Technical Information: Reaction Injection Molding (RIM)

Download the PDF version of this document

What is it?

Simply stated, in this process two liquid components - - component "A", a formulated polymeric isocyanate, and component "B", a formulated polyol blend, are mixed in a high pressure head and then pumped into a mold cavity. A reaction then occurs in the mold, resulting in a high density polyurethane structural foam part.

How, Why & When to Use It:

  1. To produce covers, bases, keyboards, bezels and housings for computers, business machines and medical applications.
  2. For prototype through medium volume applications (1 - 2,000 pieces).
  3. There is considerable design freedom to produce complex shapes.
  4. Molds can be resin, spray metal, cast aluminum or machined aluminum.
  5. Tooling is low cost and allows for ease of modification.
  6. A variety of castings, sheet metal and threaded inserts can be molded in place.
  7. Alternative foams are available which offer a range of insulating properties.
  8. UL traceability.

Design & Technical Information

Size

Up to 48 in.

Weight

Up to 18 lbs.

Finish

If required:

  • No bake prime and paint
  • RF shielding
  • Silk screening

Wall thickness

Can vary but should not be less than 1/4 in., although local thicknesses of 1/8 in. can be produced.

General tolerance

Note: tighter tolerances can be negotiated.

  0 in. -   3 in. +/- 0.010 in.
  3 in. -   6 in. +/- 0.015 in.
  6 in. - 12 in. +/- 0.020 in.
12 in. - 18 in. +/- 0.030 in.
18 in. - 48 in. +/- 0.040 in.

Holes

All holes molded to size.

Draft

Recommended 1 - 2 degrees, but no draft is possible when specified.
Radii and fillets - should be as liberal as possible (1/8 in. to 1/4 in.).

Density

Can be varied, depending on foam used, to offer a variety of insulation properties.

A variety of materials are available that offer a range of insulating and mechanical properties with 94V-0.
Detailed specification sheets are available on request (email requests to sales@armstrongmold.com)

Comparison Chart RIM vs. Injection Mold Properties

Material Units R I M Polystyrene ABS Modified
PPO
Specific gravity   0.85 0.85 0.89 0.85
Thickness (in.) 0.25 0.25 0.25 0.25
Flexural modulus (psi) 220,000 275,000 240,000 261,000
Flexural strength (psi 9,500 5,700 6,000 6,800
Tensile strength (psi) 5,800 2,300 3,000 3,400
Elongation (%) 10 20 - - 16
Gardner impact + + (in-lb) 74 28 52 55
Falling ball (ft-lb) - - - - - - 18
Dart impact (ft-lb) - - - - 10 - -
Heat distortion temperature          
  @ 66 psi (F) 212 183 177 205
  @ 264 psi (F) 180 168 162 180

The above properties are intended as a guide only and may vary depending on thickness and shape.

Download the PDF version of this document

 
AS9100 Rev CArmstrong RM tagline ITAR certified Armstrong RM tagline

©2009 Armstrong RM Corp. All Rights Reserved.