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  1. #21
    Jonathan - thanks for your "useful summary" link - good to see you're still your usual patronizing little self.

    Irving - thanks for correcting my shoddy maths - however you just model holding torque - most people want their steppers to move - in which case your maths say nothing.

    Cret - many years ago when some folks on here were still in short pants - all I had for my first machine were unipolars and I had them wired full coil bipolar. Mariss from Gecko drive (but hell what does he know?) suggested I try half coil instead and the difference was dramatic. Try both (it's allowed) - see which best suits your requirements.

  2. #22
    Cret's Avatar
    Lives in IOM, United Kingdom. Last Activity: 06-04-2014 Has been a member for 7-8 years. Has a total post count of 19.
    Thanks for all the input guys - as a newb to messing with steppers (aside from the experience with the 3D printer I've built recently) it's all informative, interesting, and useful. Please don't snipe at each other though - I appreciate all the different arguments and perspectives.

    I will indeed meddle with it all but it'll likely be quite some time before I can assemble something anyway in all honesty due to the need to come up with hardware. If I fry these steppers in the process it'll be a shame but I won't be upset, as long as I don't take out any drivers in the process of course!

    I think I have one or possibly two more of these steppers spare as well but I'd have to check.

    I need to figure out I'd be better looking at those X3 bits on offer over the stuff on ebay but I'm not yet sure entirely about the pros & cons of both, relatively speaking.

    And after that I need to figure out mounting hardware etc. I did have an idea that potentially I could fabricate temporary mounting hardware for the steppers using my 3D printer, just until the mill can machine its own ally stuff.
    People probably scoff at the thought, but the printed plastic has an awful lot of strength and I'm sure would be capable of doing the job just fine. Nothing really to lose by trying anyway.

    I'm not learned in making 3D designs though and have limited free time, so if I can find .stl files for the hardware it's a huge headstart.

  3. Quote Originally Posted by stirling View Post
    Irving - thanks for correcting my shoddy maths - however you just model holding torque - most people want their steppers to move - in which case your maths say nothing.
    On the contrary, if he's using the original leadscrews he'll need the higher low-speed torque just to get some motion. To a first approximation you get 70% of holding torque up to the corner speed. Agreed the corner speed will be higher with the lower inductance of the single coil, but that's moot if it stalls before it gets anywhere close.

    But I agree, he should try it both ways, can't hurt.

  4. #24
    Cret's Avatar
    Lives in IOM, United Kingdom. Last Activity: 06-04-2014 Has been a member for 7-8 years. Has a total post count of 19.
    I wish I knew more about the maths of this stuff currently but it'll come in due course I'm sure.

    In the meantime though, I think I spotted something of a bargain that might be perfect for what I need for the X2 to get started, with 3 options I'm pondering on. Yes I was going to try on the dirt cheap with the steppers I've got but these kits are cheaper than I thought, and viglink sent me a few £ earlier today that helps so I'm thinking it may be best to just get a kit with all the bits needed from the outset.

    I found this first kit for £110 inc 3x 270oz steppers, driver board, and PSU delivered.
    The 270oz steppers should be ok from what I've seen but I'm not hugely keen on the single combined driver board & how good it'd be. Plus I don't know if 270 is enough for my Z axis. I do have an air ram fitted so I'm guessing so but still....
    怐Free SHIP怑 3 Axis Nema23 Stepper Motor 270oz in 3A 4LEADS 3Axis Board CNC | eBay

    So more realistically there are these two:

    3x 435oz steppers, 3x driver boards, breakout board & 2x PSUs - $299
    怐Germany SHIP怑3 Axis NEMA 23 Stepper Motor 435oz in Single Shaft 4LEADS CNC | eBay

    3x 425oz steppers, 3x drivers, breakout board & psu - $319
    怐Promotion怑3 Axis NEMA 23 Stepper Motor 425oz in 112mm 3A Driver DM542A CNC | eBay

    Wanted to do it cheap (in my nature) but these kits look great value and I'm thinking I should bite the bullet here.
    What I'm curious about is why the kit with the higher power steppers (435 over 425oz) is cheaper and includes 2x PSUs instead of a single one in the dearer kit. Have I missed something?!

    Appreciate comments on these - they look just the ticket and am VERY tempted, but don't want to be rash. Not too rash anyway...

  5. #25
    Cret's Avatar
    Lives in IOM, United Kingdom. Last Activity: 06-04-2014 Has been a member for 7-8 years. Has a total post count of 19.
    Yes by the way. I'm on original metric leadscrews in my X2. I do plan to change to ballscrews but might be quite some time before I can afford to. Probably one axis at a time from the one with most backlash first etc.

  6. #26
    Quote Originally Posted by Cret View Post
    I wish I knew more about the maths of this stuff currently but it'll come in due course I'm sure.
    Have you spotted Irving's spreadsheet, here? If you want the maths, then there's I post I made about it a few years ago here.

