Silicone Prototypes & Short Run Parts


Casco Bay Molding produces prototypes, or short run liquid silicone rubber (LSR) parts, with quick-turn tool steel core and cavity sets. These core and cavity sets run in one of our LSR tool steel mold bases. Normally, we can turn around core and cavity sets for simple parts in 3-7 weeks, subject to prior orders and assuming we receive a clean Solidworks, STEP or IGS file.

Minimizing the customer’s up front tooling investment is an important part of our product development service. Casco Bay Molding’s in-house engineering and mold shop, enables us to provide quick-turn tool steel core and cavity sets and mold modifications for short run or prototype LSR projects.

Direct Inject Cold Runner System
Casco Bay Molding has invested in a Micro Molding Silicone core and cavity set that is integrated with a valve-gated Micro Molding system.  Shot to shot consistency is obtained with accurate valve gate control per the Casco Bay Molding Kipe Mold “cold deck” mold base, and used for short run or high production LSR part production.

3D Printed Prototypes
To our knowledge, there currently is no Stereo lithography (SLA) or 3D Printer capable of producing Silicone based material available. The closes SLA- 3D Printed material that mimics silicone durometers is a PolyJet vinyl based material. PolyJet is far from ideal when compared to LSR, as it is brittle, has no real elongation, and out gases vinyl. However, a PolyJet part can be a valuable visualization tool, giving customers something to hold in their hand and immediate feedback on their part.

Hand-Injected Mold Trials
Another technique is to hand inject small molds with our tabletop LSR injection unit. These shortcuts can be helpful for checking actual Silicone shrinkage for a given LSR supplier and grade with a given part thickness or cross sectional area.

RTV Prototypes
Generally, we do not quote Room Temperature Vulcanized (RTV) Silicone Rubber parts. RTV Silicone does not have the same physical characteristics as LSR and is normally a 10:1 ratio requiring special pumping equipment or hand mixing.  Frequently, RTV parts are “baked” in an oven after injection to accelerate part curing.

Aluminum Tooling
We have employed Aluminum tooling, however, the small material savings is not worth the disadvantage of having the AL warp after thermal cycling. Core & cavity (C&C) sets are ideal for producing LSR parts, generally running between 300 and 390°F in one of our LSR mold bases.