Before manufacturing silicone parts, it is important to select a finished durometer for the part or product that you will be molding. Depending on the requirements of the project, the silicone finished part may be near gel-like or very stiff. Durometer is a measure of hardness that is used in elastomers, polymers and rubbers. Hardness may have many definitions, but in our case with regards to Shore durometer, hardness is defined as a material’s resistance to indentation.
The Shore durometer scale was created by Albert F. Shore in the 1920’s. Originally, the result was just signified by a number, for example 50 durometer. As time progressed, multiple durometer scales were created. The Shore durometer scales that are most commonly used in plastics, rubber and silicone are the A, D and 00 shore scales.
There are two main differences amongst these scales. First, the configuration of the indenter that is pressed into the material is different with each scale. Second, the hardness range is different with each of the three scales. The Shore 00 Scale measures rubbers and gels that are ultra soft. The Shore A Scale measures rubbers that range from soft and flexible to hard with almost no flexibility. The Shore D Scale measures the hardness of hard rubbers and hard plastics.
Below is a table of common finished products and their respective durometers.
Here at Albright, we use the Shore A scale to quantify our molded silicone durometers. The Shore A scale ranges from 0 to 100. An example of a “0” durometer Shore A silicone molded part would be a very soft shoe insole. Near the opposite end of the scale, an example of an “80” durometer Shore A silicone molded part would be an o-ring seal or a stiff silicone kitchen spatula. Every day, Albright molds products in materials that range in finshed durometer from 10 to 80 on the Shore A Scale.
What materials and durometers have you molded parts in? What durometer Shore scale do your materials come in? How do you determine what durometer of material to use?
Please remember that the durometer selected will be based on the requirements of your project. If you need assistance determining a durometer for your next silicone project, Albright engineers and technical staff are here to help. In addition, we can provide samples of silicone in various Shore A durometers. Want samples of silicone durometers? Visit our free durometer sample page on the Albright web site.
Silicone is being used as a material in wearables with computer sensors. The silicone is overmolded on to the computer sensors and then attaches to the skin like a band aid. Learn more here: http://nyti.ms/1wzdh0J
Now for some quick questions regarding wearables. Were you aware of the predominate usage of silicone in wearable applications? Silicone is great for overmolding applications, have you worked on any of these types of applications? If you have worked with silicone overmolding in the past, what advantages or disadvantages did you experience?
1. Our standard turnaround is 15 business days.
2. Three, five and ten business day expedites are available when you need parts fast.
3. Injection, compression and transfer molding processes are available.
4. Albright designs and manufactures all tooling in-house for complete control.
5. We have an ISO Class 7 hard walled clean room for medical and biopharmaceutical devices.
6. We stock a massive inventory of silicones to accommodate any application.
7. Albright’s Quality Management System is ISO 13485:2003 certified by TÜV SÜD.
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.
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Silicone over-molding is a process that is used to cover, bond or encapsulate an existing part with silicone material. For example, a silicone over-molding process may be used for providing a grip surface to a smooth plastic handle, a flexible septum on a hard plastic surface or for encapsulating an electronics assembly for mounting or protection from the environment.
The motivation for over-molding silicone may include a means of final assembly, enhancing physical surface characteristics and feel, providing a self-healing internal access (ie, an integrated septum), creating the finished product enclosure (such as a key-ring LED light), creating a thermally conductive path for heat-sinking or perhaps applying elastic properties to mounting components.
Important things you should know about silicone over-molding:
1. Over-molding bonding strength typically increases over time.
2. Polymers that are ideal for over-molding include: polycarbonate, nylons and other high temperature resins.
3. In order to have a clean silicone over-mold, the over-molded part must be made with the requisite tight tolerance and part samples of exact size are needed. A stable-dimensioned part is needed to develop and maintain the desired clean over-mold outcome.
Visit us at booth 802 this week, March 26 & 27, at BIOMEDevice in Boston. Stop by to find out how to get a free silicone sample and ask us questions about your silicone molding projects.
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