[MakerBot] Skeinforge settings for printing lego pieces
MakerBlock
I've been tinkering with my various Skeinforge settings in an attempt
to print up a lego piece without success. I always end up with blobs
instead of the lego pegs. I've tinkered with Unpause, Stretch, and
extrude width/height/speed settings (among others) without success.
If you've successfully printed a lego piece, would you mind sharing
your Skeinforge settings? I realize those setting won't work out of
the box for my 'bot, but at least it would probably be a good place to
start.
Thanks,
MakerBlock
Cliff Biffle
> If you've successfully printed a lego piece, would you mind sharing
> your Skeinforge settings?
If you're printing over a serial cable, try printing from an SD card.
My experience (finally!) printing a copy of my chess set was that the
firmware's serial communications are too slow to keep up with small
curved features, so you wind up slowing down the head and extruding
too much plastic.
-Cliff L. Biffle
MakerBlock
By the way, I've printed two of your knight pieces - they're pretty
incredible.
MakerBlock
Cliff Biffle
> By the way, I've printed two of your knight pieces - they're pretty
> incredible.
Heh, that's funny, the knight is my least favorite.
If the SD print doesn't fix your issue, let us know. I may be able to
help tuning the extrusion parameters in Skeinforge.
-Cliff L. Biffle
MakerBlock
my avatar on Thingiverse.
Admittedly, it would look slightly cooler if the indentations for the
knight's head were deeper or more defined. But, it would only be a
marginal improvement over a fantastic piece.
It's tied with my shiny new TARDIS as my favorite piece.
MakerBlock
Cliff Biffle
> It's tied with my shiny new TARDIS as my favorite piece.
From your picture of the TARDIS I can offer some more thoughts.
From the fill on top, I can see that you're getting what I call
"puddling" -- tight fills get too much plastic, and don't stay
confined to their Z-layer. This is a sign that your Extrusion
Diameter Over Thickness and Extrusion Width Over Thickness knobs
aren't quite right. This may also affect your ability to print the
Lego studs.
In my experience there are basically two ways to work around this:
1. Tune Skeinforge to understand how much plastic you're extruding
(procedure below).
2. Make the head go faster, depositing less plastic in each place.
This has its own problems and I don't recommend it.
3. Make the extruder go slower (i.e. lower the PWM value).
My highest print quality has come from doing #3, then tuning (#1) with
this procedure:
- The independent variables you control for this procedure are Layer
Thickness, PWM Flowrate, and Feedrate (speed of head movements).
There are others, but the defaults are probably sane. In my case, I
take the default feedrate and thickness, and adjust PWM Flowrate down.
- Do a test extrusion into the air. Measure its diameter, D. Look up
your configured layer thickness, T. Divide D/T and set "Extrusion
Diameter Over Layer Thickness" (in Speed, iirc?) to the result. This
is how Skeinforge determines how many mm^3/s of plastic it's emitting.
- Print something with thin walls, where you can measure the width of
a single extrusion pass, W. Do not use any extrusion from the raft,
or the first layer on top of the raft -- too variable. Divide W/T and
set "Extrusion Width Over Layer Thickness" (in Fill, iirc) to the
result. This is how Skeinforge determines how tight to print a solid
fill.
Once these values are correct, many others are useful (but not
mandatory in my experience) for tuning, such as the overlap of grid
corners in infill (Fill), infill density, and the Unpause and Stretch
modules.
Hope this helps.
Also, you've probably noticed, but you've got a small Z-rod wobble.
It doesn't appear to change over the height of your TARDIS, so it may
be a slightly warped rod (but it could be a simple bearing
misalignment at the base or top).
-Cliff L. Biffle
MakerBlock
Thank you for that!!! I will try that method.
As for the Zrod wobble... the rod is only very slightly warped. I
noticed this when cleaning the rod initially. I put it in the drill
and it spun around kinda wildly. Never a dull moment!
MakerBlock
Owen M Collins
Cliff Biffle
> I know the rod in the makerbot kit are M8 or roughly 5/16" I didn't see an
> equivalent at McMaster carr.
Switch the page to metric, "roughly 5/16" isn't good enough.
Doesn't look like the acme rods go down to M8, though.
-Cliff L. Biffle
Eric Smith
misnomer as Acme is specified for imperial units only; it really is
called "trapezoidal thread". Acme uses 14.5 degree flank angle, while
trapezoidal uses 15 degree.
For the Makerbot, I think you would want TRxX1 or TR8X1,5 trapezoidal
thread leadscrew, which has 8mm major diameter and 1 or 1.5mm thread
pitch. That's somewhat hard to find but not impossible.
Another possibility, somewhat easier to find in 8mm but a lot more
expensive, is a ball screw. Nook has some:
http://www.nookindustries.com/ball/BallMetricAvailability.cfm
Their ECS-08020-RA looks ideal for a MakerBot. You'd just have to
change the cutout in the Z stage and add the appropriate bolt holes.
Rick Pollack
Let me know if you decide to try printing the pulleys as I have some extra belts that fit the Thingiverse pulleys.
Rick
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