Category Archives: Silicone Manufacturing

This category contains useful articles on Silicone manufacturing related questions or topics

Learn Albright’s 3 Secrets to Overmolding Silicone onto Electronics

With the growing popularity of electronic wearables and advances in medical diagnostic equipment, silicone molders are seeing an increased demand for parts molded onto electronic substrates. There are many additional considerations that a molder must be wary of when taking on an electronics over-molding project. We’ve highlighted three of the most important considerations in this post.


1. First, when designing a part, be mindful of the dimensions. Allow enough clearance to avoid damaging the substrate, while simultaneously shutting-off on the substrate to prevent overflow of material onto unwanted areas.  This can be something of a delicate balance and will likely be different, based on part geometry and material used.

2. Secondly, when over-molding onto electronics, be mindful of temperature restrictions.  For some electronic devices, there are components that have a lower operating temperature range than what is ideal for silicone over-molding (125°C – 175°C).  Typically, this is true of battery’s capacitors.  The normal operating range for most capacitors is -30°C to 125°C with nominal voltage ratings for a working temperature to be no greater than 70°C for plastic capacitors.  If possible, it is best to avoid these components when over-molding electronics with LSR.

3. The last secret to over-molding electronics is surface compatibility to improve adhesion to the substrate.  When two materials are chemically dissimilar, certain options are available to improve bonding:

  • It is always important to make sure that the substrate is clean prior to molding.
  • Mechanical surface preparation; such as roughening via sanding and grit-blasting, can produce good adhesion.  For further improved bond strength creating undercuts or thru-holes in the substrate.
  • Chemical surface preparation; such as primers or other adhesion promoters, can be purchased with the suppliers of the liquid silicone such as Shin-Etsu and Wacker Silicones.
  • Another type of surface modification process is applying plasma to change the surface tendencies of polymer.  Plasma is compressed energized gas that is applied onto the polymer molecules to break up some of the bonds.  When some of the molecules are broken apart, the surface of the material will create available binding sites.  Atoms from the silicone material are then allowed to come in and fill up these binding sites.
  • Corona discharge works very similarly to plasma treatment, but differs in that it uses an electrical arc to free up the bonding sights instead of gas and flame.  Due to this corona treatment is also an effective means to improve adhesion with metallic substrates.

Compression Molding of Silicone Materials: Pros and Cons

Many Inventors, Engineers and Project Managers believe that injection molding is the best solution for their molded silicone products. However, this is not always the case due to the many variables and constraints of manufacturing silicone parts.

First and foremost, anticipated volume is always a true concern. If you only need to mold 1 to 20,000 pieces then a compression mold is more than suitable. Secondly, do your parts have multiple undercuts or is the geometry highly complex? If so, then a compression mold may be the most viable option.

Compression Molding

During the prototyping phase, a compression tool allows for rapid turnaround time. At Albright Technologies, we will produce a compression mold manufactured out of aluminum, along with engineering samples in 15 business days or less. Now, let’s take a look at the pros and cons of compression molding.

Compression Molding


  1. Parts are dimensionally to specification and made with specified materials
  2. Short set-up times, allowing materials and colors to be changed quickly
  3. Flexibility in mold design
  4. Tools with multiple cavities can be made with less concern of balancing
  5. Welding allows for tool modification
  6. Faster mold manufacturing turnaround time
  7. Parts with multiple undercuts can be manufactured
  8. Mold tool cost is lower than injection
  9. Cost of compression molding machines is low
  10. Reduced molding process development time (day(s) not weeks)


  1. Slower part production rates
  2. Can be difficult to control flash

Due to the nature of our business as a silicone prototyper and low-volume production molder, compression molding is a great fit. It offers our customers a less expensive, yet rapid option (when compared to injection mold tooling) to turn their product designs into reality. We provide our customers with silicone parts that are molded from complex mold tools with many undercuts as required.

Now, it is time for some questions for discussion. Do you or your company utilize compression mold tools to manufacture silicone parts? How would you rate your overall experience with the compression molding process? How much of your molding business is processed utilizing compression molds?

When turning your design into a silicone prototype, select the World’s Premier Source for Silicone Molded Parts. Get your 3D Models quoted today, visit our RFQ page.

