Glass Bead Blasting | Airblast

Applications

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Glass beads are a non-metallic blasting media, which can be used on various substrates like steel, aluminum and stainless steel. The purpose can be both esthetical as functional:

• Glass bead blasting is effective in removing contaminants like rust, oil, dirt, and light coatings from surfaces, without creating a surface profile on the work piece.
• To esthetically improve the surface and create a matte satin like finish on stainless steel.
• Removing the blue heat marks from welding or bending marks on stainless steel.
• Smoothening the surface of (stainless) steel, making it difficult for dust and contaminants to stick onto. The surface stays cleaner and is easier to clean as well.
• Improving the fatigue life of metal components by peening.
• When using the right equipment and correct glass beads a roughness acceptable for the food grade and medical industry can be achieved.
• Improving resistance against corrosion.

On stainless steel the glass bead blasting can be the final treatment of the object, but it also creates a good basis for powder coating.

Roughness and pressure

With normal grit blasting or sandblasting, the goal is often to clean the substrate and create an anchor profile for the coating to adhere. With glass bead blasting the goal is to lower the roughness and polish the surface.

Glass bead blasting is performed in a blast room or blast cabinet and the glass beads can be reused / recycled. When using  glass beads as the blasting media, the pressure is normally set at a relatively low level, from 2,5 to 5 bars. This way the glass beads gently polish the surface for the best result and the glass beads have a better durability.

The glass beads are normally rather fine in grain size as compared to other blasting media. Typically glass beads 100-200 um (or 0,10 to 0,20 mm) are used, but also even finer glass beads when food grade specifications need to be achieved.

With normal glass bead blasting a roughness of RA = 1,5 um can be achieved at low pressures. When using the Rotin principle in combination with Rotin beads, roughness of RA < 0,8 um are possible.

Are you interested in learning more about Blasting Glass Beads? Contact us today to secure an expert consultation!

ROTIN Blasting Principle

With the Rotin blast nozzle, glass bead blasting without stains or bead blasting to very low roughness within the parameters set by the food- and medical industry are possible.  The ROTIN blasting principle is developed by Cees Kalfsvel from Holland after years of experience in glass bead blasting.

How Rotin works

Normal blast nozzles use a straight narrow jet, which have a hotspot of beads impacting within the blasting pattern. There will always be the operators risk of incorrect overlap of his blasting passes, creating ugly stains on the stainless steel work piece.

The rotating insert (ROTIN) is placed before the blast nozzle. This insert widens the rotating jet proportionally, and sprays it at an angle. The hotspot of beads impacting within the blast pattern is eliminated. The surface will be blasted with a wide uniform rotating jet at equal intensity at every angle.

Rotin blasting is done with a finer abrasive at a lower pressure (2,5 – 3 bars) for the best result.

Advantages of Rotin blasting principle

For more information, please visit 80 Grit Glass Bead.

Hey everyone! I'm new to the forum and am currently doing a complete rebuild of a CB550 motor that I have pulled apart. Every single piece of the engine has been disassembled (with the exception of the cylinder head studs). I have new seals, bearing, o-rings, and hardware labeled and ready to be installed. HOWEVER, I want to clean all of the cast aluminum parts prior to assembly. The ultimate goal is to prep the entire exterior surface for paint so that after it has been reassembled, I can take it to the paint shop and have it coated. I have access to a vapor blaster that uses 20% glass media, along with the high pressure water.

My question to experienced members is if the glass particles actually "embed" themselves in the surface of the cast aluminum. I have read on many other forums and boards that people have used glass blasting with a lot of success; however, there were no follow up posts to say that X number of miles later, there were still no problems. (No news is good news, right?) As this will be a winter project, I will take my time cleaning the parts to purge all of the glass media, re-tap the threaded holes, clean oil journals, etc...

I would love to hear if others have cleaned their parts with glass and have had success. If you had a failure due to glass ruining the internals, what was the extent of the cleaning that was done to purge glass left inside? This has been a labor of love so far, and I want to put this engine back together and be proud that I didn't take any shortcuts and possibly compromise the longevity of the seals, bearings, etc... Reaper pinged me with a PM to ask me to chime in. Sorry I have been absent from my favorite web forum recently, have been flat out with the new shop setup and operation.


>> Here are the questions I have for you:

>> 1. I am planning to clean, reassemble, and send the motor out for painting. Do I need to do all of this very quickly to avoid the surface becoming unsuitable for painting? (i.e. surface oxidation)

Not an issue. I'm in favor of letting a freshly blasted part dry overnight for one last blast with compressed air anyway. Then degrease the aluminum with lacquer thinner or acetone and have at it. I've painted blasted parts the next day and a month later, everything was fine.


