Equality Healthcare with a Smart Telemedicine Solution

Manufacturing Services

3D SLA printing (master patterns); CNC machining; laser cutting and etching; vacuum casting with overmolding; silk screening and pad printing; polishing; painting

Materials

Heicast 8263, Al-5052, UPX-8400, PMMA, PX-5210, AL-6061, Somos 14120

Qty

20 Sets

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.

VisionFlex parts awaiting delivery from Star Rapid

Parts awaiting packing and delivery. Finally assembly takes place after the electronics are installed.

Exploded part assy, visionflex at Star Rapid

Our engineers worked closely with VisionFlex to optimize manufacturability of a complex design.

The Advantages of Vacuum Casting

There are a few decided advantages to vacuum casting for making rapid prototypes or first-article samples. These advantages help product developers to refine a design while slowly ramping up to bridge production and then higher volumes.

Economy

It’s an economical process, not requiring hardened metal tools such as would be used for plastic injection molding.

Speed

Silicone molds can be made in a matter of days once a master pattern is available.

 

Quality

The quality of the cast copies is excellent, easily able to reproduce even fine surface detailing from the original patterns.

Versatility

There are many casting resins available that can simulate a variety of production grade plastics and elastomers.

Making Master Patterns

3D Printing

Although patterns can be made using any method, it’s common to employ some form of 3D plastic printing for this purpose.

Advantages

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.

 

Wet sanding 3D printed master at Star Rapid

Careful wet sanding preceded a final primer coating on these master patterns.

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.

Split Lines

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.

Vacuum cast master patterns at Star Rapid

Master patterns, in white, compared to black vacuum-cast copies. Notice the location of the split line skirts on the masters.

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.

Dowel rods for VC at Star Rapid

Dowel rods are temporary fixtures and should be located where they will not damage the patterns.

 

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.

Vacuum casting box at Star Rapid

Patterns must be held away from the bottom and sides of the casting box.

Pouring silicone at Star Rapid

Liquid silicone was first heated and stirred, both to make it easier to pour and to remove trapped air bubbles

Curing the Molds

Once poured, the boxes were placed in an oven and left overnight to cure completely.

Vacuum casting molds drying at Star Rapid

Larger molds are usually cured overnight.

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.

Opening a VC mold at Star Rapid

Strong directional light sources were used to clearly identify the part edge inside the mold.

Open VC mold cavity at Star Rapid.

Notice the fine surface detailing preserved in the silicone.

Vacuum Casting

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.

Stapling vacuum casting mold at Star Rapid

Molds need to be sealed in the correct orientation.

Pour spot on VC mold at Star Rapid

A simple funnel is sufficient for pouring casting resin into the mold.

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.

VC cast resin copy at Star Rapid

After curing, we opened the mold to reveal the resin copy of the original master pattern.

Removing VC cast copies

The additional plastic flash around the edges was caused by vacuum pressure pulling out excess air in the mold.

Over Molding

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.

Secondary mold for over molding

Placing the master pattern over the secondary mold.

Overmolding at Star Rapid

The gap between the first and second mold is filled with resin.

Over molding at Star Rapid for Pro EX

Sealing the secondary mold over the pattern.

Opening the over mold at Star Rapid for Pro EX

After opening, the rubber bezel is now permanently bonded to the top unit.

Painting

A great paint job is the secret to making a beautiful finished product, so we take pride in offering premium quality prep and painting services on every project.

Paint mixing at Star Rapid

We use top-quality PPG automotive polyurethane paint in a clean room environment.

White painted parts for PROEx at Star Rapid

Most of the components were painted with UV-stabilized high gloss white.

Masking off prototype at Star Rapid

Attention to detail is critical when masking off areas for painting.

Painting EMC coating at Star Rapid

Painting the inside of the top enclosure

EMC coating on ProEX at Star Rapid

Detail of EMC coating

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.

CNC Machining

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.

Laser-cut metal plate at Star Rapid

An industrial laser was also used to make some of the detailed cut-outs.

Threaded studs on metal base plate, Star Rapid

Threaded studs were spot welded to the base plate as mounting points.

Wrap Up

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.

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