The result is that the filament gets fed in a pulsing motion which gives you a line that is slightly blobby rather than straight.  It is the most obvious on the first layer where the squishing exaggerates the effect.  In the print, it shows up as a moire pattern on flat sides, or a slight dashed line effect.

A gear requires the motor to take a lot more steps/mm which makes the pressure much more continuous.  The original Solidoodle used a stepper motor with a gearbox attached which required something like 760 steps/mm rather than 110.  Those are more expensive, and the gearbox was dropped for the S2 and S3 to cut costs.

hello adrian,
when you refering to "direct drive" are you talking about the default extruder? in comparison to "bowden" style?

Yup

As seen in this image: , there is a smaller gear driving the larger gear - the 'hobbed bolt' as they call it in that setup is the bolt through the middle of the big gear - the reverse side of that is cut like the pulley on the SD Extruder Stepper.

This particular gear setup is usually 37:11 or 43:10.. the larger number being the output gear.

The effect of this that torque, or force, is amplified. Whilst the input gear (the one attached to the motor) has to spin faster to move the larger gear at a reasonable speed, it generates more torque (force) as a result.. Just like when you use a 'low' gear in a car or bike.. you can't go very fast even when revving high or pedalling fast.. but its very easy to get moving...

Net result in an extruder means, you can use motors that are lower spec in torque to begin with, or, using the same motor spec, you can move the filament with more force (but to do it quickly means the stepper has to spin faster - but thats ok because it barely spins to begin with...)

Direct Drive is 1:1; which is the equivalent of the top gear in a sedan usually (sometimes even lower, like 0.93:1...) This makes it very hard to accelerate as you have much less torque than in a lower gear - but because the engine spins slower (particularly in the <1:1 ratios) it usually consumes less gasoline, resulting in being able to 'cruise' on a highway @ 55mph and consume less gasoline  than the same speed in a lower gear (which would need higher RPMs to maintain the same speed as a higher gear....).... and in the extruder scenario this means you can drive the filament at a faster speed, but you have less torque available to do so, and thus, filament might jam or the motor stall more easily if you dont have perfect viscous filament (and thus, lowest resistance to the extruder motor)

Dunno if that explains it or just confuses it more

So I've been googling around looking at the Bowden extruders.  Is there any significant differences in the print quality or robustness of the Bowden as compared to the solidoodle extruder?  I'm also seeing mention of the mk5. What is that?

At a technical level, one can argue either way on merit. In practice, they are much of a muchness once dialled in. Bowden, as it has mechanical forces applied to the filament when the head moves, can occasionally have more oozing than a direct-drive setup (for example, when the print head moves from the front to the rear).. but you can more than compensate for this by setting an appropriate 'retraction' setting..

But on the plus side, as you often gear a bowden setup (you can 1:1 it as well), you end up with a cleaner print as you dont get 'globbing' like you can with a direct 1:1 drive if you dont have perfect stepping and speed settings, you end up with thicker segments in walls...

Many printers run bowden setups.. Prusa's, Sumpods, Repraps, etc. And arguably, many of those produce higher quality prints than the Solidoodle...

The key reason you need bowden is the reduced weight - Trying to move 2 NEMA17's motors on the X/Y Carriages quickly becomes unworkable with the motors on the solidoodle - your print speed ends up having to drop to comical levels to stop motor stalling. And even if you upgrade the motors to compensate, you have considerable issues with 'overshoot' - bigger mass means greater inertia, so you tend to loose lots of quality as the head changes direction and tends to overshoot where it was supposed to stop...  This isn't theoretical - its factual in that less mass means you have both quicker acceleration and quicker deceleration, which inherently provides a quicker print as well... as well as the stepper can move the platform to a fundamentally higher speed than one which has greater mass on it...

Plus, strapping two NEMA17's + Extruder Mechanisms onto the existing X-Axis would see you loose around 60mm's of build space in the x-plane... your 200mm's becomes 140mm's give or take a few mm's... With bowden, you can keep the two extruders much closer, and loose only the width of the extra extruder nozzle + a reasonable seperation between the heads (you can't put them right ontop of each other, as the heater core from one will effect the other causing all manner of temp stability issues...)

You *can* do multiple direct-drive extruders... just not with the mechanical design of the SD as it stands...

So I've been googling around looking at the Bowden extruders.  Is there any significant differences in the print quality or robustness of the Bowden as compared to the solidoodle extruder?  I'm also seeing mention of the mk5. What is that?

Bowden moves mass off the head so in theory you could print faster due to less weight being accelerated.  You trade off a bit of filament control for that though, as there's bound to be more slop in a bowden line than in a standard extruder.  The MK5 is a new print head created by the user lawsy.  Its good if you want to add accessories (fans, dial indicators) to your print head.  Hope this helps

adrian wrote:

he has the new motherboard - its a printrboard recloned - i.e, not a sanguinolulu.

Huh... didn't know that.  Thanks for the clarification!  BTW does anyone know when the switchover happened?  My printer shipped beginning of april still with the sanguinolulu.

1st week of june

he has the new motherboard - its a printrboard recloned - i.e, not a sanguinolulu.

Huh... didn't know that.  Thanks for the clarification!  BTW does anyone know when the switchover happened?  My printer shipped beginning of april still with the sanguinolulu.

You might want to look into a RAMPS 1.4 setup for dual extruders.  The standard sanguinolulu isn't the most expandable thing and you'll be dropping a good amount of money trying to upgrade it for dual extruders (and anything else you may want to add).  RAMPS give you 5 stepper controllers right off the bat.  That being said... getting another 12V plug spot does seem pretty nice.  I may break out my heater MOSFETs to a separate board and run that exclusively off a 12V EPS plug.

he has the new motherboard - its a printrboard recloned - i.e, not a sanguinolulu.

Only other info besides the schematics/board layout over at printrboards github is http://www.printrbotter.com/printrbot-e … ard-f-a-q/

all the info on the origins of your motherboard is at http://reprap.org/wiki/Printrboard

Read the page http://printrbot.com/shop/printrbot-extrudrboard/ carefully about the power supply requirements.

Note - you wont be able to use a second direct-drive extruder - the weight of an additional NEMA17 will kill the x-axis and severly hamper the y-axis. If you wish to double-extrude, you will need to seriously consider Bowden setups, or, upgrading your X and Y axis motors...

Now for the question:  Will the SD3 motherboard run the second head?  does it understand the gcode for the tool change?

Sorry for such a long post for such a simple question
thanks
-John