New Plasmacutter

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05 Jul 2021 12:18 #213760 by Giuseppe
New Plasmacutter was created by Giuseppe
Hi,
after i finished my cnc cutter i do some tests and the problem i have is that the arc sometimes whant not start correct.
Sometimes it stucks.
So i think is the better choise to buy a cutter with a pilot ignition.
Now i see some videos how peaples connect a wire from the clamp to the toarch to realise a pilot ignition.

Is this the same way how the expensive cutters work? Or are there some differences?

kind regards

Giuseppe

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07 Jul 2021 00:04 #213918 by tommylight
Replied by tommylight on topic New Plasmacutter


Is this the same way how the expensive cutters work? Or are there some differences?

There are differences, quite a lot actually:
-High Voltage start uses a transformer at 50 or 60 Hz to raise the voltage to over 2000V, a huge resistor to dump some of the power and is wired directly to the electrode on one side and to the nozzle on the other side, also there is a RC filter to protect the rectifier from destruction at every arc start. Highly reliable, causes plenty of interference, especially as the nozzle/electrode get black inside and the arc is harder to start.
-High Voltage / High Frequency start uses a smaller high frequency (usually over 20 kHz) transformer and switching electronics on the primary side that creates 15000V through a sparc gap and another winding on a ferite core to witch the main electrode wire is also wound with the other side going to the nozzle, also has RC filters to protect rectifiers and a dumping resistor. Very reliable, causes huge amounts of interference, less sensitive to electrode/nozzle getting all black inside.
-Blow back start uses a spring loaded electrode that gets pushed back when the air is turned on while at the same time lets 3 to 5A of current through the electrode to the nozzle, so when the electrode retracts the sparc is created at what point the full cutting power is released. Pretty reliable, costs a lot in electrodes as they fail much faster due to current passing through a spring, less interference than both of the above.
-Scratch start uses ... well scratching the nozzle to the material to create a sparc, so it has nothing that the above machines have. Not sure about wiring as i never used one. Most probably creates more interference than BlowBack, but less than other two above.
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08 Jul 2021 18:50 - 08 Jul 2021 18:50 #214044 by Giuseppe
Replied by Giuseppe on topic New Plasmacutter
Yes thats right but there are lot of cutters with pilotignition out there but i dont know if the cheaper one works also for cnc?

for example this one

link amazon

i have this one


link amazon
Last edit: 08 Jul 2021 18:50 by Giuseppe.

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08 Jul 2021 21:54 #214051 by tommylight
Replied by tommylight on topic New Plasmacutter
Unclear if you want or have the StahlWerk, but either way they are nice, a friend has one for nearly a year and it is working just fine.
 www.stahlwerk-schweissgeraete.de//plasma-cutter/

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10 Jul 2021 19:53 - 10 Jul 2021 19:53 #214212 by Giuseppe
Replied by Giuseppe on topic New Plasmacutter
I have the Stahlwerk. But sometimes i have ignition problems.
I am not shure but this one has a hf ignition and it is not necessary to scrat the metal to start. It is enought to told it 1-2 mm away from the metal. Or not?

Why is sometimes the ignition stucks?

Thats the reason why i whant to buy a cutte with pilot ignition.
 
Last edit: 10 Jul 2021 19:53 by Giuseppe.

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10 Jul 2021 21:40 #214220 by tommylight
Replied by tommylight on topic New Plasmacutter
StahlWerk has pilot start so it should work even from 3 or 4 or 5mm from the material.
Reasons for arc start failing:
-to low air pressure
-to high air pressure
-charred electrode and nozzle (black inside)
-nozzle and electrode not tightened/inserted properly
-nozzle touching the material
--
Yes, nozzle on the pilot plasma must NOT touch the material as that will fail to start
Air pressure should be 5 to 5.5 Bar while air is running, not when air is stopped, use the built in regulator to check and adjust air.

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11 Jul 2021 07:09 - 11 Jul 2021 07:17 #214235 by Giuseppe
Replied by Giuseppe on topic New Plasmacutter
I have upload a video with the issue and some pics of a testcut

file.io/VjqzlbHP0nJc

I am not really happy with the result.

 

 

This is cut with 1000 mm / min

 

and this with 2000 mm / min

What do you thing is the problem, is the machin not stiff onough?
Attachments:
Last edit: 11 Jul 2021 07:17 by Giuseppe.

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11 Jul 2021 07:36 #214236 by tommylight
Replied by tommylight on topic New Plasmacutter
Pictures of the machine ?
That is from vibrations for sure, but what acceleration are you using ?
Try lowering accelleration a bit, but anything under 200mm/s/s is to low for cutting thin sheets.

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11 Jul 2021 11:04 - 11 Jul 2021 11:05 #214243 by Giuseppe
Replied by Giuseppe on topic New Plasmacutter
[AXIS_X]
# set to double the value in the corresponding joint
MAX_VELOCITY = 400.0
# set to double the value in the corresponding joint
MAX_ACCELERATION = 1800.0

 
 
 

I think the z axis is the problem but is it so wobbly? I think no..
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Last edit: 11 Jul 2021 11:05 by Giuseppe.

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11 Jul 2021 11:27 #214245 by Giuseppe
Replied by Giuseppe on topic New Plasmacutter
This is the entrys under
[JOINT_0]
TYPE = LINEAR
HOME = 0.0
MIN_LIMIT = -0.001
MAX_LIMIT = 1370.0
MAX_VELOCITY = 200.0
MAX_ACCELERATION = 900.0

why is here other entrys

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