jeepsr4ever
We have some customers that are very expienced and have owned CNC plasma tables in the past and some still own other brands. Not everyone has this kind of experience. The CNC plasma can make exceptional cuts and high quality pieces but its not going to make it without a little understanding of what can affect the quality. (Unless your very very lucky in which case you would have already bought a winning lottery ticket) [U][B][COLOR=#ff0000]First and foremost check your consumables[/COLOR][/B][/U]
Oval holes
Ovality in holes can be caused by
1. Cut height too high
2. Tip volts too high
3. Speed too fast
4. Loose gear, loose setscrew ie..motion issue
[B]1. CUT HEIGHT TOO HIGH[/B]
[COLOR=#0000cd]If your cut height is too high and your using a THC delay (which is recommended) you may be cutting your hole or even already cut your hole before THC turns on. THC will superceed any cut height you used in your sheetcam settings. This means after it is turned on (after the THC delay) it will cut at the tip volts height you have in your Mach 3 screen. The higher the tip volts the higher the torch tip is off the material. The lower the volts the lower the torch tip is off the material. If you see your torch lowering just a second or two into your travel you may want to lower your cut height in sheetcam (sheetcam/tools)[/COLOR]
[B]2. TIP VOLTS TOO HIGH[/B]
[COLOR=#0000cd]Tip volts are what the digital torch height control is reading and is making changes in real time. If your tip volts are say 180 and your cutting 1/4" steel your torch will cut at a height of around 5/8" off the material. This is too high and will allow the plasma beam to wander (we like to use this easy term). This can cause coning and ovality on your holes. Follow your book for recommended cutting tip volts. Also keep in mind your mfgs recommended setting may be slightly more or less than your real world result. Most plasma mfgs will give you a tip volts setting per material and per consumable amperage and in the same area will give your a height at which your torch will be off the material. If your not sure do a practice cut and when THC is on and the torch is cutting press the stop button in Mach 3 and measure the distance between torch tip and material. You can do this and get fairly close using a drill bit index. Use drill bits of different size to estimate the height and adjust tip volts from running another test with either lower or higher tip volts.
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[B]3. SPEED TOO FAST[/B]
[COLOR=#0000cd]Here it is in a nut shell. Circles and arcs must be cut slower than strait line moves to obtain the same cut quality. Here is why.. If your cutting a 1" line and it takes you 10 seconds and then you cut a 5/16 hole at the same feed rate your time cutting the 5/16 hole is less than 10 seconds. The reason it is smaller is the same reason a runner running at the same rate on the outer part of a track will have to run further as a runner running at the same rate on the inner part of a track. The runner on the inner part of the track will win the race in a shorter period of time. For a plasma cutter this means it is not heating the material at the same rate as a strait line move if your using the same cut speed. [/COLOR]
[COLOR=#0000cd]There are two ways around this. Open your drawing in a CAD program and change your circle to another layer then process the drawing in sheetcam using "Operation/Plasma cut" twice and pick one layer as the circles (always first if they are inside the outer parameter). The other way is to manually watch for the plasma cutter to start cutting the circles and click the feedrate over-ride down a touch maybe 20-30 percent making sure to up it back to 100% after the holes are done[/COLOR]
4. [B]LOOSE GEAR, LOOSE SETSCREW...MOTION ISSUE[/B]
[COLOR=#0000cd]There are several of you out there that are building from gantry kits. This means your are setting your gears up for zero backlash, tightening your set screws and plugging in your motor cables. Any one of those things out of place and you will have a motion issue. There are 6 set screws for each motor X, Y, A and any of these come loose or start loose motion will suffer. Look at your motor assemblies and do a once over before operation.[/COLOR]
[COLOR=#0000cd] Backlash will also cause issues. When your table is assembled at our factory we set your backlash and it should be good for life however if you hit the gantry with a forklift you may have to reset your backlash using a method where your loosening the 3 9/16 head locknuts on the motor assemblies and pushing upward to force the gear into the rack whicle tightening the same nuts on the studs to set your axis to zero backlash. Gantry kit customers must do this for operation initially. Some gantry kit customers may line up the teeth so there is no mesh thinking they have achieved zero backlash. A quick way is visually inspecting the gear into the gear rack and with the power on see if your can manually push the plate attached to the axis back and forth. If you can something is not right check your gear mesh or setscrews. [/COLOR]
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A motion issue would be a plug not plugged all the way in. This would present itself as an axis not spinning. This can cause an issue with the dual drive axis (X) where one side moves and the other does not. These machines are built to perform and have gobs of torque. They will snap retaining bolts on the gantry like they were twigs so make sure all is plugged in before operation[/COLOR]