How Albright’s Quality System Affects Your Non-Medical Part

The main benefit of Albright’s QMS for non-medical customers is the overall Quality System emphasis on improving compliance to repeated processes. The Quality System is especially important in the integrity of the silicone material Albright uses and in the consistent, high-tech quality inspection applied to finished parts.

Click her to read more.

Made In Massachusetts: Creating Jobs In The Bay State

Last month Susan Windham-Bannister, Ph.D., President and CEO of Massachusetts Life Sciences Center, participated In the latest installment of the WBZ NewsRadio 1030 Business Breakfast series. The panelists of business leaders & experts discussed the importance of making products and profits in Massachusetts. The group also discussed how the state’s manufacturing sector is staging an epic turnaround. The event examined and discussed the stories behind manufacturing success and how the state is helping to foster this growth and the beneficial ripple effect it is creating for the Commonwealth and beyond.

Click here to watch the video of the Business Breakfast.

Click here to learn more about Massachusetts Life Sciences Center.

What is the best test to determine the sealing capability of a silicone compound or design?

Two common tests are (1) to put the device or component under pressure using regulated compressed air and then submerging in water or other fluid. The leaks will show as bubbles or (2) use a colored die solution that contrasts with your part colors under pressure and the die will highlight leaks.

Ultimately whenever possible pressure testing of the final assembly under the working load or more, in as close to the final environment as possible can help identify failures caused by condition stack up.

Alternatively for many applications there may be published standard test methods that have been shown to be effective. Medical devices and aerospace both have test standards and you may find some relevant test standards under ASTM.

Click here to learn more.

What shrinkage value should be used when designing a silicone mold?

Question: What shrinkage value should be used when designing a silicone mold?

Answer: Shrinkage is defined as “the amount or proportion by which something shrinks” ( A material’s shrinkage must be accounted for when designing a mold to produce a silicone part that meets all required dimensions. Silicone normally can shrink from 1% to 4%. The shrinkage analysis is sometimes not provided when we buy silicone from manufacturers. Based on my personal opinion, 2% can usually be used for a standard shrinkage value when designing a silicone mold. Nevertheless, variation between material lots can significantly affect the shrinkage percentage as well as the part’s geometry. For example, a long hollow cylinder part that has a thin wall is going to shrink differently on different axes. Specifically, the long section of the part is going to shrink more than other axes. In this case, the part must be scaled differently on different axes.

The suggested shrinkage value will work most of the time. However, in a case where the material’s shrinkage doesn’t meet the standard shrinkage allowance or a part has a similar geometry to the one described above, educated estimation on shrinkage value should be made when designing a silicone mold.

Question: What is the difference in cycle time for molding medical silicone parts vs cycle time for molding medical thermal plastic parts?

Question: What is the difference in cycle time for molding medical silicone parts vs cycle time for molding medical thermal plastic parts?

Answer: The processing conditions can be optimized to match the tool design, part geometry, and material but each presents limitations. Injection process times are driven by material. Silicone parts can often be released with no draft angle or even undercuts due to the high elongation and low modulus that save time on actions but knock out pins may often damage parts. Silicone part removal is often done by automated brush, hand pull, compressed air, or another way that may take additional time compared to plastic.

Curing time can be reduced in silicone by increasing processing temperature until filling fails or surface quality diminishes. Plastic cooling rates may be more limited by internal stresses causing warping or property changes from rapid cooling. Other contributions to the cycle time include heating and cooling rates, curing or solidification time of the material, injection time, mold travel time, and other smaller contributions increase the cycle time.

Direct comparisons between cycle times of medical plastics and medical silicones are not readily available. Your molder may be able to go into detail for your application if cycle time is critical.

When molding medical silicone parts in the same mold will changing the durometer change the dimensions of the molded part?

Question: When molding medical silicone parts in the same mold will changing the durometer change the dimensions of the molded part?

Answer: The final part dimensions will depend on inherent shrink rate and processing conditions. Different materials molded in the same mold with the same shrink rate should produce the same size parts.

Durometer changes require different materials or additives which often changes the shrink rates. Higher durometer materials often have a greater raw viscosity and may achieve greater cavity pressures that can sometimes produce slightly larger parts compared to lower durometer materials. The difference has been shown to be less than 1% for a 40 durometer change without resetting the optimal processing conditions. Generally, changing durometer in the same series for most suppliers will not significantly affect the final dimensions but a first article is recommended. If you are considering trying multiple materials then I would recommend letting your molder know as early as possible.