Equality Healthcare with a Smart Telemedicine Solution
About the Product
The ProEX Telehealth Hub by VisionFlex of Australia is a brilliant solution to a problem facing millions of people who lack direct access to advanced medical personnel and facilities.
With a variety of interchangeable probes, sensors and cameras, the ProEX lets primary caregivers perform a range of diagnostic tests including heart rate, blood pressure, spirometry, ECG, ultrasound and more. This data can then be wirelessly transmitted to clinicians or doctors anywhere in the world. This makes the ProEX ideal for remote communities, home hospice and elderly care, secure facilities, refugee camps and military personnel in the field.
About the Project
Working on the ProEX was a challenging but very rewarding project for Star Rapid. There were many parts of differing materials that needed to come together in a complete assembly with the fit and finish of a full production model.
We think it came out great, a testament both to the skills of our technicians as well as the careful design and engineering of VisionFlex. Let’s take a closer look at the details involved in bringing this special product to life.
It’s an economical process, not requiring hardened metal tools such as would be used for plastic injection molding.
Silicone molds can be made in a matter of days once a master pattern is available.
The quality of the cast copies is excellent, easily able to reproduce even fine surface detailing from the original patterns.
There are many casting resins available that can simulate a variety of production grade plastics and elastomers.
Making Master Patterns
Although patterns can be made using any method, it’s common to employ some form of 3D plastic printing for this purpose.
3D printing is inexpensive and can make solid shapes quickly and economically. Another advantage to 3D printing is that it’s easy to modify the design as necessary without making new tools each time.
On this project we used SLA 3D printing to cure SOMOS 14120. This is a photosensitive resin that, when cured, makes a solid plastic part much like nylon.
After 3D printing, we carefully sanded and polished the patterns to achieve the perfect surface finish. We later sealed this surface with a coat of primer for a more uniform texture.
Preparing Silicone Molds
Once the patterns were ready, we then needed to create molds for vacuum casting. Preparing these molds required us to pay attention to many important details.
The first step is to carefully analyze every component. We look for the ideal place to locate the split line for each part. The split line is where the mold will open into two or more sections. This line is important for a few reasons.
Our mold makers need to be sure we can easily remove the part later without damaging the surface or losing fidelity on any important features.
Also, the split line might leave behind a thin mark on the finished part. We try to hide this whenever we can, either by incorporating it into the overall design, or putting it in a place where it can be sanded off in post-finishing. This can be tricky to do with some complicated shapes.
Once the split line was located, we placed a thin film or skirt around the perimeter of the part. This film is essential for allowing the mold to separate after it’s solidified.
All patterns need to be mounted on a dowel rod. These rods are used to suspend the patterns inside the molding box, preventing the patterns from touching any of the sides or the bottom when the silicone is poured in.
Pouring the Molds
With the dowel rods attached, master patterns were lowered into the casting box and held stationary with a temporary mounting plate. These patterns must be located so that they don’t touch the bottom or sides of the box.
Curing the Molds
Once poured, the boxes were placed in an oven and left overnight to cure completely.
Removing the Master Patterns
After the molds were fully cured, the molds were opened and the patterns removed. This job is trickier than it looks, and must be done very carefully.
We then use a strong light source to peer into the translucent depths of the mold. We cut a sawtooth pattern along the split line, being careful not to damage the pattern itself. Later, this sawtooth cut will be important for re-sealing the mold in the correct orientation when the molds are put back together for making copies.
Once the molds are ready, they can be re-used up to twenty times to make identical copies of the original master patterns. After that they begin to degrade and need to be remade.
Once the molds are sealed, liquid resin is poured into the cavity and the molds are placed in a vacuum chamber for several hours while the resin cures.
Vacuum casting allows us to mold two or more dissimilar materials together. In this case, a soft elastomer rubber bezel was molded over the top enclosure, surrounding the aperture where a display monitor will later be installed.
Notice here the metallized copper paint on the inside of the enclosure. This is an electromagnetic compatability (EMC) coating, a mixture of silver and copper. Since plastic by itself is usually transparent to electrical signals, this coating provides shielding for the delicate electronic components that will later be installed inside the case.
The metal base of the enclosure was made from 1.5mm aluminum 5052 sheet metal.
If this were high-volume production, such a plate would be stamped from a sheet using a custom-made die. However, that trouble and expense is not justified for a prototype, so instead we used a CNC mill to cut out the general profile of the plate.
CNC machining was also used to make a heatsink from Al-6061, tempered to T6.
Providing health care solutions to those in need is something that Visionflex can rightly be proud of. We’re honored we were able to make the ProEX a success, and are standing by to help you do the same on your next project.