Speeding up design and test cycles in medical device development with in-house 3D printing

Company: Coalesce

Industry: Medical devices

Profile: Coalesce Product Development is a medical device design company focused on developing drug delivery products for pharmaceutical companies and medical startups. Headquartered in Cambridge, UK, the company is equipped with a state-of-the-art design centre, an analytical science laboratory, an ISO Class 7 cleanroom, and an engineering development and testing suite. Coalesce employs 20 engineers, consultants, and designers.

Challenge: Prototyping an inhaler with a tightly toleranced fit, as well as jigs and fixtures for testing, required long lead times using traditional methods.

Solution: By using stereolithography 3D printing in-house, Coalesce produced a finished and painted prototype for testing and showcasing to clients within a few days.


  • 80–90% reduction in lead time, from 1–2 weeks to 1–2 days.
  • 96% cost reduction, from £250 to £11.
  • The 3D printed prototypes were used in a clinical study and were mistaken for a marketed product at a conference.

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UK-based medical device design company Coalesce develops drug delivery devices including inhalers and injectors.

Medical devices often have complex shapes that are difficult to prototype using traditional methods. They need to fit the organic shapes of the human body, and so must strike the perfect balance between size, weight, and shape while being fully functional for tests and iterations.

Coalesce needs to produce prototypes that serve as external forms for human factors evaluation and internal mechanisms for technical evaluation. To test the products, the company also develops its own test rigs, jigs, and fixtures.

In-house 3D printing allowed Vinnay Chhabildas, industrial designer at Coalesce, to take complex, customized forms developed in CAD, and turn them into physical prototypes within days instead of weeks.

Coalesce uses 3D printed prototypes to test both design and functionality. Here, printed parts in Formlabs Clear Resin are used to test how quickly different springs fire.


Coalesce’s Breath Profiling Device (BPD) was designed to digitally assess an asthma patient’s F flow profile. Spirometry machines, which are used by clinicians to measure a patient’s lung function, tend to be either expensive and bulky, or portable but low-tech. The BPD is an inexpensive and portable alternative to spirometry machines.

Chhabildas needed prototypes to have a smooth surface finish, robustness, and durability, and the ability to hold mountings and fixtures for the internal PCB.

For many years the company outsourced stereolithography (SLA) 3D printing to service providers. Having experimented with other prototyping solutions, such as fused deposition modeling (FDM) 3D printing, they found SLA technology unmatched in terms of surface quality.

“Before we invested in the Form 2 printers, we relied entirely on outsourced prototyping. Rather than make several iterations in a day, as we can with the Form 2, the iterative cycles were longer and we had less control over the amount of hand finishing of critical geometry.”

Coalesce’s Breath Profiling Device was 3D printed in White Resin at 25 micron resolution.


Coalesce used two Form 2 SLA printers to develop and prototype the crucial architecture for the casework of the BPD device in-house. The designers chose White Resin for its smooth finish and mechanical properties, which allowed them to drill and add brass inserts.

“Stereolithography offers a good balance of feature resolution, surface finish, durability, choice of materials, and dimensional accuracy. Because we develop devices with moving parts, we needed an effective way to prototype small mechanisms in-house. We kept an eye on advances in 3D printing technology over the past few years, and we liked the Formlabs approach. When the Form 2 was released we ordered one immediately, followed by a second just a few weeks later.”

Post-processing involves removing the supports and preparing the 3D printed parts for priming, painting, and assembly.


Initially, the 3D printed prototypes were used to develop the product’s architecture. When the design was stable, the printed parts were painted and taken to a conference, Drug Delivery to the Lungs (DDL).

The prototypes looked so realistic that they were mistaken for a marketed product. Eventually, the same device prototypes were used in a clinical study. Participants were asked to inhale on the device ‘as they thought they should’. The results showed how much variation can occur between different uninstructed inhalation profiles.

Using third party vendors would have cost approximately 20 times more than the raw cost of printing the parts in-house. The caseworks of the BPD cost £11 to produce on the Form 2 compared to around £250 when outsourced. According to Chhabildas, however, the real benefit is the time saved: the parts took only eight hours to print and could be finished and painted within a few days. The same process would take an external contractor a week or two.

“Both of our Form 2 machines are in almost constant use. We have learned how to get the best results from the machines and the materials, and how to finish the parts to make them look as close to manufactured parts as possible. We can design parts with functioning clips, or even add threaded inserts so parts can be screwed together.”

Application Outsourced 3D printing 3D printing on the Form 2
Inhaler casework Cost £250 £11
Lead Time 1–2 weeks 1–2 days

Coalesce’s prototypes looked so realistic that they were mistaken for a marketed product.

Using Formlabs 3D printers, Coalesce Product Development has shortened lead times for its medical device’s casework by 80–90 percent, and achieved 96 percent cost reduction.

Coalesce’s Toolkit:

2 X Formlabs Form 2
Formlabs White Resin

Buy Now Request a Sample Part

Coalesce’s Toolkit:

2 X Formlabs Form 2
Formlabs White Resin

Buy Now Request a Sample Part

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