POC: stoppering machine for pharma cartridges

Challenge

Can these fingergrips be placed and clicked onto cartridges at high speed and with absolute precision? Can we guarantee flawless placement and a 100% success rate?

These questions were critical to validate the business case for a custom-built cartridge stoppering machine for a pharmaceutical client.

Since a previous attempt by another company to automate this assembly step had failed, this proof of concept (POC) had to guarantee the technical feasibility, as both the cartridges and stoppers posed significant challenges.

Sleeved cartridges

The cartridges have a very specific shape, making it difficult for standard machines, and especially standard grippers, to handle them correctly.

Furthermore, the surface is highly sensitive and scratches easily during handling.

Stoppers

The fingergrips are extremely fragile. If they are not perfectly aligned before the clicking process, the lips break off. Like the cartridges, they are made of plastic and are prone to scratching.

Additionally, the tolerances of the fingergrips are not guaranteed by the supplier.

High speed, high precision, and quality control

The stoppering machine must operate at a speed of 165 pieces per minute. It is also crucial that every fingergrip is placed 100% correctly to eliminate any risk of contamination or product failure.

The goal of this stoppering machine POC

We designed this POC to eliminate all risks associated with the combination of:

component fragility;
high-speed operations;
and pinpoint precision.

All of this we had to validate, while keeping the costs of the setup under control.

Solution

Two components were pivotal in proving the technical feasibility of this business case:

A custom gripper: we designed and built a gripper to handle the unique dimensions of both the cartridges and stoppers.
An inspection system: we set up a vision system to detect all possible quality issues.

Let’s take a closer look at these two critical elements of the POC for this cartridge stoppering machine.

1. Designing and manufacturing a custom gripper

We first validated the clamping of the fingergrip with a 3D printed counterpart. We performed several iterations to determine the perfect dimensions. Once we got it right, we manufactured the final counterparts in steel.

We then designed and manufactured the complete custom gripper: from idea to realization. Finally, we mounted this gripper on a rented robot arm and started testing.

The key was to give the fingergrips a certain spatial freedom as they rotate, so the fingers can find their way into the cartridges holes before clicking. This prevents the fingers from breaking off.

2. Setting up an inspection system

To ensure perfect placement and quality, the cartridge stoppering machine had to be able to inspect the completed units from all angles.

An inspection system utilizing four cameras proved to be the optimal set-up. We 3D-printed a custom fixture to hold both the cameras and the cartridges in the exact required positions, allowing us to fine-tune the positioning. For the cameras, we collaborated with Keyence.

We then trained an AI model to perform the quality control. Since the exact nature of potential non-conformities was not yet fully defined, our engineers simulated a wide range of possible errors:

broken-off lips
scratched surfaces
incorrectly positioned stoppers
contamination or debris
…

By contrasting these simulations with images of perfect assemblies, we taught the AI model to identify even the most subtle defects with high reliability.

Results

The POC confirmed that our initial concepts for this stoppering machine were robust and reliable.

By proving technical feasibility, we successfully addressed all initial concerns and mitigated the primary project risks.

Following these positive results, we provided a fixed-price proposal for the full-scale development, manufacturing, and commissioning of the complete assembly line.