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Thread: Chinese plasma cutters-who's got one?

  1. #1
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    Chinese plasma cutters-who's got one?

    So I am seriously pleased with my old chinese tig machines-I have had two of them, one for 8 years, one for 7 years-both do WAY better than expected.

    https://www.amazon.com/Kohstar-WSE-2.../dp/B06VXG4L5L

    (YES-that is listed under "kitchen utensils and gadgets" on amazon!)

    That's the same unit-for the same price I paid years go, but mine was that much shipped and delivered. Only complaint is the gas valve inside the machine leaks-so make sure you turn the tank off when you're done or it'll be empty in a few hours. Only started leaking a few years ago, and I haven't replaced it-it's a standard off the shelf part so I probably should go around and do it.

    Now, I'm building a CNC plasma table to make header flanges and chassis parts faster and more repeatable, maybe do some alloy valve covers and the like. Hypertherm/Thermal Dynamics are 5 to 10 times the cost of the ebay fodder. Who's used a CUT-50P, or similar? What do you think of the machine, don't give two shits about the torch or consumables because I'll be replacing it pretty much right off the bat with a locally obtained replacement-easy to get consumables and a straight torch for the CNC table that way.

    Currently I'm looking at:

    https://www.ebay.com/itm/Pilot-Arc-P...gAAOSw~RNZlzrD

    And

    https://www.ebay.com/itm/Pilot-Arc-P...cAAOSwuhhXUgMb

    I looked for the Jasic brand-the factory has been pretty responsive over the years concerning replacement parts and repair information for the motor drives I've used by them. I've never had to buy any welder parts from them but I have repaired a few of the VFD's that they built. Unfortunately, the only Jasic-built plasmas that have a pilot arc function are the 60 and 80 amp models. The 40 and 50 amp models are touch-start only, which is no good for CNC.

    Requirements:

    50A maximum cut, 60% or better duty cycle at 40A.
    Pilot arc function, no HF starts or touch starts.
    Fukkin' cheap. I should be able to buy at least two of these for the cost of a new Hypertherm or Thermal Dynamics of the same rating.
    IGBT switches preferred. They're more rugged. Not a dealbreaker if MOSFET based, though.

    Like I said-torch doesn't much matter. I'll be replacing it with a CNC-duty torch anyway, with local consumables. I've actually taken the TIG machines apart and added additional switches to the boards-each side of the inverter had spaces for two extra switches, so I installed the additional components and never looked back. I've abused the shit out of my Jasics after that, hours at at time at 200A+, welding up aluminum cylinder heads.

    Anyone used any of these yet?

  2. #2
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    I have a no name eBay 50A plasma, it's been great.
    I wouldn't hesitate to buy a Jasic branded one.
    Last edited by uuheels; 07-12-17 at 10:03 AM.

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    Unregistered User Permit Roadsailing's Avatar
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    I had a look a while ago and was surprised at how much more a yumcha plasma cutter is than a yumcha arc welder seeing as how a plasma cutter is just an arc welder with duster nozzle blowing on the arc

    no experience but I reckon you will go OK, any details on your build? I reckon a CNC plasma would be hard to beat for cutting at home. Guessing you aren't going to have a Z axis, as I imagine that would allow you to use touch start

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    There is a Z axis, yes-but it's used to automatically pick up the thickness of the sheet and maintain the torch at the correct height. Like for piercing you want to be 1mm off the surface, but for the cut you need to be 0.5mm off. But you NEVER want to touch the part-touching the part causes the electrode cup to wear out much faster and also allows crap to weld to the face and distort the cutting pattern. Would suck to set up a complex part or a nested set of parts and walk away, only to come back and find everything cut out with a 45* bevel to the left! Still researching the needs of the Z axis, but in any case by not touching the sheet the consumables are supposed to last a LOT longer.

    The need for a pilot arc is for if any paint, rust, dirt, etc were to break the contact arc, a non-pilot-arc system may not reestablish the arc, and you will simply stop cutting without a good way to re-start the program.

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    Unregistered User Permit Roadsailing's Avatar
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    Quote Originally Posted by Xnke View Post
    There is a Z axis, yes-but it's used to automatically pick up the thickness of the sheet and maintain the torch at the correct height. Like for piercing you want to be 1mm off the surface, but for the cut you need to be 0.5mm off. But you NEVER want to touch the part-touching the part causes the electrode cup to wear out much faster and also allows crap to weld to the face and distort the cutting pattern. Would suck to set up a complex part or a nested set of parts and walk away, only to come back and find everything cut out with a 45* bevel to the left! Still researching the needs of the Z axis, but in any case by not touching the sheet the consumables are supposed to last a LOT longer.

