SoliForum - 3D Printing Community — VREF values n stuff

Re: VREF values n stuff

2014-12-16T20:57:35Z

It serves no purpose with an e3d but I think with the stock hotend the fan on the left blows across the top of the peek barrel. It prevents the filament from softening in the extruder from the heat of the barrel. This is just a guess. I ran without it for a while with the stock hotend and had no issues whatsoever.

40mm fans are dirt cheap on eBay and fairly priced on Amazon.

Re: VREF values n stuff

2014-12-16T20:28:04Z

Okay then.

BTW jagowilson, do you think I can take the fan on the left side of the extruder and use that? i remember you saying it doesn't change much for you and I would get a cm more of bed size if I do that.

Re: VREF values n stuff

2014-12-16T19:49:27Z

elmoret wrote:

Hot isn't bad, steppers are rated for 80C plus.
Steppers actually run hotter when idle (not moving) than moving.

+1. I recommend you put a fan on it, however. It gets hot and it can melt your carriage (see attached pic of my old stock carriages). I also ran the belt pretty tight and the stock carriages couldn't take it.

Re: VREF values n stuff

2014-12-16T19:43:33Z

Hot isn't bad, steppers are rated for 80C plus.

Steppers actually run hotter when idle (not moving) than moving.

Re: VREF values n stuff

2014-12-16T19:29:33Z

If that's the correct values, how come the X motor set to 0.8 Volts can get hot when its not even doing anything?
Several users have reported this, not just me.

Re: VREF values n stuff

2014-12-01T22:03:50Z

According to the A4982 datasheet: I=Vref/(8*Rs)
0.1 ohm sense resistors: I=Vref/0.8

Substituting in the current ratings of each motor gives the Vrefs:
X: 0.8 V
Y: 1.064 V
Z: 1.344 V

The extruder motor should be set to whatever value results in the smoothest movement. Too low and it's not enough power to keep up, especially at higher speeds. Too high and it will pulse, causing uneven extrusion. We did some testing across many printers and found the best quality at around 0.17V, but had to be run very slow. We found 0.25V to be a good value that performed reliably well at typical speeds while keeping quality.

Re: VREF values n stuff

2014-12-01T08:55:59Z

I can try that.

I wonder why SD4 is shipped with these VREFs:

X motor- 0.8V
Y - 1V
Z - 1.2V
E - 0.26V

I've asked few others to check and it's the same for them as well.

Re: VREF values n stuff

2014-11-27T19:35:53Z

I would try the values for the Pololu A4988 and go with that if it sounds good and nothing gets too hot.

Re: VREF values n stuff

2014-11-27T12:20:15Z

Thanks. According to reprap wiki it looks like Printrboard/Solidoodle uses "Allegro A4982" stepper driver which I don't see in that list.

Re: VREF values n stuff

2014-11-27T01:10:28Z

Here is a chart, I think it might have been adrian who posted it a while ago and I saved it.

VREF values n stuff

2014-11-21T21:15:25Z

The "around 1V" for X,Y, and Z stepper chips sounded wrong to me and I got few others to check the wiki page and they think it is too much.

I check my SD Rev e motherboard and from the factory it is
0.8 V for X
1.0 V for Y
1.2 V for Z
0.26 V for the extruder motor.

What are the right numbers?

I know some of you adjust by ear, but for those who dont and know the physics behind it maybe you could share the info? or maybe the guys who were able to adjust by ear unlike me could check by a voltmeter what they have adjusted to?

(PS. For SD4)