October 8, 2021

It’s all about stability

Did you know that the first thermal spray gun, produced over a 100 years ago, was called the ‘pistol’? The Swiss inventor, Max Ulrich Schoop, also known as the father of thermal spraying, was among the first to submit patents for thermal spray guns. Surface modification and enhanced engineered surfaces began a movement in the manufacturing industry, virtue of thermal spraying. Since the conception, thermal spray applications have increased many folds, in both sophistication and volume. Starting with lead coatings for dental light bulbs and bronze coatings for lamp posts, thermal sprayed coatings today are being considered to create high strength engineered bulk materials for armored combat vehicles.


Through all those years of technological developments, thermal spray processes have evolved and improved. However, something that is still a challenge today in thermal spraying is process instability. Most if not all thermal spray processes are prone to instability due to their multi-parameter and multi-response nature. Controlling the parameters is one thing but due to the use of consumables and equipment wear it becomes even more difficult to maintain process stability. This phenomenon applies to almost all streams of thermal spraying. In conversation with a colleague who has decades of thermal spraying experience, I was told that in a thermal spray process, if we know one thing for sure is that there is instability.


There is an abundance of scientific work that has been done to improve process stability which is well documented in literature. Statistical analysis, prediction modelling, factorial designs and many other experimental studies have been performed in efforts to learn, optimize, and control the spray properties. However, experimental, and statistical studies can quickly become very time consuming and cumbersome. The use of diagnostic sensors has remedied this problem by reducing the time required to optimize and control thermal spray processes. Online diagnostic sensors, such as the Accuraspray 4.0, are now being used to monitor and control process stability, consequently making the thermal spray process significantly more efficient. Diagnostic sensor integration has allowed for the creation of fully automated ‘smart’ multifunctional spray booths, that perform high volume, high precision spraying. This growth in technology has been one to witness. In 100 years, we went from coating lamp posts with the ‘pistol’ to fully automated spray guns coating complex engines. What’s next?