Thursday, 9 June 2011

Skeinforge Version 41

I have been using Skeinforge for just over 1 week now and I'm starting to get a grip on this most fantastic program.
After initial machine setup and printing with Reprap Java Host I always wanted to move over to Skeinforge, but it has a bewildering array of settings and control, quite daunting when you first start.
- But well worth the effort - 

This image shows my best possible print quality I managed from Java Host to generate Gcode (on the left) and one of my very first Skeinforge prints with initial 'good' settings, and it's still getting better and better all the time I learn more about Skeinforge.

Some excelent information and advice from long-term Skeinforge users for the new Version 40/41 can be found on the Reprap forum here -,75635
And also on the Mendel-parts forum here -

Many thanks to everyone as I would have wasted a lot of time if not for this head-start.

The Skeinforge manual and settings descriptions are also found here -

My setup is not typical of a Mendel or other Reprap, so your exact settings will be different, but the following information, notes and advice may help you get going if you are new to Skeinforge and are not sure where to start.

One of the first problems I had was the fact I didn't know how well my machine would print so it was quite hard to judge when I actually had it calibrated to a good standard.
Other than looking at other people's prints on thingiverse it's hard to say how good your machine should be?

First Step - Measuring E-steps/mm for the new Dimension changes in V40/41

I'm using a Bowden extruder setup that has some extra issues ascociated with controling filament hysterisis but the following is required for any extruder in any configuration.
My extruder being belt driven is also different from a Wades or Adrian's geared version, but in principle operates in the same manner, but with different gear ratio etc.

I setup my Extruder on a stepper motor test jig I had made to test Pololu modules, it's just providing a simple button to full-step the stepper motor.

I'm using 1.75mm Feedstock and now Dimension requires you to set 1mm of INPUT feedstock. 
Before the firmware required 1mm of Extruder Feedstock, this is an important change and makes a big difference for making nozzle size changes easy and generally everything else easier.

I marked the filament with tape on the extruder output and then counted how many full-steps (button presses) were needed to extrude 10mm of feedstock.
I did this again in the reverse direction to make sure of my count. Take as accurate measurement as you can for this.

10mm of driven feedstock = 348 full steps
I am really running my Extruder at 4 x microstepping, so 348 x 4 = 1536

And in the Firmware you need to provide a value for 1mm of feedstock so that would be 1536/10 = 153.6
So I used 153, recompile and download.

Then you need to accuratly measure your feedstock, I measured with a digital micrometer 10 random section of the coil and the average was 1.792mm

These settings need to be entered into the 'Dimension' tab in Skeinforge.

Many of the sections in Skeinforge do not need messing with, the ones you will need to play around with are 'speed' 'raft' and 'fill'

After setting your input filament perameters Feed and Flow under 'speed' are the most infulentual settings to play with along with 'infill width over thickness (ratio) in 'fill'

The next bit of advice is to make your machine Go Slow for initial test and calibration of flow/feed, I wasted quite a lot of time trying to run my machine too fast before I had these settings correct, you can easily speed it back up afterwards.
So set the 'speed' for the machine to 20 or 30mm / sec

Set your flow/fill speed -

Set the extruder speed Feed and Flow the same value, I started at 16mm/sec and went up and down from there.

This picture shows the effect of Flow/Fill on my machine (0.25 layer height) 160 layer 40mm tall 10mm cube.

I decided to turn off 'Limit' as I have acceleration in my Firmware, but you may want to enable it to help protect your machine from over-speeding especially on the Z axis.

If you are not using a heated bed (or even if you are) you may want to make the first layer go slower than the rest to help it stick to the bed.
Raft can do this, although you don;t actually need to make a raft just use it for slowing down the first build layer outline and initial fill.
See the Above links to Reprap forum and Mendel-parts for more on this and all the other sections.

Then tune your solid fill rate - 
Some of the guides talk about setting 'infill width over thickness (ratio)' to 1.7 from the standard default of 1.5. I found that my solid layers had too little plastic at 1.7 and 1.5 so my setting is 1.4, this gives me a perfectly filled solid layer without any 'spare' plastic, if your nozzle is pushing about plastic on subsequent layers of a solid fill (object base) then raise this number. if it's too sparce and you have tiny gaps between filament make this number smaller.

This solid base was with it set to 1.5, I settled on 1.4 in the end.

These are the different tool-paths for 1.0, 1.5 and 1.7 infill width over thickness (ratio) settings

Correct Filament Reversal length -
* Very important with a Bowden extruder *

I did get lucky with my first guess at required Filament reversal length, but the above image show the effect of not having enough reversal (lots of strings)
On the left is a 1mm reversal, middle is 2mm and printing on the right is a 3mm filament reversal. I may be able to get away with 2.5, but for now I'll stick to 3mm.

It's easy to fool yourself into thinking you have ok settings using a standard test cube, I have found that this model (below) is an excelent peice for machine calibration and it's quick to print so you can try out settings quickly.
It's a hollow pyramid by (3dprinterbot) found on Thingiverse -.

This was still early on in the Skeinforge tweaking, but even so a great improvement over Java host.

No Strings !
Java host generated on the left, and Skeinforge V41 on the right. (With strings, but in the right places)

This was my most recent print, with super-refined settings. 
This proved to be a good test of filament spanning, you can see the solid layers at the top, under this is hollow, and then a solid base at the print bed.
I stopped the print as I have hit a problem with Gcode generation on Hollow objects. 
I'm going to need some help on sorting that.

Anyone like to guess on what this object is? 
When I get it all printed out you can see if you were correct.

If you are new to Skeinforge, I hope that some of this may help you or at least show you that it's worth learning how to use it.

Thanks for reading.