    In the meantime though, I think I spotted something of a bargain that might be perfect for what I need for the X2 to get started, with 3 options I'm pondering on. Yes I was going to try on the dirt cheap with the steppers I've got but these kits are cheaper than I thought, and viglink sent me a few £ earlier today that helps so I'm thinking it may be best to just get a kit with all the bits needed from the outset.

    Keep an eye on the inductance of the motors you're looking at - one of them is pretty reasonable. These motors from CNC4You have good specifications (I've measured them) and a good price, but I strongly advise you to try using Irving's spreadsheet (or my script here, with a few tweaks) to get a better estimate of what size motors you require. The slides and leadscrews on an X2 will exhibit quite a lot of friction (compared to linear guides and ballscrews), so if comparing with other milling machine conversions bear in mind that you'll need bigger motors (to get the same feedrate) if you decide not to use ballscrews.
    Last edited by Jonathan; 02-04-2014 at 01:01 AM.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  7. #27
    Cret's Avatar
    Lives in IOM, United Kingdom. Last Activity: 06-04-2014 Has been a member for 7-8 years. Has a total post count of 19.
    Thanks Jonathan

    I will have a look at those to see what the requirement is etc and if these suit.
    I definitely want ballscrews though, and it may be the case that by the time I get it assembled and figure out the electronic/software setup etc that I already have them or have got the money together so it shouldn't be too much of an issue, just that if I'm not quite at that point I might have to be a bit wary perhaps of using anything?

  8. Quote Originally Posted by Cret View Post
    I wish I knew more about the maths of this stuff currently but it'll come in due course I'm sure.

    In the meantime though, I think I spotted something of a bargain that might be perfect for what I need for the X2 to get started, with 3 options I'm pondering on. Yes I was going to try on the dirt cheap with the steppers I've got but these kits are cheaper than I thought, and viglink sent me a few £ earlier today that helps so I'm thinking it may be best to just get a kit with all the bits needed from the outset.

    I found this first kit for £110 inc 3x 270oz steppers, driver board, and PSU delivered.
    The 270oz steppers should be ok from what I've seen but I'm not hugely keen on the single combined driver board & how good it'd be. Plus I don't know if 270 is enough for my Z axis. I do have an air ram fitted so I'm guessing so but still....
    怐Free SHIP怑 3 Axis Nema23 Stepper Motor 270oz in 3A 4LEADS 3Axis Board CNC | eBay

    So more realistically there are these two:

    3x 435oz steppers, 3x driver boards, breakout board & 2x PSUs - $299
    怐Germany SHIP怑3 Axis NEMA 23 Stepper Motor 435oz in Single Shaft 4LEADS CNC | eBay

    3x 425oz steppers, 3x drivers, breakout board & psu - $319
    怐Promotion怑3 Axis NEMA 23 Stepper Motor 425oz in 112mm 3A Driver DM542A CNC | eBay

    Wanted to do it cheap (in my nature) but these kits look great value and I'm thinking I should bite the bullet here.
    What I'm curious about is why the kit with the higher power steppers (435 over 425oz) is cheaper and includes 2x PSUs instead of a single one in the dearer kit. Have I missed something?!

    Appreciate comments on these - they look just the ticket and am VERY tempted, but don't want to be rash. Not too rash anyway...

    Don't touch last one, 9mH motors are not great, needs to run on 80v+ drivers.
    First one is poor, single board and only 24v

    Second one is best of bunch, uses reasonable steppers @3.8mH, but these ideally want 4.2A and the drives only give 3A RMS, 4.2A peak. Also PSU is only 36v. Not sure how you use 2 psu across 3 drives; you can parallel up PSUs, but not generally a good idea.

  9. #29
    Cret's Avatar
    Lives in IOM, United Kingdom. Last Activity: 06-04-2014 Has been a member for 7-8 years. Has a total post count of 19.
    Ok that's more great info and I'm learning from this stuff thanks! Great to have this assistance in avoiding some of the packages I might end up regretting.

    I might message the seller and ask about the PSU thing.

    In respect of the drivers and the current they can output & the rating of the motors, do the motors only pull the full rating when a load on them demands that? Or do they somehow draw that constantly? I'm not quite sure how that works sorry.

    Be nice if there's a package at a sensible price that suits the X2 specifically so I'll look a bit further but may potentially come back to this second one. Maybe.

  10. #30
    Cret's Avatar
    Lives in IOM, United Kingdom. Last Activity: 06-04-2014 Has been a member for 7-8 years. Has a total post count of 19.
    On another note - looks like someone already started doing 3D printer produced stepper mounts:
    Stepper Motor Mount Nema23 for Homemade CNC Router | eBay

    So will see if I can find design files somewhere....

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