A CNC Controls Retrofit Case Study

Automating a process using a custom Computer Numerical Control system

Due to their critical nature, key parts of rocket engines must be X-rayed to ensure their integrity and thus their safety.

The process traditionally has been time-consuming and inefficient. Even with the most skilled technicians, it has been more of a trial-and-error experiment than an effective manufacturing strategy.

The Problem: Human Error

To capture an accurate X-ray image, the x-ray tube, the part to be inspected and the image receptor all must be perfectly positioned. This traditionally was done manually, using a yardstick and twine. The operator would then examine the first image to determine if the pieces were properly set up. If not, adjustments were made and more X-rays taken. It’s easy to see the inefficiencies. While this company had refined the process using motorized arms, the arms still had to be manually jogged into place. So human error continued to affect results.

Trial and Error

To ensure quality control, rocket engine parts are inspected using X-ray images. Accurate X-rays are crucial. So one of the biggest challenges is making sure the X-ray tube, the part to be inspected and the image receptor are perfectly aligned.

Having a technician manually position each element creates plenty of potential for inconsistency. It also requires the technician to leave the lead-lined room after positioning the element, take an X-ray image and examine the image to determine whether the components are properly positioned. If not, the technician makes adjustments and takes more images.

Given that each engine part requires inspection at multiple points, it’s easy to see how large chunks of time can be eaten up with this process.

Building on the customer’s previous improvements

This customer was all too familiar with the challenges, and had refined the process to cut down on human error. They incorporated motorized arms that held the X-ray tube and image receptor. However, loading the part and setting the X-ray tube and image receptor were still manual processes, and the data points from the registration process needed to be translated and the arms manually jogged into place. So human error continued to come into play, and the company saw room for continued improvement.

They called on us to develop a custom Computer Numerical Control (CNC) system to further automate the process.

The Solution: CNC Controls Retrofit

We proposed and engineered a system with a CNC controlling the arms, positioning them based on the registration information entered by the technician and a preprogrammed recipe for that part. The X-ray tube and image receptor move in concert around the part, always opposite each other, stopping to take the necessary shots and then moving on to the next. Since both arms are under common CNC control, the moves are tightly synchronized.

Precise and Programmable

With the solution proposed and provided by our engineers, the CNC now controls the arms, positioning them based on the registration information entered by the technician and a preprogrammed recipe for that part. The X-ray tube and image receptor move in concert around the part, always opposite each other, stopping to take the necessary shots and then moving on to the next. Since both arms are under common CNC control, the preprogrammed moves are tightly synchronized around the part, avoiding any fixed obstacles.

The operator can adjust the position of the devices from the workstation, and program in routines for repeat parts.

In addition, the technician now only enters the room to load and register the part and then unload it when the inspection is completed. The need to rerun parts is essentially eliminated when the part is properly registered and the data is correctly entered. With the new system, if an error is made it can be quickly detected and corrected.

The Results

Now, after the CNC control system retrofit, the technician enters the room only to load and register the part and then unload it when the inspection is completed. The need to rerun parts is essentially eliminated when the part is properly registered and the data is correctly entered. As a result, parts are now loaded, registered and inspected in 30 minutes, on average, compared to a previous average of two hours. Aside from improved speed and accuracy, the customer reduced an ergonomic risk: the repeated opening and closing of the heavy lead-lined door.

Learn More About Our Control Retrofit Capabilities

CNC Control Retrofit: Project Details