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  1. #1

    Newbie Build advise for steppers ?

    Huy Guys
    Ok a newbie here, and just wondering if I am on the right forum.
    I am another guy building his plasma table for cutting out 14 and 16 gauge mild steel. Looking at the Amazon stuff, but I am like a deer in the head lights when I get to this part. I am semi-retired and looking for a hobby making small signs and fascinated with motion travel.
    I am at the part of building the steel table to cut only 4x4 sheets of metal due to the size of my small shop.
    I am looking for advise on stepper motors , I have been racking my brain looking and reading for the past 6 months , I could purchase a ready built machine but the cost is way too much with shipping and duties and also the exchange rate here in Canada , so I love to build and weld stuff.
    So here are a couple of things that I will be doing , taking in consideration keeping this simple and the weight of the axis down and not over building this project.
    My x axis is running on Linear Rail Kits SBR20-1200mm Linear Slide Rails + Ball Screw SFU1605-1200mm Set with Coupler, BK/BF12, Ball Nut Housing. And this was purchase last year thinking I would go ahead and start the project at that time.
    The frame for this table is 2x4 and 2x2 0.125 Steel except for the sides where it will be 0.188 thick to give be a little more meat for threads for the rails and slider.
    The Y axis I trying to keep the weight down to around 20 pounds so my question here is that I am looking to purchase the steppers and drivers that will move this around there so many out there and I don’t want to over kill this build . Looking at the amazon stuff, butt I am like a deer in the head lights when I get to this part. I am semi-retired and looking for a hobby making small signs and fascinated with motion travel.
    The Z axis I am purchasing already built here in Canada from a small company that just makes these
    Here is a pic https://step-motion.com/products/z-a...ating-head-diy
    I will be installing a THC control and I will be going with Hypertherm Max45 , unless there another machine that does just a good.
    So once again advice for a complete kit steppers, drivers, power supplies, possibly Nema 425oz ?
    Thanks Gang
    PLasmadog ( I hate this name lol)

  2. #2
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    Re: Newbie Build advise for steppers ?

    Hi Plas - Well the 5mm pitch ballscrew will move a small truck so don't worry about weight now. Use a large Nema 23 or 24 and it will be fine. Since a plasma does not cut ie there are no tool loads only inertial loads usually you would use a 10mm or 20mm pitch so it moves faster... What is the target cutting speed? I'm not up with plasma parameters. Just remember that steppers will run out of grunt at 700rpm so your machine speed will be limited to say 700*5=3500mm/min if you have to go faster then that then you will need a bigger pitch screw. Peter

    I looked up the max45 cuttings speeds and I think your going to have to change the 5mm pitch. The chart shows for thin stuff you'll need 10m/min. So a 10mm pitch will give you 1000rpm and this could be a stepper flat chat so no torque. I think a 20mm pitch direct drive or you will need to gear it. Plus at these speeds its best to have a high voltage driver 48V or more.... Need to work thru your target speeds and sort that out before going fwd. Peter

  3. #3
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    Re: Newbie Build advise for steppers ?

    Hi Plas - I looked at small plasmas and they do 7000-8000mm/min so I think you have to gear (use a belt) or change the 5mm pitch screws. 10000mm/min/1000rpm=10mm pitch and at 1000rpm you'd need to use hybrid steppers to maintain steps and they would have little torque. If you used 1616 ballscrews then your on the way. 10000/16= 625rpm and 8000/16= & 8000/16= 500rpm. This is midrange for std steppers so a 48V plus system would do this easy and you still have half the static torque available. If you use a 3:1 up gear with the 5mm pitch you may run into vibration issues so think about changing the screws. Peter

  4. #4
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    Re: Newbie Build advise for steppers ?

    Hi Plas- If your stuck with the 5mm pitch then use a 1:3 upspeed pully and it looks like it will work to give you over the 8000mm/min and the shaft won't whirl. Using a pully also allows you to reflex the motor so its out of the way. (BUT ) I've found cheap ballscrews don't like going fast and they maybe not straight at delivery so it could be a punt at that speed ie the screw doing 1500rpm.... Cheers Peter

  5. #5
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    Re: Newbie Build advise for steppers ?

    Forget steppers. Get some 400w Delta AC servos.

  6. #6
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    Re: Newbie Build advise for steppers ?

    Hi,
    I have to agree with dazp1976. I use Delta servos, both 750W on my new mill and several 400W on two different retrofits, and they have been superb.
    My regular supplier based in China still has 400W B2 series servos kits (driver/motor/cables) for $398USD.

    https://www.fasttobuy.com/220v-127nm...ol_p28069.html

    The entry level B2 series (160,000 count/rev encoder) are rated to 3000rpm but have a maximum speed of 5000 rpm. That could, in theory, propel your
    5mm pitch ballscews to 25m/min (5000 rpm) or 15m/min (3000) rpm. This would easily match and exceed the cutting speeds that peteeng has recommended.
    There is a question that needs be researched and that is 'would the ballscrews whip at these rotational speeds?'

    While servos are a definite step up in cost over steppers/stepper driver/power supply they well and truly outperform steppers, so much so that I will probably never buy another stepper
    ever again.

