Bead Blasting vs Sand Blasting: Two Metal Surface Finish Types Compared
In this post, I’m going to personally review two popular surface finish type for CNC machining metal part: bead blasting and sand blasting.
We have deep researched each finish to uncover the difinition, difference and the beneift. So make sure to read this guide until the end. That way you can make the best decision for your project.
Bead blasting involves the use of tiny spherically shaped beads to prepare a surface. The beads are fed into a machine that is connected to a pressurized air supply. The pressurized mixture of air and beads travels through a blast hose and is then fired out through a blast nozzle directed onto the surface. On impact, the beads dimple the surface causing the removal of coatings previously applied.
The process can therefore be used for cleaning surfaces, wooden surfaces, metal surfaces and plastic surfaces. The look produced depends on the parent material of the surface as well as the specific conditions of the bead blasting process such as working pressure. The beads are processed to a uniform size in order to give the best results. This process usually occurs inside a blast cabinet.
Reference Post: Bead Blasting Finish: The Complete Guide in 2022
What is sand blasting?
The sandblasting process is similar to bead blasting in many respects except for the media used. Silica sand used in sand blasting is crushed sand and irregularly shaped. It is an abrasive material, and it leaves a coarse feel on the surface on which it acts and for this reason it is sometimes referred to as an abrasive blasting technique.
In most applications, sand blasting is a higher-pressure application as compared to bead blasting.
Difference between sand blasting and bead blasting?
As the names suggest, sand blasting uses sand while bead blasting can be glass beads or plastic beads. The beads do not crack or leave shards on the work surface whereas with sand blasting, particles can be left on the material. As such, bead blasting is a common choice for obtaining a polished look or uniform finish.
With bead blasting, it is possible to reuse the media. You can devise a method to collect the beads and use them again. However, this is not possible with sand blasting. Once the media has been used you cannot recover it.
Safety precautions for the two processes are also different because sand blasting produces very fine silica dust. Sand blasting is therefore usually heavily regulated to ensure that operators do not inhale the fine airborne dust produced and have adequate respiratory protection and body protection.
The type of finish obtained after sand blasting and bead blasting are different. The abrasive particles in sand can result in a coarse look. Fine glass beads are known to produce a satin finish on metals.
Due to the regular sphere shape of the beads, bead blasting can also achieve surface hardening. Each bead hits the workpiece surface with a fairly similar force throughout the process and this produces a surface hardening effect which can be likened to shot peening.
Which is better?
Advantage of Bead blasting
Generally, bead-blasting uses less media per unit area worked as compared to sand blasting. This can be attributed to the uniformity and regular shape of the beads. The spherical shape allows for more contact between media and workpiece.
Bead blasting is also a more environmentally friendly process as it does not require extensive cleaning after the blasting process is complete. Sand blasting on the other hand can cause negative downstream effects if cleaning up after the process is not done thoroughly. There are also far fewer health risks associated with bead blasting.
Bead blasting is a gentler process and produces uniform surfaces. With sandblasting, on close inspection it is possible to observe some minor damage. Some of the parent surface material can be chipped off by the sharp-edged sand being fired under pressure.
Bead blasting does not alter the dimensions of the workpiece whereas in sandblasting, the shape/dimensions of the workpiece can be altered.
Benefits of glass beads is that they are a chemically inert option and are a reusable material.
Advantage of Sand blasting
Sand blasting usually comes cheaper than other methods of impact blasting. This is because there is not much processing that is required to turn regular sand into a medium suitable for sandblasting.
Sand blasting has the quicker removal rate and is favored for surface preparation where the surface is not required to be smooth. Bead blasting is a slower process.
Sand blasting a desirable option if a secondary material is to be applied on the workpiece surface. The abrasion of sand particles on surfaces aids the adhesion of a secondary material such as paint or other industrial coating.
It goes without saying that both processes should be done by a skilled operator in order to obtain the best results. There are many variable factors that affect the final look of a component such as; the angle of firing, the air pressure, the grit size of the media and also the distance from the blast gun to the work surface.
It is therefore necessary to weigh the various factors for a particular project before making a choice. While sandblasting is a quick process, it may alter the dimensions of the underlying materials causing the workpiece to lie outside of tolerance ranges. While bead blasting is a relatively safer operation, it takes longer to complete. One method may be suitable for softer materials more than the other, hence you must always weigh all options before settling on a choice.
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