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Leadscrews

Discussion in 'General Talk' started by DarkAlchemist, Sep 1, 2016.

  1. DarkAlchemist

    DarkAlchemist Veteran
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    I am moving away from my GT2 belt design for Z and swaying towards a leadscrew BUT I cannot find a TR8X2 single start and for Z I demand that for my next build.

    So, why is it so hard to find single start? I did find one supplier on Aliexpress but I have to purchase 10 of them for 80 dollars. Heh, I only need two and the other 8 would rot as I have no wants to relist them on ebay or some other thing.

    Seriously, single start for Z is the way to go since you do not need greater than 30-40mm per second of travel and the accuracy is awesome AND, most importantly, the weight of Z has far less of a chance of sliding down when the power is off (yes, my Z has slid down before using the type of leadscrews OB sells).
     
  2. Rick 2.0

    Rick 2.0 OpenBuilds Team
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  3. DarkAlchemist

    DarkAlchemist Veteran
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    Perfect, and with Anti-Backlash nuts too. win-win

    Thank you.
     
  4. DarkAlchemist

    DarkAlchemist Veteran
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    Now I just need to find a 16T gt2 pulley/gear with an 8mm bore. :(
     
  5. Kyo

    Kyo Master
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    Here you go "Link" they offer both 5mm and 8mm bore so just let them know you need 8mm when checking out.
     
  6. DarkAlchemist

    DarkAlchemist Veteran
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    WOW, life savers and I was looking on eBay (I haven't had much luck with Ali over the last two years) and the price is so cheap but OMG, 60 days is guaranteed (Estimated Delivery Time:20-39days). OUCH!

    Thank you and at least there is hope now. :)

    Almost half the price and sold in pairs so almost 1/4 of the price when you add tracking shipping - 3D Printer Parts Accessory 2pcs/lot GT2 16teeth 16 teeth Bore 5mm/8mm Timing Alumium Pulley fit for GT2 6mm Open Timing Belt-in 3D Printer Parts & Accessories from Computer & Office on Aliexpress.com | Alibaba Group

    edit: Do you think only one set screw will be enough for the 8mm leadscrew so it doesn't slip? Most times I see these, and the ones I have purchased, are with 2 set screws?
     
    #6 DarkAlchemist, Sep 1, 2016
    Last edited: Sep 1, 2016
  7. Kyo

    Kyo Master
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    Might just be the photo. All mine have been 2 set screws as well. both 16t pulleys I have each have two. might be worth asking them before ordering.
     
  8. DarkAlchemist

    DarkAlchemist Veteran
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    Says in the description they ship two pulleys and 2 screws. Seems all of those 16t on Aliexpress only has one BUT the picture has two as one is barely visible. Pictures are reused and they don't post right so I am going to ask them.
     
  9. Kyo

    Kyo Master
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    yeah i see a lot of reused photos on listings lol. best to ask. While i don't think a single set screw would pose a problem you could always add another down the line to.
     
  10. DarkAlchemist

    DarkAlchemist Veteran
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    I got a response and "Sorry sir,I don't understand what do you mean?". The language barrier is too much for this one I think and as I wrote it I can only imagine what the translator made of grub screw.

    I replied back but, as is typical of the Chinese, he is probably just a seller with absolutely no knowledge about anything he sells.
     
  11. DarkAlchemist

    DarkAlchemist Veteran
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    He showed me a real picture and here it is (like I said they just all reuse the same pics). No reply except the picture.[​IMG]

    edit: Order amount: $ 4.55- two 5mm bore and two 8mm bore via epacket for the tracking (trust me my post office is horrible and they caught those postal workers in California but the FBI needs to look at my local station too).
     
