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I. Common Questions

In industrial design or medical device development, customers often face this dilemma: you need a large‑sized plastic enclosure (e.g., medical equipment covers, robot housings) but are caught between two options:

· Production injection molding: high cost, long lead time, not economical for small batches

· CNC or 3D printing: expensive for large sizes, parts need to be spliced, surface quality hard to guarantee

Low‑pressure casting (RIM) becomes the ideal solution to this contradiction.

II. What is RIM?

In one sentence:

Reaction Injection Molding (RIM) — two liquid components are mixed and injected into a mold at low pressure, where they chemically react and cure to form the part.

Key features:

· Low pressure, low temperature, low mold cost (cheaper than steel molds, though still requiring some investment)

· Suitable for small‑to‑medium batches and high‑mix production of large‑sized parts

III. 4 Reasons Why RIM is Ideal for Large Enclosures

1. Low mold cost and suitable for small‑to‑medium batches

· Options include resin molds, ABS molds, or metal molds, priced lower than injection molds but still with certain costs

· Suitable for small or medium batch production

o Resin mold: 20–200 pcs

o Aluminum mold: 100–5000 pcs

o Steel mold: >20,000 pcs

· Short mold manufacturing lead time (1–2 weeks), facilitating rapid trial production and quick changeovers for multiple product variants

⚠️ Note: If your quantity is too small (<20 pcs) or too large (>5000 pcs), RIM may not be the optimal choice — the mold type and cost economics need to be evaluated carefully.

2. Excellent flowability, filling large sizes with ease

· The mixed material has low viscosity, flows at low pressure over long distances, easily filling large and thin‑walled structures

· Unlike injection molding, which requires extremely high clamping force, RIM uses much smaller equipment investment

· Especially suitable for uniform filling of large‑sized, thin‑wall areas

3. No sink marks on thick‑walled parts, excellent appearance

· During the reaction process, the material does not foam or shrink, keeping thick‑wall areas flat and smooth

· Ideal for enclosures requiring a sturdy, high‑strength feel

· Reduces post‑processing costs, especially suitable for high‑appearance‑demanding applications like medical and robotics

4. Adjustable material properties, similar to engineering plastics

· By adjusting formulations, we can simulate hardness, toughness, and heat resistance of materials like ABS, PC, and PP

· Corrosion‑resistant, impact‑resistant, and weather‑resistant, meeting requirements for medical, robotics, and industrial equipment

IV. RIM vs Other Processes

Key point: RIM excels in small‑to‑medium batch large‑sized parts. Different mold types suit different quantities — the choice should be based on actual production needs.

V. Our Differentiating Advantages in RIM

· Years of practical experience: Serving medical, robotics, aerospace, and other fields with numerous successful cases

· One‑stop support: After RIM molding, we perform sanding, painting, silk‑screen printing, and assembly all within the same facility

· Flexible mold options: We recommend resin, silicone, aluminum, or steel molds based on quantity — never blindly push for expensive steel molds

· In‑house material development: We master various PU formulations to meet special requirements such as flame retardancy, anti‑static, and weather resistance

VI. Which Products Are Best Suited for RIM?

· Medical equipment enclosures (e.g., ultrasound devices, CT covers, medical carts)

· Robot housings (service robots, AGVs, industrial robot protective covers)

· Aerospace ground support equipment housings

· Large instrument and meter casings

· Thick‑walled parts with appearance requirements and no sink marks

Low‑pressure casting (RIM) is one of the ideal solutions for large‑sized, small‑batch plastic enclosures.
We offer a complete RIM solution from mold design to finished product delivery.
If you have a large enclosure that needs custom manufacturing, feel free to send us your drawings for a consultation — we will recommend the most suitable approach for you.