Advice on upgrading from 8mm Lead to 2mm Lead T8 screws



  • For those who have upgraded to 2mm Lead screws, have you seen much difference and what was your source for the screws?

    I've got what started life as a CR-10S running on a Maestro. I've read about this upgrade in several places including this one from @Phaedrux :

    https://duet3d.dozuki.com/Guide/Ender+3+Pro+and+Duet+Maestro+Guide+Part+5:+Upgrades/54?lang=en#s208

    The one thing that strikes me is that with 2mm lead it's evenly divisible for any layer height, no more being restricted to certain layer settings.

    My rods are the stock Creality and they were both slightly bent and pretty rough. I've cleaned them up and straightened to "pretty good" but still would like to dump 'em.

    How much impact have those who have this noticed or is this just another hole for money?

    One problem I face is the rods on my CR-10S are 515mm, an odd size. Although I can cut down larger and re-bevel it's a pain.

    I've found two local sources on Amazon, one after contacting the manufacturer on AliExpress, and a bunch of other on Ali too, of varying quality.

    Here's the Amazon ones for anyone else doing this:
    https://smile.amazon.com/dp/B07QFL6D46 <- Expensive but looks good quality (close up pics on AliExpress, here: https://www.aliexpress.com/item/32921211173.html)

    EDIT:

    Other Amazon source: https://smile.amazon.com/dp/B0851F5P7Q <- This is HALF the price, but no reviews so ... Of course in this day of fake reviews, that may be a blessing! Also they would have to be cut 550mm not 515). <- This is confusingly described and is actually a 8mm Lead.

    Like anyone doing upgrades I'd love to get polished, straight rods for $2 each ... LOL. But I have found paying for quality usually pays off. Still if anyone has a good source for quality rods for little outlay, I'd love it.

    Thoughts and advice welcome!



  • @PuterPro I published my own thoughts about Z axis lead screws on my blog back in 2017 https://somei3deas.wordpress.com/2017/01/31/z-axis-lead-screws/. That was in the days when some trapezoidal threaded rod was described as "threaded rod" rather than lead screw, which lead to some confusion. That is to say, a lead screw is a threaded rod by definition. The important thing is that the thread form should be trapezoidal to prevent binding. And yes, multi start, course lead screws are designed to give a large linear movement for a small angular movement. So where speed is more important than positional accuracy. In 3D printing terms, they are best suited to X and Y axes but not Z where positional accuracy is more important that speed.

    I use 1mm lead screws (single start, 1mm pitch) but 2mm would also be fine. I bought mine from China via Amazon. They arrived well packaged, straight and true, and they have been fine for the last 4 years or so. As well as being able to use layer heights which are always multiples of full steps, a fine lead also has better "gearing" than a course lead so you can lift a heavier bed with a smaller motor. And you can hold that weight with zero motor holding current, whereas the weight of a heavy bed acting on the steep helix angle of a 4 start thread might cause the bed to drop when the motors are deactivated.



  • @deckingman said in Advice on upgrading from 8mm Lead to 2mm Lead T8 screws:

    @PuterPro I published my own thoughts .... https://somei3deas.wordpress.com/2017/01/31/z-axis-lead-screws/

    Thx, I'll read that.

    I use 1mm lead screws (single start, 1mm pitch) but 2mm would also be fine. I bought mine from China via Amazon.

    Read it. Nice post, I knew most from my research (like 1 start vs 4) but you made some points clearer. BTW - I forgot the name of your blog, but as I was reading I grabbed my COLD coffee then started laughing.

    So, 2mm vs 1mm. Any real difference in choice? Obviously the 1mm give a touch more accuracy. I've been looking for 2mm lead but I'm open here.

