Motors

Running a ramps 1.4 with A4988 drivers powered by 27amp power supply.
What is the recommended motors to use with this setup ?
Volts ? and amps ?

If you recommend a different driver please do

Thanks for looking

Any bipolar stepper with up to 2A phase current will do.
Most common are 1.8° NEMA17 steppers with 0.4 - 1.7A.

and would that be any voltage up to 12v

no, voltage is misleading...

you typically drive steppers with 2-4 times 'rated' voltage

so you want 12/4 ie 4.8v max. (most say 3-5 V)

Forgive me but I don't understand
2-4 times rated voltage of what?
at a guess its the power supply voltage?

Of the stepper motor voltage

Ie if the stepper say its 12v, it need to be driven from 24-48volts

Ok thanks for the info I now understand

So 2.8v 1.68a 45Ncm stepper would be fine to run on 12v
or would
2.8v 2a 59Ncm be better

Build plate will be between 300mm x 300mm to 400mm x 400mm with a build height of around 700mm

Actually, steppers work best operating at 8-20X their rated voltage. Most of the stepper motors used in 3D printers are rated for 3-4V, so 12V supplies work, but are not ideal. It is better to operate from higher voltage if your drivers can handle it. I have 3.2V steppers in the X and Y axis of my printer and operate them using external drivers and separate 32V power supplies. I get fantastic print quality.

The RAMPS board is your limiting factor here. The motor drivers on it can't handle more than about 1.7A continuously or they'll overheat and either die or shut themselves off. Either case will have disastrous results for your prints. Trying to run the RAMPS board from 24V is often problematic because some of the parts on the board may not be able to handle 24V. Stay with 12V and hope for the best. Be sure to get some spare motor driver modules- you're going to need them- you'll probably kill a few before you get the machine dialed-in.

You might want to look into external stepper drivers and power supplies. You can run just the steppers off a higher voltage supply- look for 24-36V, and then pick up external driver modules like these: [www.ebay.com] for $12 shipped. See all that heatsink area? Compare that to the heatsinks on the pololu driver modules. Those modules will connect to the step/direction/enable lines on the RAMPS board very easily. You'll pay $5 for the little pololu modules, so this isn't a very big step up in expense but it will be a huge step up in reliability.

If you want to get a little fancier, you can try DSP based driver modules like this: [ZUAAOSwAHZUQ3E7" target="_blank" rel="nofollow">www.ebay.com] These have additional settings for microstepping, handle higher voltage supplies, and sense resonance and suppress it by modulating the drive current. They will make your printer run whisper quiet.

If you aren't married to the RAMPS board, look at Smoothieboard. The on-board drivers will handle 2A continuously without overheating. You can connect 24V with no worries. It has about hundred other benefits, the biggest of which is not requiring a firmware recompile each time you change a machine configuration parameter. You just edit a text file on the board's memory card and reboot the board. The config file is read each time the board boots up. No screwing around with flaky Arduino IDE.

Edited 3 time(s). Last edit at 01/17/2016 09:32AM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

The 2.8v 1.68a 45Ncm stepper would be best of those two.

Despite their advertising pololu modules top out at about 1.7 amps
The 2amp stepper may work, but will not get the 2amp for full torque so will be under the rated torque values

If you are planning to move that large bed in the Y axis, a NEMA-17 motor won't do the job. They top out at about 100 oz in torque, which won't be enough to control the motion of a large, heavy bed unless you plan to print very slowly. You need to estimate the moving mass of the bed, undercarriage, heater, and belt, then decide on the speed/acceleration you want and the precision you want, and plug all those numbers into the motor sizing tools at Oriental Motor's web site. It will then calculate the required torque. You then shop for a motor that can deliver that torque, and then you look for the electronics that can drive the motor.

Edited 1 time(s). Last edit at 01/17/2016 09:50PM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Thanks for the input guys, much appriciated
Not looking to build a all singing and dancing bot just something that will give resanable results.
The bed will be Z axis only with 2 motors. Was thinking along the lines off a sq frame with a 240v heating pad (with ssr) suspended on wires with a glass bed sat on the frame to keep the weight down

What would be the outcome if I used 8825 steppers? I know they can be problematic but is it worth it? could I go to 2amp motors. Also thinking about adding a counter balance so the motors don't have to work as hard?????

Re counter balance, this increases the mass of the axis so doubles your momentum, means you get more backlash... (terminology is probably not correct here)

drv8825 do allow for more current and can increase mircostepping to 1/32, this also lowers your max speed. I wouldn’t bother with them unless you have a 32bit controller that can generate the steps pules fast enough to be worth while.

Edited 2 time(s). Last edit at 01/19/2016 12:51AM by Dust.

Counterweight is prob a better discription