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  1. #11
    Im confused, you say im not going to get any type of performance out of the 34's because they need 100v however they are not rated that high voltage and all but "Z" was working fine.

    The upgrades consist of new limit switches/E-stop, rewire from 22 gauge to 16 gauge on the stepper motors, and new connectors between the two modules, what i call the brains (computer and breakout circuit (software)) and the working module (Stepper motors X Y Z and limit switches (hardware)).

  2. #12
    The rated voltage is much lower than the voltage you can actually drive them at using pulses (ie what the stepper driver voltage is)
    I'm afraid Neil is correct and you have built a mismatched system. 36V is way too low for Nema34. You can either accept that or wait for someone to post the technical reasons why.
    You are also running lead screws not ballscrew and have anti backlash. This all adds to the friction when lifting the Z axis. To add to it further they are on skate bearings although that should be a minor factor in terms of allowing a smooth lift.
    The cheapest way to stop loosing steps would be to swap out the Nema34 on the Z to a Nema23, and probably turn the voltage down a touch to be kind on the chips. Keep the acceleration and velocity at modest levels and you should avoid loosing steps.
    If your leadscrew pitch is 1" per turn then I think you would also benefit from a 2:1 pulley on the Z
    Last edited by routercnc; 21-03-2015 at 05:36 PM.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  3. #13
    If i wait for someone to post the technical reasons, I probably wouldn't understand the post anyway.
    I
    will go with the Nema 24 on the Z. for now.
    Could you expand your thoughts on the pulley? Are there any pics of this system?
    If i continue using Neman 34 (thinking about expansion) what would you recommend?

  4. #14
    Just noticed that I've typed Nema 24 where I should have said Nema 23 on my posts - corrected. I should also add that you need the lower inductance ones -I'm away from my computer but remember somewhere around 2-3 mH being a good choice. Hopefully someone can post up a good spec.
    If you look through the build logs here you should see some of them using pulleys. Your screw pitch is very high putting a lot of load on the motor so the pulley ratio will give the motor more torque with less chance of stalling

    If you want to stick with the 34s then you need to buy 4 separate stepper drivers and a break out board. This will be a lot more expensive than your current board and it's all because of your choice of motors which are a bit big for the machine you describe.
    When I'm back at my computer I'll try to find the ones most people use. I think Kinko do some mains powered ones which will really make the best use of them.

    This thread talks about using 34s
    http://www.mycncuk.com/archive/index.php/t-8248.html
    Last edited by routercnc; 21-03-2015 at 05:43 PM.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  5. #15
    Quote Originally Posted by shipper506 View Post
    If i wait for someone to post the technical reasons, I probably wouldn't understand the post anyway.
    I
    will go with the Nema 24 on the Z. for now.
    I'll give it in simple Technical terms. Large motors have more Inductance or think of it as Resistance to flow of current thru it's windings and Current gives us Torque.
    Then think of voltage as the force pushing current thru the motor windings.
    So with higher inductance you need more Push to achieve the same speed as motor with lower Inductance. Then because torque mostly comes from current and your struggling to Push the current thru the windings then Torque is also lower.
    Think of it as trying to drive a manual gearbox(don't think you have many of these in US . .Lol) Car Slow in too high gear!! Because your speed isn't enough then Motor stalls.

    Now you have the worst mix match of components because Nema 34 motors have high inductance but you have Low voltage. Made worse by Drive/s that don't allow higher voltage and like has been said your very lucky you haven't fried them already running so close to there Max voltage.

    Unfortunatly it gets worse when it comes to speed because you have high friction linear components in the form of Lead screw and Skate bearings.

    This translates into Driving Car Slowly in high gear with the brakes Sticking and the end result motor stalls at lower speed.!!

  6. #16
    So my take on this is:

    get a Nema 23 stepper motor to go on the Z axis and use what I have

    or

    get a larger power supply and stepper motor controllers?

    The largest motor controllers I have found are 80v. Will they do?

  7. #17
    Quote Originally Posted by shipper506 View Post
    So my take on this is:

    get a Nema 23 stepper motor to go on the Z axis and use what I have

    or

    get a larger power supply and stepper motor controllers?

    The largest motor controllers I have found are 80v. Will they do?
    Well it's a close call really. .? . . . . Nema 23 motors are cheap and if you combine these with 2:1 ratio using pulleys then they will probably do the job with 36V. . . . Think personally in your position I would so go for this option as it's cheapest and easy.

    If it doesn't work then I would say Start again with new drives, Nema 23 motors and PSU that match better and sell your existing stuff.

  8. #18
    What do you think about a new "Z" axis like this one ( http://www.ebay.com/itm/CNC-Z-axis-S...item4185589de0 ) to replace the one i have? would this work?

  9. #19
    It's less than ideal as it uses unsupported rails so will flex when cutting giving a poor finish. Depends on what you're wanting to cut really...
    Neil...

    Build log...here

  10. #20
    Quote Originally Posted by shipper506 View Post
    What do you think about a new "Z" axis like this one
    Not a lot.!!

    It's just too whimpy for a good router, It uses round unsupported rails and thin aluminium plate so will flex and vibrate giving a poor finish. The bearing and motor coupling design looks poor so chances are accurecy is on lower side. Also poor design with how it connects direct to motor will shorten motor life.
    The screw is 16 turns per inch so thats a high pitch(1.6mm) so your Max feed will be lower, 8 turns(3.175mm) would have been better choice.

    But if you are just doing light work in softer materials then it will probably be ok.

    Just be aware thou the motor isn't included in this sale.!

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