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Nema 08 via ramps 1.4?

Posted by panterateama 
Nema 08 via ramps 1.4?
December 11, 2018 04:23PM
Hey guys, as the title implies I'm wondering if you can drive a nema 08 (mini stepper) the same way as a nema 17 using a ramps based board like ramps1. 4 or rumba. I'm not going to use it as my main drive motors, but as an accessory to do auto bed leveling instead of a servo.

The servo method is too cumbersome for what I want to do in a tight space and actuators are super expensive. But if I use a nema 08 motor with a screw to move the bed leveling device (switch, sensor etc) up and down, I think I can get the precision I want for cheaper.

The rumba board has 3 extruder steppers and I will only use 2 so I thought if I wired this to ext3 and did some programming it might work.

Re: Nema 08 via ramps 1.4?
December 11, 2018 05:36PM
Yes, you can drive the little steppers just the same as the "big" ones, there's no essential difference between them. Just make sure you're driving them within their spec current and voltage.

Idea of carrying an extra stepper (although a smaller one) instead of a hobby servo seems a bit excessive. You want to reduce the moving mass at all cost – that is why tiny plastic servos are used in the first place. Typically, you'd use a 9g servo for bed levelling. That '9g' stands for NINE GRAMS. Smaller NEMA-8 stepper I've seen where in the ballpark of 60 to 80 grams. That's HUGE weight difference and it won't go unnoticed in the print quality (unless you have a ridiculously 9000% overbuilt machine).
Re: Nema 08 via ramps 1.4?
December 11, 2018 11:04PM
Well the machine is over built lol, it will be able to do cnc machining as well as 3d printing so it is going to be a heavy duty machine. Thanks for the info. Assuming I use a rumba or ramps 1.4 with drv8825 stepper drivers, I should just be able to tune the trim pot to get the current tunes in yes?
Re: Nema 08 via ramps 1.4?
December 12, 2018 06:45AM
Are the NEMA-8 motors bipolar? If not you may have to modify them or you won't be able to drive them with the drivers on most 3D printer boards.

The Duet controllers have the ability to drive multiple Z screw motors independently for bed leveling. I think you need an expansion board to get enough drivers, but all the necessary control is built into RepRap Firmware that runs on the Duet boards.

Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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