Some Parameter Settings That Should Be Paid Attention To During The Design Process Of Rotational Molded Products

1. Corner radius:

A gentle corner radius helps improve the flow of material within the mold and creates a uniform wall thickness. It also helps distribute stress to a large area, thereby increasing the strength of the product. Generally speaking, a larger arc radius is often used at the corners of rotational molded parts to facilitate the flow of materials, improve the uniformity of the wall thickness of the product, and help suppress the occurrence of internal stress and warpage of the product. Of course, the arc radius It cannot be increased infinitely, otherwise the outer surface of the corresponding part will be concave.

2. Corner:

The ideal rotational molding product is spherical. Smooth corners allow the powder to flow and form a uniform wall thickness distribution. Sharp corners will increase stress accumulation and make it difficult to fill during molding. The minimum corner angle of rotational molded products is 20 degrees, and the recommended angle is 30 degrees.

3. Small spatial distance between parallel walls:

Rotational molding products have unique requirements regarding parallel walls. The two walls can be configured at a short distance, making double-walled products suitable for manufacturing insulated containers, or for making boats. When deciding how far apart the walls should be, one fact must be taken into account: most rotational molding powders are three times as dense as the finished material. Therefore, the required space within the mold is at least three times the space that the powder can fill into the wall thickness material. Theoretically, the wall spacing factor can be three times the wall thickness, but typically 5 times or more will be required to make the filler job easier to implement. Therefore, the small space distance between parallel walls is 5 times the average wall thickness. If the wall thickness of the product is 5mm, then the spacing is 5×5=25mm, and the small spacing should be 3 times the wall thickness.

4. Dimensional tolerance:

The dimensional error of plastic products depends on many factors such as product design, plastic type, and molding process. Designers should strive to apply concepts that allow for the widest possible tolerances. Over-setting tolerances will inevitably lead to higher costs, mold trimming or machining. There are two variables in the size of rotational molded products. One is the quality and accuracy of the mold, which can be processed using CNC machines. The second is the shrinkage rate, which requires understanding of the materials used, size, product thickness, and product design complexity. The dimensional tolerance of rotational molded products is generally 2mm, with a high precision of 0.5mm.

5. Try to avoid large flat designs and reduce large areas to small areas.

Since rotational molding does not have an inner core, the large flat surfaces of the rotational molded part can be pulled away from the mold cavity surface during the cooling phase, causing warpage. Therefore, it is necessary to try to avoid the existence of large flat surfaces.

6. Small width of stiffener:

The use of reinforcing ribs to eliminate the existence of large flat surfaces is a relatively successful approach in industrial applications. The use of reinforcing ribs can not only prevent warping of rotomolded parts, but also improve the rigidity of the product, thereby reducing the wall thickness of the part, improving the use effect of the product, and reducing costs. Generally, the width of the reinforcing rib is 5 times the average wall thickness of the rotomolded product; the height: 4 times the average wall thickness.

7. Flatness accuracy:

Standard flatness ±0.50mm, economical flatness ±0.20mm, high-precision flatness ±0.10mm

8. Draft angle:

Generally speaking, rotomolded products are easy to demould, and some products can even be successfully removed from the mold without any draft. However, a moderate draft can reduce the external force required during demoulding, and have It helps shorten cooling time, improves production efficiency to reduce production costs, and also helps to prevent internal stress and warpage of products.

9. Wall thickness range of rotomolded products:

The wall thickness of plastic products depends on its load-bearing conditions in use, and the same applies to rotomolded products. However, rotational molding products are made under normal pressure and take a long time to form. The strength of rotational molding products (tensile strength, bending strength, impact strength, etc.) is slightly lower than injection molding products of the same plastic. When designing rotational molding products , this factor needs to be considered when calculating wall thickness.

Wall thickness range 1.5~13.0mm; large wall thickness 50.0mm; small wall thickness less than 0.25mm

10. Wall thickness uniformity of products:

It is difficult to produce products with uneven wall thickness by the rotational molding process, and usually rotational molding products are relatively uniform. Except for corners, the wall thickness error can be controlled to ±20%, and in some cases can be controlled to ±10%.