Small Batch Production for Medical Telehealth Devices with Vacuum Casting

About Customer and Product

The customers are from a transnational company dedicated to medical device design and development. They were seeking a manufacturer who was able to help them with small-batch production as they were in the middle of upgrading the new-generation telehealth device. These small batch products are for final design verification, as well as submitted to the rules to apply for the license.

The new medical device is widely used to provide medical consultation, diagnosis, treatment, and monitoring tasks. The upgrading generation has these features: lighter and smaller; better material and air-tightness, flame retardant, and anti-corrosion for multi-environments.

How to Choose the Suitable Manufacturing Methods?

As we can see, the main structure of this medical device is a typical machine casing with display functions. For the production of the casing, there are some technologies to choose from: CNC machining, vacuum casting, SLA, and injection molding.

First of all, injection molding requires the creation of expensive metal molds and is widely used for large-volume production, which obviously is not suitable for this project. Moreover, the support features as circled in the picture above are very hard to de-mold in the process of injection molding. This makes injection molding impossible to produce this medical device.

Second, if all casings use CNC machining to produce, the cost will be extremely high due to the long processing time, so it is not selected eventually.

Between SLA and vacuum casting, the latter is the preferred manufacturing method. Vacuum casting is increasingly being used in the production of medical devices. That’s not only because the method offers reasonable prices and available materials, but also because it provides greater design freedom compared to other processes.

Considerations and Solutions for Machining Medical Device Casing

In this production process, there are some key points such as the selection of materials, over-molding, surface finish, and assembly to overcome. Check how WayKen solved these machining points.

Selection of Vacuum Casting Material

Choosing the most proper materials was the first key thing to think about. This batch of casing parts would be used for both design verification and license application, so quality was extremely critical.

In this project, Hei-Cast 8263 was used to produce the top and bottom casing. It is a flame retardant type resin with grades of UL94 V-0 and 5VA, which provides good air-tightness and corrosion resistance for medical devices.

Hei-Cast 8150 was another material applied in this medical device casing. It is an ABS-grade resin. Well-balanced physical properties, excellent cure properties and superior dimensional stability of Hei-Cast 8150 make it very suitable for small-batch production.

Consider Overmolding

Normally, two separated parts produced by vacuum casting cannot provide a high grade of sealing performance at the four-pointed sides after assembling. To deal with this problem, WayKen tried Overmolding in the vacuum casting process for making these medical device casings.

Briefly, the overmolding process requires casting one part first and using the technique to mold again with another part’s master in a new silicone mold. Liquid material is then poured into the cavity. When material is solidified, a single part is created by over-molding eventually.

However, this technique requires skilled mastery. When the process is not well-controlled, plenty of bubbles and disengagement may be caused, which affects the final quality.

In this project, the two vacuum casting parts of this medical device have a significant difference in size. This made overmolding even harder. Due to the smaller part being soft rubber, it would be easily shifted from its position. With careful analysis and pre-simulation, WayKen decided the bigger part was molded first so that the small part with snap fits could be better molded afterward. Finally, we have successfully produced these casings with overmolding.

Surface Treatments

In the process of surface treatment, there were different types of finishes being applied in this medical device casing. For the soft rubber part, a matte finish is required. The majority of the hard material part was white painting. Silk printing was done for the Logo, as well as the control panel icons.

Due to this medical devices would often use medical alcohol to disinfect equipment, and the quality of the surface paint and silk screen must be able to withstand use in an alcohol environment. Therefore, we used high-quality American paint brand PPG, and UV equipment to enhance adhesion. The quality of surface treatment passed the Cross-Cut Test and Anti-alcohol Tests, which achieved the expected quality.

Assembly for Medical Device Components

Quality check is the final step. There were about 16 components of this medical device to produce via different processes, it must to guarantee final assembly. So, before the production began, WayKen’s engineering team carefully checked and analyzed all assembly-functional features. The detailed plans were made in the early of production to prevent key features on main casings from severe deformation and shrinkage.

Here is an example, the above CAD drawing shows an assembly involving two casing parts and one inner metal part. The second and the third parts, as marked in the image, should perfectly match the threading pillars on both sides. So, when machining the master for vacuum casting, these critical sections were not split in order to ensure the best accuracy was achieved.

Besides, like injection molding, material in vacuum casting also has issues if the shrinkage is not well controlled. We have very experienced engineers who can avoid the influences caused by shrinkage with thoughtful measures in preparation, which ensures the correct dimensions for key features.

Feedback and Future Plan

After receiving the products, the customer was thrilled and highly satisfied with the quality of the delivered goods, as the overall result far exceeded their expectations. They also expressed their appreciation for the successful testing. Next, the coming orders will be the selling products. They will consider working with WayKen and using the same technology in future runs.

WayKen is your trusted rapid manufacturing supplier, offering one-stop services from prototype to production. With the capabilities of vacuum casting, CNC machining, rapid injection molding, and surface finishes, WayKen can provide custom machining solutions according to your specific requirements with high efficiency and affordable prices. If you are looking for a professional manufacturer, please contact us and learn more details.