Rubber flash at the tool parting lines requires additional manufacturing processes to remove it, additional quality assurance (inspection) steps to monitor the level and effectiveness of flash removal, creates scrap rubber which must be handled and accounted for, all of which adds to the overall production cost. Also, some types of rubber parts have such critical surface finish and dimensional tolerances that only trimless mold technology can be used to produce them. Although the capital cost of the tooling is much higher and the maintenance requirements are stricter, trimless tooling virtually eliminates part flash and its associated margin-reducing production costs.
These molds provide better performance if transfer molding is used due to the high control of injection volume they permit. Although this type of molds are high end and tend to be expensive, they may be considered a cost efficient solution for certain particular purposes. A careful review of the customers requirements is conducted for each case so as to determine whether using these molds is worth.