E-Archive

VOL. 26 January ISSUE YEAR 2025

Cover Page

in Vol. 26 - January Issue - Year 2025
Opening the Last Black Box. Real-time Abrasive Analysis Is Possible.
The camera takes snapshots of the operating mix in real-time

The camera takes snapshots of the operating mix in real-time

Abrasive analysis using sieves is labor-intensive

Abrasive analysis using sieves is labor-intensive

Abrasive condition dashboard in Monitizer | DISCOVER

Abrasive condition dashboard in Monitizer | DISCOVER

The analysis of the abrasive is shown on the HMI. The graph shown follows the format of a sieve analysis.

The analysis of the abrasive is shown on the HMI. The graph shown follows the format of a sieve analysis.

Frank Eiterig, Project Manager &Digital Products at Wheelabrator

Frank Eiterig, Project Manager &Digital Products at Wheelabrator

Tight control over the abrasive condition and operating mix is important for many shot blast processes from high-spec peening to precision surface prep before coating. And yet the abrasive system remains a black box with no live view of critical process parameters. A new imaging technology can change this.

To assure a stable abrasive composition (and document it for customers), operators still use labour-intensive periodic checks that trade off accuracy/frequency against practicality and cost. The lack of a better method for monitoring abrasive condition stands in the way of more efficient, higher-performing blast processes in critical applications. Here, taking limitations of current abrasive condition monitoring into consideration, we present a novel real-time method that opens the black box and brings the shot blast process control to a new level.  

The perfect mix?

MFN readers know what we mean by a good abrasive operating mix and why it matters, but for the purposes of the discussion, let us briefly recap. 

The operating mix is the composition of the abrasive running through the machine at a given moment. It is always a mix of freshly refilled and already circulated abrasive, with the exact make-up of that mix and how it fluctuates over time being a major determinant of blast performance - both in terms of the resulting surface and part quality and the efficient operation of the machine. 

Ultimately, this is about shot size. New abrasive introduced to the mix has an initial size that is then gradually reduced over time until it is separated out. The range of shot sizes present in the operating mix as well as the relative share of different particle sizes have a significant impact on the machine and process.

In cases where running the right operating mix is critical for the blasting results, operators will pay special attention to it and (depending on customer and quality requirements) either check the abrasive condition visually, which requires experienced eyes, or conduct periodic sieve analysis, where abrasive samples are passed through multiple sieves to separate and measure different particle sizes. 

For applications where the blasting results don’t have to be precise, operators often don’t monitor the abrasive condition at all, but simply refill new abrasive as needed. This means they cannot notice any operating mix problem until it is causing quality issues. By that point, a deteriorating operating mix will already have affected running costs, cycle time and wear of machine parts.

What happens if the mix is far from perfect?

The impacts of abrasives with poor performance on different applications vary. Here are a few common issues of an operating mix that’s gone off-piste, and the (current) measures needed to keep it in check.

Shot peening

In shot peening, particle size and shape are of critical importance for the process effectiveness. Shot size (via the shot particle’s mass) determines the kinetic energy applied on the part surface and the compressive stresses introduced.

Shot particles that are too small will result in a lower blast intensity and reduced coverage. That means longer blasting for the same coverage, which in turn means longer cycle times, lower productivity. But crucially, undersized shot/below-spec shot sizes can result in insufficient fatigue strengthening of the parts, which could ultimately lead to recalls, repairs or premature part failure.

How do shot peening experts know their operating mix is in top condition other than waiting until they see it on an Almen strip? Currently, the answer is sieving - periodically, once a week, for example, to catch major drifts in abrasive condition but risking flying blind between checks, or more frequently, three times a day, for example, committing significant resources to assure customers.

                                                                                                                                          

Example: Gear peening

A Wheelabrator customer specialising in the manufacture of automotive gears and shafts peens gear teeth to extend the operating life of gears. In order to prove that the fatigue strengthening process is consistently effective, they carry out Almen tests as well as report the abrasive quality. This is done via manual sieve analysis twice a week. Between checks, the process remains a black box.

                                                                                                                                          

Surface preparation for coating

Whether shot blasting precedes plating, powder coating or painting, when it prepares a surface for coating to achieve a precise roughness level and profile for good coating adherence and a consistent finishing, shot size determines the roughness and profile, while a stable operating mix determines the roughness consistency across large volumes of parts or large areas. 

