Vol. 21
September Issue
Year 2020

Good Vibrations

in Vol. 21 - September Issue - Year 2020
Quality Assurance In Mass Finishing – The Present And Future

control panel of a mass finishing system

quality check - media sticking in a work piece

quality check - corrosion after mass finishing operation

quality check after mass finishing operation

Series production on an industrial scale requires stable and reproducible processes. The key factors are traceability, reproducibility and complete logging of processing data. In order to identify and assess risks and avoid complaints, it is necessary to plan processes with foresight. In the best-case scenario, measures should be derived from this data to make sure that all process sequences are completely monitored. Is mass finishing at a good state of development in 2020?

What has been established for decades in electroplating technology is only gradually becoming known and put into practice in mass finishing: Continuous logging and documentation of all quality-relevant parameters throughout the process in order to make processes stable and reproducible, identify risks and derive measures from them. 
Galvanic processes in series production are closely monitored: The bath temperature, cycle times, chemical analysis of the electrolytes, movement of goods and other quality-relevant parameters are continuously monitored. After the last work step of a batch, a log with all important information is generated from the central control system. This can be used as evidence during the batch process, and the QA is then immediately available as a verification tool to evaluate the process. In the event of deviations or complaints, it is easy to trace the point in the process at which problems occurred.
At what state of development is mass finishing? Has development progressed in the same way in recent decades? To put it mildly: There is still room for improvement. In many cases, vibratory finishing processes are underrated. The complex interrelationships between machine/drive, water/chemistry and abrasive media are often only discovered when systems are installed in an industrial environment and run unsatisfactorily. This leads to frustration, complaints, disputes and incalculable costs. Once a system has been put into operation, it has to run and often it is a year-long battle between Manufacturing and QA before effective measures to improve process stability are implemented. 
Some examples from practice: 
Which system is used to indicate when abrasive particles have reached a critical size due to wear? In the best-case scenario, it is the machine operator, when he discovers workpieces with abrasive particles stuck to them. In the worst case, it is the customer who complains about exactly this appearance. One solution is precisely coordinated and systematically developed separation or detection systems (e.g. camera systems) that remove abrasive particles from the process or sound the alarm if they reach a critical size or shape. Established suppliers of automated vibratory finishing systems/processes offer solutions that can be used for specific applications and tailored to the process.
Which system is used to indicate a defective dosing pump for cleaning and corrosion protection agents? Usually it is the first employee discovering soiled or corroded workpieces in the process chain. This is unpleasant and can turn out to be expensive.
A solution is a system that constantly monitors the flow of all media together with the flow rates in parallel with the process, logs the recorded information in a batch log via the control system, and triggers an alarm or interrupts the process if necessary. Such a system makes the peripheral equipment of the vibratory finishing system considerably more complex and also more expensive, but if the complaint rate and quality costs can be reduced as a result, the extra cost can be quickly amortised. 
Which system is used to indicate when the filling level of the abrasive media in a vibratory finishing system does not meet the specifications? Usually it is the employee who discovers damaged workpieces and is surprised why. Even a reduction of the filling level by only 10 % can lead to changes in the process which cannot be detected with the naked eye, but which can influence the quality of the workpieces. Especially when it comes to multi-shift operation, nobody tends to feel responsible for specific control tasks that are required on a regular basis, and it is precisely then that it can be important to develop and establish aids or semi-automated control equipment in order to get things running smoothly in production. 
As a solution, the system could also be monitored by a camera system or alternative technical tools that monitor the fill level. Through the integration with the control system and the system specific to the company, machine operators and also QA can monitor the process at any time with regard to such criteria.
How can the machine operator see at a glance all setting parameters of the machine, including the drive motor imbalance setting? In some cases, this can be successfully done via the control system, because some parameters are entered there and can be called up at any time. In some cases, however, the parameters that can be called up and logged via the control system are incomplete. The truth in many departments: A colleague from the night shift takes a note of how he has adjusted the machine on a piece of paper. It is possible that the writing cannot be understood well or he forgets important information. Mistakes, fluctuations and a disturbance of the process stability are unavoidable in this case. Even if it is only a simple deburring process, the chain of consequences cannot be calculated. In any case, the bottom line is that nothing good comes out of it. 
Generally speaking, the better solution would be an override control system, which only releases the machine for machining if all machining steps and parameters previously defined and described in detail by QA have been entered. The safest variant is of course a program with all this data stored within the control system. However, this requires a suitable control system, which not every vibratory finishing system has. 
When investing in a vibratory finishing system, the user should not only have the machine price and the installation location in mind, but he should also delve deeper into the process technology right from the planning phase. It is important to understand that this is a technology and not some simple operation that performs more or less by itself. 
Well-known and established suppliers operate departments that are primarily concerned with application technology. Even before launching series production, application engineers can optimise all production conditions, both in the planning phase and on-site at the operator's premises, so that frustrating experiences with vibratory finishing processes are avoided wherever possible. 

Author: Dirk Gather
Good Vibrations
Contributing Editor MFN
and Managing Director of
surfaced GmbH, Germany
Tel. +49.3301.5232.0 
Fax +49.3301.5232.29
E-mail: dirk@mfn.li