Custom Rubber Molding

Rubber Production Capability

Ro-Lab has the press capacity for small, high-volume production as well as production of large-scale parts.  We have over 75 presses up to 80” wide with 40-2500 ton capacity. Platen sizes are up to 20 feet long and 50 feet wide.  In-house Branbury mixing allows us to produce custom compounds.

Rubber Molding Processes

Ro-Lab has several processes available to produce the ideal rubber part for your application.

  • Rubber Compression Molding: Rubber compression molding is the most widely used production method for rubber molding and the simplest method used for the production of elastomeric materials. In this process, material is placed directly into the cavity of the mold. Pressure is applied which forces the material to conform to the cavity shape. The cure occurs as the pressure and heat cause the thermoset material to crosslink. For the ability to meet close tolerances, compression molding is the preferred process for gaskets, seals and o-rings.Ro-Lab’s 1,400 ton compression press is ideal for large molds, or thin sheets with close tolerances. There is ample capacity for production of large-scale parts; as well as smaller, high volume runs. Multi-cavity molds can produce tiny parts down to two grams. Our equipment allows for continuous curing for long, uninterrupted items.

  • Rubber Injection Molding: This process most commonly injects preheated thermoplastic or thermosetting polymers directly into a mold. It is capable of molding parts more intricate than both transfer and compression molding. The advantages of injection molding: – Delivers faster curing times than compression or transfer molding –  Shortens cycle times – Ideal for high volume component production Compared to compression molding, injection molding is a more complex process that injects a preheated material into the cavities of a closed mold.

  • Rubber Transfer Molding: In a process that is a hybrid of compression and injection techniques, a piston forces preheated material from a transfer pot into a closed mold. Transfer molding advantages include: increased productivity, product quality and product consistency. Molding with inserts is possible where either a metal or ceramic insert is placed into the cavity prior to injection and the heated plastic bonds to the insert during rubber molding process. This process is capable of molding part shapes that are more intricate than compression molding. This is because transfer molding uses a closed mold and can therefore achieve tighter tolerances. It produces a good surface finish and has dimensional stability.​In summary, the benefits of rubber transfer molding are:
    • Finished components with intricate shapes
    • Compatible with the use of delicate insets
    • Delivers tight dimensions and tolerances
    • Usable for all rubber durometers
  • Special Rubber Processes: Ro-Lab produces hoses, rolls, lined pipes, and other mandrel-made products.

  • Hoses are hand built on a mandrel (cylindrical form) in a variety of configurations:
    • Soft or wire reinforced walls
    • Plain ends, or duck and rubber flanges with back-up rings
    • Built-in nipples
  • Other Mandrel-made products:
    • Non-hose mandrel-made products with 4” – 60” diameters with lengths to 50’
    • Rubber transition chutes
    • Mandrel-made endless belts
  • Industrial and agricultural rolls:
    • Rubber or urethane covers
    • New or stripped/recovered cores
    • Roll regrinding
    • Crowns and grooves
  • Rubber-lined pipes for mining, oil and gas

Rubber 101

Rubber Basics – There are two types of rubber, natural and synthetic. Natural rubber is an elastic polymeric substance made from latex of a tropical plant and synthetic rubber is produced from the polymerization of oil byproducts. Rubber whether natural or synthetic, is a great alternative to plastic and metal for applications that require a more elastic solution. Rubber also has waterproof, electrical insulating and tearing resistant properties. Some types of rubber are resistant to oils, solvents and other chemicals.

Durometer (hardness) – Depending on the type of rubber the hardness will range from Shore A (softer) to Shore D (harder) to Shore 00 (foam/sponge). Rubber products range from sponges and erasers to bowling balls and tires.

Tensile & Tear Strength – The tensile (tension) and tear strength of rubber will vary based on the type of rubber.  For the most part, rubber in general has a fair to excellent tear and tensile strength. Therefore it is important to select the proper rubber type that best fits your application.

Advantages Varied Resistances Levels
Elasticity Abrasion
Resilience Impact
Hardness Flexibility Shearing/Tearing
Tensile & Tear Strength Flexibility Atmospheric (Oxygen/Ozone/UV)
Machinability Temperature
Noise Reduction Water
Vibration Reduction Chemicals

Compare Properties

Property Polyurethane Nitrile Rubber Neoprene Rubber Natural Rubber SBR Butyl
Tensile Strength (MPa) 20.7 to 65.5 13.8+/- 20.7+/- 20.7+/- 18.8+/- 18.8+/-
Durometer 5A to 85D 40 to 95A 40 to 95A 30 to 90A 40 to 90A 40 to 75A
Specific Gravity 1.10 to 1.24 1.0 1.23 0.93 0.94 0.92
Tear Resistance Outstanding Fair Good Good Fair Good
Abrasion Resistance Outstanding Good Excellent Excellent Good-Excellent Good
Compression Set Good Good Fair-Good Good Good Fair
Rebound Very High to Very Low Medium High Very High Medium Very Low
Gas Permeability Fair-Good Fair Low Fair Fair Very Low
Acid Resistance Fair-Good Good Excellent Fair-Good Fair-Good Excellent
Aliphatic Hydrocarbons Excellent Excellent Good Poor Poor Poor
Aromatic Hydrocarbons Fair-Good Good Fair Poor Poor Poor
Oil and Gas Resistance Excellent Excellent Good Poor Poor Poor
Oxidation Resistance Outstanding Good Excellent Good Good Excellent
Ozone Resistance Outstanding Fair Excellent Fair Fair Excellent
Low Temperature Resistance Excellent Good Good Excellent Excellent Good

Durometer (Hardness) Scales

Relevant Resources

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