Need Help! Are there steppers any good


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  1. #1
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    Default Are there steppers any good

    Im looking for 4 stepper for woodcutting and 3D work in wood..

    Found these but have no idea if they are any good..

    https://www.ebay.de/itm/1PC-Nema-23-Stepper-Motor-Schrittmotor-High-Torque-3Nm-4-2A-113mm-10mm-Shaft/392238722433?hash=item5b533fed81

    Maybe someone know the manufacturer OSMTEC..

    And how can i figure out how fast they can move.. Yeah im a noob ????????

    Thx

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    Default Re: Are there steppers any good

    Hello Kristjan,

    the linked steppers are the absoulute basic design you can get. No encoders, nod dirvers included. Those will have to be bought seperate.

    About the speed, that can be calculated. But for that you/we need more information. Ballscrewpitch and diameter, transition if any and the weight of the to be moved parts. So if you have more information about your machine I can help you with that.

    PS:
    Also, normally you would go the other way around. Define you parameters with what you want to work on and how fast/precise. Then Choose the apropriate drivers. If there are none make compromises/engineer around it.

    Greetings, Nightlight



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    Quote Originally Posted by Nightlight View Post
    Hello Kristjan,

    the linked steppers are the absoulute basic design you can get. No encoders, nod dirvers included. Those will have to be bought seperate.

    About the speed, that can be calculated. But for that you/we need more information. Ballscrewpitch and diameter, transition if any and the weight of the to be moved parts. So if you have more information about your machine I can help you with that.

    PS:
    Also, normally you would go the other way around. Define you parameters with what you want to work on and how fast/precise. Then Choose the apropriate drivers. If there are none make compromises/engineer around it.

    Greetings, Nightlight
    Hi Nightlight..

    Thx for info... I have already TB6600 drivers , a Breakout board and powersupply.. Im not at home at the moment but basicly the machine i have is the Workbee 1500*1500 bought through aliexpress.

    I bought only mechanics on aliexpress.. the electronics are bought in china also but the steppers themselfs i just want to be sure that they are not complete junk and that they will suffice at driving my machine in woodworking and doing it at least a good deal faster then my current which is an old old thing from Isel germany.. it runs only at 16 mm/s... Not alot but it is an old isel 2030 machine and made for precicion not speed ????.

    I will be Running with an amb 1050 spindle..

    The following is a link to the kit i got 1500 x 1500 with ballscrew.

    https://h5.aliexpress.com/item/32910234018.html?spm=a2g0n.seo-amp-search.searchResult.32910234018

    Thx again for the info ???? is it ok if i pm you if i run into troubles with my build ?

    Best regards kristjan



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    Default Re: Are there steppers any good

    Hi Kristjan,

    yes you can PM me if you want but my abilety to help depends on the Problem at hand, so no promises =)

    Back to the Machine, lets do some math/assumtsions/data gathering:

    -->Ballscrews
    |-->1.5[m] in length
    |-->? diameter
    |-->?pitch

    Not much to calculate here without diameter and pitch in terms of nececcery motor power. But we can do some assumptions based on literature[1]. Assuming that the ballscrew is fixed at both ends with axially stable bearings we get a miximal rpm of about rpm_max=2500[rpm] for an 25xx[2] screw.

    Next step:Acceleration

    Your old machine was 16[mm/s] or 0.016[m/s] which gives an acceleration of 0.064[m/s^2] via a = (4*s_ps)/t_ps^2, where distance is s_ps=16[mm] and time t_ps=1[s]
    If we assume a pitch of h=5[mm/turn][4] for your ballscrew on this machine we get a needed rpm of 384[rpm] via n_rpm = 1/2*(t_ps*a/h)*60, just to get a feeling where we come from here.

    So with the above number of rpm_max we could go to round about 80[mm/s][3] before our ballscrew starts to get funky. For now this is the limiting factor of how fast you can get with this kind of system at all[6]. What your spindel can handle is anotrher story and, sadly, not my expertise[5].

    Due to the length we are dealing with here we should make a sanety check in trms of the force that will work axially on the ballscrew if we really go for it. We can simply use our acceleration for 80[mm/s] and assume a gantry mass of about 15[kg] to calculate F=m*a with 15*0.32=4.8[N]. A 1500[mm] 2505 can take about 10[N] before it buckels[7], so we should be in the green... if you have at least a 2505 screw which I sadly cannot read out of the product page. Can you provide the data?

    Next step:POWER!

    We will have to calculate the nececcery energy requierd to move your assembly at the desiered acceleration based on its mass and the kind of movement, meaning linear or rotation and then finally get to make a decision about the steppers.
    Assumptions:
    The to be moved mass of the system, lets say 15[kg]
    The to be rotated mass of the screw J_s=(pi/32)*d_s^4*l_s*rho
    with:
    d_s=screw diameter
    l_s=screw lenght
    rho=material densety, here steel with 7850[kg/m^3]

    We get for J_s=7.5760e-05

    And for our gantry we get:

    MA = m*a*(h/(2*pi))-->Momentum
    w_p = 2*pi*(a/h)-->Angular acceleration
    J_n = MA/w_p-->Load momentum

    J_n=0.0025

    J=J_n+J_s=8.2093e-05

    With that we can calculate out torque to:

    T=J*w_p=0.033[N/m]

    And yes, these values tend to be that small... remember that these 3[Nm] are holding torque, not what the stepper can put out when turning.

    And the neccecery power with:

    w = 2*pi*n_max-->turnrate
    P= T*w-->power

    P=37[W]

    So our Stepper requierments:

    -->RPM=2000[min^-1]
    |-->Power=37[W]
    |-->Torque=0.033[N/m]@2000[rpm]

    And how does that apply to your steppers? I found a torquecurve that seems to be close to your motors:
    https://us.misumi-ec.com/linked/item.../HT23%2048.JPG
    You can see that torque drops drastically with rpm, but yours should be fine. Sadly I did not find anny information about the Max rpm of these....

    Conclusion:

    Given the assumptions above, your steppers should do fine assuming they can pull off 2000[rpm]. Without a exact datasheet, we can only assume that they do, or you contact the supplyer. What I know so far is that these rpm may be critical to archief. If you provide further data I can do a precice calculation, I have written a small script for that.

    Hope I could help and did not confuse you further.

    Greetings, Nightlight.

    PS:You should think about an encoder on these. I did not read in your post that you have one one the screws or annywhere else.



    [1]sadly, due to copyright I do not know if I am allowed to share these.

    [2]this is independent from pitch and determinates if it will start to wobble or bend under its own weight. Also, my source does not include smaller diameters

    [3] an 0.8 safety margin is included in this number to avoid the Ballnut to block because of the angle the deformation would produce.

    [4] an higher pitch will reduce the nececcery rpm but may reduce accuracy in terms of distance per increments of your encoder.

    [5] I study produktion technology and do not have the education a machinist has

    [6] Annything faster would require a bigger screw or some other system entirely like belt or rack/pinion

    [7] The graph is a bit hard to read here.



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    Default Re: Are there steppers any good

    EDIT:I made a small mistake in terms of the buckling load, the Graph reads [kN] not [N] so you are really in the Green there =)



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    Default Re: Are there steppers any good

    I found another site with more info on those motors (and in English). The inductance, at 3.8 mH, is on the high side. To get the best performance out of them, you'd need to supply 62 volts of DC. As far as I know, the maximum voltage your TB6600 drivers will handle is 42vdc, so I'd have to say these motors wouldn't be the best choice to use if you're determined to use those drivers.Look for steppers with about 2mH of inductance and they'll go faster.

    Andrew Werby
    https://computersculpture.com/


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