in Vol. 16 - September Issue - Year 2015
Eco Friendly Mass Finishing
Example of centrifugal filter applied to three finishing machines
Dry finishing of aluminium laser-cut parts with suitable abrasive media in polymer
Looking at the evolution of mass metal finishing from the point of view of ecology, it seems indeed that nothing has changed since the early eighties until now, a part of the reach directive.
Indeed, most of the finishing processes like vibratory finishing or barreling, are almost unchanged in the last 35 years.
Statistically, the majority of them are still based on ceramic media and plastic media in wet mode.
This generates effluents to be treated, chemically and physically, with suitable systems or, simply, filtered with mechanical systems, like centrifugal filters, with the aim to re-cycle the effluents and the chemical compounds for finishing, as much as possible.
On one hand, it is true that the most modern centrifugal filtering systems are offering high efficiency, towards the systems of third generation that are able to process important volumes of effluents if in full automatic mode, including:
• Automatic collection of the effluents into a suitable reception tank, with stirring and mixing;
• Automatic dosing of flocculants or coagulants into the stirring and mixing tank;
• Feeding of the effluents, with pre-determined flow, into the centrifugal filtering area;
• Feeding of the filtered liquid into the buffer tank;
• Automatic distribution, with pre-determined flow, of the filtered liquid to the vibratory finishing units;
• Automatic removal of the mud accumulated into the filtering area, some modern systems also without mechanical blades or mechanical systems - this new system assures very low maintenance, although working 24/24; the removal task can be scheduled at regular intervals of variable entity (i.e.: every hour, or every 3 hours, etc.) and takes about 60" seconds each time to perfectly clean-up the centrifugal basket from the mud slurry;
• Automatic refilling of water level;
• Automatic refilling of compound concentration;
One example of automatic centrifugal filter, of modern conception:
1. Effluents In
2. Filtered Effluents Out
3. High pressure pump for water Jet In (Automatic mud removal system, with water Jet blade)
4. Mud Out
5. Metering pump for coagulant / flocculant
6. Optional Metering pump for antifoam compound
The above is only an example, but of course, the possible combinations are many, depending on volumes, quality of filtered water required, presence of oil or not to be removed actively maintaining the chemical compound in re-circulation, and other options.
Finally, concerning the wet mode process, today's possibilities offered can reduce pollution and limit the maintenance costs and interventions of the worker to very reduced numbers.
On the other hand, more and more fields of application are opening their doors to the dry-mode finishing process.
One field of application is, for example, the oxy-cut and laser cut of steel and other metals, like aluminium.
A common feature of the modern systems of barreling or vibratory finishing in dry mode is the vacuum filters, which are satisfying several needs like:
• Removal of dust particles from the finished items
• Assurance of safe and secure operative environment
• Collection of the residuals of the finishing processes
The future of the dry finishing process is offering wider opportunities to several kinds of industries, although the diffusion of this kind of technology is still far away from being defined as a "mature" solution for every application.
The pathway to proceed, by point of view of R&D in this direction, is still long, but one thing is sure: modern dry finishing is taking more and more places in many different areas and fields of applications.
Some examples of dry finishing applications in recent years:
• dry de-oxidation of welded components in stainless steel, as an alternative to the wet process using aggressive acids;
• dry deburring and smoothing of aluminium components of all kinds, also in cases where small greasy surfaces have to be treated;
• dry process complete of deburring, smoothing and fine polishing of copper or brass components;
• dry smoothing of wood parts, also with relatively soft surfaces, sensible to shocks, thanks to specifically designed low density suitable media;
• composites, also with extremely high porosity surfaces (typical of rapid prototyping);
• laser-casted components;
As well as for the big markets (i.e.: automotive), where there are rules acting on the markets, like EURO6 statements in Europe, Hybrid motors worldwide, etc. - it would be interesting to fix new parameters and a similar challenge also in the vibratory finishing and mass metal finishing markets; fixing modern rules to reduce pollution and substitute old technologies with new eco-friendly technologies.
by Paolo Redaelli
Contributing Editor MFN and Rollwasch® Italiana S.p.a.
Tel. +39.0362.930 334
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