MakerFarm Prusa i3 and i3v 66 oz. in. Stepper Motor Specifications

[DrLuigi]

So how much should the amps be on the ramps board realy?

I thought i rememberd that Colin told me it was 0.38.
But i do get some skipping sometimes when doing around 60-80mm/s, so i kinda just wanted to ask if it would have been that.

[clough42]

So how much should the amps be on the ramps board realy?

I thought i rememberd that Colin told me it was 0.38.
But i do get some skipping sometimes when doing around 60-80mm/s, so i kinda just wanted to ask if it would have been that.

Colin specifies .39v in his build document for the 8" i3v. This translates to a 2.5x.39=.98A current limit. In practice, the motor never reaches this current because its DC resistance of 18.2 ohms limits the current to .66A, which isn't too much higher than the actual rated motor limit of .5A. When the motor starts moving, the inductance reduces this current even further, depending on how fast you step.

The extra current doesn't hurt the motors, but it does make them get hot. The heat is only really a problem with the extruder motor, which is mounted to a plastic part. You can either turn down the current on the extruder motor, or you can add a fan with an appropriate shroud. My shroud is here: http://www.thingiverse.com/thing:343026

Or you can ditch the Greg's extruder altogether and use something else. Here's what I'm currently using: http://www.thingiverse.com/thing:389105

Technically speaking, the voltage on the drivers should be set to .5/2.5=.2V. Since the motors are running right near their current/torque limits at 100mm/s, this may or may not cause more skipping. I'm running with the .39v default, and I'm printing at 100mm/s and bridging at 120mm/s.

Edit: fixed broken link

[DanSilov]

The extra current doesn't hurt the motors, but it does make them get hot. The heat is only really a problem with the extruder motor, which is mounted to a plastic part. You can either turn down the current on the extruder motor, or you can add a fan with an appropriate shroud. My shroud is here: http://www.thingiverse.com/thing:34302

Looks like the wrong link, or I don't understand how that thing is used with motors

Or you can ditch the Greg's extruder altogether and use something else. Here's what I'm currently using: http://www.thingiverse.com/thing:389105

How is that extruder really different from Greg's? Except for the belt general construction looks very close, motor is still mounted directly to plastic. I have a great heat problem with extruder, it melted original small gear that came with the kit, and now it melted mount I printed with PLA. I gets so hot I can't really touch it, and it's set to 0.37v.