13 Questions for Designing Parts in Silicone

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Every part design poses the same initial question, “what is my design intent?” There are many decisions to be made when designing a silicone part. Have you considered the following questions before finalizing your part design or requesting a quote?

 

Material

  • Is your material compatible with the part’s intended function? Different grades of silicone are processed in different level controlled environments; the higher the grade (more pure) the more stringent controlled environment is used. Some silicone producers will certify every batch of silicone that they manufacture. Medical device companies will require lot traceability, which at Albright goes back to the material supplier. There are many silicones available that are suitable for contact with the human body. There are also grades available for short and long term implants. Silicone is a key material to the medical industry with many applications.
  • Will colorant or additives need to be mixed in to your material? Some silicone can be mixed with other materials; such as colorants. Other additives available include barium sulfate, tungsten and titanium dioxide, which are all used so that silicone parts can be detected in x-rays or other medical operations.
  • What durometer material would you like? Silicones are available in multiple durometers depending on the strength your design will need. If your durometer is too soft the part will feel very sticky. If you want a very high durometer your part will feel glass like.
  • Will you be overmolding a silicone part? Overmolding takes a bit of practice to find out which materials adhere best to one another. R&D hours are normally charged to cover the development of an overmolding process, which involves molding to a substrate.

Design

  • What tolerance will allow your part to function correctly? Silicone is very deformable and generally tolerances are over specified. Tighter tolerances lead to more expensive molds and parts. To stay within a reasonable cost consider following RMA A3 tolerance guidelines.
  • How many undercuts should you create? Undercuts create irregular parting lines and result in multiple plate tools. This will increase the cost of your mold and extend production times, increasing the cost per part.
  • Where will your parting lines be? Whether your parting line can be visible or not, plays a factor. Parting lines are also affected by the amount of undercuts in your design. If you can avoid undercuts, your mold will be less expensive because it will reduce the amount of time machining and reduce production cycle times.
  • What modifications would be acceptable without affecting the part function? After getting back your engineering samples you may need to change your design. Shrinkage can occur during the molding process. Although we scale your part for shrinkage, each project is a little different, depending on your durometer, part size and undercuts.
  • What is the thickest area of your part? The thickness of the silicone material plays a large part in molding cycles, particularly in the curing phase. Just remember, the thicker the part, the longer the cycle, the higher the cost. What is the volume of your part? We specialize in prototype and low-volume production molding. We are not suited for molding tens of millions of parts for pennies a piece.

Cost

  • How fast do you need the parts? The longer the turn around time the lower the cost will be.
  • Do you want an injection, compression or transfer mold tool? Depending on where your parting lines are, how many parts you need to produce and how long you have to produce these parts, can all factor in to which type of mold to build.
  • How much money do you want to spend per part? Depending on the amount of parts required, you may want to consider a multi-cavity tool. This may be more expensive up front while purchasing a tool, but will quickly pay off through reduced production time, which means getting your parts FASTER!

Now for some questions regarding designing your parts in silicone materials. How many iterations did it take to get your design acceptable? Avoid multiple revisions by covering all aspects before designing your parts. This will save you time and money before having to go back to the drawing board. Did you know we mix your silicone in-house for control, but also mix and provide custom materials that meet your specifications? Are you curious if silicone adheres to specific plastic or metal materials? We can experiment in our lab with primers from the major silicone suppliers and provide different surface textures to create adhesion on your parts, whether they be plastic,metals or silicone.

 

Looking to manufacture your design prototypes in silicone and want to know how much it will be? Send your models and information through our RFQ page. We will respond within 24 hours. If you “needed your quote yesterday,” please call Christi or Ryan at 978.466.5870. They can assist you with all of your silicone molding needs.