    #11 DarkAlchemist, Sep 2, 2016
    Last edited: Sep 2, 2016
  12. DarkAlchemist

    DarkAlchemist Veteran
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    I am about to give up on Aliexpress as I have not had one single good experience with them in the last two years and about 6 orders. I just received a message of this - "Sorry sir,I just notice that the 8MM size was sold out already.can we send you 4 pieces of 5mm?" I told them to cancel my order as I don't need four of them but I noticed the out of stock was an option for me to cancel it so I did. I just had 3 previous communications with them about the 8mm bore too. *sigh*
     
  13. DarkAlchemist

    DarkAlchemist Veteran
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    I contacted every seller and none of them have the 16t 8mm bore so I must believe, especially since I can't find it anywhere else, that it was just a click bait.

    If I use a 16t on the motor and a 40t on the leadscrew it is the leadscrew's pitch that counts in steps per mm and use that to for the math, correct? The 40/16 is 2.5 so I should have 2.5 times the torque and speed is irrelevant for my purposes.
     
  14. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    So now why is it again you need an 8mm 16t? Does you stepper have an 8mm shaft? And if it is the 2.5 ratio that is important, robotdigg has a 50/20 combination in 8mm.
     
  15. DarkAlchemist

    DarkAlchemist Veteran
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    16t is what I use as it has no errors involved in it so you do not have to account for Z height. The 8mm is the leadscrew so a 1:1 would be the 16t I use on all of my steppers and need to use on my leadscrews BUT if it doesn't matter then I could just go to a 40t 8mm bore for the leadscrews while still using my 16t on the Nema 17 stepper to increase the torque. I forget exactly how much weight it will be lifting but iti s over 2 pounds and will be configured as 1 motor with two leadscrews on each side to share the load.

    RobotDigg I do believe lists a 16t 8mm but the shipping was hideous to me for the one that has insurance otherwise it was 2 months delivery and that is when I went looking elsewhere and I still have two GT2 40 Tooth 8mm Bore Pulley in my cart on them.
     
  16. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    On the shipping time it's not as bad as they claim. (And it can be even worse, but I'll get to that.) My first order with the slow shipping arrived in about two weeks. My second order never arrived. But I've learned from it. Watch the tracking and if it doesn't show up in a US port of entry within a week after it processes through China post send a message to find out if it has been returned by China post. I made the mistake of being patient and waiting 5 weeks and it turns out it was returned just 4 days after it went out but apparently shipping never notifies the order processors when something comes back.
     
  17. DarkAlchemist

    DarkAlchemist Veteran
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    Oh, so that is what possibly happened to something I ordered on AliExpress because it never left the China port and they kept telling me to wait so I did then AliExpress notified me I was about to run out of protection time and I filed on them.

    They kept saying it was my Post Office and to ask them where the package was and I had to tell them that tracking info will not be available to me on USPS.com because it never left your Guang something port of call and no tracking info will be available until it hits customs here. Aliexpress had to get my money back from them. This is the first time this happened and I have had items confiscated by customs (like glue sticks) but it wasn't my customs that did it.

    As far away as China is I have had ten thousand times worse luck with my local post office and I have said they caught those Postal workers in California but they need to come here and investigate this place.


    So, am I correct in thinking that it doesn't matter what I use for tooth count on the motor and the leadscrews because it is the leadscrews' pitch that will determine my steps per mm to plug in to the controller? Doing a 40:1 and a 16:1 that should give me 2.5 times the torque too if the first part about steps per mm is correct.
     
  18. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Steps per mm = (steps per rev of stepper/mm per rev of screw) x ratio of gears

    = (200/8) x (40/16)

    = 62.5

    Torque will be approximately the (motor torque) x (ratio of gears) but not quite. The motor has to spin 2.5 times faster for the same output speed as an un-geared system and as motors spin faster the less torque they produce. How much torque the motor loses should be in the data graphs on the spec sheets for the motor.
     
    Mark Carew likes this.
  19. DarkAlchemist

    DarkAlchemist Veteran
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    Nice, I would be exactly the same as the Prusa m5 allthread in all respects. Steps per mm will be 4000 using 16x microstepping and 2mm pitch acme rods.
     

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