Automated optical inspection (AOI) is an automated visual inspection of a component. It uses cameras to check for defects. For our purposes, we are excited to use AOI in the quality inspection of precision glass tubes. The road from prototype to production was not an easy one, but we are proud that, as of 2017, we are using an automatic optical inspection system for the optical inspection of automotive pressure sensor components, among other uses. Read on to learn more about our story of automated visual inspection and how we were able to implement it.

Why Is AOI a Great Achievement?

Over time, we found a high demand for a fire-polished precision tube used in the manufacture of automotive pressure sensors. We wanted to bring the AOI system into our production to keep up with the increasing demand. AOI systems have been around for quite a while in most industries, with the glaring exception of optics. Computer vision systems have historically struggled to identify defects on the glass. Because of the transparent nature of glass, the system had to be able to determine whether the defect was on the front or backplane. 

Additionally, we were measuring and inspecting glass tubes. So, now we need to add in the radius, which quickly distorts the size of the defect, depending on the angle of view. Next, there is the reflection from the glass to deal with, and finally, the system needed to handle these parts without scratching them. 

The system had to be able to pick up individual tubes from a stack, place them into the inspection area, inspect 16 discrete criteria on both ends and the entire circumference, and then finally place them in the packaging. Further, it needed a cycle time of under 7 seconds! This was a huge request, and many an automation shop quickly shooed us along. But we finally found a brave enough partner to take the project on, and after a long development and approval phase, we had our first AOI for glass tubes!

What Does Our AOI System Do?

An AOI machine is used to ensure that components, such as fire-polished glass, precision glass tubes, and pressure sensor tubes, have the best surface quality possible. 

More specifically, the AOI machine inspects small glass tube edges and surfaces for dimensional specifications, concentricity, perpendicularity, and surface defects, including chips and scratches. ​It is able to detect defects down to the micron level. Measurement is done ​optically utilizing seven separate inspection cameras to catch defects. 

Our current weekly output is as follows:

  • 50,000 to 60,000 pieces a week
  • Cycle time of roughly 7 seconds per part
  • Resolution of 0.001 mm

More about IRD and AOI

Of course, it takes time to become acclimated with a new process and new machine, and we found that we needed to make some adjustments along the way. So, we implemented some in-house mechanical improvements. The AOI is an extremely complex machine that utilizes 30,000 pages of code in four different programming languages. Its automation is unparalleled, as it can decide what to do with and where to place the parts that it inspects all on its own.

Some of the in-house mechanical improvements we made include:

  • Full redesign of the robotic end of arm tooling
  • Modified the pressure differential area to be more repeatable
  • Implemented several software and programming updates, which:
    • Improved remote machine controllability
    • Increased machine up-time and lights-out (after hours) production
  • Redesigned the gripper nozzle to be spring-loaded

After the improvements were made, we were ready (and excited) to implement the automated optical inspection machine. 

The Future of IRD and AOI

The journey from prototype to production for us had some roadblocks, but we were thrilled to be able to implement a machine that provides the best surface quality for precision glass tubes. 

Along the way, we identified many learning opportunities with respect to qualification procedures with automation equipment. We also gained useful knowledge about the different systems used within the machine. We are confident for the future, knowing this knowledge will prove to be useful in upcoming automation projects and integration.

IRD Glass has been the leading supplier of customized precision glass, optics, ceramics, and sapphire product fabrication for over 39 years. To learn more about our capabilities, speak to a representative today for a quote.