CNC Plasma Cutter Training
- 1 Background Material
- 2 Terminology
- 3 Equipment
- 4 Safety
- 5 Designing Files
- 6 Cuttable Materials
- 7 Preparing Files with PlasmaCAM Software
- 8 Cutting with the PlasmaCAM
Hypertherm has a good explanation of what plasma is and how it can be used to cut metal. See their page What Is Plasma? for more information. The method available at the makerspace is conventional plasma cutting (first on the list).
One common description of plasma is to describe it as the fourth state of matter. We normally think of the three states of matter as solid, liquid and gas. For a common element, water, these three states are ice, water and steam. The difference between these states relates to their energy levels. When we add energy in the form of heat to ice, the ice melts and forms water. When we add more energy, the water vaporizes into hydrogen and oxygen, in the form of steam. By adding more energy to steam these gases become ionized. This ionization process causes the gas to become electrically conductive. This electrically conductive, ionized gas is called a plasma...
Numerical control is a method for computers to control equipment, also known as CNC. This content will be familiar to some members but if this is new take a minute to review the basic concepts of numeric control. Wikipedia has a good article on numeric control.
Another simple way of defining plasma is that it is controlled lightning. We use plasma to cut metals. Plasma torches work by passing electricity through the torch tip, through the plasma gas (yes plasma conducts electricity) and into the metal to cut and through the table and finally into the ground clamp attached to the table.
- Before cutting through material the plasma torch needs to punch a hole through the material.
- Metal piece on the end of the torch that directs the flow of the plasma and air.
- Copper piece inside the torch that is on one side of the arc.
- Parts or supplies that are used or worn out as the machine is used.
- Width of the cut in the material, thicker material means a wider kerf with the plasma cutter.
- Dross or Slag
- Melted metal and junk left on the bottom of material after being cut.
The plasma cutter is a Hypertherm Powermax 1000 with a handheld torch. The manual can be downloaded from the manufacturer website under the service section. Everyone using the machine needs to read the complete operator manual. Direct links to the manual are provided below (PDF warning).
The table is a PlasmaCAM DHC (digital height control first generation). Unfortunately the documentation and software are not readily available online. See the computer attached to the PlasmaCAM for documentation or request documentation during a training session.
The CNC plasma cutter is dangerous in just about every way a tool can be dangerous. It's hot, loud, heavy, automated, sharp, and powerful. This is not a comprehensive list of the dangers.
- Rack and pinion drive for the table can sever body parts
- Plasma torch can severely burn or sever body parts
- The light emitted from the plasma torch is very bright and you must use s shade #5 glasses or darker if you look at the light from the torch
- Recently cut metal parts will be extremely hot
- Table grid and cut parts can have razor sharp edges
- Spilled water could cause someone to slip or get electrocuted
- Prolonged exposure to plasma cutting can cause hearing damage
- Thick steel can be heavy and a drop hazard
Cuts are made based on vectors (Illustrator, Inkscape, CAD programs) and the ideal format to import into the PlasmaCAM software is DXF (2D) which can be exported from most vector based software. Cuts can either be open like a line or a closed shape like a circle. The type of material should be kept in mind when designing files to cut because the thickness of the material causes the kerf to be wider (width of the cut). So intricate designs will be easier to cut from thin material than thick material (e.g. 20ga sheet compared to 1/4" sheet).
The plasma can cut most materials that conduct electricity. See the list below for commonly cut materials.
- Mild steel
- Stainless steel
Other materials can be cut such as titanium and magnesium but it is not recommended because these metals are more flammable and it tends to burn too far and make a mess. Mild steel is easiest to cut and copper and aluminum are more difficult to cut because they conduct heat away from the cutting area much faster. Mild steel up to 1" thick can be cut, but steel that heavy is very heavy. A crane or gantry mechanism will need to be used to lift the material on and off of the table.
Preparing Files with PlasmaCAM Software
Do as much design elsewhere as possible because the software is fairly cumbersome and buggy. Import a DXF file from the File menu and in the dialog select the option to "Link segments" which will keep closed paths closed. If paths get imported as open paths when they should be closed double check that this option is enabled when importing the file.
There's another option for "Import paths as cuts" which can be used if the paths are ready to cut as-is without any modification. This is usually not the case unless all of the cuts are open paths without any overlapping of paths.
Creating Cut Paths
In order to be cut the paths must be designed as cut paths by PlasmaCAM. Open paths can be converted to a cut path without any options or further interaction. Closed paths will ask for a point to use for "lead-in" so there's not a bulge on the path where the pierce is made. Clicking the mouse somewhere near the path picks the location for the lead-in and ends the cut just before it comes back ground to the lead-in.
Clicking inside or outside of a closed path has an affect on the outcome of the cut path. For example if cutting out a sign where the letters should be negative space the lead-in should be inside the letters. The lead-in will be inside the letters so the letters will be throw away material, but the cut around the letter will be clean and without and bulges leaving a clean negative of the letters in the sheet. If the letters are positive space and will be kept and used the lead-in should be outside the closed path of the letters which will result in clean cut letters but the sheet will have lead-in cuts for every letter.
In other words closed path cut will have a piece to keep and a piece to throw away because of the lead-in. If both pieces need to be kept and a bulge on the path is acceptable then the lead-in length can be reduced to zero so the pierce is made on the path rather than off the path. This should only be done if both the inside and outside pieces of a closed path cut need to be kept.
Moving and Copying Cuts
Cuts that have already been setup can be copied or moved to other locations on the table. This is useful for cutting out many copies of the same object or for moving the cut to an area on the table where material is available. Selected cuts can be moved or copied with the hotkeys M and C (see the documentation for other hotkeys).
The table has support points to hold up material. In the PlasmaCAM software those support points show up as blue dots. If at all possible the support points should not be under cut paths. If a cut goes over a support point it reduces the useful lifespan of the grid which will eventually need to be replaced for a few hundred dollars.
Cutting with the PlasmaCAM
Members cutting for the first few times should have another member present who is familiar with the plasma cutter.
The configuration of the machinery may change and this information should be updated to reflect any changes. Use the list below to make sure the machine is ready to cut.
- The 220V power for the plasma cutter is shared with the Tesla charger and welders so check that it's plugged in.
- Compressed air is needed for the plasma cutter. Use the meter on the front to confirm pressure or turn the amperage knob to zero to test.
- Water in the water table should be mostly full which catches sparks and slag.
- The PlasmaCAM control box should be connected to the plasma cutter (MIDI cable) and the computer (parallel cable).
- For prolonged cutting open the bay door and turn on the workshop exterior fan to reduce the smoke buildup.
Start up sequence
- The plasma unit should be powered on, checking the status lights on the front of the unit for correct air pressure
- The computer should be powered on
- The plasma table control box should be powered on
- Start the PlasmaCAM software on the computer and initialize the machine
- Load your material onto the plasma table
- Select the material that matches closest the material you are trying to cut from the material configuration software and press the button to send the settings to plasmacam
- Load the file you are to cut into the Plasmacam software
- Set the cut order from the menu
- Move the machine to the corners of your design to make sure that your design will fit onto the material that you have on the plasma table
- Optionally, run the machine over the file without cutting to make sure it is doing what you expect
- Start the cut, after each pierce, make sure that if any parts that are cut out don't swing into the path of the plasma cutter head, or the plasma cutter head might be damaged if it crashes into that part (DO NOT LET IT RUN UNATTENDED AT ANY TIME!!!)
Cleaning Up/Shutting Down
- After you are done with your job, shut down all the equipment that you started including the plasma unit, computer and plasma table
- Clear your material off the table and any parts that are cut off