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  1. #1
    Join Date
    Jul 2011
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    48

    problem with angled cut

    i just finished my cnc-plasma and made my first cut 2 days ago. i borrowed a a budget plasma-machine and hooked it up. i managed to get a descent surface finish on 2mm mild steel that was coated with something grey. i got quite alot of dross on the backside but my problem is that the cut is angeld alot, atleast 20-30 degrees. i tried diffrent amps on the plasma-machine, diffrent feedrates and torch-height. i also changed the nozzle. if you look at the picture, the edge closest to the camera is angled more but has almost no dross on the backside. the edge away from the camera got rougher surface, more dross but the angle is better.





    i also cut some 5mm stainless, probably 2333 but this was to much for the machine. you can still see the angle here more clearly.



    same thing with the thicker piece. the side with the dross got rougher surface but less angle.

    anyone got an idea why this is happening?

  2. #2
    Join Date
    Jan 2008
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    2247
    The varying angularity and dross levels on the steel part can be caused by:

    1. Older technology/design plasma system
    2. Damaged nozzle (tip) orifice from drag cutting or piercing too close.
    3. Inadequate torch height control.


    The stainless cut that you show just indicates that your plasma likely is under-powered for the thickness.

    All plasma systems are not created equal......expect better cut quality with better plasma technology. Torch height control for pierce height and real time cut height is critical as well.

    Here are some pics from one of my cnc machines with a Hypertherm 45 amp plasma with a good height control system.

    1st pic is 3/8" steel, second is 1/4" steel, third is 3/16" stainless, last is 3/16" aluminum

    Jim Colt
    Attached Thumbnails Attached Thumbnails IMG_2637.jpg   IMG_2360.jpg   powermaxcutsamples 001.jpg   IMG_2766.jpg  


  3. #3
    Join Date
    Jul 2011
    Posts
    48
    ok thanx. what settings did you use for the 3/16" stainless? feedrate? amps? torch height? pierce height?

    what are the signs if i got the torch to close or to far off the workpiece?

    is there a standard torch height or is it diffrent between material and thickness?

  4. #4
    Join Date
    Jan 2008
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    2247
    All of the parts in the pictures were cut with a Hypertherm Powermax45 on a PlasmaCam DHC2 cutting machine.

    The 3/16" stainless cuts were exactly as listed in the detailed cut parameter charts listed in the Hypertherm operators manual.

    Amperage: 45
    Pierce height: .15"
    Pierce delay time: .5 seconds
    Cut Height: .06"
    Cut speed: 70 inches per minute.

    Remember though....unless you use the same plasma you will not get the same results! There are a lot of technology differences...model to model and brand to brand.


    Jim Colt Hypertherm


    Quote Originally Posted by da_Rayman View Post
    ok thanx. what settings did you use for the 3/16" stainless? feedrate? amps? torch height? pierce height?

    what are the signs if i got the torch to close or to far off the workpiece?

    is there a standard torch height or does it differ between material and thickness?

  5. #5
    Join Date
    Jul 2011
    Posts
    48
    ok. there got to be something wrong with my plasma machine. it was set to 40 amps but i couldnt go faster then 450mm/min (17 ipm) to even penetrate the 5mm stainless.

  6. #6
    Join Date
    Jul 2011
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    48
    i used a better machine when i tried today, but still the same problem. 5mm stainless cut with 60A and maybe 1200 mm/min. not much dross but still the damn angle... anyone got an idea?


  7. #7
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    Jan 2008
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    2247
    You have not mentioned the brand and model of the plasma. Plasma cutters are not all the same.....some have better control of the arc energy desity, and can provide very square clean cuts.

    I would recommend a Hypertherm plasma.

    Jim

  8. #8
    Join Date
    Jul 2011
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    48
    i dont know the brand or model since i rented it from a company that sells welding equipment and machines. the arc seems to be stable considering that the cut is very even.

    the cut is not conical but is a parallellogram. this is a section view with the yellow bit ofc being the arc...

  9. #9
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    Jan 2008
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    2247
    I could see that in your cut pictures. Usually that indicates that the nozzle orifice is damaged....which can happen on the first pierce if you are not piercing at the proper pierce height. ule of thumb....pierce height should be 2 times the cut height.

