Pololu A4988: Can I run with these motors? Using RAMPS 1.4
July 07, 2013 06:48PM
HI,
Trying to get my RAMPS powered up, then I noticed the stepper motors I have is rated 2.5A(U). It is the wantai 42BYGHW811, 1.8deg/step.
Can go ahead and use the combination on my printer? The Pololu A4988, are the original ones. My power supply is 12V/30A.
Thanks!!

Edited 2 time(s). Last edit at 07/07/2013 06:57PM by Topicawox.
Attachments:
open | download - WP_20130704_020.jpg (103.1 KB)
Re: Pololu A4988: Can I run with these motors? Using RAMPS 1.4
July 08, 2013 09:18AM
Yes,

The stepper is rated for maximum 2.5 Amps

You don't and probably won't need to run the motor at it's maximum rating unless your 3D Printer is a custom large beast of a heavy machine.

Also make sure your Pololu A4988's have heatsinks on them, and run a fan at 100% over the RAMPS board to keep them cool.
Re: Pololu A4988: Can I run with these motors? Using RAMPS 1.4
July 08, 2013 09:41AM
Hey ShadoRam!!
Thanks for the info, will definitely put a heat-sink on the drivers.
Re: Pololu A4988: Can I run with these motors? Using RAMPS 1.4
July 10, 2013 03:38AM
Chances are if you run it lower than 1.25A you will loose the majority of your torque rating curve, especially at speed. Unfortunately I wouldn't trust those chips running over 1.5A.

I.e., a motor designed to run at 1A and run at 1.2A will run way better (but hotter) than a motor design for 2A and run at 1.2A...in my opinion. I can't back that up with equations but it has been my experience
Re: Pololu A4988: Can I run with these motors? Using RAMPS 1.4
July 10, 2013 04:02AM
Hmmm, what would then be the best case scenario?, Once I am all set up and done with assembling? and ready to do long runs...

1) swap the driver for higher one that still fit on my ramps (..which one?)
2) swap the motors for lower current ones that runs well on the A4988( ..again which motors? )

what combinations do you have or know that should work especially for prints that runs for hours? mostly with RAMPS, since it is the board I have .
Re: Pololu A4988: Can I run with these motors? Using RAMPS 1.4
July 10, 2013 04:05AM
1) Swap for DRV8825 will get you a reliable closer to 2A
2) There are tons of stepper choices out there.

The whole idea behind current control using stepstick is to be able to run high voltage through low-voltage low-current motors without upping the current (so they turn faster with reasonable torque). A 2.5A motor may be huge and not intended for this purpose (i.e. it is rated 12V instead of 2.7V, maybe)? I had a prusa with one of these, and it was weak. That doesn't mean it won't work, I should have said it's torque could be significantly diminished compared to its rated - so you might see 5KG-cm, by only get 1.4, and that would be the difference between an extruder success and fail.
It shouldnt matter for X/Y/Z but it will for the extruder.

I would do the build and see what happens. I have some experience too - what are the motor specifications /source

Edited 1 time(s). Last edit at 07/10/2013 04:08AM by Simba.
Re: Pololu A4988: Can I run with these motors? Using RAMPS 1.4
July 10, 2013 04:28AM
Simba Wrote:
-------------------------------------------------------

> some experience too - what are the motor
> specifications /source


[www.electronicaestudio.com] rated 3.1 Volts,
Re: Pololu A4988: Can I run with these motors? Using RAMPS 1.4
July 10, 2013 04:48AM
Looks like the ones on the prusa that I had. Should be fine, but it will need a smooth extruder with a bearing and hobbed bolt of small diameter to ensure there is enough force - or a gear based wades extruder will work too. You won't need to redo anything after.
Re: Pololu A4988: Can I run with these motors? Using RAMPS 1.4
July 10, 2013 05:48AM
If you just had used the search option, you would've noticed theres already an abundance of topics on these exact motors winking smiley

And yes, I have two printers running those motors now, so no problemo here.
Re: Pololu A4988: Can I run with these motors? Using RAMPS 1.4
July 10, 2013 11:44AM
These are the motors I'm using

http://www.shadowram.ca/wp-content/uploads/2013/04/20130409_151000.jpg

This is the size of my machine
http://i.imgur.com/VB5BTeC.jpg

The Pololu A4988's are running this thing at less the half of their max current rating.

I have enough torque to move this thing around extremely fast, and it doesn't skip steps.

Trust me, any small reprap machine you have going on, the Pololu A4988's will run your steppers without a problem.

See www.shadowram.ca for more info.
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