Category Archives: Silicone Prototyping

This category contains useful articles on Silicone Prototyping and related topics.

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.

How Micromachining Patience Speeds Prototype Production

Article From: Modern Machine Shop, Derek Korn, Senior Editor

Albright Technologies has become adept at micromachining molds for silicone parts such as the one to the right. This has enabled the company to become effective in quickly generating prototypes for medical device manufacturers pressured to speed new products to market. Many of the silicone components it creates are either tiny themselves or have miniscule features measuring just a few thousands of an inch. What’s interesting is that the company has found it can produce prototypes faster by taking a slower, more conservative approach to micromachining molds using end mills that measure just a few thousands of an inch in diameter.

Plus, while one might assume that very high spindle speeds are needed to effectively mill molds using such small tools, the machine that performs micromachining at Albright—a 30-taper VMC—typically spins 0.005-inch-diameter tools at just 9,000 rpm. Although that means feed rates and cycle times are relatively slow, there are a number of reasons why a company focused on quickly turning prototyping work finds this acceptable. David Comeau, Albright’s president, and Robert Waitt, vice president, explained why during a recent visit to the New England-area molder.

Click here to read the rest of the article.

Learn more about implantable silicone

Question: I’d like to know more about implantable medical silicone.

Answer: Implantable medical silicone has the capability of being implanted in a living body without the risk of rejection. Commonly, the implantable medical silicone is categorized into two types: short term (restricted) and long term (unrestricted) implantable silicone.

The short term implantable medical silicone is used for a temporary medical application – normally ranging from 1 to 29 days. For example, a suture sleeve is made of short term implantable silicone to hold parts of a medical device to keep them in place during a suture. Once the suture is done, the suture sleeve is removed from the patient’s body. The long term implantable silicone should be able to remain inside the patient’s body for 30 days or more. A good example of long term implant application is the Left Ventricular Assist Device; this device helps the patient maintain the pumping ability of a heart that can’t sufficiently pump blood throughout the body on its own. This device isn’t removed until the patient has a donor.

Each medical silicone implant application requires certain implantable silicone. A medical device containing implantable medical silicone or other biomaterials must be carefully evaluated according to ISO 10993 before it is implanted into a patient’s body; the ISO 10993 contains a series of standards for evaluating the biocompatibility of the device. Also, it sometimes is tested according to ASTM (American Society for Testing and Materials) depending on individual application.

There are commercially implantable medical silicone materials available in high consistency silicone rubber (HCR) and liquid silicone rubber (LSR). Color additives can be added to meet the requirement of a medical application, but it is recommended that the color additives should have the same class and manufacture as the implantable silicone to prevent defects. The implantable medical silicone can also be mixed with additives such as tungsten and barium that allows the implants to be viewed easily with medical imaging equipment.

Therefore, selecting an implantable medical silicone for a medical device should be thoroughly evaluated prior to implantation. If you have any other questions, please email Phayhean Soo directly at psoo@albright1.com.

What is the least expensive way to prototype a part made in Liquid Silicone Rubber?

Question: With all the new options today, could you please tell me what is the best and least expensive way to prototype a part (about 3″ x 2″ x 2″) made in Liquid Medical Silicone Rubber?

Answer: For low volume prototyping of medical silicone parts your best option is typically to create a single cavity aluminum (faster and cheaper than steel) compression or transfer molding tool.  While others may swear by jumping straight into an injection molding tool, it could take a machinist and technician longer to set up and process a liquid silicone injection molding tool than it would to make 25 parts in a compression mold.

If cost is your most critical concern, and your target first run of medical silicone volume is extremely low, you may also wish to look into getting an acrylic mold made (instead of aluminum).  The costs of fabricating an acrylic mold is significantly less than a metal mold.  But be forewarned, if you purchase an acrylic tool, you will likely be stuck running an RTV (Room Temperature Vulcanization) material (so your cycle times will be long), you won’t be able to put any real pressure on it (so your dimensions could vary significantly), and your mold is going to wear out FAST.  You might only get 10 parts out of an acrylic tool, vs. 10,000 out of an aluminum tool, and 100,000 out of a steel tool.

