1 Topic by redbarret

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Topic: VREF values n stuff

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)

Solidoodle 4

2 Reply by mdrVB6 (edited by mdrVB6 2014-11-27 01:11:05)

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Re: VREF values n stuff

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

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SD4 w/ RUMBA, E3D Volcano, all bearings, glass bed

3 Reply by redbarret

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Re: VREF values n stuff

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

Solidoodle 4

4 Reply by mdrVB6

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Re: VREF values n stuff

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

SD4 w/ RUMBA, E3D Volcano, all bearings, glass bed

5 Reply by redbarret

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Re: VREF values n stuff

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.

Solidoodle 4

6 Reply by soliryan

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Re: VREF values n stuff

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.

Former Solidoodle employee

7 Reply by redbarret (edited by redbarret 2014-12-16 19:30:39)

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Re: VREF values n stuff

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.

Solidoodle 4

8 Reply by elmoret

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Re: VREF values n stuff

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

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

Filastruder - the robust, inexpensive filament extruder
E3Dv6 All Metal Hotend - the premier 3D printing hotend

9 Reply by jagowilson

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Re: VREF values n stuff

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.

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10 Reply by redbarret

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Re: VREF values n stuff

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.

Solidoodle 4

11 Reply by jagowilson (edited by jagowilson 2014-12-16 21:01:43)

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Re: VREF values n stuff

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.