You really want to use 10mm or 20mm pitch ballscrews. 5mm will be very slow with stepper motors.
I'd probably try some low inductance 960oz motors with 10mm pitch screws. With higher pitch, you can go a bit higher on the torque.
Hello Guys,
my main frame (3000mm x 1650mm) is finished (400kg weight until now), and soon i will start to build the gantry (pre version). Travels will be (depending on the gantry size) at least 2600mm x 1300mm
I will use ball screws on all axis (2505 on Y - long axis / 2005 on X-axis / 1605 on Z-axis), but for the long axis i will use rotating nut instead of rotating screw, so i want to start order aluminium plate to build the rotating nut system parts, but currently i am wondering what size steppers i should use.
The pre-version gantry with Z-axis and all parts will weight for sure more than 100kg (later i want to build something heavier when the cnc router is ready to cut in metall), so i dont know if 3.1Nm would be enough. Of course they are cheap and thats a big plus, because in the first year when the router is finished i will do only privat jobs so i dont have to worry about time. Later i would (maybe - if neccesary) update to closed loop Leadshine hybrid steppers or servo motors, so i dont want put much money in parts which i will later upgrade and sell, but also i dont want to be disappointed with the results when choosing too small steppers.
Hope you can help me out with that, because slowly i would like to order the parts
Here are some pictures of the build and finished frame . On those pictures are missing some welds, because i first did fix all tubing with small welds and later i finished them (yesterday).
Just as info info: I did mount the rails just to check if i drilled all holes correctly. I will use epoxy to level the frame for the rails.
Thanks in advance!
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You really want to use 10mm or 20mm pitch ballscrews. 5mm will be very slow with stepper motors.
I'd probably try some low inductance 960oz motors with 10mm pitch screws. With higher pitch, you can go a bit higher on the torque.
Gerry
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Thanks for your reply ger1.
05 pitch will be fine. At 2000rpm i should achieve 14mpm, so its totally fine. I think i will go with 3.1nm with AM882 Leadshine drivers and in future i will change to servos if necessary.
You'll never get anywhere near 2000 rpm with stepper motors on a machine that size. You'll be lucky to get 1000-1200 rpm.
3.1Nm is way too small.
Gerry
UCCNC 2017 Screenset
[URL]http://www.thecncwoodworker.com/2017.html[/URL]
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[URL]http://www.thecncwoodworker.com/2010.html[/URL]
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[URL]http://www.g-forcecnc.com/jointcam.html[/URL]
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
so, does that mean that i should take bigger steppers because of the heavy gantry e.g. 8,7Nm ?
Thanks in advance
Thank you !! @ James Newton
Now i am pretty happy that i asked, before i just bought 3.1Nm steppers...
I will buy at least 8.0Nm steppers, but now i have found some good price for an complete kit on german ebay. Thats the kit: ã€German Ship& No Tax】4Axis Nema34 Stepper Motor 1232oz,6A,118mm CNC Foam Miller | eBay
I could save a lot when ordering that kit, but what do you think about regulated Power Supplies and one per each driver (4) ? I heard that its better to use an transformer/unregulated supply, instead of regulated, but are regulated really that bad? I have seen many poeple using that kind of supplys even with closed loop leadshine steppers/drivers.
The board i think i will not use, because i wanted to order Mesa 5i25 + 7i76 plug&go kit on LinuxCNC.
About the drivers i read only positive reviews, but first i wanted to order the Leadshine AM882 from aliexpress, but that would cost me at least 250€, so i think the Wantai DQ860MA could be an good alternative.
The big plus is of course the price of the kit and that i will get it pretty fast without any duty costs, because WANTAI has an warehouse in germany..
Hope someone could help me out with that and let me know if thats an good kit or if it would be "MUCH" better to use unregulated supply, etc...
THANKS IN ADVANCE!
Your frame looks nice but did you have any issues with it torquing or curving because of the welds? I don't have a ton of experience welding but was thinking about doing something similar.
Hi JSSCNC,
nice to hear that you like the frame.
First of all, its still not finisshed, and i think it will take at least 2 more month. I was stuck for almost 30 days, because i tryed to level the frame with epoxy and it took me 4 runs until i got it done (if you will do the same, then i can give you some advise, so that you do not make the same faults as me ). Since couple days its ready and i order the parts for the rotating nut, and today i want to pick steel tubing for the gantry.
Because of torquing/curving etc.. of the frame: I do also have not much experience with welding. Before i build/weld the frame i only build the workbench which you can see on the pictures, so that was my only welding experience i had. I was thinking for some time how i can keep it from warping and had the idea to use some kind of "sandwhich"style design . Its difficult to explain, but instead of using and typical "table" design like that one: http://www.cncrouterparts.com/images...lk-ns_1920.jpg , i wanted to make sure that the whole frame is connected like it would be one piece, thats why i used long tubing at the bottom around the whole router and build some "leveling pads/legs" which are welded to the lower tubing. Of course i also used vertical tubing on the front and back side of the frame (between upper and lower tubing), but i made the pictures before it was done.
I am really not sure if that design will prevent it from warping. If i just think logically about that, then i cant imagine that it will warp, but i read a lot about welded constructions before i start to build the frame and maybe the only way to prevent it 100% from warping is to use stress reliefing (heat) as soon as the welding process is finished. But, what i also have read is, that if you dont mill the surface of the tubing for the linear rail guides, but uses epoxy to level the frame, then there shouldnt be a problem with warping. Very important is that you first fix the whole frame with small spot welds, and later you can finish the weld with short welds e.g. 50mm. The point of it is to not put to much heat on the same spot, so the best is if you for example make one weld, then do the next weld on the end of the tubing. You could also pre-heat the spot before you weld, to lets say 70°C. That takes a lot of time, and i havent done it even it was my plan...
Maybe iam writing more then i need to, but its the first time i (maybe) can help someone, because usually i always get help from here or other cnc/machinist forums .
The most important thing: Take your time. Its better meassure 100 times, to make sure everything is like it should. I mean, i would say its not possible to build the frame 100% precisly by welding, but in my case the epoxy did the work to level the whole frame for the linear rail guides, and that is the most important thing at the end. Still, without epoxy i got both sides pretty parallel. There was only 0,5mm difference in height. Before i level the frame with epoxy, i mounted the linear rail guides and connected the carriages with an 60x40x2mm tubing. The "test gantry" moved pretty smooth, and when i sit on the gantry it moved that well that i even thought to not use epoxy to level the frame, but the paralel and height tolerances of the HIWIN rails are so low, that i feared to damage the bearings pretty quickly.
Unfortunately i have no milling machine, lathe, band saw, etc., so it all takes a lot of time, but since yesterday i know how to continue
My advice: Design the whole router with e.g. Solidworks, and then start to work...
Let me know if you have any questions. Maybe you are also an beginner like me and i really like to help if thats possible.
Denis