Flexible Parts - Rapid Prototyping (RP) and Low Volume Production
Many parts designed from rubber or flexible elastomers require prototyping. However, there are few options that give an acceptable result, especially if the component is part of a sealing system. This is frequently compounded by a degree of uncertainty relating to the hardness of the material being specified.
Direct Rapid Prototyping (RP) solutions include elastomers and resins that can be used within the polyjet (Objet) or laser sintering processes. However, the speed advantage that this brings also carries a downside, in this case material strength or surface finish.
Vacuum casting or injection moulding carries a time penalty compared to the direct methods but does offer a variety of hardness's and superior surface finish.
These and others are covered though the links opposite to assist you in sourcing the most applicable option for your requirement. If you are in any doubt, then please contact Plunkett Associates directly.
From a prototyping perspective the attraction of Objet is the 16 micron layer thickness, especially when dealing with flexible materials that are very difficult to post process. A number of Shore hardness’s are available direct from the process. Surface finish is significantly better than the Laser Sintering options, but tear strength can be low.
Laser Sintering (or Selective Laser Sintering - SLS)
There are several material options available that will achieve hardness ratings from circa 40 – 80 Shore A. These materials are typically infiltrated after sintering and this can be used to affect the hardness and add colour. The materials offer a reasonable degree of functionality and elongations exceeding 250% can be achieved.
Ideally suited to producing a small batch of flexible prototypes. The biggest advantage must be the ability to easily bracket a hardness rating when the desired value is unsure. Utilising a CNC or RP pattern, a silicone tool is used into which the polyurethane is cast. Finishing of the pattern dictates the resultant surface finish of the part as the silicone picks up every detail. Parts require no further dressing, only feed and riser removal.
Usually only considered as a production process, injection moulding will give the production intent material properties. A wide range of TPE’s offer a variety of mechanical properties to suit most applications. Leadtime remains a function of geometry unless the flexibility of the part can be used to assist demoulding.