    The need for a pilot arc is for if any paint, rust, dirt, etc were to break the contact arc, a non-pilot-arc system may not reestablish the arc, and you will simply stop cutting without a good way to re-start the program.
    makes sense, I was looking a while ago and figured an X Y would get it done with setting height manually as the Z axis adds a lot of cost, didn't think about the different heights during cutting.

    I like the non contact aspect, means the whole thing can be built pretty light compared to a router or something and no need to hold it down. You've probably thought about it already but a tray under the grate full of water/coolant/antifreeze should cut down on the dust and smoke a lot.

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    Yeah, I'm planning on a water tray. Only needs maybe 25mm of water under the grate to cut the sparks down. More worried about the iron nitride powder that will be getting into all the rail slides, I don't really want to have super expensive linear rails grinding themselves to dust.

    Probably going to use some older, much more tolerant prismatic ways with roller bearings. Easier to clean, cheaper to replace bearings when they wear out.

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    Baked Dachi Benonymous's Avatar
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    Quote Originally Posted by Xnke View Post
    Yeah, I'm planning on a water tray. Only needs maybe 25mm of water under the grate to cut the sparks down. More worried about the iron nitride powder that will be getting into all the rail slides, I don't really want to have super expensive linear rails grinding themselves to dust.

    Probably going to use some older, much more tolerant prismatic ways with roller bearings. Easier to clean, cheaper to replace bearings when they wear out.
    Bro, on a Chinese Plasma cutter, the rails won't be THK they'll be fully sik Chinesium. Replacements will be cheep. Most likely, they'll be two row bearings and not 4. THK are 4 row and stuff like HiWin is 2. Most of the Chinese made ones are 2 row and basically copies of HiWin.
    “Buy the ticket, take the ride.’”
    ― Hunter S. Thompson

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    Hiwin rails aren't bad-I have used them before and they come in two row, four row, and six row designs.

    Wouldn't matter though, all the guys I have seen that use them say they wear out in weeks of use-the nitride powders get inside the bearing blocks and grind them down pretty quick.

    Right now the plan is box tube and roller skate bearings, even if it doesn't work I can always buy 1500$ worth of eBay hiwin stuff to fix it. Looking at 32$ if I go the skate bearing route.

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    Ease Up Turbo Commotion's Avatar
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    We have a hycut cnc plasma cutter running I believe the biggest thermal dynamics consumer level plasma available. It’s pretty rubbish really. It gets random errors in position and we have replaced the nc board, servo drives and still not been able to fix it. It could be too much resistance in the gantry or just a cheap crappy system. There is an electrical thing in the panel which is supposed to monitor voltage or amps and adjust the height but that doesn’t work properly so u have to watch it and adjust height as it’s cutting. Probably not answering ur question. Good luck with it

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    What kind of linear bearings does yours use, Commotion? Fancy slide rails, round bars with rollers, flat ways? The loosing steps problem sounds like dirty slides or undersized drive motors-is it belt drive, screw drive, or rack and pinion?

  11. #11
    Ease Up Turbo Commotion's Avatar
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    Rack and pinion. Long direction it has train track type rail with a rollers running on 3 sides of one rail and the top side only of the other. It has a 400w servo motor and reduction box on each side with pinion gear. Short side has 2 pieces of aluminium extrusion with hard steel rods. Rollers run on them.

    I have a spare plasma and oxy carriage. Has a little motor and lead screw to raise and lower the head. Freight might be a bit to get it over to you tho. We bought the machine second hand. They bought it but it arrived damaged so the supplier sent another. They got impatient and bought a laser instead and sold them both when the replacement arrived so we got a few spares.

  12. #12
    Registered User Asteroid's Avatar
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    Old/ basic plasmas don't use any sort of linear bearing. They just run roller bearings on solid rails. Overall they are quite flimsy basic machines.
    Losing steps is unique to steppers - proper cncs run closed loop servos which are accurate providing backlash is kept I check.

    If you want a small profiler it's probably best hunting for an old single sided Koike or similar and tarting it up.

  13. #13
    Ease Up Turbo Commotion's Avatar
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    Ours has ac servo motors not steppers but they are leadshine or copies. Could never figure out what caused it. Cut a whole nest with 4 plates the same. Overlay the plates and 3 off the plates are within a mm. The fourth one has most of the part within a mm but say 2 or 3 edges have shifted 10mm. Frustrating.

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