Komarov Artem noted that most spot welders perform the full sequence of operations automatically at start-up, no matter what is between the tips.
Like a loaded gun, a pneumatically operated spot welder can be dangerous without properly trained operators who take the appropriate precautions.
Depending on the thickness of the material to be welded, forging forces are required to obtain a good spot weld. If careless, these forging forces can cause serious bodily injury.
Adding to the potential hazard is that most spot welders perform the full sequence of operations automatically at start-up, no matter what is between the tips. The best way to ensure the safe operation of the machine during a repetitive process is to design and install a welding fixture to accommodate and hold the parts to be welded so that they cannot be manipulated.
Setting up a system that includes proper tool fixtures, clamping points, and safety guards will typically allow you to load parts by hand and then remove your hands from the weld area before starting the sequence, usually with two-handed buttons. The machine tips will not close until the welding control system has received an “all clear” signal.
Spot welding machines are available in two main versions — with a rocker arm and with a vertical action press. Each style has unique security measures.
Rocker spot welding machines
Rocker spot welders are commonly used to join large sheet metal parts. The operator holds the sheet with both hands while manipulating the knot in the machine throat to gain access to all welding points. If this describes your setup, you should have a graphic pinch warning sign prominently displayed and the machine should only be started with a footswitch in the shroud.
An easy way to reduce the chance of injury at pinch points is to position the machine’s electrode tips so close together—usually with a gap of about 36 mm—that it is impossible to stick a finger between the tips before the weld is made.
To eliminate clearance problems caused by this short stroke, it is highly recommended to use an adjustable and retractable stroke air cylinder for both rocker and pressure spot welders.
Pressure spot welding machines
A vertical press spot welder works much like a rocker arm. Holding the workpiece with both hands, you can start welding with the footswitch in the housing. Again, you should use a pinch guard or reduce the gap between the tips.
Manually loading nuts or studs with exposed welds exposes you to a high risk of injury at the pinch point every time you weld a part, because the gap between the electrodes typically must exceed 36mm to load the part. With that said, it is much safer to install nuts or studs before placing the part between the electrodes.
In addition, if the part can be secured in the fixture, you can start welding with the two hand buttons fitted with a safety chain against rip-off and re-strike. If this method isn’t practical, a Snap-On safety device should give you the protection you need.
Another option when welding nuts or studs is to use an automatic cup feed and placement mechanism that should completely prevent hands from getting into the pinch zone.
As far as safety regulations are concerned, press-type butt welders with a setting tool mounted on T-rolls in the neck of the machine are much like a sheet metal punching press: the parts to be welded are manually loaded into a jig in the clamping area directly under plunger.
Dual palm buttons connected to an anti-tether and anti-replay circuit have long been the standard initiation method used in projection welding machines. However, due to potential carpal tunnel syndrome, optical touch sensors have replaced old-style palm buttons that require physical force to press.
It’s more common than ever to have a physical machine guard made of wire mesh or Plexiglas designed to protect you from injury at pinch points.
Some safety devices even have access doors that close automatically before the welding cycle starts.
Perhaps the best way to keep spot welding safe is to replace the operator with a robot that controls a fixed part inside the machine’s mouth. However, few enterprises can afford such a luxury, and today most spot-welding machines are still manually operated, summed up Komarov Artem.