in Vol. 20 - July Issue - Year 2019
Continuous Precious Metal Finishing Line
Continuous Precious Metal Finisher CPM 33 with 2 robots and visual inspection
ABB-Robo Mr. Outfeed at teamwork with CPM 33
"Metal Finishing" has become a description to cover a huge range of many different processes to surface finish metal… or even better to surface finish materials.
So does the description "Gleitschleifen" – a German way to say that a mix of parts and finishing media will be married to each other for "x-time" until a targeted change of the surface of a parts is achieved.
Tumbling, Vibratory finishing and Centrifugal finishing are still the Three Categories in which most of the mass finishing applications can find their home. Most of them include the usage of water and appropriate chemicals.
All three categories have motivated engineers and experts within the mass finishing sector to develop more specialised and automated finishing concepts. All concepts are dedicated to the specific surface requirements of the parts combined with the sensitivity of the parts towards possible damages: Damages, because a "part on part contact" during the finishing process would damage critical areas of the part.
Surface finishing of parts "contactless" to each other has many different technical solutions within the mass production world…
Drag finishing is well established over decades, describing a parts holder dipping the pieces via a kind of robotic arm into the vibrating media, or dip rotating parts into a "rotating basket of media", whereby the centrifugal force of the basket will shorten the cycle times drastically to finish the parts appropriate, though with no risk of damaging the part due to part-on-part contact.
Vibratory through-feed systems have also been known in the market for decades. Cycle times around 8 to 20 minutes cover a large variation of applications. "Through-feed" describes a continuous infeed into the finishing line as well as a continuous outfeed of the finishing line.
The thought of combining continuous through-feed and centrifugal force has led to a new technical development:
Within the need for the Mint Industry, a new through-feed finishing concept is available now.
The principle shown combines a railway to hold the parts to travel through the centrifugal finishing bowl. As a result, the parts will not damage each other while they will still undergo the enormous centrifugal force of the finishing media. Cycle times between 25 and 90 seconds are measured for the treatment of gold or silver bars.
The used media is a high-density polishing media, which will not only allow the parts to look highly polished, but also result in a slight surface hardening if required.
The infeed and outfeed of the part is supported by two little robots. "Mr. Infeed" will place the pieces perfectly positioned into the rail, whereby "Mr. Outfeed" will collect the pieces after they have been rinsed and dried at the end of the railway!
A camera inspection system (2D or 3D) will inspect each part from both sides and may detect surface irritations from earlier production steps, possibly showing up after polishing – such as blisters or deep rolling marks.
As gold ingots and gold blanks do not hesitate to stick together during a standard centrifugal finishing process, this is a well-accepted solution to surface finish the pieces.
As chemicals and water are part of the treatment, it is essential that this finishing concept can be combined with existing water recycling plants or can be operated with its own water recycling unit, allowing the separation of possible gold residues from the waste water stream.
This concept has found its market niche not only within the mint industry, but also partially within the 3D printing world.
The combination of automation and integrated inspection of finished parts will lead to even more reliable and repeatable processes within the mass finishing industry!
Process data can be stored for research and development reasons. Visible at the machine interface or on your mobile device if you wish it so!
by Thomas Hogenkamp
Contributing Editor MFN and
Sales Director, Spaleck
Tel. + 49.2871.9500.14