If the surface roughness profile fluctuates, downstream processes have to be constantly adjusted to compensate. If the fluctuation goes undetected, the part may end up with insufficient coating quality that either couldn’t pass quality control or results in customer returns. If parts are blasted in large batches, issues with the abrasive mix will affect a lot of parts at once, possibly requiring rework or ultimately being marked as scrap.

Likewise, frequent manual checks are currently the only option to ensure downstream process parameters can be adjusted in time. 

                                                                                                                                          

Example: Preparing forged parts for plating

A Wheelabrator customer manufacturing premium hand tools shot blasts the forged parts before plating. If the surface roughness and profile delivered by the blast process change, the plating may fail completely or require interventions to adjust temperatures and chemical composition of the immersion bath. The customer is therefore looking to run an extremely stable blast process. Fluctuations in the abrasive mix may cause the surface roughness or profile to fall out of tolerance, which is a real challenge and requires sampling and stopping production to allow the plating process to stabilise.

                                                                                                                                          

Sweep blasting and steel descaling

In applications (like cleaning) where changes in the blasting results are easier to be spotted, the right, stable abrasive condition ensures blasting results are achieved cost-efficiently. For gentler processes (sweep blasting of sensitive surfaces or mechanical descaling of steel, for example), it also ensures the treated surfaces aren’t damaged. 

In all of these applications, the same cosmetic result can be achieved with a broad range of operating mixes, but not all of them are cost-effective, productive or machine-friendly. For example, a high share of fines in the abrasive can lead to increased wear and reduced operating life of wear parts. Fine abrasive can creep into machine components, causing them to become jammed or shot-locked. 

When an abrasive mix has gradually drifted to smaller, finer shot, it loses effectiveness, meaning either longer cycle times and reduced production output or higher abrasive velocity through higher wheel rpms and increased energy consumption. At the other end of the spectrum, if a rapidly deteriorating operating mix is balanced by adding new abrasives more frequently, then abrasive costs will shoot up.

There is currently no simple, in-line method to check abrasive condition to either prove process stability or catch drifts and fluctuations before they turn into problems.

Getting a true picture

To address the last area of the blast process that is still evading tighter controls, a team of shot blasting and digital experts here at Wheelabrator has been working with customers to develop an in-line, real-time abrasive monitoring method. 

The objective is to perform fast and simple measurements/analysis of the abrasive during operation, with easy-to-read, visualised results that allow quick corrective action in real time.

The method, that has subsequently been tested and proven in customers’ production environments, uses a bypass system to divert a continuous sample stream from the abrasive silo. This sample then runs over a vibrating chute to form a thin curtain that is captured continuously by a camera. The whole system can be fixed or mobile, and can be integrated into new machines or retrofitted on existing equipment.

The camera image clearly shows shot size, shape and composition of the operating mix. Automatic image analysis converts visual data into relevant metrics (for example into the same result format a sieve analysis would produce). Measurement results are shown at the machine interface or, if available, a digital dashboard. Crucially, gradual developments and trends of the abrasive condition are made visible so they can be monitored and tracked easily.

Measurements are triggered automatically according to set protocols, with different measurement profiles available to meet different requirements. Alerts can be set to notify operators of out-of-tolerance abrasive and give instructions for corrective action.

IIoT-ready abrasive data

A major advantage of the unit is that it generates digital data from visual readings very quickly. This makes abrasive condition data readily usable for digital process optimisation and allows operators to analyse abrasive data in the connection with other data sets. 

The unit is designed as an IIoT device that can be built in digital systems like Monitizer | DISCOVER, enabling users to create dashboards and run historical analysis on the data.


For operators of shot blast processes that require frequent checks of the operating mix, whether it’s for shot peening or before coating, this new in-line monitoring method unlocks more economical ways to meet the quality assurance demands from end customers. But more importantly, it opens up the last remaining black box in shot blasting, offering new insights and enabling a whole new level of process control, with significant positive impacts on quality and efficiency.

Ultimately, the vision is to build a system capable of self-correcting, constantly making small adjustments to automatically keep the whole process continuously at the optimum.


For Information: 

Wheelabrator Group GmbH

Industriestraße 55

48629 Metelen, Germany

Tel. +49.2556.880

E-mail: Frank.Eiterig@noricangroup.com

www.wheelabratorgroup.com