If I design a printer with leadscrews on all axis’s, what type of speed can I expect to get for printing and for rapid travel? Thanks in advance for any help.
Plug your PSU and motor specs into my torque curve predictor (https://github.com/rcarlyle/StepperSim) and depending on how conservative you want to be, pick an RPM at either the right side of the high torque plateau, or about 50% torque. That’s your top safe RPM. Then multiply that times the screw’s travel per rev (usually 2mm or 8mm for lead screws) and divide by 60 to get mm/sec top speed.
For example, if your top motor speed from StepperSim is 300 RPM, and you use a Tr8x2 lead screw, the top travel speed is 600 mm/min = 10 mm/sec.
Then you need to check the step pulse generation frequency limits of your control board. Marlin/RAMPS can only output 40 KHz of step pulses. 300 RPM * 200 steps/rev * 16 microsteps / 60 = 16,000 Hz so that’s fine.
For very long screws, you also have to do a critical whipping calculation, but that isn’t usually an issue under 400mm long or so.
it really depends on the lead of the screw. I have one with TR8x8 and nema17 and it goes max 30-40mm/sec.
I have another with 25mm lead screws (they are 8 start and move 25mm per rev) and they can go around 120mm/sec with triple stack nema17 run at 24v and max current.
Thanks guys. Next question, would I be better off staying with belts, or do leadscrews allow for a better quality print?
lead screws are a lot noisier, and I suspect for a 3D printer do not offer any advantages, except on Z probably.
Belts are better for printers on XY. Lead screws have backlash unless you use anti-backlash nuts, but those add a lot of drag. They also have a lot of inertia and require high rotor speeds so they don’t do jerks well.
If you want a combo printer+mill, then preloaded ball screws with a fairly long lead (like 10-16mm/rev) are a good option. Expensive though. Otherwise, if you want more stiffness in a 3d printer, you should design a better belt stage.
Low-hanging fruit for stiffer belt stages:
- Genuine Gates GT2/GT3 belts (makes a huge difference)
- 9mm wide belts instead of standard 6mm (or two 6mm belts side by side)
- Put a 2:1 or 3:1 gear ratio reduction of some sort in; this could be a pulley gearbox (like the E3D BigBox design) if you just want more force from the motor for higher acceleration without losing position. Or you can make a block and tackle type arrangement pulling the carriage if you want more force AND belt stiffness. (Note that CoreXY is effectively a 1.41:1 ratio block and tackle arrangement, so you automagically get some of the benefit of compound belt stages just by building a CoreXY.)
The limited stuff that I recall is that someone had a leadscrew based delta printer a few years back. I think it might have been a multi-threaded set of leadscrews that provide a nice amount of travel per rotation. The project was in this community and it had a project name. I think it was basically done to see how well it would work.
Maybe this was it? https://www.myminifactory.com/object/3d-print-screwdelta-3dprinter-35732
Oh. This guy did a modification of that. The post also contains the guy behind the link that I gave a moment ago. https://plus.google.com/109030437761050098329/posts/M6a58cUATNS
@NathanielStenzel yeah, Shauki is big on trying new things and reducing costs by doing stuff the rest of us didn’t think would work, like using a screw as one of the linear rods in a delta 
He used 25mm/rev Igus screws iirc, which is in an entirely different league from a 2mm/rev cheap China lead screw…
@Ryan_Carlyle 2mm per revolution? Those sound like the zinc plated rods that a standard nuts go on and can be found at a local hardware store. If they are not those zinc plated ones, they will not wear out as much and will probably be quieter, but probably not much performance improvement over the zinc plated ones for the short term.
I wonder if you can get leadscrews and nuts with recirculating bearings for use in a delta printer. Now that should probably be some killer performance as long as the pitch was high enough or the motor was fast enough. Most motors typically used in 3D printers do not have the RPM needed and the higher RPM have less control, I think.
Is all this not solvable by gearing? To get your lead screw to move at double the rpm you simply need a gear with ratio 1:2.
@Baldur_Norddahl the motor will have less holding power that way, but maybe. I think there are extra long stepper motors that can put out more power and some are built in a way to accept a separate axis that could be shared with another stepper motor.
@Baldur_Norddahl sure, but why bother with a screw at that point, or why not pick a different screw?
If the motor can move the carriage at x mm/s with a belt drive it will be able to do the same with a lead screw and apropiate gearing.
@Baldur_Norddahl sure, if you want to use more parts and moving mass and complexity to accomplish the same thing the belt alone would do
I am not the one who composed the question. I imagine he wants the rigidity and precision that belts lack. Belt and pulley will flex and give some on rapid direction changes. You see this on test cubes with corners that are not as sharp as it could be.
Anyway I was just trying to point out that both can achieve same speed, power, torque etc. It is all just a matter of calculating the correct gear ratio. Also we are talking about a very simple gear here and it can replace the usual flex coupling, so not more complicated really.
Just hope you do not get a bent rod which will probably get worse with rapid spinning.
@Baldur_Norddahl you’re ignoring the reflected inertia of the screw. A 1:4 overdrive gearbox makes the load look 16x heavier to the motor. So you’re wasting tons of torque accelerating the screw to high speeds. And if you try to do a corner jerk, the motor will have to abruptly change the screw’s rotational speed by a huge delta… and it’s a high risk of losing position registration. You’ll get much lower performance than just the belt alone. (There are better ways to make belt stages stiff.)
@NathanielStenzel 2mm/rev (Tr8x2) is the standard Mendel/i3 type Z lead screw. You want a single-start screw so it is self-locking under load and the nozzle doesn’t fall on the bed / gantry lose alignment upon power-down.
Z-bed lead screw stages with only one screw more often use an 8mm/rev four-start screw for higher speed.
Metric threaded rod is 0.7-1.0mm/rev in our size range.