>>2. Will the vapor blasting (depending on the grade of glass being used) leave particles of glass lodged in the aluminum? I've heard nightmarish stories of guys putting their engines back together even after cleaning (maybe not as thoroughly as they should have) and the piston rings and bearing surfaces were destroyed after particles became dislodged and got suspended in the oil.
Here is a video showing what I mean ( - The glass blasted one looks like it has glass lodged in it based on the shiny and reflective surface. I don't know if any cleaning was done on them after dry glass blasting.

As Cal points out above, this is "Monsters under the bed". I suppose it is theoretically possible to drive glass bead so hard and so directly that it could embed, but that would be shattered glass bead dust by then, and harmless. Most of the pressures used in vapor blasting, plus the use of the water slurry make this highly unlikely.


>>3. What is the best strategy for purging the blasted pieces of all glass? I've heard multiple hot baths with Tide, then pressure washing, cleaning with air and brushes, re-tapping holes, and then hot bathing the parts again is the best way to reassure myself no glass will destroy the engine.

Two things in general are critical:

First and foremost, do not vapor blast an oily or sludge-ey part. If your parts are CLEAN, and the rest of the process is good and the vapor blaster is setup properly, media will not stick, it will rinse off. I mean CLEAN. We use a hot water parts cleaner plus a solvent tank, rotary bore brushes, Q-tips, brake cleaner by the case, and more. We also remove all the oil gallery plugs. BEFORE we vapor blast a part it is spotless. Then we spend about as much time rinsing and clearing afterwards as we did vapor blasting, in the instance of a set of cases or a cylinder head. Other parts are easier.

Second, you need to plug any threads 6mm or smaller, and any blind passages, plus the oil passages. Media will lodge in those 1.0 threads and in blind holes, and you can blast water and air in them all day without clearing it. Don't let it get in there in the first place. We use powdercoater's plugs, and stainless socket head cap screws to plug. We have and use hundreds of both.

>>This bike is a winter project for me and I am replacing all of the seals, most of the bearings, and all of the o-rings. I just don't want to get the whole thing together, painted, and in the frame to find out that I did something incorrectly and have wasted all my time and money. I love working on the bike and am taking every step I can to make sure I rebuild it to the best of my abilities.

Good man, you are asking smart questions. When it comes time to reassemble, buy yourself a set of thread REPAIR taps, different than cutting taps, and a can of Tap Magic and a can of brake cleaner and strap on some personal protection for your face, eyes and hands. Crack open a beer, put on some tunes and settle in. Start out with a blast of compressed air, then put a drop of the TapMagic on the clean tap, run it in, run it out, inspect. Clean it off if it was cruddy and repeat if necessary till a new screw runs in and out very smoothly. Give it a shot of brake cleaner when you are done and then one last blast-out with compressed air. Repeat in the next hole, and always start with a clean tap. Pro engine builders will always start with this - so should you.

Good luck!

N.


I have no experience with painting engine components, nor any experience with vapor blasting, but I do have extensive experience with surface preparation techniques for structural bonding of metallic and composite structures in the military, aerospace, automotive, and sporting goods industries. Structural bonding has considerable overlap with painting, so there is still some relevance there.

As Nil points out, I would agree that glass embedding itself is something of a "monsters under the bed" kind of fear, with a slight modification. Sand and glass bead blasting are frequently considered no-no's in the aerospace industry due to fears of the media embedding itself into the adherend (the surface of the object to be bonded, e.g. an aluminum structure). The hesitation stems from the fact that aerospace and automotive industries generally require 6-sigma processes or higher (i've even heard of 9-sigma in some aerospace applications), which means (more or less) that there are less than 4 out-of-spec parts for every 1,000,000 parts produced (9-sigma would be an un-fathomably small number). If there is a small physical possibility that glass can be embedded into the aluminum, then they probably cannot use "conventional" blasting processes and meet the 6-sigma requirement. Because aero and auto drive a huge amount of the manufacturing and finishing industries, I would speculate that this fear has trickled down to reach our DIY cosmetic applications, even if the fear is not really a true concern.

Now, the above statement is really only true if you are properly cleaning the surface after blasting. Complex geometry, holes, etc. make it more difficult to properly remove the media, and this would be the concern that folks like us should be worrying about the most.