【Technical Q&A】Fancier Surface and Lower Cost Thanks to RIM 2.0

YIZUMI presented ReactPro Integrated Solution of Polyurethane and Injection Molding (short for RIM) at CHINAPLAS 2021 after the CHINAPLAS 2019 and Germany K show 2019. The 2.0 version of the solution produces parts that are not only soft-touching, self-repair, corrosion-resistant, and scratch-resistant but also have a high-gloss, matte appearance. The total cost will be reduced significantly when adopting domestic PU materials.

The ReactPro Solution is jointly developed by YIZUMI and FRIMO Germany, which offers one-step injection molding for parts and their polyurethane coating by a single injection molding

Technical Q&A

——ReactPro Polyurethane and Injection Molding Integrated Solution

Q:How can ReactPro achieve injection molding and polyurethane coating in one single step?

A: The one step parts production process of injection molding and polyurethane (PU) coating is made possible through a combination of injection molding machine and PU system. The key is the mix head which connects the two machines.

Both injection mold and PU mold are mounted on the injection molding machine with the PU mold connected with the PU system through the mix head. The plastic substrate is made first by the injection molding machine and then moved to the PU mold by a robot. PU material is formed by two groups of ingredients: A and B (polyol and isocyanate). They are stored in two storage tanks of the PU system separately and conveyed to the mix head through feeding pipes. The A and B materials will be rapidly and evenly mixed in the mix head under high pressure and then injected into PU mold cavity by the injection nozzle. The ingredients will react under certain conditions and solidify on the surface of the plastic substrate. This is a continuous process, which saves the time and cost of bonding the plastic substrate and PU layer as semi-finished products. It greatly improves the efficiency and quality of the production.

Q: What is the hardness of the high gloss surface treated by ReactPro technology?

A: Soft touch PU on engine cover: Shore hardness about 80A

Hard touch PU on engine cover: Shore hardness about 70D

Surface hardness can be adjusted according to customer’s requirements (in the range of Shore hardness 70A~80D)

Q: How thin the PU layer can be by using ReactPro technology?

A: With part yield guaranteed, the thickness of PU coating can reach 0.3mm for partswith simple structures such as flat parts. If the part has a more complex design with curved surface, rounded corners or different thickness requirements on the same plane, the thickness may be increased according the customer’s requirements and the performance supported by the PU material.

Q: What are the common defects of PU coating?

A: If the processing conditions are not controlled properly during the injection process, you may find blowholes in the PU coating or short shots in the mold cavity. In such case, you need to increase the pressure in the mold to solve the problem.

Q: What requirements does the PU coating have on the sprue design? Is there any special requirement on the shape of the sprue?

A: PU materials have low viscosity and good fluidity after melting. Similar to the design requirements for most materials, the layout of sprue should follow the principle that results in shorter runners and properly allocated to cover all sections of the mold through mold flow analysis.；

Thesprue feeding process is similar to water control in the hose. With the sameamount of PU supply, the sprue that has a wide and round shape will show lesspressure and larger flow. When the shape of the sprue is flattened, it willdemonstrate higher pressure and smaller flow. Therefore, it needs to beadjusted according to the specifications, processing temperature, and meltviscosity of the PU material.

The ReactPro solution adopts the InPUR "1+2" mold technology jointly developed with GK Concept Germany, in which two PU molds alternately coordinate with one injection mold to create a shorter cycle time. Although the polyurethane reaction time still takes about 2 minutes, the molding cycle is greatly shortened to about 1 minute. In addition, the InPUR “1+2” mold technology doesn’t require any swivel units such as conventional horizontal or vertical rotary tables and therefore the design is more compact, considerably saving the cycle time of batch production.

The engine cover with the soft and self-repairing PU surface below is produced by the ReactPro solution. Its surface transparency and color can be adjusted according to the needs of the customer, and 3D depth surface effect is also available for the customers. Additionally, high-gloss effects and matte effects can appear on the same surface. The PU thickness of the engine cover is about 0.5-0.6 mm, and the PU material we use is self-releasing, which makes it very convenient for the entire production.

YIZUMI’s ReactPro solution is suitable for the production of new-generation automotive upholstery (such as instrument board, door panel, and intelligent component). Some automotive upholstery from BMW and Benz has used polyurethane coating on its decorative surfaces and functional surfaces. Meanwhile, the polyurethane coating has tremendous potential in the 3C and appliance industries due to its good performance, raising the possibility of better product design.

Product: Engine Cover

Molds：InPUR 1+2 innovative molds

Material: AKROMID® RM-D GF20 + Puroclear®

Part size (L x W x H)：400 × 350 × 25 mm

Product Weight: 470g

Cycle time: 70s