Molded Rubber Maintaining Quality


There are many steps involved in producing a quality molded rubber part. Some of the most critical elements are:

Custom Molded Rubber Products

  • The rubber compound must be high grade, and free of impurities.
  • The mold must be made of the best materials
  • Equipment
  • Deflashing
  • Manual cutting
  • For medium sized parts
  • Cryogenic freezing

1. The rubber compound must be high grade, and free of impurities. Most people do not realize that because a rubber is labeled NBR, SBR, Viton, FKM, Neoprene, Etc.. Does NOT mean it is 100% made of that material. The Raw rubber used to make parts is called a "compound" because it is actually a blend of materials. The identifying label of the type or Rubber does indicate that the majority of the material in the compound is that material, but it is the highest percentage of that material. This is why there can be quality NBR (for example) parts and inferior NBR parts. American Seal & Packing only works with quality materials.

2. The mold must be made of the best materials and to the tightest tolerances possible for that shape. Molds can be made from Metal, Clay, Glass, Wood, Fiberglass, etc. Anything that can hold the shape, and tolerate the heat of melted rubber. It's important for repeatability, that a quality mold be made, and maintained to produce parts consistently to specification.

3. Equipment - The decision of a single cavity mold or a multi-cavity mold (and how many), must be determined based on your current quantities as well as your projected quantities. Making thousands of parts on equipment that will only accommodate a single cavity mold, will not only slow deliveries, but also increase costs. Knowing what type of equipment is best is also critical for quality parts. Transfer molding, Compression Molding, Injection Molding, Extrusion, and Calendaring and die cutting are all possible ways of making the same part. Knowing what is the best method based on quality, quantity, tolerance and cost is where American Seal & Packing can help.

4. Deflashing - Once a part has been made, there often is a small bit or rubber that shows where the molds that made it mated. That little bit of rubber is referred to as "flash". From a cosmetic standpoint flash is never desirable. From a functional standpoint, it can cause a part to fail, especially in the case of a seal. Flash can provide a leak path. So how do you remove flash ? That all depends on the thickness of the flash, and the type and size of the part. There are several methods

5. Manual cutting. For low quantity large parts, cutting the flash off by hand is the easiest solution. The part may also be buffed to smooth the edges.

6. For medium sized parts, in smaller quantities a removal jig may be used. Place the part in the Jig, and close the razor edge of the jig to remove the flash quickly and easily.

7. Cryogenic freezing: Because "Flash" is thin it will freeze hard faster than the rest o f the part. If frozen via CO2 gas, or Dry Ice nuggets and then tumbled (with deflashing pellets) the flash will break off and leave a smoothly finished part. This method is used for high volume parts that have been compression molded.

Once a completed part has been produced, it must then be inspected and processed for packaging and shipment.