Contactless Substrate Measurement Machine using lasers to capture the height and diameter of samples
- The accuracy in the measurement increased tenfold in comparison to manual methods and the utilisation of Pi Tape using the Contactless Substrate Measurement Machine.
- The measurement speed increased threefold.
- The element of risk from human error has been significantly reduced thanks to the results now being automatically added to the clients’ central database rather than being manually entered. This was also a huge time-saver.
- The rugged touch-screen display designed for the system is intuitive and has reduced training time significantly for operators, thanks to its slick user interface.
- Engineering modes allows measurements of new or prototype products to be carried out therefore aiding research and development.
We were approached by Eminox; a designer and manufacturer of exhaust after-treatment systems, who had undertaken an upgrade of their production cell and wanted to automate some of their processes for a Contactless Substrate Measurement Machine.
Eminox machines are primarily designed for heavy-duty vehicles and equipment such as buses, trucks, non-road mobile machines and trains. As such, their products help vehicle and equipment manufacturers to meet ever-tightening emission restrictions.
As part of the upgrade of their production cell, Eminox required a Contactless Substrate Measurement Machine that would automate the measurement of substrate material and feed the data back to a central database. They needed to measure and log the diameter and height of substrates ensuring the outer bodies of the substrate material were formed to the exact size.
Several other machines further down the production line are reliant on this data so accuracy was of extreme importance. It was also imperative that the Contactless Substrate Measurement Machine could do all of this fast enough to keep pace with the rest of the production line to keep and even increase the efficiency of their processes.
Austin Consultants solution to the challenge was to build a freestanding Contactless Substrate Measurement Machine that fits within the production line which automates the data capture and logging.
Eminox provided us with design specifications for the Contactless Substrate Measurement Machine and asked us to write the software which would get the mechanics of the machine functioning to their requirements.
The Measurement Challenge
The biggest aspect of this application was the actual measurement of the substrate product. This needed to be accurate to 0.1mm. To achieve this we selected Micro Epsilon compact laser sensors, specifically the optoNCDT 1700 series.
As well as meeting the accuracy requirements the lasers also have some unique built in features such as their Real-Time Surface Compensation (RTSC) feature. This RTSC feature allowed the laser to get an accurate reading despite the hollow surface of the substrate. The lasers also integrate with the LabVIEW software environment. Eminox provided us with design specifications of the Contactless Substrate Measurement Machine and asked us to write the software which would get the mechanics of the machine functioning to their requirements.
We worked closely with Eminox to understand their requirements and the reasons behind developing the system. We carried out feasibility tests to ensure that the proposed solution would meet the requirements of the project, and that software and hardware would work together to meet the challenge. Once these were complete, we set to work on developing the software.
The mechanical build was provided by a third party who we worked in parallel with throughout the project while we wrote the software. We worked closely with Micro-Epsilon to ensure that the lasers we selected to carry out the measurements would meet the requirements set out in the specification.
We tested the machine regularly with known samples to ensure the results it was producing were accurate.
To measure the diameter of the substrate, a laser is positioned in a static place then the substrate is rotated at 30RPM. An encoder is used to trigger the laser measurements to ensure that we capture the exact number of data points for an entire revolution.
A data stream of ‘distances’ is then returned to the LabVIEW environment, which take this data along with the encoder data and maps out the circumference of the substrate. From this data we calculated the diameter. The Laser is then moved on an SMC electrical actuator to the next position. A series of diameter measurements are taken up the length of the product and then used to calculate an average diameter for the substrate.
Large Range of Sizes
The next challenge was that the Contactless Substrate Measurement Machine had to support a large range of products from 140mm to 300mm in diameter and 100mm to 400mm in height. In order to get the measurement accuracy required the laser must have a measurement range of 100mm.
This did not cause an issue for the diameter measurement as the machine effectively measures the radius of the product which has a range of 80mm. However the height range required was 300mm. As a result, the height laser is fitted to a pair of SMC Electronic actuators which move the lasers into place. SMC actuators were selected due to their accuracy and repeatability of positioning which is critical for the software to calculate an accurate value. The actuator is controlled via a National Instruments DIO card.
The Speed Challenge
The final challenge was to ensure that the Contactless Substrate Measurement Machine did not slow or hold up the production line. The machine was designed to save the operator valuable seconds so the entire delivery process was scrutinized to identify where time could be saved.
The second stage was to rethink the user interface of the machine. The controls were replaced with a resistive touchscreen panel that requires a single button push to start the test process. A resistive touchscreen was selected as it allowed the operator to wear standard safety gloves and still operate the machine and configure the settings. The screen also needed to provide valuable information throughout the process, so rugged hardware and a good user interface would ensure that it would survive in a workshop environment.
Finally, previous machines have had the user interface accessible via a door, so to save valuable seconds a light curtain was fitted instead, allowing the machine to remain safe but to increase speed of accessibility.
This was the final challenge and the one component that pulled everything together. The application was developed in LabVIEW due to its ability to create easy to use industrial user interfaces and built in processing and data analysis features. By leveraging these analysis functions, Austin Consultants were able to ensure accurate and repeatable measurements.
Not only did this allow us to calculate the product diameter, but it also allowed us to compensate for the product not being totally central to the machine. This again saved time, as the operator wasn’t required to spend valuable seconds aligning the product on the turntable.
As well as the production mode, the software also offers verification and calibration modes and off line measurements meaning that prototyping research and development products could be tested without the system writing this data to the main production database.