Abrasive Blasting 101
If you’re experiencing static shock from sandblast cabinets, you want to implement a quick and easy solution as soon as possible. This blog gives a simple explanation about how and why static electricity happens, and how to minimize it when you’re sandblasting.
Because harmless static is not like an AC electrical shock, there are many locations for the static to build and wait to discharge via the water in your body. Static is mostly accumulated in the sandblast cabinet but also in the part being processed, abrasive hoses, and gun itself. Glass beads and plastic abrasives are more likely to create static shock than cutting abrasives like aluminum oxide or silicon carbide, but they can all create static.
ProTip: The largest condenser for storing static is the cabinet itself.
Although the machine is grounded, occasionally you, the machine operator, offer a more attractive ground. This requires a special grounding installation that’s very similar to the ground for a home’s Lightening Rod. The benefits of lightning rods are beautifully depicted in The Lightning Field of New Mexico, built as a land artwork by sculptor Walter De Maria. This field is 1 mile x 1 kilometer and consists of 400 stainless poles all within 1/4″ in height vertically just looking to attract a lightning strike during the monsoon season.
Static is created when two dissimilar items are rubbed together creating different static charges. Normally the moisture in the air allows the items to equalize their static charge via electrons using the overcharge of one item and the air to balance the two charges. On dry days, the lack of moisture in the air makes it much harder for different items to equalize and the static charge can build higher before discharging.
ProTip: With the part, nozzle and cabinet all connected using simple ground to the cabinet techniques a grounding kit attaching you to the cabinet will eliminate most of the static created in the cabinet removing the ability for the static to jump or be felt.
Real World Example: You walk across the room on a wool carpet on a dry day. You reach of the metal doorknob and get a shock. You can hold the doorknob and rub your feet on the carpet all day long and never experience the static spark, why? The static charge is simply and harmlessly dissipating through your body to ground as it equalizes from high to low static location. This happens because you are in contact with the doorknob at all times.
If these four steps do not eliminate static shock from sandblast cabinets you can install a static operator mat for the operator to stand. This is seldom required, but in climates of dry humidity, application using plastic or glass bead abrasives and even some new 3-D parts using polymers this additional machine grounding can be suggested. Please keep in mind the machine will then require a more sophisticated ground for the equipment itself.