    Jim

  10. #10
    Join Date
    Jul 2011
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    48
    ok. how about the cut height? is it the same on all materials and thicknesses? i used the same on the 5mm stainless as you did, 1,5-1,6mm but i got other materials to cut.

  11. #11
    Join Date
    Jan 2008
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    2247
    Cut height and pierce height is dependant on the torch design. Most of the Hypertherm air plasma systems use .06" as the cut height from 30 amps up through 85 amps.....pierce height varies depending on materials thickness. Thermal Dynamics air plasma systems are designed generally to run at much higher cut heights.

    Your pictures show cut angularity wildly varying around the perimeter of the part...that indicates a damaged nozzle....or a seriously bad gas (air) flow problem in your torch....could be a worn or damaged retaining cap, swirl ring, shield, or a restriction in a flow passage in the torch. Likely it is a damaged nozzle.

    Jim

  12. #12
    Join Date
    Jul 2011
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    48
    no all the parts in the torch handle was fresh when i rented the machine. the gas-flow regulator on the back of the machine is set to 5 bar (72 PSI) wich is max according to the warning-label.

  13. #13
    Join Date
    Jan 2008
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    2247
    Well....then it sounds like the consumable parts were good, and you had the proper pierce and cut heights.....so there has to be an issue with either the design of the plasma....or there is a defect with the plasma. I would not be able to reproduce a cut with any of my cnc plasma's that had cut edge angle variations as bad as the ones in your picture!

    Since you don't know what the plasma is (brand, model, power level, gases used, etc.) then it is virtually impossible to offer good advice.

    Jim

  14. #14
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    Jul 2011
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    48
    ***

  15. #15
    Join Date
    Jul 2011
    Posts
    48
    the machine is a tecmo P-60 Plus.

    i changed the nozzle this morning and got a decent cut at the 3rd try. less then 1 degree out of angle, decent cut-surface but quite alot of dross. after that i spent a few hours trying to find good parameters but all i did was to wear out my last nozzle. i finally found good parameters so i got no dross and decent cut surface but quite a bad angle. i am guessing that the angle is because of the ramp next to the hole on the nozzle(both look the same) but would i get a better cut surface with a fresh nozzle? considering the dross i guess i didnt hit the sweetspot as well with the first part as the last.

    the part i mentioned first is the one with the hole:



    i turned up the air pressure to 7,5 bars that helped with the dross. the warning-label was on the other machine...

  16. #16
    Join Date
    Jul 2011
    Posts
    48
    i have been cutting with another machine, a Deca PAC55 and managed to get some pretty good results. the angle is reduced to 5-7 degrees but the ripples is not straight as you can see in the pictures. i read somewere that this is because of to high feedrate? is this also causing the rounded corners on the backside? i got some dross on the backside that was easy to remove. i read in a hypertherm manual that this would indicate to low feedrate. the nozzle was quite worn out when i was cutting these pieces..



  17. #17
    Join Date
    Jun 2010
    Posts
    0

    Miller angeled cut

    I am using a miller 625 spectrum plasma 40 Amps 30 IPM .120 cut height
    with brand new tip and electrode.
    It cuts fine in one direction but when it turns the corner
    I get a bad angle on the cut.
    I checked the torch and it is not angled.
    It dose not do it all the time.




  18. #18
    Join Date
    Nov 2012
    Posts
    4
    Hello everyone,

    I allsow have a problem with angular cuts, My plasma resonator is a Rofin Sinar DC035 (3500W), and the CNC is CR-Electronics. I will post later during today some pictures of my cutt results on mild steel 4mm thickness.

  19. #19
    Join Date
    Nov 2012
    Posts
    4
    Hello again,

    some explanations about the CNS's symptoms, if you want to cut round pieces, on top (the piercing side) the cuts are perfect, round, on the bottom they are oval (angular) on the X axys.

    Pleas can somebody helpp me.

  20. #20
    Join Date
    Nov 2012
    Posts
    4
    yes i am interested in findig out the reasons why the angular cutt apears.

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