    I'm running the little motors Creality used, but being there's two of 'em I imagine I'll have no trouble driving either rod choice. I'm currently limiting them to 900ma. here's my motors section:

    M350 X16 Y16 Z16:16 E16 I1                         ; configure microstepping with interpolation
    M92 X80.00 Y80.00 Z400.00 E412.00                  ; set steps per mm
    M566 X900.00 Y900.00 Z12.00 E120.00                ; set maximum instantaneous speed changes (mm/min)
    M203 X12000.00 Y12000.00 Z600.00 E1200.00          ; set maximum speeds (mm/min)
    M201 X500.00 Y250.00 Z16.60 E166.00                ; set accelerations (mm/s^2)
    M906 X1000 Y1000 Z900 E800 I30                     ; set motor currents (mA) and motor idle factor in per cent
    

    And for reference, here's the (VERY hard to find) motor info:

    Brand: Creality 3D
    Item name: RepRap 42 Stepper Motor
    Item number: 42-34
    Step angle: 1.8 degrees
    Nominal Voltage: 4.83V
    Current Rating: 1.5 (A)
    Rated speed: 1-1000 (rpm)
    Rated torque: 0.4 (NM)
    Ambient Temperatuar: -20℃~+50℃
    Length: 34mm
    Application: 3D printer
    
    Resistance: 9.6Ohm
    Inductance: 7.6mHy@1kHz (frequency used in datasheets)
    
    JK42HS34-0844YA-03F  - Offered by Tiny Machines as direct replacement for Z
    
    

    So I'm running about 60%. I am running the Maestro right around 27v .

    You see any issues here?

    And you can hold that weight with zero motor holding current, whereas the weight of a heavy bed acting on the steep helix angle of a 4 start thread might cause the bed to drop when the motors are deactivated.

    This has always been a problem for the CR-10S series. Something I liked about the Duet is easily telling it to hold idle to reduce this. Not currently a problem for me but nice that it lessens the drop potential.


  • Moderator

    @PuterPro said in Advice on upgrading from 8mm Lead to 2mm Lead T8 screws:

    So, 2mm vs 1mm. Any real difference in choice? Obviously the 1mm give a touch more accuracy.

    2mm will be a tad faster than 1mm.
    1mm will lift and hold a heavier bed.
    2mm with a 1.8degree motor will give you more than enough resolution. Going to 1mm for resolution won't make a difference. The +- accuracy of the motor itself will likely play a bigger factor. And I doubt anyone is going to want to use 0.2875mm layer heights.

    Go with 2mm unless you have something really heavy to lift.



  • @PuterPro If your existing motors are driving the Z axis with 8mm lead, then they'll have no problem driving 2 mm lead screws. 2mm vs 1mm ?? Not much in it - I'd say go for whichever is cheaper/more readily available. Your not going to be struggling for torque if you can drive 8mm lead screws, so no usable benefit "leverage" wise. Resolution? - Well a 1.8 degree motor gives you 200 step (full) per mm. So with 2mm lead you have 100 full steps per mm or 1 full step = 1/100 mm = 0.01mm. Any layer height that is divisible by 100 will use full steps. 1mm lead will double that resolution but you won't make us of it.



  • @Phaedrux said in Advice on upgrading from 8mm Lead to 2mm Lead T8 screws:

    And I doubt anyone is going to want to use 0.2875mm layer heights.

    HA! You don't know what I'm planning! {Insert evil chuckle}

    That's about what I came away with from my research. My 310x310mm bed isn't that heavy, especially with the load on two motors. Thx.



  • @deckingman
    Thx! @Phaedrux was quicker on the keys! Appreciate the help, as usual my friend.
    2mm here I come. now to find some that they don't want $50 USD for a pair.

    I have to deal with WAF.

    I think I found someone on AliExpress that will cut down a 550mm to 515 and appears to have nice quality, I just have to wait until Thanksgiving or so ... LOL.



  • @PuterPro said in Advice on upgrading from 8mm Lead to 2mm Lead T8 screws:

    @deckingman
    Thx! @Phaedrux was quicker on the keys!.............

    Yes - by 9 seconds 🙂


Log in to reply