I think I out build myself here. 2.7 x 1.8 meter. X and Y axis seems to cope fairly well but the steppers used to do the z axis cant seems to lift it. Weighed the z axis and it’s about 12kg. Any ideas how to solve this minor (?) setback with the nema 17 steppers ?
Much appreciated.
Do you have an enormous router on there? The allthread had a lot more torque, but much lower top speed.
All I had available when I started this was your normal plunge routers. So I had to made a couple of modifications to the original designs to upscale it. So yes it is a monster sitting on that stainless rails. Can I maybe change the rods to a finer pitch ? I’m trying to print a gearbox that would change it to a 4:1 ratio but to print gears that small is a challenge on its own.
If during your changes you offset the Z screw in anyway it can be bad. Honestly you have a huge amount of unknowns, pictures might help but if you changed things we really can’t offer much advice without knowing exactly what you have and what you changed.
Gear it down, 4x…sure, slow it down 4X and the fiction and backlash goes up as well.
Ok so after Ryan’s video I stripped everything and checked that the Z lead-screw was aligned and for testers took of the router. Guess what ? Still no luck. Test no 2. Ran only one motor at a time. All of a sudden it lift the single side connected. Making me think maybe the drv8825 driver is a bit suspect. Gonna get a couple extra and test again.
Thanks for the help so far !!
Came across this on the polulu site. Might this be my problem. My VREF was set at .598 as this is 1.2A steppers.
https://forum.pololu.com/t/drv8825-with-dual-motors-in-series/10308/3
The instructions on the site say .7
Correct. But the steppers I have is only rated 1.2A, whereas the steppers Ryan have is 2A. You think 1.2A is not gonna smoke it ? What tickles me is that Pololu reckons if you run steppers in series you need to double the VMOT which I assume is the same as VREF ?
Ahh, should have read the whole thread, you’re probably going to need either a smaller router, or beefier steppers. I wouldn’t gear it, you’ll run into backlash issues.
The motor drivers send a controlled current to the motors, which is dependent on VREF. VMOT is the input power supply voltage, not at all the same. Pololu is technically correct that equivalent performance for series motors needs twice the supply voltage, but this only matters at high speeds much faster than your machine will ever go. For realistic speeds there is no need to increase the supply voltage.
That and we are already typically 3-4x the voltage needed at 12V most steppers are only a few volts. We have voltage in abundance not amperage. (my limited understanding of the drivers) I had first incorrectly recommended parallel wiring for this very reason.
Ryan,
How difficult will it be to use E0 or E1 as the second z axis driver ?
Thanks,
Martin
We do it with the dual endstop firmware, but that is not your issue, series on one driver is not lacking in power in anyway.
Ok I manage to replace the DRV8825 driver for the Z axis tonight and a huge improvement. Still not perfect but I think if I change the 1.2A stepper with 2A steppers it might resolve my problem. Now to find 2A nema 17 in this country ?.
Thanks Ryan
Speaking of it: I am in the final phases of putting together my Generation 0 of my Lowrider. I’d like to drive all motors individually, so I have installed the dual endstop firmware on my RAMPS stack. I find it difficult to figure out from the code which will be which, though:
E0 = X2 or Z2?
E1= X2 or Z2?
I’d prefer to wire it up correctly and not to try it out. Can anyone tell me which one it is?
Thanks!
Hajo
Hajo, it would be best to start a new thread for that.
Im having simular problems. I`ll link to the stepper motors i bought and maybe anyone can tell me if i need to upgrade them.
its working fine on the x and y axis without testing it with the router milling anything.
Gut reaction is that you got underpowered steppers. 28N.cm is just shy of 40oz/in. In theory, it might be enough, but as a reference, the steppers Ryan sells are more like 57N.cm. From my recent shopping, you’ll probably need to expect to spend around $10/motor for the steppers you need, even on AliExpress or BangGood.
here is a list of things to troubleshoot to determine why your z axis might be slipping.