Using glass bead in your Dana-Ridge wetblast machine
Glass bead is one of the more popular media for blasting in a Dana-Ridge wet blaster. It’s the one that gives the bright uniform finish that wetblasters are best known for. It’s not to be confused with crushed glass however, crushed glass which is angular in shape, gives a matte finish and is more aggressive. Glass bead has more of a ‘scrubbing’ action as it rolls across the surface.
(Angular grits also perform well with the wet blast process and we will cover media such as crushed glass, garnet, aluminium oxide and others in future articles)
The glass bead that Dans-Ridge supplies is in 25kg bags and is made by Potters. It has letter designations to denote the size of the bead and these can be seen in the chart below:
Glass bead size comparison
Above: Here you can see the glass bead compared to scale. This diagram is simplified, as you can see from the chart above, there is actually some overlap between some grades.
Below: some of the more common sizes up close…
Advantages of glass bead
- Rapid results: clean, finish, peen and deburr in one step
- Controlled results: clean finish without significant metal removal or changing tolerances
- Versatile: create a wide range of reproducible surface finishes
- Economical: can be recycled/reused many times
- Environmentally friendly
- Contains no dangerous free silica
- Chemically inert: no ferrous or other residues
- Larger beads are able to remove coatings such as paint or remove carbon deposits
- Small bead gives a nice bright finish, even on soft materials such as brass, copper and aluminium.
The spheres are made from soda-lime glass, so they don’t contain the harmful ‘free-silica’ that can cause long term health issues and of course when used in a wet blaster any potential fine dust is suppressed by the water. This means there is no need for expensive dust filtration units that you find on dry units.
In a Dana-Ridge wetblast unit, due to the superior agitation and a common collection point, a good mix of water and bead is achieved. This slurry is then directed to the gun and is further accelerated out the process nozzle with the aid of compressed air. The water provides a cushioning effect that can be increased or decreased depending on what finish the user desires. It also ensures that there is no media impregnation into the part itself that can cause issues later. Not only that, there are different sized beads that can be chosen to ‘fine tune’ the available surface finishes. Let’s look at some scenarios where glass bead would be useful.
- A customer has an un-coated aluminium part and they want a nice bright finish from the wetblaster. Any size glass bead will give a beautiful result but to give the best possible finish we would use a small (fine) glass bead such as AD or AH and perhaps wind the air pressure back to 40-50psi. It will give a fantastic finish and won’t take long. If you use larger size glass bead such as AB for example, the finish will still be bright (far superior to a dry blaster with the same bead), will have a certain ‘satin’ quality and will process faster.
- Another customer has painted part and wants it removed but also wants a nice finish. The small glass bead may do the job, but you may sacrifice processing time as the particularly fine media has less mass. In this case a mid to large size glass bead might be more desirable with the air pressure perhaps at around 70-90psi. It will remove paint and will still give a great result.
- Another, has an engine part with carbon deposits they want removed but still wants a nice finish using a media that will not ruin tolerances or damage anything. A large sized glass bead at around 80-90psi will be best here. The part will look like it has just been cast.
- A plastic part that is dirty and just needs to be cleaned would do well with a very fine glass bead (AH or AD) at a fairly low pressure. It will also clean rubber parts of dirt and grime.
- Other uses for glass bead include frosting glass, cleaning wood (not common as wood can swell in wet environments), Peening, light deburring, stress-relieving, removing heat -affected zones, providing a uniform finish and more…
Times where glass bead might not be the best choice may be seen in the following examples
- A customer brings in a part that has been powdercoated properly and the powdercoating is still in good condition. In that case, glass bead would take too long and you would look to an angular grit such as aluminium oxide instead. Perhaps another part would require a nice ‘keyed’ surface for a new coat of paint to stick to. In this case an angular grit would also be desirable.
- A component that has internal moving parts and you are unable to block the ingress of media or disassemble the part for blasting, in which case, it may be more desirable to use soda instead.
- Parts that have a mirror-finish that you do not want to affect. In this case you may be able to protect the parts you don’t want to blast by using cloth impregnated tape to protect it from the blast stream.
Dana-Ridge supplies Potters glass bead and this ensures good quality media that is up to the task. It can be used in dry and wet blasters alike. Be careful with cheaper low-quality glass bead. Some will not be graded sufficiently into the various sizes. We have also had a customer change to our bead after the bead they were using dissolved in water!
Using glass bead with a wet blaster vs a dry blaster
A wet blaster provides a water cushion that helps give a superior finish to a dry blaster in which the bead inpacts directly on the piece.