CNC Cutting System Information
Purchasing a CNC cutting table
If you haven’t purchased your CNC cutting system yet, there are a few things to consider.
Ideally, you need to set up your machine indoors on a concrete floor. Allow enough space around the machine to safely access all sides as well as allow for material loading and unloading. Having adequate space around the machine is important because you will often need to cut and remove pieces at any given spot on the table.
Smoke and Sparks
Plasma torches can output a large amount of smoke and sparks that need to be controlled. The smoke output from plasma cutting can spread a large amount of metallic dust throughout your shop.
There are two effective ways to control sparks, smoke and dust.
1. Water pan – Placing a water pan directly under your cutting grate can remove up to 90 percent of the smoke created by the plasma cutting process. Most of the smoke is released from metal particles that continue to burn on your shop floor. Water pans immediately extinguish the hot sparks while not allowing them to continue burning. Typically, water pans are made of steel or galvanized sheet metal with a drain plug and contain 1-4 inches of water. Even 1 inch of water will remove an enormous amount of smoke.
2. Ventilation – There are several ways to remove the remaining smoke that is not captured by a water pan.
a. Downdraft collector – this is typically a sheet metal enclosure under your table that is slightly larger than your water pan. This enclosure typically collects all of the remaining smoke and is vented to the outdoors. You can make the downdraft collector either positive or negative pressure. Some shops use their existing wall cooler or fan to bring fresh air into the shop and force it out through the table. Positive pressure requires that you close all of the shop doors. Negative pressure is simply having an exhaust fan on the vent of your downdraft collector and sucking the air outside.
b. Shop fan or household fan to blow the smoke out the door. Although this is not the most ideal, it is better than breathing the smoke! Also, keep in mind local ordinances and EPA regulations.
Keep in mind that a water pan is the most effective way to control smoke, dust and sparks even without a air ventilation system. Water pans and downdraft collectors are not typically offered by plasma cutting system manufacturers so you will either need to build them yourself or have a local HVAC (heating and cooling) sheet metal shop make them out of galvanized sheet metal. Often, sheet metal shops can build these faster, cheaper and better than you can.
Typically you will need a 240-volt plug to run your plasma torch. Your table will usually require a 120-volt receptacle. Your table control box and PC computer must be plugged into a surge-protector battery backup. Often, other power tools can influence the data signal of the controller to the table. If you are still having interference problems, you can pick up a power conditioner, which looks similar to a battery backup, except it cleans up the electrical power source to the table controller.
Some CNC plasma table owners prefer to keep their computer in a cabinet. During use, the cabinet doors are opened and a keyboard and mouse tray is pulled out. After use, the cabinet is closed and the PC is isolated from dust, paint and sparks that may be present in your shop.
Small (typically 4×4)
· Smaller and easier to fit in your shop.
· Often 4×4 table owners will order their steel in 4×4 sheets. They are easier to handle than 4×8 sheets. Ideally, you can incorporate a steel rack to store the new sheets under your cutting table near the floor.
· If you need to cut something out that is longer than 4 ft, you need to index the material. First, you cut half of the sheet and then slide it forward or pull it toward you. Then you manually jog the torch over to the point where the cutting needs to continue. Large pattern cutting requires material stands on one side of the table to hold up the sheet that is hanging off.
Large (4×8 or 5×10)
· Cuts long pieces without the need for moving the material and indexing.
· Great for large production. The more sheet on the table, the more parts that can be cut.
· Floor space
· Moving and loading a 4x8ft sheet of steel can be backbreaking. Special material movers or additional help are often required.