FAQ

     The positioning jig is a part of the rotomolding mould. rotomolding mould is suitable for manufacturing large-sized products, and the shrinkage rate of such products is relatively high. For products with size requirements, we will need to use the positioning jig.

Materials Used in Rotomolding

The most common material used in roto molding is Polyethylene (PE), accounting for 97% of rotomolded products. This material is versatile, available, and easy to mold. It can be easily ground to powder, which is suitable for this technique (which usually requires powder over granules).

Other options for rotomolding include:

• Polypropylene (PP): Although this material has poor impact strength at cold temperatures, it has great resistance to cracking from chemical and environmental stress, superior stiffness, and a higher thermal distortion temperature.
• Nylons (PA): Because of their excellent technical performance, nylon materials are perfect for rotational molding applications. Though some nylon types (Nylon 6) require an inert atmosphere (usually nitrogen), making the roto molding process a bit complicated, its low cost can make up for the challenge.
• Polycarbonate (PC): It’s a translucent, high-strength polymer with built-in flame retardancy. Polycarbonate may need extensive technological processing due to its poor impact resistance.
• Plasticized polyvinyl chloride (PVC): It’s a liquid substance that resists certain chemicals and has good weathering and aging qualities. Each grade has different flexibility, impact, and temperature performance.
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How Does The Roto Molding Process Work?

The roto molding process consists of 5 simple steps:

• Powdered plastic material is poured into a hollow mold.
• After starting a biaxial rotation, the mold is moved inside an oven.
• The mold keeps rotating while the resin gradually melts and covers the mold’s walls.
• Once the melting process is finished, the mold is transferred to a cooling station to cool down by air or a fine mist of water. During the cooling stage, the resin solidifies into the desired form.
• After stopping the rotation, open the mold and remove the finished object.
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Youge Rotational Mold Factory discusses with you:

1) The structure of the mold is very important.

2) The melting and adhesion capabilities of plastic materials are closely related to the mold temperature.

3) The rotational speed requirements for processing different products are different.

4) The level of processing technology is very important.

Welcome to the Youge factory to find the best solution.

What are the causes of pinholes and bubbles in rotational molding products?
The gas in the raw material was not completely expelled. During processing, the raw material in the mold gradually melted and flowed due to heating and adhered to the mold cavity. During this process, the gas remaining in the raw material was gradually pushed towards the surface. However, due to the existence of the surface tension of the melt, if the force to push the gas outward is insufficient, it will be unable to detach from the surface of the melt and can only remain trapped in the raw material. Thus, bubbles and pinholes are formed on the surface of the product.
2. The diameter of the mold vent pipe is too small or blocked. In some molds, the pressure inside and outside is not balanced enough. The internal pressure increases, and the resistance increases when the gas escapes, resulting in residual gas in the raw material and causing bubbles and pinholes in the product.
3. Improper selection of raw materials. Research shows that the melt flow rate of raw materials is related to the number of bubbles produced on the surface of the product, and the size of the bubbles is also related to the particle size and particle size distribution of the resin and additives used. The larger the particle size, the larger the bubbles and the fewer the number of bubbles.
4. If bubbles and pinholes appear at the parting line on the surface of the product. It might be due to the fact that the parting surface of the mold does not fit tightly.
5. If there are sand holes and air holes on the cavity surface of the mold, or air holes at the welding points of the mold, it will also cause corresponding bubbles and pinholes to appear on the rotational molding products during molding.
6. If the product only has bubbles and pinholes in some local areas, it indicates that the mold structure in these areas is not conducive to gas leakage.
For more rotational molding technology solutions, please contact Youge Rotational Molding Mold Factory!

Cindy:
Why do bubbles appear on the threads of rotational molding products? Now let's explore together: 1. Material issues:
The materials used may contain a large amount of volatile substances or moisture, which will produce bubbles during the heating process. A too low melting index of the material may also lead to the formation of bubbles.
2. Temperature issue:
If the heating temperature is insufficient or the heating time is not enough, the material will not be heated thoroughly, making it difficult to adhere to the mold and thus resulting in bubbles.
3. Mold Design:
If the diameter of the vent pipe in the mold is too small or blocked, the pressure inside and outside the mold will not be balanced enough. The internal pressure will increase, and the resistance will increase when the gas overflows, resulting in residual gas in the raw material and thus causing bubbles in the product.
If the parting surface of the mold does not close tightly or there are sand holes and air holes on the cavity surface of the mold, it may cause bubbles to appear on the rotational molding products during molding.
4. Gases in raw materials:
The gas in the raw material was not completely discharged. During the heating process, it gradually melted and flowed, adhering to the mold cavity. During this process, the gas remaining in the raw material was gradually pushed towards the surface. However, due to the existence of the surface tension of the melt, if the force to push the gas outward is insufficient, it will be unable to detach from the surface of the melt and can only remain trapped in the raw material, thus forming bubbles on the surface of the product. For more information about rotational molding, please contact Youge Rotational Molding Mould Company!

1. About YOUGE Mould Factory

We are a professional rotary mold manufacturer in China, with more than many years of experience.

2. How do we guarantee quality?

Molds and products are inspected by UTG QC team.

100% pre-production samples before mass production;

100% final inspection before shipment;

3. What can you buy from us?

Rotary mold and PE products, tailored for you.

4. Why do you buy from us instead of other suppliers?

With more than 16 years of professional rotoplastic team, high-quality aluminum mold, fast delivery, reasonable price, from engineering design, mold to the final plastic product OEM service. Own QC team, transport arrangements.

5. What kind of services can we provide?

Acceptable delivery methods :FOB,CIF,EXW,DDP, express;

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Payment accepted: wire transfer, Letter of credit, Western Union;

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