Table of Contents
Plasmacutter
The plasma cutter cuts all electrically conductive materials such as aluminum and steel.
Very good introduction to plasma cutting
See the Plasma Cutter in action: Plasmacut Bat'leth (YouTube)
Model: Xinhuo Ping Pong
Machining area: 240x150cm
Plasma jet (cutting groove) diameter ('kerf'): at least 1.4mm [YET TO BE TESTED] (at minimum power, 0.7mm steel, feed rate 1500mm/min). Remember to add kerf/2 in each direction to your design if you are not using kerf-aware CAD/CAM software!
Plasma cutting leaves a 'burr', i.e. a rough edge, on harder materials than aluminium, mainly on the underside of the cut, which usually needs to be cleaned up, for example by chiselling or mechanically grinding with a sharp knife. This is a completely normal and unavoidable phenomenon, although adjusting the power and feed rate can significantly affect the removal of the burr.
Inside the plasma booth, next to the door on the left, there is a logbook (beige booklet) hanging, in which it is advisable to record your own cutting observations, i.e. material used, material thickness, feed speed, power, etc. The machine cuts, for example, 0.7 mm steel well at minimum power and 1500 mm/min feed speed, and apparently even 12 mm steel can be cut. [YOU MUST CHECK THE SPECS, 12MM SHOULD BE EASY TO USE]
The control computer (laptop outside the plasma booth) uses Linuxcnc as the software. http://linuxcnc.org/
Plasmacutter procedure
SW/preparation
- [You will receive the laptop theme after attending the training session]
- Make sure the compressor is running and that there is pressure in the tank! The plasma cutter's cutting head is raised/lowered by compressed air.
- Turn on the CNC machine [PHOTO] - this MUST be done before you start the LinuxCNC software on the control unit!
- Start LinuxCNC on the control unit and turn on the monitors (plasma booth camera and computer screen).
- Load the G-code you generated earlier
- Click 'emergency stop off' or press 'F1'
- Home each axis (X,Y,Z) separately [SCREEN CAP]
- [The LinuxCNC error messages that appear when starting work are “normal” (?)]
Workpiece layout
- Place the piece to be cut (metal sheet) on the plasma cutter bed. Cutting very small sheets (precisely) is practically not possible, because the plasma cutter's airflow, the cooling water jet and the contact of the cutting head's insulation cup easily move the piece.
- You can place weights on the workpiece, as with a laser cutter, as long as they do not hit the plasma cutter's path IN ANY WAY.
- Move the cutting head to the desired 'zero point', i.e. the starting point of the cut, and click “touch off” (on the desired axis). The plasma booth also has a wireless keyboard, which can potentially move the cutting head more accurately/faster to the desired starting point. The LinuxCNC control system draws the path of the cutting head on the screen, which may also help with alignment.
- In the plasma cutter, the X axis is the long axis and in the camera view (for some utopian reason) the Y axis is a mirror image (right/left).
Cutting
- Attach the ground cable to the piece to be cut. [PHOTO]
- Turn on the plasma cutter. Adjust the cutting power and select the cutting mode. The middle selection on the cutting mode switch is the de facto setting for normal cutting and the top selection is the setting for perforated plate. [PHOTO]
- Open the air valve. [PHOTO]
- Open the water tap, but only about two-thirds of the maximum (no need to waste water).
Yleisiä plasmaleikkausvinkkejä
- The plasma cutter produces quite good results with longer continuous cutting 'strokes', but each start of the cut (plasma arc ignition) produces a wider initial hole than the normal cut seam and more burr than normal. It is worth starting the cut, if possible, 2-5mm outside/inside the actual cutting interface and after the arc is ignited, move the cutting head in a circular arc or spiral path to the actual cutting groove. Immediately extinguishing the plasma arc after the cut is finished also causes a worse result, which is why 'lead-out' geometry is also used when ending plasma cutting, i.e., like the entry, the arc is directed away from the cutting groove and extinguished only at a certain distance. For example, Fusion 360's post-processor can automatically generate the optimal cutting path code using parameters entered by the user (radius/diameter of the lead-in/out arc).
- A plasma cutter is definitely not the ideal tool for making (small) holes. Igniting the plasma arc itself is already a rather imprecise process, and the diameter of the holes to be plasma cut should be smaller than the thickness of the part to be cut. If small holes must be made with plasma, it might be most sensible to move the plasma cutting head to the center of the hole to be 'drilled' and burn a single point, which would then be mechanically drilled to the desired size. However, Fusion 360 does not (yet) support this feature.
- When cutting metals containing chromium/nickel such as RST/HST (stainless/acid-resistant steel), it is advisable to stay outside the booth and keep the door closed during cutting.
[head movement with keyboard, alignment, raising/lowering] [arrows movement right/up] [file → edit: feed - probably the only command after F360 that needs to be adjusted. Don't mess with G-code if you really don't know how!]
F8: raises and lowers the head. A little water drips from the lowered head onto the material.
To configure the postprocessor:
Start of machining movement
- M8 Cutting head down * G4 P0.2 Wait 0.2 seconds for the cutting head to be down
- M3 Plasma flame on * G4 P0.6 Wait 0.6 seconds for the flame to penetrate the material. This can be increased if necessary if you are trying to cut something thick.
End of machining movement
- M5 Plasma flame off * M9 Cutting head up
Examples
100 mm x 100 mm square cut
- Line.ngc
G21 //Units mm F2000 //Feed rate 2000 mm/min G90 //Absolute coordinates G0 X0 Y0 //Rapid movement XY M8 //Cutting head down G4 P0.5 //0.5s delay M3 //Plasma ignition G4 P0.8 //0.8s delay G1 X100 Y0 F1000 //Feed movement X100 Y100 //Feed movement Y100 X0 //Feed movement X0 Y0 //Feed movement Y0 G4 P0.8 //0.8s delay M5 //Plasma shutdown M9 //Feed head up M30 //End of program
Fusion 360 postprosessori
After use
It would be advisable to clean up after yourself and turn off the equipment if other members on site do not need it. There may still be things to note here. Added. Fill in the logbook (beige booklet hanging inside the plasma booth next to the door) how it went in your opinion. Good, bad for what parameters, what material you plasmated, etc. free design. The idea would be to collect information on how different processes succeed. Report any failures via the media or at least in the blue failure book in the hallway.