Updated: Aug 31, 2020
Vibratory finisher, vibe, tumbler, rumbler, shakers, polisher, or however you might call it, is loud, messy, and never works as it used to right?... well it comes down to a few tweaks keeping it from being the most reliable, repeatable, and your all-time favorite machine.
The vibratory process has a handful of variables, each as important as the next. Media seems to get blamed for many of the issues surrounding this finishing discipline when really, the issue is the process as a whole. When a vibratory machine goes unmaintained, time-cycles will increase, parts will become dull and dirty, and dissatisfaction with the process can shy people away from utilizing vibratory machines to their full potential.
Glazed media can be a big reason for the loss of productivity in a vibe. Just like a grinding wheel, media is designed to provide some surface altering characteristics by means of abrasive. Without proper process controls, soils and contaminants will build upon the surface of the media, significantly reducing the effectiveness of the media's intended job.
This "glazing" can be attributed to improper compound selection, compound flow rates, part-to-media ratios, filtration/waste stream management, cycle times, or machine setup.
The media in this evaluation was a Washington Mills "C" bond, which is considered a "medium cut" media containing enough abrasive to do some surface refinement and deburring while maintaining a lustrous appearance. In this particular case, there is enough soil buildup on the media surface to effectively eliminate all deburring and refinement potential, resulting in exponential increases in time cycles as well as unpleasant finish quality. The graphical comparison below shows a roughness differential of over 200µin between a properly conditioned media sample and a "glazed" media sample from an unmaintained vibratory process.
You will notice glazing propagates faster when the materials being processed are on the softer side like brass, copper, aluminum, and some non-heat treated steels. Processes containing high concentrations of manufacturing soils like greases and oils, high part-to-media ratios, and low-quality metallurgical properties will produce a dark, concentrated waste stream, which should be an indication that a process audit should take place frequently.
In a vibratory process, Some discoloration is to be expected, however, if your wastewater discharge is as concentrated as the above images, there is a high probability the media is glazed to some degree and should be monitored for productivity loss.
As mentioned before, one reason for glazing can be due to improper chemistry selection and/or dosing methods. Chemistry selection is based on many factors such as materials being processed, types of manufacturing soils, and resulting finish requirements. Many times we will find chemistry being used because " it came with the machine" or the ... "that's what we use for everything". ... answer.
If a process or wastewater restrictions require the drain on a machine to be closed, avoid extended time cycles that concentrate soils loads. Frequent filling and draining may be required to avoid re-depositing soils back onto the parts. Ideally, for a process that has high part loads, the drain should remain open and the fluid should be able to flow freely through the machine. This flushing action will allow the compound to carry out the media residue and soils creating a clean finishing environment while increasing the luster and cleanliness of the part.
Cleaning glazed media is actually fairly simple. Our chemistry line, Chemtrol, manufactures chemistry to do just that. Depending on what your media is glazed with, our Sales Engineers can recommend a product like Chemtol 409
to recondition media with proper cycle time and concentrations.
Utilizing dosing pumps or batch processing, the Chemtrol product is added to the media mass to begin emulsifying and dissolving residual manufacturing soils and metals. There is no standard cycle time for this process, however, you will start to see results in minutes. If your process is part intensive and glazing can not be avoided, it is a good idea to incorporate media maintenance into your PM's. Reach out and we will put you in touch with your Sales Engineer who can guide you on media conditioning processes as well as help you improve the root cause of the glazing.
- The Precision Finishing Team
"Committed to better results... We'll prove it."