Extruder Problem - buzz and no movement on first extrude

A video of the behavior I'm trying to describe.

Can anyone tell me if this is normal behavior for an extruder motor? The first manual extrude command I send it after a cold boot causes the motor to vibrate and make a loud buzzing noize, but the gears don't move (except for an immediate clockwise turn). Every extrude command that follows, the gears move fine.

1) Is this normal? If so, why what is the point? If not (more likely), what did I do wrong or should I look at/change/fix?
2) Once the gears do turn, is the speed normal for an extruder with no filament? It seems like its in an awful hurry!

I'm using Sprinter firmware with a RAMPS 1.4 board I bought from Ultimachine. The XYZ axes all work fine. The PC software doesn't matter, it does this with Reprap Host and RepSnapper.

I greatly appreciate any insight anyone could provide.

You're extruding too fast. Turn down the speed.

The host software defaults to 3000mm/min, so I changed that to 300, but all that did was shorten the duration of the initial buzz and the amount of time the extruder gears spin on the subsequent attempts. It doesn't slow anything. Is there somewhere else I should be looking? I didn't see extrude speed or anything in the firmware or host software settings..

I just went through this about 2 weeks ago. Both of the the previous answers are correct.

Make sure your stepper driver is turned down to around 25% on the Pololu.
Do you have all the jumpers on under the Pololu stepper driver? Are you using 1/8 or 1/16 stepping? Should be all jumpers if 1/16th stepping. I am guessing you might not have the jumpers on the pins.
In Repsnapper, or whatever interface control software you are using, make sure you turn down the speed value as far as possible. For testing try 100-200 just to make sure the motor turns and does not 'sing'.
If the motor starts running fine without singing make sure the temperature of the motor is bearable. If it is warm it is ok but if it is hot you need to adjust the Pololu drivers.

After a bunch of playing around, it turns out it was the firmware. I switched to Tonokip and everything is working fine (except for the 'home' commands).

What firmware are you using? I'm going to give FiveD a try, I think that's the most up to date...?


Thanks for all the help everyone!

Scratch my last post, I'm back on Sprinter. I found the settings I needed to change and values they needed to be so it wouldn't extrude so quickly.

I found the values in this post which mentions step per unit should be 25 and speed should be 2000.

So in config.h, I changed line 24 from:

float axis_steps_per_unit[] = {80, 80, 3200/1.25,700};

to:

float axis_steps_per_unit[] = {80, 80, 3200/1.25,25};

and line 100 from:

long max_acceleration_units_per_sq_second[] = {1000,1000,50,10000};

to

long max_acceleration_units_per_sq_second[] = {1000,1000,50,2000};

Everything appears to be working as it should. Plus, the home command works too. The max X, Y, and Z values look a bit off, but otherwise, I think I'm content for the time being. Now all I have to do is finish the hot end and I'm in business! Thanks again!

The steps per unit for the extruder depends on the extruder design and the software for generating g-codes that you're using. Earlier versions of software defined this parameter in terms of extruded filament length. But the latest versions of Skeinforge define it in terms of feed length. I don't use the reprap host or repsnapper anymore so I don't know if they have adopted the newer definition. It's not something that you can just copy from someone's post without considering those factors.

Understood. I'm sure I'll be adjusting things once I get my hot end built, but at least I know it's closer than it was before.. Thanks again!