While many can be seduced by the $500 – $1,000 price tag on an acrylic mold, it might take 10 of them to make 100 parts, at this point, an aluminum tool would already have been paid for, and well into a small scale production run.  It is for this reason that Albright Technologies does not fabricate acrylic molds.

If you have any other questions, please email Kevin Franzino directly at kevin@albright1.com.

 

 

 

Are you capable of over-molding medical liquid silicone to thermoplastic materials?

Question: In your prototyping experience, are you capable of over-molding medical liquid silicone onto thermoplastic materials? If so, what is the lowest melt temperature material that you have been successful without deforming the substrate (ABS, Nylon, Polycarbonate, etc.)? Additionally, do you find that a silicone primer is always necessary when over-molding?

Answer: In our experience, we have had success bonding medical silicone with certain thermoplastic materials. Since different types of materials require different temperatures to work with, it would solely depend on that specific material. Over-molding medical silicone to plastics is limited to either using low temperature or faster cycle time. Plastic substrates would not deform under low temperature, but it will increase the cycle time during the over-molding process. In contrast, using high temperatures can lower the cycle time, but can potentially damage the plastic substrate. Using silicone primer helps the over-molding process, there are some other options available such as adhesive grade medical silicone and surface treatments.

If you have any questions please feel free to post a comment or email me  directly at veasna@albright1.com.

Is over-molding onto thermoplastic materials possible?

Question: In your prototyping experience, are you capable of over-molding onto thermoplastic materials? If so, what is the lowest melt temperature material that you have been successful without deforming the substrate (ABS, Nylon, Polycarbonate, etc.)? Additionally, do you find that a silicone primer is always necessary when over-molding?

Answer: In our experience, we have had success bonding silicone with certain thermoplastic materials. Since different types of materials require different temperature to work with, it would solely depend on that specific material. Over-molding silicone to plastics is limited to either using low temperature or faster cycle time. Plastic substrates would not deform under low temperature, but it will increase the cycle time during the over-molding process. In contrast, using high temperature can lower the cycle time, but can potentially damage the plastic substrate. Using silicone primer helps the over-molding process, while there are some other options available such as adhesive grade silicone and surface treatments.

If you have any questions please feel free to post a comment or email me directly at veasna@albright1.com.

Bonding Silicone to a PVC Surface

Question: I am working on a prototype that involves bonding a silicone rubber to a pliable pvc surface and have had a difficult time bonding them together. Is there an adhesive you can recommend, that could assist me in this process?Answer: Although I have never attempted to bond/overmold silicone to polyvinyl chloride, I have had good results using other plastics.  Some processing techniques you may wish to consider incorporating into your process, are surface abrasion on the pvc (via sanding/sandblasting), the use of a self-bonding silicone material that contains adhesion promoters within it, the use of plasma treatment prior to the application of the silicone, and lastly, the application of a platinum primer to the substrate.

If you have any other questions you can comment or ask me directly at kevin@albright1.com

Are there any Restrictions for Molding One Silicone to Another?

Question: I am developing a new silicone part design which requires two different hardness levels on a single silicone part. Is there any kind of restriction and/or special requirement to over-mold a lower level of hardness silicone over another one?

Answer: There is no standard requirement for molding one silicone to another but points to consider: The softer silicones deflect more easily risking increased variance between parts and/or part failure. Silicone to silicone bonding in same series materials is often easier to predict than materials in different series or from different manufacturers. Two major considerations are holding and shutoff. The first shot part needs to be located and held in a mold while the over molding is done. Shutoff offs control the transition line between the two materials and directly relate to the geometry of the final part and all its components.

Friction Control

Bob’s Question was: I am trying to reduce the coefficient of friction on the surface of a molded silicone part. Does anyone know what my options are to achieve this? Is there a specific material or coating that I can use? Or does it mainly have to do with surface finish?

Our experience is that surface finish is the most controllable way to change the coefficient of friction – very smooth or highly polished surfaces increase the coefficient of friction while textured surfaces decrease the coefficient of friction for liquid silicone parts. Texturing is probably your best option. Coatings may get you into bonding or bio compatibility issues.