    Craig

  7. #7
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    Re: Newbie Build advise for steppers ?

    Hi,


    I will be installing a THC control and I will be going with Hypertherm Max45 , unless there another machine that does just a good.
    I worked for seven years for a company that sold and serviced welding equipment, I myself was involved in servicing and repair, electronics being my thing.
    Hypertherm are superb plasmas....there is Hypertherm ....and then there the rest. Don't waste your time or money on anything less than a Hypertherm.

    Craig

  8. #8

    Re: Newbie Build advise for steppers ?

    Hey Wow Thanks for the great advise guys , i will be looking into that for sure .
    My buddy also has some lead screws that he never used here are the specs / 3/8”-8 4-Start ACME Lead Screws and Acetal Anti-Backlash Lead Nuts, 1/2” 5-Start Lead Screw (X) this is what he sent me , he was going to build his machine with some Nema 23 steppers also but gave up and moved to another project . Just wondering if this would be good also ,i can pick up these screws cheap , i beleive he said they wher about 48 inches long ??

    You guys are great

    Thanks

  9. #9

    Re: Newbie Build advise for steppers ?

    Yes for sure the Hypertherm there is a couple of places near me in Ottawa that sell these.

  10. #10
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    Re: Newbie Build advise for steppers ?

    Hi,
    if I'm not mistaken 3/8x8 4 start means 3/8 inch diameter and 1/2 inch movement per rotation.
    If you target 400ipm movement that would require 800rpm steppers. I rather suspect that a 48 inch screw 3/8 in diameter would whip like hell at 800 rpm.

    I would certainly want to check my assumption and confirm or debunk my rough calculation before committing to a purchase no matter the price.

    Craig

  11. #11

    Re: Newbie Build advise for steppers ?

    Here is a question it might stupid butt i have to ask or will kick myself if i dont ! on the X axis with both screws on each side of the table is there a right and a left hand thread ????

  12. #12
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    Re: Newbie Build advise for steppers ?

    Hi All - The prior attached calculation shows the screw will whirl at 2000rpm and Hiwin recommend a service factor of x0.8 so a "safe" speed of 1600rpm. Plus as I have mentioned cheap screws can come slightly bent so they don't like speed & can whip early. So a 3000rpm servo is out. I suggest new screws with bigger pitch are obtained. I agree that the use of servos is a great way to go, comes down to budget. Or change the design to belts. Belts can provide a big speed range from a N23 motor and have little inertia. Peter

    re: lead screws what pitch are they? and a screw support could be added near halfway on the screw that could help stopping the screw sag which starts the whipping but if the screw bounces it may still whirl or judder... the 5mm is not a great fit for this job. Personally I'd convert to belts for this type of machine.

    Re: LH & RH thread yes you can get these but not needed in this application. LH threads are many $$$ I expect out of your budget.... Looking at this size plasma many designs use a cantilever gantry so its driven by one side only. Reduces cost (less motors and controllers) have a look at commercial machines these will give you clues on how to jump.

  13. #13

    Re: Newbie Build advise for steppers ?

    OK Craig will do i will see where he got these specs , i know he had 280 onzce steppers for his project thow.

    Thanks

  14. #14

    Re: Newbie Build advise for steppers ?

    Yes petteng i am looking at belts also at this point , those screws will just warp in the long run as you mentioned.

    Thanks for the research on this , wow .

  15. #15
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    Re: Newbie Build advise for steppers ?

    Hi Plas - Re: Belts - I recommend you use fully returned belt drives vs U-drives. U drives have a few issues which you will uncover if you go down that path. I have made three routers with "single return" belt drives and they have worked really well. I'd use a 12mm or 16mm belt for the plasma. Good luck. Peter

    the image is a small router called Brevis - it uses 10mm belts. The prior one used 16mm and if I use belts in future I'd use 25mm.... just to overkill it and belt cost is not much delta. Oh by the way this type of belt drive will easily achieve 20m/min so well over what you need for a plasma spec...

    eg Brevis and Scoot-1 used 20T pulleys (on Dia8mm shafts) so their diameter was 31.8mm so one rev =100mm so at 500rpm motor speed the belt is doing 50,000=50m/min. I regularly did finishing cuts with Scoot at 20m/min easy... most cutting was done at 1-2m/min so a big speed range there.

  16. #16

    Re: Newbie Build advise for steppers ?

    Wow nice buil Love it , I am lokking for a maximum cut speeds of 300 inches per minute on mild steel 14 gauge ! definitly lok at the belt drive

  17. #17
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    Re: Newbie Build advise for steppers ?

    Hi Plas - 300in/min is 7620mm/min. Easy with a belt. Brevis can do that I've set max speed at 6m/min needs a bit more length (run up) to go faster. Brevis uses a 24V system but I find 48V runs a little smoother. Use the highest voltage system you can... Pay attention to belt tensioning. The tighter the belt the better they run. If you haven't got motors (I think you have, get 10mm dia shafts much stronger and stiffer) Peter

  18. #18
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    Re: Newbie Build advise for steppers ?

    I have played a lot of games, but this is the best one Flappy Bird. wonderful.

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