Why not lead screws for 3D printer control?
Besides me, I got an old Ender 3 V2 that still works fine. For control of its z position it has a lead screw. For other two axis it uses belts as everyone else. But why can't all axis have lead screws? As I'm looking at it, the small motor that governs the lead screw is not strong. I believe its under 1 ampere, and there is a whole custom tool head and on top of that two stepper motors. I bet it's more than 1 kg, and it still moves normally. It is slow, however there are faster lead screws. Probably need more power to operate those, but today's motor drivers can withstand 2 ampers or more, so we can just add stronger motors.
This is not a blog post about how I created the lead screw motion system. It's purely a thought experiment about how would it be if we used lead screws. Because it just seems so much easier than belts. Belts are not complex, but lead screws are still simpler to think of than belts. So why not?
Surfing on the internet I found Hackaday post about printer with lead screw motion for all axis [1]. It's not a good example for what I'm trying to explain xD. It seems really professional and expensive, with giant stepper motors. However, the original creators say this:
"While most 3d printers use belt driven motion in the x and y axis to increase print speed but loses quality when more weight is applied to the gantry or carriage. The lead screw used on the Workhorse has a high helix pitch with multiple threads to allow increased print speeds while maintaining the quality provided from lead screw and ball screw motion." [1] ~ Shane Hooper.
The whole idea in my head was the lead screws are not as expensive and can be implemented simply. No need for belt tightening system, no need for belt pulleys and maybe just one aluminum rod that goes in pair with lead screw.
However, the more I explore about this stuff, the more convicted I am that the lead screw is no good, except for z axis.
I found this one post on Reddit from 7 years ago where a person asks for an opinion on lead screws on all axis, and a person by the name of u/OtherBarry1992 gave a nice explanation about how hard for motors it is to rotate lead screws fast.
"Your moving mass, especially rotating mass, is quite heavy if you go with lead screws. Think about acceleration and jerk. You have to spin the lead screws up fast enough for travel moves and other quick start stop motions. You lose torque the faster the stepper spins as well leaving you prone to missed steps when you're throwing around the x and y axis." [2] ~ u/OtherBarry1992
Seems like lead screws are used in big CNC machines, however we are here in 3D printer territories. It's almost like a toy compared to real CNC machine. Maybe belts are superior to everything. I was just hoping to try out making a printer with lead screws and finding out that it is superior lol. Don't think that will happen, but it is possible. People proved it, but can't compare to speeds of belts here. However, belts still bug me. Seems to me that there is too much going on. Maybe it's not a subject for me. It's more of a mechanical engineer thing. I should stick to electrical stuff. Governing stepper motors.
REFERENCES:
[1] https://hackaday.io/project/177793-large-diy-3d-printer-with-all-lead-screw
[2] https://www.reddit.com/r/3Dprinting/comments/bhbg81/building_a_3d_printer_and_am_deciding_between/
