Automatic Monitoring of Industrial Cold Spray Processes
At the core of the Cold Spray process is the bonding of feedstock particles to the workpiece. Effective process monitoring therefore requires information about both the particle impact at the workpiece and the operating condition of the spray nozzle.
Voline Systems combines spray spot monitoring with Schlieren-based nozzle condition monitoring to monitor the process consistency of industrial Cold Spray applications.
How Cold Spray Monitoring Works
Spray Spot Monitoring Vision SH / Vision SL
The particle jet has an impact intensity that increases with both impacting feedstock mass and particle velocity. These are the two decisive particle-jet parameters determining the impact intensity. This produces a correlated luminescence of the spray spot, which is measured and evaluated by Vision SH and Vision SL.
The spray spot shows where feedstock becomes a coating — and where coating layers become additively manufactured parts.
Stable Process Conditions Powder • Gas • Nozzle
Industrial Cold Spray systems provide stable powder feeding and constant gas parameters. Powder quality is controlled before entering the process.
With uniform powder injection and constant gas conditions, nozzle integrity becomes the key remaining variable affecting particle acceleration.
Nozzle Condition Monitoring Vision GM / Vision CR
Aluminium, titanium and nickel alloys can form deposits on the inner nozzle wall. These deposits first disturb the gas flow and may later cause spatter and deviations from the specified particle velocity.
Vision GM and Vision CR use Schlieren imaging to detect these conditions before workpiece quality is affected.
Complete Process Consistency Monitoring
Combining Schlieren-based nozzle condition monitoring with optical spray spot monitoring provides complementary information about two critical parts of the Cold Spray process: the operating condition of the spray nozzle and the particle impact at the workpiece.
Together, Vision GM / Vision CR and Vision SH / Vision SL enable comprehensive monitoring of process consistency for industrial Cold Spray applications.
Technical Background
Learn more about the process conditions that determine Cold Spray stability and why preventive nozzle condition monitoring is important for industrial applications.
Process stability in industrial Cold Spray
Process stability in Cold Spray is achieved through consistent powder quality and reliable operation of the spraying system. In an industrial Cold Spray process, the powder is inspected before it is loaded into the system — not while it is being sprayed.
Monitoring the correct operation of a Cold Spray system is considerably more straightforward than in other thermal spray processes. As long as the gas parameters remain constant, powder injection is uniform, and the nozzle is clean, particle acceleration is as constant as technically possible, as there are no further influencing factors in the particle acceleration mechanism.
Why nozzle integrity matters
Modern Cold Spray systems used for industrial applications automatically provide stable powder feeding and constant gas parameters. The one component they generally cannot monitor continuously is the integrity of the spray nozzle.
Monitoring the nozzle requires additional sensing technology in the supersonic section of the flow, which is currently available only as additional equipment. This is why continuous nozzle condition monitoring requires dedicated sensor technology beyond the standard Cold Spray system.
Deposits, particle velocity and preventive monitoring
Technically important feedstock materials such as aluminium, titanium and nickel alloys can cause deposits on the inner walls of the spray nozzle. Over time, these deposits can lead to spatter and deviations from the specified particle velocity.
Once these effects become apparent, workpiece quality may already have been affected. Preventive nozzle condition monitoring makes it possible to detect such developments early and to replace the nozzle before significant process deviations occur, while it is still relatively easy to clean.
Deposits inside the nozzle first disturb the gas flow. Vision GM and Vision CR use Schlieren imaging technology to detect these operating conditions before workpiece quality is at risk.
Conference Contributions
Selected scientific conference contributions presenting the foundations of our optical monitoring approach, process analysis and quality monitoring for Cold Spray applications.
