How to Ensure a Plasma Table’s Bridge is Square

It’s common knowledge that precision is one of the main advantages of plasma cutting systems.

However, it is important to take steps to maintain that precision in a few key areas, including bridge squaring.

To operate efficiently and protect machine components, operators must ensure the bridge is square, with the rail and dual gantry axes adjusted accordingly.  

What Causes a Bridge to be Out of Square? 

First, let’s look at what causes this problem in the first place. Reasons a bridge can be out of square include:

• Pushing it around when the emergency stop is engaged. 
• Lack of maintenance to the rails, bearings or gear rack. 
• A machine crash due to motion or external factors. For example, hitting the bridge with a plate or forklift during loading/unloading. 
• The machine has been on for a year and not homed since installation. 
• Motors are not set correctly. 
• The age of the machine. For example, worn out components supporting motion. 

What Happens When the Bridge is Out of Square? 

Since the rail and dual gantry are independently driven, there is a homing switch on each. When homing out the bridge, a switch is depressed on each side. If both side switches don’t depress at the same time, the machine forces one side to move, putting tension on the bridge to be straight rather than it naturally sitting straight.  

This can cause one side’s motor to work harder than the other. If a certain threshold is reached, that side of the machine will e-stop and show a dual gantry or rail position error. This increases the load on the machine’s components. 

How to Square a Bridge 

Because it can be difficult to visually determine whether the bridge is out of square, the simplest way to find out is to perform a tension test. 

First, home the axes and drive the bridge to the middle of the table, where it’s least likely to be sitting at any point. 

Next, check the rail and dual gantry position values. For an example of 75 inches, both values must read 75.000”. At that point, press the e-stop, kill the motors and watch the values. If there is a large numerical change, the machine shows how far it moved when the power was taken away, in order to go back to actually being straight. If the movement amount is over a certain value (.010″), the bridge should be re-squared. If the value is less than .010″, no adjustment is needed. Tolerances are very tight because accuracy is the goal.

AKS Cutting Systems machines can easily be squared with the bridge squaring guide procedure. When performing this function, never move the ramps (the switch/trip dogs) from the factory position; if that happens, the machine will be permanently out of square.