulding
Steps: The ABS sheet is heated partially or integrally according to the needs, so that it reaches a softening temperature range of about 100-130°C. Afterwards, pressure is applied with the help of moulds or tools to shape it into the required shape, and the shape is fixed after cooling.
Advantages: Highly flexible and adaptable to complex shapes such as curved surfaces and concave-convex structures; low equipment requirements and low cost, simple tools such as home ovens and heat guns can be used; fast moulding speeds, which is an obvious advantage in small-lot or single-piece production scenarios.
Limitations: Due to manual operation, there are limitations in precision, which may lead to uneven surface and size deviation; for complex shapes, custom-made moulds are often required, which may increase the cost investment; there is a risk of overheating in the operation process, and once the temperature is too high, the material may be scorched and harmful gases will be released at the same time.
2. Vacuum forming
Steps: The whole ABS sheet is heated to a soft state first, covered on top of the mould, and then by vacuuming, the sheet is adsorbed to fit the surface of the mould, and then demoulded after cooling.
Advantages: high moulding precision, especially suitable for thin-walled, large-area and uniformly shaped products, such as packaging boxes, shells, etc.; high production efficiency, suitable for mass production; smooth surface of the moulded product, generally without additional grinding process.
Limitations: high cost of equipment, need to be equipped with vacuum forming machine and special moulds; there are certain limitations on the thickness of the plate, usually for 1-5mm thin plate, thicker plate for vacuum moulding is more difficult to operate; the design of the mould is more complex, encountered in the negative angle or the deep cavity structure, there may be a difficulty in the release of the problem.
3. CNC machining
Steps: Directly use CNC machine to cut, drill, engrave and other processing operations on ABS sheet.
Advantage: high processing accuracy, excellent performance in the production of precision parts, such as gears, structural components; processing without heating, effectively avoiding the material deformation due to heat; design flexibility, easy to adjust the processing path through the software.
Limitations: the phenomenon of material waste is more serious, the cutting process will produce a lot of debris, low material utilisation; the need for professional equipment, and high requirements for the skills of the operator, the cost of investment; the edges of the processed parts will produce burrs, which need to be followed up by grinding treatment.
How to avoid air bubbles in ABS plastic sheet moulding process?
In the process of ABS plastic sheet moulding, the appearance of air bubbles will affect the quality and performance of the product, here are some ways to avoid the appearance of air bubbles:
Raw material selection and processing
Choose high quality raw materials: buy reliable quality, high purity, low water content of ABS plastic sheet. High-quality raw materials have low bubble content and stable performance, which can reduce the risk of air bubbles during the moulding process.
Drying treatment: ABS plastic sheet may absorb moisture during storage and transportation, and the moisture will vaporise into water vapour and form bubbles when heated for moulding. Therefore, before moulding, the ABS plastic sheet should be fully dried according to the moisture content of the raw material and the requirements of moulding. Generally, it can be dried in an oven at 80-90°C for 2-4 hours, and the specific time and temperature can be adjusted according to the thickness and moisture content of the sheet.
Control of moulding process
Temperature uniformity: Ensure that the temperature of the heating equipment (such as oven, hot air gun, strip heater) is uniform and stable. If the temperature is not uniform, and the ABS plastic sheet is partially overheated or under-heated, the over-heated part may generate gas and form bubbles due to thermal decomposition, while the under-heated part may form bubbles due to air encapsulation caused by uneven softening. When using the oven, you can place the temperature uniformity test device inside, regular testing and calibration; when using the hot air gun to maintain the appropriate distance and speed of movement, so that the heat is evenly transferred.
Avoid overheating: Strictly control the heating temperature and time to prevent the ABS plastic board from overheating. Overheating will cause the plastic to decompose and produce gas, thus forming bubbles. The heating temperature and time required for different thicknesses of ABS plastic sheets are different. Generally speaking, as mentioned above, the heating temperature of the oven is in the range of 100-130°C, and the heating time is 5-10 minutes.
Experienced operators will choose a conservative temperature to test at first, and then adjust the parameters based on the first test. Five to eight rounds of testing are generally required to determine the most appropriate parameters when first working with this material. If you have questions about blister moulding, you can contact us to recommend the right parameters for you.
Pressure control: When moulding or vacuum forming, the appropriate pressure should be applied. Insufficient pressure may prevent air from escaping between the plastic sheet and the mould, resulting in the formation of air bubbles; too much pressure may damage the plastic sheet or the mould. When vacuum forming, make sure the vacuum level is sufficient, generally the vacuum level needs to reach 0.08-0.1MPa, which can be monitored and adjusted by vacuum gauge.
Air venting operation: In the process of mould design and use, it is necessary to reasonably set up air venting holes or air venting slots, so as to let the air out smoothly during the moulding process. For complex shaped moulds, it may be necessary to set up exhaust structures at multiple locations to ensure that air can be discharged from all parts in a timely manner.
Environment and Equipment Maintenance
Environmental humidity: Keep the moulding working environment dry, humidity is generally controlled at 40%-60%. High ambient humidity will increase the possibility of the plastic sheet absorbing moisture, resulting in air bubbles during moulding. Dehumidifying equipment can be used to adjust the ambient humidity.
Equipment cleaning: Clean the heating equipment, moulds, etc. on a regular basis to prevent dust, oil and other impurities from mixing into the ABS plastic sheet, which may cause air bubbles or affect the flow and fusion of the plastic during the moulding process.
