But good if you have a better result.

If your extruder is calibrated accurately, you should have the extrusion multiplier in slic3r close to 1. Basically, if you need to push it down to lower than 80 or upper than 1.20, it means your extruder needs a better calibration.

With my SD3, and an E3D hot end (that doesn't change the extruder calibration) I found my E was around 109 step/mm in the firmware. Just to give you an idea. But every extruder acts differently, that's why it needs to be calibrated to your specific machine.

For the Vref, the best way to adjust it is by ear. You set it to extrude, and while it does it, you turn your Vref down on the stepper (with a ceramic screw driver better, but if you don't have one, just use a steel one, and make sure you insulate your fingers from the body of the screw driver), and then turn up until you see the stepper moving without missing steps. you'll see it runing smoothly. If you go too low, it will miss steps, if you go too high, it will get very noisy ! You'll feel it very well.

If you can post some pictures of your prints, to help.

Take care, and happy printing.

(avec ton pseudo, je comprend que tu dois être français, si tu veux, on peut passer sur la section française pour continuer. C'est plus facile de comprendre dans la langue natale des fois !! A bientot!)

Thanks for your response, i did all what you say (bed levelling, extruder calibration) when i got my solidoodle but i can try a new time.
I use the stock threaded rod and when the machine is off i can't spin the Z motor with 2 fingers.

What's the Vref for the Z motor ?

First of all : You really need to get your extruder calibrated by following the wiki. You can't change the firmware value like that without any references. The only thing you can play with eventually is the multiplier in slic3r.

Now once that is done, you will have to level your bed properly too,

If your extruder is properly calibrated and your bed is totaly leveled, then we can start troubleshooting other things:

you probably have bad Z step setting in firmware ? Are you using the stock threaded rod ? Or did you upgrade to metric?

Or a bad Z mechanical movement... When the machine is off, can you spin the motor shaft of the Z screw with 2 fingers ??

Once that is all checked, you'll have to check your Vref for the Z motor.

Good luck, I know that calibrating the extruder and leveling the bed can be a pain, but it is well worth it!! No magic can be operated without the good basis at first...

I've solidoodle 4th generation,

Gradually, as the layers build up, the distance between the nose and the bed decreases. The object comes loose. There is a problem of ABS quantity, i try change speed of E in firmware and the multiplier in slic3r but nothing change can you help me ?

sorry for my bad english